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Enhanced European Coordination for Accelerator Research & Development

Final Report Summary - EUCARD-2 (Enhanced European Coordination for Accelerator Research & Development)

Executive Summary:
Particle accelerators are contributing to the advancement of physics and, through accelerator-based X-ray and neutron sources, to the progress of medicine, biology and material science. With more than 30,000 accelerators worldwide in the industrial and health sectors their use is rapidly spreading outside of the scientific environment, to address societal challenges and to generate economic growth. To deal with the increasing demands from basic science and to enhance the diffusion of accelerator technologies towards applied science and societal applications, future particle accelerators need to be more powerful but at the same time have smaller footprint, better energy efficiency, and higher reliability. A common development strategy to face these challenges was the subject of the EuCARD-2 (Enhanced European Coordination for Accelerator Research and Development) Integrating Activity Project. It brought together a consortium of 40 European universities, accelerator laboratories and technological institutes on a programme that, over 4 years, has mobilised a community of more than 350 researchers, organising more than 100 workshops and events and producing 62 high-level deliverable reports, 282 publications and dissemination activities and 4 applications for patents.
The EuCARD-2 Networks have generated a large amount of studies, initiatives and new ideas in a wide range of fields related to accelerator technologies. Activities were centred on future circular particle colliders, storage rings for intense beams, superconducting hadron linacs, and polarization challenges. Novel ideas included sequences of large circular colliders, new schemes for the production of cold muon beams, future acceleration concepts based on crystals or nanotubes, and new concepts and techniques for lattice optimisation in synchrotron light sources. The activities on Novel Acceleration techniques generated a new successful series of bi-annual international Workshops and a new Design Study supported under Horizon 2020. Other Networks covered subjects closely related to innovation, societal challenges and applications, organising three “EuCARD-2 meets industry” events on selected subjects from the project technology portfolio: medical isotope production with accelerators, new materials for extreme thermal management, and environmental applications of low-energy electron accelerators. Other activities covered the evaluation of conceptual aspects of the energy efficiency of particle accelerators, as well as the efficiency of typical component technology used in particle accelerators. The Network on Accelerator Applications has identified existing and new applications that could benefit from accelerator technology, documenting these in a comprehensive document, the “Applications of Particle Accelerators in Europe”.
Three accelerator test facilities provided Transnational Access for a total of 10,557 access units.
A Joint Research Activity (JRA) made remarkable progress in the application of High Temperature Superconductivity (HTS) to particle accelerators, selecting suitable superconductor, tape and cable design, and achieving the world record of 1.3 kA/mm2 current and realising a coil tested in a magnet at 3.3 T field. Another JRA developed and improved novel composite materials for collimators exposed to high luminosity beams. A third JRA on innovative Radio-Frequency technologies has demonstrated new thin film deposition techniques to realise superconducting accelerating cavities at lower cost, and has contributed to the design manufacturing and testing of high gradient accelerating and deflecting structures to very high performance. The last JRA progressed in the field of plasma wakefield accelerator. Higher brightness beams, external injection, and feasibility of femtosecond-level synchronisation between lasers and beams have been demonstrated, together with the particular operating regime of a plasma excited by an intense proton beam.
Project Context and Objectives:
Context

Accelerator-based activities are rapidly growing today, with more than 30,000 accelerators currently in operation world-wide. While a few large accelerator research infrastructures are particularly visible, and the Higgs search at the Large Hadron Collider (LHC) at CERN has fascinated the public as well as particle physicists, most particle accelerators are dedicated to applied research, medicine and industry. A marked interest has arisen in the fields of energy and environment, where the potential of particle accelerators could become revolutionary. With such a multitude of applications, accelerator technology is reaching the frontiers of performance, energy efficiency, cost, and size to name a few. Advances in technology are needed to face the challenges of both research and society.
In this context, the main drive for particle accelerator development still comes from fundamental research in particle physics, which is now at a turning point. The start of operation in 2009 of the LHC has allowed Europe to regain the world leadership in particle physics, a key sector of knowledge and technology. A challenging upgrade of the extremely complex LHC collider has been recently approved, requiring new sophisticated technologies and putting new strain on the operational parameters of the entire CERN accelerator complex. This major step will deliver sufficient information on rare processes to shed light on the existence of new particles.
In parallel, three major accelerator projects which represent important milestones in the ESFRI (European Strategy Forum on Research Infrastructures) roadmap are starting operation or are in an advanced construction phase. The European XFEL at DESY (Hamburg) is beginning its operation; providing ultra-short intense X-ray pulses at short wave-length to a variety of users it will open new perspectives for a wide range of applied sciences. The European Spallation Source (ESS) laboratory in Lund, Sweden, is in an advanced stage of construction and will provide its first neutron beam to users in 2019. This third generation neutron source will give a new insight on all types of materials, from molecules to medicines, from plastics to proteins. Finally, a new large international accelerator complex, FAIR, is in construction at GSI (Darmstadt). Its goal is to gain new insight into nuclear matter by providing ion beams at the intensity frontier, with increased energy, brilliance and beam power. Besides these large international research infrastructures, a significant number of small but unique research accelerators share the objectives of enhancing performance, while reducing cost and environmental impact.
In a similar way, applications of accelerators are rapidly growing. One of the most visible fields is cancer therapy, where particle therapy, directly based on the technology of research accelerators, is increasingly successful. With 19 centres for particle therapy in operation and 10 more under construction, Europe is the leader in this advanced health treatment, whose diffusion is only limited by the cost and complexity of the accelerator and beam delivery system. While the use of small scale electron and ion accelerators keeps growing in industry, accelerators have high potential in new domains related to the energy and environmental challenges that our society is facing.
In this stimulating environment, two fundamental requirements have to be fulfilled to face the demands of the present and future generations of particle accelerators. The first is the need for international collaboration: all present and future large projects go beyond the capabilities of individual European countries and need to be implemented as large European or world-wide collaborations. Setting up a European collaborative environment today is instrumental to achieving the goals of tomorrow. The second requirement is the availability of new technologies which may be brought to maturity in a collaborative environment and made available to the wider community, across projects and national borders.

Project Objectives

In this particular and challenging context, the main objectives of the EuCARD-2 project were:
• To connect transversally the different large accelerator laboratories and reinforce a collaborative approach to outstanding upgrades of major accelerator infrastructures, by establishing links between laboratories, universities, research institutes and industry.
• To concentrate the common resources on focused Research and Development activities of excellence, where Europe can keep or gain leadership in outstanding research infrastructures and develop favourable conditions for innovation beyond the primary research goals.
• To share the challenges of high-gain high-risk R&D studies.
These wider objectives translate into more focused objectives for the individual Networks, Transnational Access (TNA) and Joint Research Activities (JRA) that are given below.

WP2 (Innovation): Its main objective was to maximize the likelihood that the knowledge and technology produced across the EuCARD-2 work packages (WP) is transferred to society and industry, thus enhancing the resulting impact. The strategy to achieve this objective was based on examining the technology developments made within the project in detail, and then ensuring that these were known to industry, via joint workshops with members of industry and/or via the Technology Transfer offices of each partner. The collaboration between research laboratories, universities, specialized institutes and applied research institutes was intended to facilitate the identification of potential innovations and route to exploitation. The organization of “EuCARD-2 meets industry” events on selected topics aimed to create direct person-to-person contacts and collaborations, thus filling the observed gap between academia and industry.

WP3 (Energy Efficiency): New particle accelerator based research facilities aim for increased performance, but this often corresponds to higher energy consumption. The goal of this WP was to analyse conceptual aspects of modern accelerators as well as specific accelerator subsystems defining strategies and technologies aimed at reducing the electric power from the grid during operation while keeping the required performance. The key technologies for maximising energy efficiency of accelerator facilities analysed by this Network were heat recovery from cooling circuits, efficient Radio Frequency (RF) generation, energy management in a virtual power plant, energy storage, and energy efficient beam transport.

WP4 (Applications): Particle accelerators are already extensively used for a range of applications, in particular in the health and industrial areas, with more than 30,000 in regular use. However, the accelerator technology used is rather old. The aim of this Network was to study both applications and the accelerators required for their use, to assess areas which could benefit from newer accelerator technology developed for Research Infrastructures (RI), as well as identifying possible new applications. This was achieved by the organization of workshops on a wide range of topics and documenting the knowledge gained via a high-level document. An additional objective was to identify further work to be done and to form collaborations to carry it out.

WP5 (Extreme Beams): The WP5 Network explored the collider and accelerator frontiers with the objective of pushing the limits of present accelerator beams, in terms of energy, luminosity, intensity and polarization, and, specifically, at maximizing the performance of major European projects now under construction or being proposed, in particular the High-Luminosity LHC (HL-LHC), FAIR, ESS, and future accelerators presently in the design stage. The primary goal was to provide a forum for exchanges between researchers, to discuss innovative ideas and to define common strategies or solutions for the upgrade and/or construction of large accelerator facilities. This Network also aimed at enlarging the boundaries of the community, interconnecting with similar initiatives outside Europe and with other scientific communities whose competences relate to the challenges of future accelerators. The final goal was defining European strategies for the development of future extreme beam facilities.

WP6 (Low Emittance Rings): The Network’s objectives focused on ultra-low emittance rings, i.e. pushing the beam density in lepton storage rings by reducing its size, well beyond present limitations. Its primary goal was to bring together a large community of accelerator physicists and engineers working on three different types of accelerators, damping rings, colliders and synchrotron light sources that have been traditionally separate, despite the many common scientific and technological challenges. The overarching goal was to communicate, identify and promote common work on topics affecting the design of low emittance electron and positron rings, with a particular focus on increasing the performance of the large and strategic European infrastructure of synchrotron light facilities. The main topics considered were lattice design, beam dynamics and technical challenges.

WP7 (European Network for Novel Accelerators): The goal of this Network was to promote novel accelerator technologies that can provide orders of magnitude higher accelerating fields and thus have the potential for significantly reducing the size and cost for new accelerators. The first goal, bringing together 54 institutes worldwide, was to structure and coordinate a strong but dispersed European community, with solid connections outside of Europe and with other scientific communities, such as the teams working on lasers. The Network’s objective was fostering research on alternative acceleration techniques (mainly plasma acceleration), collecting the experience of small laboratories and fusing the community on the exigencies of large-scale facilities. A specific objective was to focus the diverse plasma wake field community to define a common roadmap.

WP8 (Ionisation Cooling Test Facility): This work package intended to provide Transnational Access to the Ionisation Cooling Test Facility, which comprises specifically developed target and beam-line at the proton synchrotron of the STFC’s Rutherford Appleton Laboratory. The objective foreseen for ICTF was to deliver at least 2,280 access units (hours) to an estimated number of 40 users from 20 projects.

WP9 (HiRadMat and MagNet): This work package was intended to provide Transnational Access to two facilities based at CERN: the High Radiation Materials test stand (HiRadMat) using a high-intensity high-energy proton beam from the SPS accelerator, and a test stand for superconducting magnets and equipment (MagNet) operating at cryogenic temperatures based in the SM18 Hall. The objectives foreseen for HighRadMat were to deliver at least 2,400 access units (hours) to an estimated number of 40 users from 8 projects. The objectives foreseen for MagNet were to deliver at least 1,920 access units (hours) to an estimated number of 64 users from 8 projects.

WP10 (Future Magnets): The goal of this Joint Research Activity was to advance the development of accelerator magnet in HTS (High Temperature Superconductor), to reach magnetic fields beyond 16 T, which is the limit of the present (second) generation of magnets based on Nb3Sn technology. A substantial step in reaching fields of about 20 T will open new perspectives for high-energy hadron colliders and will pave the way to new accelerator designs and possibly a large wealth of applications outside particle physics. The precise objective of the JRA was the design, characterization, construction and test of the first full-bore demonstrator collider magnet using HTS technology reaching a magnetic field compatible with operation at 20 T as an insert in a Nb3Sn accelerator magnet.

WP11 (Collimator Materials): This JRA aimed to increase the capability of beam collimators to handle very high brightness beams that are required by major European projects like HL-LHC at CERN and FAIR at GSI. Peak energy densities up to 15 GJ/mm2 that are now imaginable in the LHC beam constitute a completely unknown territory for collimators in terms of materials and design. The JRA’s objective was to focus efforts on new extreme brightness and on some successful materials already identified, to come to the final choice of material and design for extreme brightness collimators, selecting between new types of Molybdenum carbide-graphite and metal-diamond composites. To this aim, extensive material studies, modelling and characterization in the partner laboratories, production by industrial partners of several material grades, and a number of irradiation campaigns under ion and proton beams to study material response were foreseen.

WP12 (Radio-Frequency): Reducing size, energy consumption and overall cost are of primary importance for all accelerators being developed today. The Innovative Radio-Frequency (RF) Technologies JRA contributed to this overall goal by focusing on the development of a range of technical solutions, with the potential to achieve a significant performance increase in gradient, efficiency and beam quality of RF-based accelerator systems. Several novel techniques in the field of normal and Superconducting RF technology have been selected, presenting the highest impact potential for the accelerator community. The main objectives being: a) the development of multi-layer SRF thin films in order to break new ground in achieving gradients well beyond present Nb technology; b) the development and test of efficient normal-conducting structures capable of high gradient operation (Eacc > 100 MV/m) but free from dangerous wakefield contributions; c) demonstration using Higher Order Mode (HOM) signals from accelerating cavities as beam position diagnostics in high-energy electron linear accelerators, with the goal of reducing accelerator cost and length; d) the development of a new generation of advanced photocathodes for use in RF injectors, thereby enhancing the ability to reach fs-scale response time, more effective electron beam generation, capture and transport with high brightness and low intrinsic emittance.

WP13 (Novel Acceleration Techniques): The objective of this JRA was to create opportunities for collaborative studies on topics exploring novel frontiers of particle accelerators having in common the extreme high-gradient acceleration of particles within plasmas. Three subjects were selected as requiring further studies. Two were related to plasma wake field acceleration, while the third was related to production and control of ultra-short electron pulses; all these activities were concerned by femtosecond time scales. The objective of the first activity was to compare methods for the production of high brightness electron beams by external or optical electron injection into a laser-driven wake field plasma accelerator. The second investigated the feasibility of coherent waves in very long plasma cell, a critical component of a proton-driven plasma wake field accelerator. The objectives of the third activity were to control at bunch level ultra-short beams at the femtosecond scale.
Project Results:
WP2: CATALYSING INNOVATION (INNOVATION)
The Innovation WP of EuCARD-2 has:
1. Enhanced collaboration between academia and industry in the field of particle accelerators, enlarging the particle accelerator R&D community to include industry as a strategic partner;
2. Identified three accelerator-related technologies that are close to market; for each of them organised a workshop to establish connections with industrial partners and defined strategies for common development. 62 European companies participated in the three events.
3. Prepared the ground for larger industry involvement in future accelerator projects in the Horizon 2020 programme and beyond.

A preliminary initiative was to carry out technology scouting of all work packages in the form of interviews with all WP coordinators, to identify developments and technologies that are closer to market and are ready to engage with industry. These interviews have highlighted three topics that became the focus for three ‘EuCARD-2 meets industry’ events, which brought researchers and members of industry together with a view to forming new partnerships and exploring the potential for knowledge and technology transfer. The following workshops were organised:
-WP4 (Accelerator Applications)
Topic: Compact Accelerators for Isotope Production
26-27 March 2015, STFC (UK)
Attendance: 70 (24 from industry)
Main outcomes: The workshop brought together industry, clinicians and academia to explore how accelerator technologies can be applied to future medical isotope production needs for both diagnostics and therapy. The aim of the workshop was not only to review the state of the art of novel accelerator technologies for production of radioisotopes, but also to initiate future joint clinical/industrial/academic collaborative projects addressing the demand in future radioisotopes. Understanding industry requirements was critical to propose strategies for continued research.
- WP2 (Collimator Materials)
Topic: Applications of Thermal Management Materials
6 November 2015, CERN
Attendance: 85 (20 from industry)
Main outcomes: Materials for collimators and other beam-intercepting devices share many requirements with advanced thermal management applications. The aim of the workshop was to understand the needs and requirements of industrial companies and institutions, essential for adequate knowledge and technology transfer. The workshop clarified the requirements and overlapping interest of the participants, through discussions and a questionnaire. Such new materials have applications in power electronics, aerospace, advanced braking systems and hot components for gas turbines.
- WP4 (Accelerator Applications)
Topic: Low energy electron beams for industrial and environmental applications
8-9 December 2016, WUT (Poland)
Attendance: 70 (18 from industry)
Main outcomes: The workshop aimed to provide an overview of the state of the art and highlight new uses/developments of electron accelerators in sterilization of healthcare products, curing of materials, new materials synthesis (composites, nanostructures, grafted surfaces and gels) and the treatment of industrial flue-gases, waste water and sludge. Leading industry experts with unique experience were brought together with researchers for presentations and a panel debate from which it became clear that low-energy electron beams hold a much higher industrial and societal potential than the present usage suggests. Understanding the barriers of market entry when conducting R&D is vital for future progress.

The first workshop sought to address the expected increase in future demand of medical isotopes for diagnostics and for targeted cancer therapies. Radioactive isotopes are commonly used in nuclear medicine for imaging of active physiological functions within the body like cancers. They are presently produced either by nuclear reactors (Technetium 99 for SPECT analysis) or by dedicated cyclotron accelerators based in large production facilities (Fluoride 18 and other isotopes for the more accurate PET – Positron Emission Tomography). The use of therapeutic isotopes for localised cancer treatment is only starting and could become an essential tool for future personalised cancer treatment. The workshop identified areas of action for the accelerator community, such as addressing concerns related to the global supply chain for Te99, which comes exclusively from a small number of aging research nuclear reactors, and developing compact low cost accelerators for production of F18 and short-life isotopes directly in the hospitals. The international meeting with industry addressed the technological and economic challenges, as well as significant regulatory aspects to consider.
The second workshop sought to investigate how novel thermal management materials used to handle the large amount of energy deposited in accelerator collimators and other beam-intercepting devices (BIDs) can be applied to industrial domains such as automotive, aerospace, electronic packaging, fusion and solar energy. Although accelerators represent a very narrow application, the materials developed for accelerator BIDs share many requirements with advanced thermal management applications in industry and aerospace. Both a dedicated survey and discussions during the workshop proved that several companies have a strong interest in the new accelerator thermal management materials, in particular molybdenum graphite (MoGr). However, production capacity was identified as a potential bottleneck: because some of the advanced materials such as MoGr are at an early development and manufacturing stage, very few actors have the capacity for manufacture of such material in volumes that are still limited. This, however, may well change in the near future.
For the third and final workshop, the selected topic was “Low energy electron beams for industrial and environmental applications”. A large fraction of more than 30,000 accelerators in operation worldwide are low-energy electron accelerators used in industry, and reviewing their status and perspectives was considered very important from the industrial and societal point of view. Although such accelerators are common or even standard in certain applications, e.g. for polymer modification, the workshop identified fields where there appears to be a very large untapped industrial potential.
Most notably, electron accelerators hold huge potential for treatment of wastewater, sludge, and flue gases. Studies show that electron accelerators can provide more efficient treatment than conventional methods while being also more cost-effective, as confirmed by several pilot plants and a few full-scale operational plants. By bringing in some of the leading experts with operational experiences, it was possible to shed more light on the barriers preventing widespread adoption and how these can be overcome. Limits to the diffusion of accelerators are related to permissive regulations, to high capital costs for a technology that becomes cost effective on the medium-long term, and to the hesitance of well-established industry to follow new approaches. If a certain number of new accelerator-based centres for treatment of wastewater, sludge, and flue gases are built in the near future, it could lead to a rapid acceleration in industrial adoption of this technology. One important message is that the focus for subsequent research and development of low-energy electron accelerators should lie in scaling down: the technology is already good enough, but must be made cheaper, simpler, and more practical in order to better appeal to industry. Therefore, the workshop resulted in the definition of a common programme bringing together accelerator manufacturers with operational experience and researchers that will be part of the next particle accelerator Integrating Activity.

WP3: ENERGY EFFICIENCY (ENEFFICIENT)
The new Energy Efficient Network of EuCARD-2 has:
1. Performed eight dedicated studies on critical topics for an efficient energy management of present and future accelerator infrastructures.
2. Compiled an important amount of information on energy management that will be available to the planners of future infrastructures.
3. Contributed to the development of specific accelerator components aimed at reducing energy consumption, as tunable quadrupole magnets and high-efficiency klystrons.
4. Increased the awareness on energy and energy management in the community of particle accelerator designers, providing them with specific knowledge and tools to increase the efficiency of new and existing designs.

The overall energy efficiency of particle accelerator infrastructures is usually quite low. Transforming the energy from the electricity grid into the energy of a particle beam is a long and complex process with inherent energy loss at different stages; beam quality requirements usually drive the design resulting in poor energy efficiencies. This Network has been the first attempt in Europe to federate a large community using sharing experience, tools and ideas towards an improved energy management.
Heat recovery from conventional or accelerator structures is a promising avenue to increase energy efficiency of research facilities. Some accelerator sub-systems, like cryogenics or Radio Frequency, are inherently inefficient and waste significant portions of the electrical energy as heat. The activities of the Network have identified potential solutions, such as:
a. Implement heat recovery systems from RF power units, as already done in some laboratories and under study for the ESS project.
b. Use waste heat for heating buildings, to reduce energy consumption and possibly generate income (Figure 1). Heat recovery systems need to be combined with heat pumping systems in order to increase the output temperature up to the minimum required by the district heating system.
Improving the efficiency of RF power systems above values that are often below 50% in operation can have a strong impact on the overall efficiency of accelerator facilities. The Network analysed in detail three technical options:
a. a new bunching mechanism called the Core Oscillation Method, which could boost klystron (electronic) efficiencies from presently 65% to up to 90%;
b. the possibility to increase the output power of the (already quite efficient) Inductive Output Tubes power sources into the MW-class by developing a multi-beam version of this device;
c. design cavity power combiners that could allow to make solid state power amplifiers attractive for large accelerators by combining the power of hundreds or even thousands of transistors to reach the MW-class.
Particle accelerators utilize energy storage systems in many areas. Storage technologies include mechanical systems and energy storage in electric or magnetic fields covering a wide range of timescales, capacities and power rates; besides the technical parameters also reliability, lifetime, and possible failure scenarios are important. Capacitive and inductive storage provide high efficiency and high power rates, but have limited energy capacity and relatively high costs. The Network explored the following options:
a. Capacitor Banks, for which research aims to develop capacitors with lower fault rate and avoiding fault mechanisms that result in a shortcut of the capacitor challenge.
b. Superconducting Magnet Storage: the development of new superconductor cables can make these systems very attractive for future facilities.
c. Large capacity systems, whose importance will increase with the fraction of renewable energy sources in the overall energy mix. The Network supported the LIQHYSMES system proposal , which is an interesting option to combine the fast reaction time of inductive storage with the huge capacity of chemical storage. Moderately sized, this system is a valid option for an uninterruptable power supply for an entire accelerator facility.
Besides energy storage, another mean of facing fluctuating energy production and demand can be a virtual power plant, formed by a pool of distributed power producers and consumers to increase the overall availability and stability of the combined energy sources towards the public energy market. Large consumers in the pool can be switched off to lower consumption on demand; accelerator facilities are major energy consumers and so offer potential switchable loads. Lowering their consumption in times of high energy demand can help stabilize the network and reduce operation costs for the facility. The WP has surveyed the overall energy consumption of eight large European facilities which operate accelerators and investigated possible scenarios for reducing consumption on demand, such as introducing energy saving cycles with lower physics output and less overall energy demand. One limitation to these approaches is that complex processes tend to work best in a steady-state operation and switched operations carry intrinsically more complexity and risk of failure.
Beam transfer lines can contribute at a fraction of the total energy consumption of any high-energy accelerator facility. A comparative study of a number of beam transfer line design options was performed (Figure 2) for a specific case, comparing normal conduction magnets (NC), cosine-theta (SC) and super-ferric (SF) super-conducting magnets, high current pulsed magnets (HCP), and permanent magnets (PM). The final cost depends on the operation time (trade-off between investment cost and operation cost) but shows a clear advantage for permanent magnet systems. For the transport of bunched beams, the magnetic guiding fields are required only for the duration of the pulse length and so high current, pulsed magnetic lenses with low inductance are a valid solution. A novel pulsed quadrupole design developed at GSI was tested up to a current level of 30 kA; field quality and reproducibility were adequate for energy efficient pulsed beam transfer lines for bunched beams.

WP4: ACCELERATOR APPLICATIONS (ACCAPPLIC)
The new Accelerator Applications Network of EuCARD-2 has:
1. Highlighted the potential of particle accelerators for new and advanced societal applications in medicine and industry.
2. Structured the European accelerator community active on accelerator applications, fostering its connections with industry that has actively participated to its initiatives, and connecting with national programmes in Europe and outside.
3. Identified two promising directions to exploit the potential of particle accelerators: compact accelerators for radioisotope production and low-energy electron accelerators for industrial and environmental applications.
4. Produced a seminal report on “Applications of Particle Accelerators in Europe” that will be the reference for all future European developments in the field.

The Network assessed the application potential of four types of accelerators and of one sub-system.
Low energy (<20 MeV) accelerators for ions are mainly used for ion implantation, to modify the electrical, mechanical and chemical properties of materials. In particular, the doping of silicon with ions such as boron, arsenic and phosphorus to make semi-conductors is a huge multi-national industry. At higher energies, protons and ions are used for ion beam analysis, to determine the surface composition and structure of materials, and radioisotope production, for imaging and cancer therapy. The latter was identified as one of the main application for which accelerator technology has a strong potential to bring improvements. A number of new and developing applications have been identified, as new engines for satellite propulsion using the Hall effect to accelerate Xe ions to as low an energy as to 300 eV, that is an exhaust speed of 20 km/s, optimal for some satellite orbit tasks. At higher energy, proton accelerators are being studied for the production of specialized neutron spectra for applications such as boron neutron capture therapy (BNCT) and for material analysis. Critical for most low-energy applications is the target where beam energy is converted into other particles, particularly neutrons. New target cooling prescriptions and a collaboration to optimize BNCT targets are among the outcomes of the WP.
Electron accelerators up to 10 MeV have a huge potential for new environmental applications in the areas of flue gas treatment, eliminating Nitrogen and Sulphur from the smokes thus reducing acid rain, and water and biological sludge treatment, killing bacteria to reduce contamination. This has resulted in the formation of a new collaboration that is endeavouring to obtain funding to study the water and sludge applications in both the developed and developing world. This was the second topic identified as bearing a large potential for future developments.
Intermediate energy proton and ion accelerators have mainly applications in medicine, for the production of radioisotope for nuclear medicine and ion beam therapy for cancer treatment. Medical applications of ion beams and, in particular, proton cancer therapy, have rapidly grown over the last ten years. While accelerators for proton therapy are already commercial items, there is a wide space for new developments in the field of gantries, the complex rotatable beam transport systems that are installed after the accelerator to irradiate the tumour from any direction. Three workshops have been organized on the design of gantries and related technology. Economical solutions based on the application of superconducting (SC) magnets for the accelerators and for beam transport in the gantry have been investigated; a first workshop has allowed establishing relevant contacts with industry, while a second workshop was essential to establish the contacts between the various groups working on different aspects of superconductivity. SC technology can also help reduce the size of the particle accelerator: after SC cyclotrons, the development of SC synchro-cyclotrons may result in even smaller accelerators with more stringent beam delivery requirements. These issues were addressed in a third workshop, which resulted in the remarkable success that commercial providers of synchro-cyclotrons are now offering pencil beam scanning for their system. Another workshop to analyse and promote the use of Helium beams for ion cancer therapy, rather than the usual Carbon, was successful. Using Helium results in significantly smaller and cheaper ion treatment facilities, with benefits about half-way between protons and carbon ions.
High beam power proton and ion accelerators have applications in the domain of Accelerator Driven Systems (ADS) for driving thorium nuclear reactors and for nuclear waste transmutation. Their potential impact is related to the use of thorium as nuclear fuel, more available than uranium and without risks of nuclear proliferation, and to reducing the environmental impact of conventional nuclear power by reducing the waste lifetime. ADS development faces several technical challenges requiring strong R&D investment. This WP contributed by way organizing three workshops on this subject, promoting interdisciplinary networking and fostering links between different universities, laboratories and industries. A direct outcome of a workshop organised on the subject of accelerator reliability was the setting up of a new collaboration to: a) collecting and sharing information related to the availability and fault tracking in accelerators via databases and web resources, and b) developing from these studies some guidelines to inform the design of accelerator projects. A final workshop on the status of ADS systems attracted participation of worldwide scientific experts from as far as India, China, and United States. It united the two different communities of accelerator and target/nuclear physicists and created useful connections between the European initiatives and their counterparts in China and India. An indirect result was to help build up momentum in Europe on R&D advancement on ADS technologies by fostering contact and networking between scientific experts and political parties from official atomic and EC institutions.
The high beam power targets used for particle production are a critical sub-component common to many of the applications considered in the WP, as the production of radioisotopes and neutrons. New technologies were explored, as the use of targets with particle beams accelerated using lasers.
Notwithstanding its many technological advances, the main scientific result of the Network was the production of a document for European science and technology policy makers, entitled Applications of Particle Accelerators in Europe (APAE). This effort describes the current applications of accelerators, improvements in cost and performance that can be achieved by exploiting technology from RIs, possible new applications and what work needs to be done to achieve these. It comes in two parts: a 6-page summary brochure and a 113 page main document with all the details. Printed copies of the brochure will be distributed and the main document will be made available online.

WP5: EXTREME BEAMS (XBEAM)
The Network on Extreme Beams has:
1. Organized a large number of Workshops (35) covering all aspects of frontier accelerator performance, which have structured and enlarged the European accelerator community and connected European accelerator research with ongoing developments in the US and Asia.
2. Defined a European strategy in four critical fields for future accelerator development: colliders, hadron beams, superconducting linacs, and polarised beams.
3. Started in EuCARD and continued in EuCARD-2 the study of a new very large circular electron and hadron collider in Europe, which resulted in the Future Circular Collider (FCC) study at CERN and in the EuroCirCol Design Study in Horizon 2020.
4. Originated and promoted new ideas and developments in many accelerator fields, as extreme energy frontiers, muon collider designs, advanced photonics applications, etc.

Addressing open questions in particle physics calls for collisions at higher luminosities and/or higher energies. The next important step for e+e- colliders is the commissioning of the high luminosity SuperKEKB B-factory in Japan, along with the design work being carried out for the “Higgs, Z, top, W” factories FCC-ee, hosted by CERN, and CEPC, its Chinese twin project. The Network has demonstrated that the design of these accelerators can exploit the lessons learnt at past and present colliders. These include: a) the possibility of high beam currents thanks to the control of Higher Order Modes and electron cloud; b) the feasibility of the crab-waist collision scheme, as demonstrated at the DAFNE collider in Frascati/Italy; and c) the need for, and possibility of top-up injection, used at many synchrotron-light sources. Novel effects must be considered in the coming projects; for example, beamstrahlung, i.e. the radiation emitted during the collision by particles of one beam experiencing the field of the other beam, will increase the energy spread and bunch length and at highest energy and may even affect the beam lifetime.
Recently, there is a renewed interest in muon colliders thanks to the first results from the MICE cooling experiment in the UK, to further improve cooling schemes, and, mostly, to novel proposals to produce the muons already with a low emittance. WP5 workshops have revealed that low-emittance muons can be generated if produced close to threshold either by the annihilation of positrons e+e- → μ+μ-, or by colliding laser photons with a high-energy proton beam circulating in the LHC or in FCC-hh. The main challenge is the low production cross section. One proposal to meet this challenge is using an e+ ring, with a thin internal target. The simplification of the muon collider thanks to using positrons for muon production is evident in Figure 4. In the long term, once low-emittance muon beams are available, the 26.7 km LHC tunnel could be filled with ~5 km of 16 T SC magnets and ~20 km of ±3.5 T pulsed magnets plus an additional 7 GeV from a pulsed superconducting radiofrequency (SRF) system in the straight sections, to construct a 14 TeV muon collider. The ultimate lepton collider might be an X-ray driven muon crystal linear collider, with an accelerating gradient of up to 10 TeV/m and a final crystal funnel. A variant would replace the crystals with carbon-nanotube accelerators and carbon nanotube funnels, respectively.
Circular hadron colliders are discovery machines, their reach determined by beam energy, which depends on only two parameters: the magnetic field in the dipole magnets and the size of the collider. Historically, new colliders were always larger and used stronger magnets than their predecessors. The 100 TeV hadron version of the Future Circular Collider (FCC-hh), addressed in several WP5 workshops, requires 16 Tesla dipole magnets in a 100 km ring. No other proposed concept, not even a muon collider, appears technically ready to provide collision energies in the 10s of TeV energy range within the next 50 years.
WP5 workshops revealed two attractive routes forward, which combine the aforementioned approaches: one such route starts from a circular e+e- collider (FCC-ee/CEPC), proceeds to a 100 TeV hadron collider (FCC-hh/SPPC), and culminates in a 100 TeV muon collider (“FCC-μμ”), which could be constructed towards the end of the century. The other route begins with 25 TeV hadron collisions (HE-LHC) followed by a 25 TeV muon collider in the existing LHC tunnel. Supporting such strategy are two possible figures of merit for future colliders: (1) The effective beam power at the collision point(s) divided by the total electrical power of the facility, and (2) the total luminosity per electrical input power. Both figures of merit clearly reveal the advantages of circular design approaches, where the same particles are made to collide over many turns.
For future large projects, efficiency and cost minimization become ever more important. Figure 5 indicates that with present technologies and technology prices only the LHC energy upgrade (HE-LHC) and the FCC-ee/CEPC may be considered affordable (with an estimated cost of about or below 10 B$ using US accounting). The cost of a 100 TeV hadron collider, FCC-hh, can, however, be reduced by three steps: a) building this collider on a site with an existing injector complex, such as CERN, b) staging (e+e- 1st, pp 2nd), and c) reducing the superconductor/magnet cost. The FCC-hh would become affordable via a staged approach (i.e. following the FCC-ee in the same tunnel), or if the cost coefficients, in particular that of high-field magnets, can be reduced by targeted R&D efforts. Other novel technologies and concepts (e.g. ionization-cooling-free muon colliders and crystal acceleration) and tools (e.g. electron lenses) may also help reduce the price of future facilities.
A number of large hadron facilities are under construction or being upgraded around the world (see Figure 6), including several in Europe. WP5 has coordinated and integrated the activities of the accelerator, nuclear and particle physics communities towards reaching the optimum performance of FAIR, ISIS and PSI-HIPA, and helping guide the upgrade strategy for the LHC injector complex. Identifying and overcoming ultimate performance limitations for the aforementioned facilities have been a primary subject. WP5 has also supported studies on critical beam diagnostics (e.g. continuous emittance control, beam-loss and halo measurements) and supported Fixed-Field Alternating Gradients (FFAGs) development in the UK.
WP5 has catalyzed community discussions on the various performance limitations of high-intensity high-brightness hadron rings. Preliminary roadmaps for the upgrade of several European facilities have been developed and validated. In particular, WP5 has brought together beam dynamicists, magnet specialists, and beam instrumentation experts in order to identify optimum upgrade solutions, including risk mitigation. Integration of the efforts has been advanced through the joint fora involving universities, small institutes and large laboratories.
The ever-increasing beam power of rings and linacs calls for better beam control and diagnostics. Concerning extreme hadron linacs, WP5 workshops revealed some key points for optimum performance. These are: a) enhanced collaboration and sharing of expertise between similar projects for fast progress at minimum cost; b) beam-loss minimization for achieving the desired levels of availability and hands-on maintenance; c) properly specified and well-functioning low-level radiofrequency system, along with good temperature control of the timing reference lines; and d) thorough preparation for beam commissioning with special attention to (redundant) key diagnostics.
Polarization offers additional handles for discovery and precision studies at lower energy. WP5 discussions revealed that: a) a state-of-the-art laser system at the FCC-ee and Compton polarimeter can measure the beam polarization with a precision of 0.1-0.2% turn-by-turn and bunch-by-bunch; b) the installation of a large number of “partial Siberian snakes” could allow for polarized proton beams in a 100- TeV hadron collider; and c) the effect of thermal stress and long-term availability of the ILC positron conversion target could be tested with a CW electron beam. In several polarization areas, further networking and R&D activities are needed. For future large-scale machines (FCC, etc.) modelling tools need to be optimized and technologies to be updated in order to make reliable predictions of what can (and what cannot) be achieved with respect to polarization performance. Significant breakthroughs can be obtained by techniques which are outside the scope of established methods, like using a cryogenic photocathode vacuum vessel together with RF operation to solve the ion back-bombardment problem for high intensity spin polarized sources.
WP5 results underline that strengthening pan-European and global collaboration is a recipe for continued success. European accelerator networks continue to play a key role in all the aforementioned areas, and they provide key ingredients for the future of accelerator development. During the next couple of years, several new projects are upcoming, such as SuperKEKB, IOTA, ESS, NICA, HEPS, HL-LHC and MESA, which are certain to provide new lessons. Many other machines, such as ESSnuSB, JEDI, FCC, CEPC, LHC-based Gamma-Factory, γγ colliders, etc. are also being proposed. Next-generation facilities offer an exciting perspective for the future, enhanced by possible novel uses of storage rings (e.g. for the detection or generation of gravitational waves), new methodologies for modelling accelerator performance and pushing their availability to unprecedented levels.

WP6: LOW EMITTANCE RINGS (LOW-E-RING)
The new Network on Low-Emittance Rings has:
1. Federated for the first time three accelerator communities sharing common problems and technologies: damping rings for electron colliders, advanced factories (e+/e- colliders), and synchrotron light sources.
2. Transferred to the European Synchrotron Light facilities the expertise and competence of the accelerators for fundamental physics research, which resulted in the implementation of the 4th generation of light sources based on the Hybrid-Multi-Bend Achromat.
3. Fostered synergies within the low emittance ring community, disseminating new techniques for lattice optimisation and supporting common R&D activities, via the organization of 4 general and 6 topical Workshops.

The emittance is the main component of the brilliance of a synchrotron light source, which is its main figure of merit. The four years of activity of the Low-e-Ring Network have seen a jump in the emittance achieved or targeted in the light source facilities with respect to the third generation ones, at the point that we can now speak of a 4th generation of light sources, entirely originated in Europe. In Figure 7 the emittance divided by γ2 as a function of the circumference is plotted: the new facilities (in construction, approved or proposed) lie on a line about one order of magnitude lower than the third generation rings.
The activities on Low Emittance Ring Design have fostered the emergence of ever more aggressive lattice design, targeting emittance in the order of tens of pm, in medium size machines. These lattices are based on ambitious extensions of the Multi-Bend Achromat (MBA) concept to build cells with M in excess of ten (M = 18 in the proposal for the upgrade of MAX IV). The original MBA is based on a rather relaxed optics, resulting in low chromaticity and relatively large dispersion, and thus moderate sextupole strength. Low emittance is obtained from the large number of cells. Miniaturization is the base for the new generation of MBA lattices. Vacuum chamber dimensions are reduced by approximately a factor of 3 compared to 3rd generation light sources and smaller vacuum chambers are the base for miniaturization of magnets, resulting in higher focusing gradients. A Hybrid-MBA cell was developed for ESRF-EBS and adopted by many other projects like APS-U, Spring-8-II, HEPS and PETRA IV. The DTBA lattice is proposed at Diamond, based on SuperB cell combined with MAX IV MBA cell and it includes transverse and longitudinal gradient dipoles to further reduce the emittance. This option is consequently exploited at SLS-2, where anti-bends are also added for optimum matching to the longitudinal gradient bendings. Dynamic aperture optimization is one of the most challenging tasks in low emittance lattice design. Different methods have been presented and discussed, such as: minimization of nonlinear drive terms, multi-objective genetic algorithms, or Beam-Based Optimization of Nonlinear Dynamics by means of robust minimizers like robust conjugate direction search.
Very aggressive designs cope with reduced dynamic aperture and explore on-axis injection schemes, because off-axis injection is no longer possible. The emergence of novel concepts for injection was another hot topic intensely discussed in the collaboration. Swap out on-axis injection seemed to take a major role in this new project and it is strongly underpinned by the progress in faster kicker technology, yet another example of successful cross fertilization between different accelerator communities of light sources and damping rings, as supported by the network.
Several methods were presented and discussed for reducing instabilities, impedances and collective effects in low emittance rings. These include numerical wake field calculations and optimization of vacuum component designs, theoretical approaches to short-range wakes, beam-based and bench measurement of impedance, impact of harmonic cavities on collective effects, development of simulation codes, comparison of beam-based measurement of instability and impedance with simulations, simulation of electron cloud build-up and use of the former in electron cloud instabilities, mitigations for the suppression of secondary electron yield, measurements of electron cloud, lattice design reducing intra-beam scattering, advanced single shot measurement using ultra-fast detectors.
The large number of studies presented at the workshops, along with their high quality, confirms the recognition by the community of the high degree of importance in understanding and mastering the beam collective effects in present and future low emittance rings, which aim to reach their designed performance via high beam intensity and low emittance.
Activities on Low Emittance Rings technology concentrated on creating a communication platform to exchange information and build collaborations on common issues affecting the design of the technical systems in present and future ultra-low-emittance rings. This extended to industry that actively participated in the Network activities. The major topics presented and discussed during the workshops, for which significant progress has been reported, are insertion devices, magnet design and alignment, instrumentation, fast kicker systems.
Either for producing high-brilliance X-rays or for damping the beam to ultra-low emittances, the magnet design and optimization with respect to field errors and alignment is fundamental for the performance of modern storage rings. The technical challenges and R&D needed include pushing the limits of high gradient and small bore apertures, the review of tolerance requirements, the development of complex dipoles (combined function, longitudinal gradient), the use of permanent magnets for achieving very large gradients, cost-effective series production of permanent magnets, precision machining (poles, mating surfaces, etc.), magnetic measurements (stretched wire with small bores) and in situ alignment. The collaboration between colliders and light sources was primarily important in the development of wigglers for fast damping of the injected beam in the case of damping rings or to be used as a photon source for light sources, in design of stripline kickers with fast rise-time and very good stability, and in the development of correction methods and beam instrumentation for achieving and measuring ultra-low emittances.

WP7: NOVEL ACCELERATORS (EURONNAC2)
The Network on Novel Accelerators has:
1. Federated and coordinated a large collaboration of 54 member institutes, mainly European, to develop novel “ultra-high gradient” particle accelerator technologies and to direct their development towards pilot applications.
2. Enlarged the scope from originally plasma acceleration (particle and laser driven) to additionally dielectric vacuum accelerators driven by optical lasers or THz sources.
3. Coordinated and set up the successful EuPRAXIA Design Study proposal for Horizon 2020 and participated to advanced R&D projects (AWAKE at CERN and AXSIS at DESY).
4. Established the European Advanced Accelerator Concepts Workshop (EAAC) and organized EAAC2013 (145 participants) and EAAC2015 (258 participants).
5. Fostered a high number of peer-reviewed publications, supporting and promoting PhD students and young researchers.
6. Co-organized the first CERN Accelerator School (CAS) on plasma acceleration with more than 100 students.

Accelerators of charged particles have been a high impact success story since the invention of radio-frequency (RF) acceleration in 1927. In their 90 years of history, particle accelerators based on (conventional) RF technology are at the core of some of the largest or most powerful research facilities ever built. Accelerators serve a huge variety of applications, including those for use in the industrial and medical fields, often limited only by the size and cost for the required RF technology. However, the potential for particle acceleration in the fundamental equations is far from being exploited. Today new ideas and technologies allow for accelerating fields that are 2-3 orders of magnitude above those used in conventional RF accelerators: for example, multi-GeV electron beams have been already successfully produced within a few cm’s of laser-driven plasma channels.
The European Network for Novel Accelerators (EuroNNAc) is promoting the research on novel “ultra-high gradient” particle accelerator technologies and development towards first applications. This goal is achieved primarily through the EuroNNAc workshops that provide a forum to form a community, to discuss results, to exchange ideas, to define common standards, to self-organize work in various experimental facilities, to explore common strategies and to bring together specialists from the accelerator, laser, plasma and application domains. The activities of the Network over the last four years resulted in a complete document on the present state of the European strategy for novel accelerators and on the roadmap to future pilot applications, published as a EuCARD-2 Deliverable (D7.2). A coordinated strategy for novel accelerators in Europe is very important given the distributed character of the research and the large variety of experimental facilities in Europe (see Figure 8). While the network is centred in Europe it is open to associated partners in Asia and the US.
A major outcome of the Network is the founding of the European Advanced Accelerator Concepts Workshop (EAAC) and its successful organization in 2013 and 2015. It is interleaved with the long-standing Advanced Accelerator Concepts Workshop (AAC) in the US that takes place in even years. The EAAC provides for the first time a European forum for advanced accelerators. The 2nd EAAC in 2015 attracted 258 registered participants, illustrating the interest and wide support for such a European event. About 16% of all participants were female scientists and about 20% were doctoral students. While there is still an imbalance in gender distribution, the innovative research on novel accelerators proves to attract more female scientists and more young researchers than usual in the accelerator field. The scientific outcome of the EAAC 2015 was impressive, with a total of 176 talks and 76 posters presented. From the first two EAAC workshops, 131 peer-reviewed papers were published, documenting the results and progress achieved. The EAAC2015 proceedings include 81 papers published in 2016. Within one year these papers were cited 83 times, illustrating the relevance and impact of this work.
The activity of the Network clearly underlined that plasma accelerators have reached the energy regime of ongoing construction projects and highly interesting applications have been identified. For example, laser-plasma based radiation sources or a plasma-based free-electron laser seem within reach for energy, while important design work on beam quality remains to be performed. There was a great interest to work together on these ideas that could have a huge impact on European science, but it clearly appeared that all resources of the participating laboratories are dedicated to achieving their internal goals, with no further resources for common work on a European facility available. This was the main motivation for a Design Study proposal that was submitted in 2014 in the Horizon 2020 Research Infrastructure programme: European Plasma Research Accelerator with eXcellence In Applications (EuPRAXIA).
This common strategic project includes 16 partners and 18 associated partners from the EuroNNAc environment was approved and funded with 3 M€ by the EU. It started in November 2015 and will provide a conceptual design report for a European plasma accelerator facility with applications by October 2019. While EuPRAXIA pursues and coordinates a common technical design, the EuroNNAc network is continuing to support the networking aspects and the strategic discussions. Common workshops ensure that the two efforts progress in full synergy and stay well aligned.
Following community demands and interests, the EuroNNAc network has expanded its scope to include all ultra-high gradient acceleration methods, not to be restricted to plasma acceleration.

WP8: ICTF@STFC
The Ion Cooling Test Facility Transnational Access at STFC provided access to 45 users from 5 institutes grouped in 5 projects, for a total of 1,186 user days and 4,957 access units, largely exceeding its initial requirement of 2,280 units.

The access opportunities to ICTF@STFC were advertised widely on websites, newsletters and specifically directed communications to laboratory directors eligible for support. All applications submitted for access were approved to receive funding under the EuCARD-2 TNA scheme. The applications came from 5 institutes, all members of the Muon Ionisation Cooling Experiment (MICE) collaboration, which is the main user of the ICTF facility. A summary of the TNA activity of the groups supported at ICTF is given below.
University of Geneva: contributed to the detector operation and support for the MICE experiment. Activities included: coordinating the work in the MICE online group; maintenance of the Data Acquisition (DAQ) system; development of a FPGA-based trigger system for MICE; tests and integration of the new trigger system into the MICE DAQ; development of a software framework for real-time data reconstruction during the data taking process (Online Reconstruction).
University of Sofia: participation in commissioning and data taking phase of the MICE experiment; maintenance of the KL detector; development, maintenance and improvement of the computer code for Monte-Carlo simulation and data reconstruction of the KL detector; data analysis.
INFN: the activity mainly concerns the PID detectors (TOF & KL systems), maintenance & running during STEP IV of the MICE project.
University of Belgrade: attendance during required shifts of data taking for the MICE experiment; training on data taking and visits to RAL on shifts trainings.
University of Radboud / NIKEF: participation in the data taking and particular focus on the analysis and characterising the effects of different absorbers in the multiple scattering distributions.
Access was provided to 45 users, for a total of 1,186 user days and 4,957 access units, largely exceeding its initial requirement of 2,280 units. With the input gained from the scientists and engineers from the supported institutes, the MICE collaboration has been able to gather valuable data to show the measurement of the multiple coulomb scattering through a LiH absorber placed in the beam line within the Focusing coil section of the cooling channel.


WP9:HIRADMAT@SPS AND MAGNET@CERN
The High Irradiation to Materials (HiRadMat) Transnational Access at CERN provided access to 32 users from 13 different institutes grouped in 7 projects, for a total of 2,940 access units, exceeding the initial requirement of 2,400 units.
The MagNet TNA at CERN provided access to 34 users from 15 different institutes, for a total of 2,660 access units, exceeding the initial requirement of 1,920 units.

HiRadMat (High Irradiation to Materials) is a facility designed to provide high-intensity pulsed beams to an irradiation area where material samples as well as accelerator component assemblies can be tested. The facility was initial contemplated as a test bed for collimator related issues. Within the years since commissioning, the research topics were gradually extended to other elements of accelerator technologies, supported by granting beam time to external users.
Within the EuCARD-2 framework, seven user teams using Transnational Access could take advantage of the facility, out of the 19 proposals that were submitted. Researchers primarily from all over Europe, but also from the US, gained access to the facility amounting to 2,940 Transnational Access units (Figure 9). The programme was dependent on the CERN accelerator programme, meaning operational conditions and experiments could not take place during the 2014 CERN accelerator shut-down. In addition a failure of the SPS beam dump in 2016 limited intensity and forced rescheduling some experiments to 2017.
One of the main aims of the facility was the validation test of collimator systems suitable for CERN accelerator operation within the High Luminosity LHC project. An important outcome of this international effort was that Molybdenum Carbide – Graphite (MoGr) and Copper-Diamond (CuCD) composites were validated as robust materials for the upgrade of the LHC accelerator.
In 2016, the HRMT34-ESScoat experiment performed an in-beam test successfully validating the proposed concept of an on-target coating allowing a screen-based beam monitoring system for the AWAKE experiment. One experiment in 2015 focused on the structural strength of vacuum windows for high power proton beams; in a wide international collaboration Beryllium was tested as window material. The primary purpose is the proton beam line for the neutrino production at FNAL, but test results will extend to other high-intensity applications. The experiment HRMT17-dBM with team leadership from the Czech Republic investigated the performance of beam monitoring based on diamond detectors. The aim of the HRMT38-FlexMat experiment was to test the dynamic response to intense proton beam induced shock for low density, high damping carbon materials and for composite carbon targets including high stiffness and high damping materials. This will include pre-irradiated materials such as flexible graphite and graphitic foams, in order to confirm that the properties’ degradation of these materials due to radiation damage proceeds slower than in isotropic graphite grades.
MagNet supported 9 projects, selected among 10 projects submitted, and provided access to interesting “high tech” projects mostly linked to superconducting and cryogenic technologies.
The very first project (FOSxCRYO), proposed by an international team with Italian leadership, is so far the most documented in international conferences, proceedings and reviews of all the projects supported by MagNet. This project is a bridge between optical fibre technologies and cryogenic applications for superconductors. The successful fibre technology is well known at room temperature, while due to material properties its use is very limited at low temperature. Developments are limited by the testing capacity in liquid Helium installation and for this reason the MagNet support was crucial for the team. A dedicated cryogen free cryostat and numerous real applications (magnets and superconducting link) were the test bed for this new technology with great success worldwide. Today, the results of this team are the references in Europe and in the US in the subject.
Another interesting test has been performed on a superconducting NbTi solenoid at low temperature (Figure 10, left). The project, from CIEMAT (Spain), was intended to “train” the superconducting magnet being the major component of a cyclotron for radioisotope production for medical diagnostics. Once the full system is finished (Figure 10, right), it will operate in a stand-alone mode in a closed cycle, but prior to this phase, the magnet must be checked to verify if it is working correctly, and as all superconducting magnets trained for the operational conditions. The goal of these measurements was to carry on the training test of the solenoids, recording as much information as possible to determine quench origins and overall performance.
In the last period of EuCARD-2, MagNet supported a team designing a Superconducting Shield septum. The project, proposed by the Wigner Research Centre for Physics (Budapest, Hungary), aimed to evaluate the feasibility of using a superconducting shield to create a high field extraction septum magnet for high-energy accelerators. This very exciting project had performed the first run of tests with not only the MagNet installation, but also using a LHC spare magnet as part of the service. After having the first excellent and promising results using MgB2, the team is planning a second run with different superconductors. This technology is very promising in other applications where high field has to be shielded as in medical installations or in space.
In addition to these projects a number of measurements have been performed on short model coils (SMC), a test bed developed at CERN for different studies and for different teams. Nb3Sn superconductors are planned to be used in the next decades for HL-LHC, ITER and FCC. It is therefore important to develop models that are correctly simulating the behavior of such conductors for the design of the future magnets. Measurements performed in the test facility contributed to the development of such tools by comparing measurements results with simulations.

WP10: FUTURE MAGNETS (MAG)
The Joint Research Activity on Future Magnets has:
1. Organised and coordinated a community, mainly European but open to contributions from other areas, determined to develop a new generation of high-gradient accelerator magnets based on High Temperature Superconductivity (HTS).
2. Compared different options and selected the most promising technologies in terms of superconductor (YBCO), tape structure, cable type (Roebel geometry) and magnet design (aligned block coil).
3. Developed and characterised the world record current density tape in YBCO.
4. Designed, constructed and tested a coil and a magnet to qualify the cable for accelerator magnets.
5. Positioned European industry at the forefront of HTS development and brought to Europe the leadership in HTS technology.

Today no single laboratory can provide significant results on HTS, given the complexity of a system that needs a multi-physics approach: from material science to thin film deposition in ultra-high vacuum, from metal shaping and delicate cabling process to cryogenics technology, and from magnetic and electrical characterization in high field-high current to sophisticated diagnostics for quench protection. To establish and consolidate a network in this field, a series of workshops on Accelerator Magnets in HTS were organised by the EuCARD-2 Consortium, to form a stable network, going beyond the institutes participating in EuCARD-2 WP10 (CERN, CEA, UniGE, UniTwente, KIT, SOTON, INFN-Milano, INP Grenoble, DTI, BHTS), to include laboratories and universities from European countries (EFL-CRRP in CH, LNCMI Grenoble and ENEA), Japan (University of Kyoto and KEK), USA (LBNL, BNL, NHMFL, University of North Carolina, University of Houston) and Russia (Bochvar Institute). About 10 companies working in the field also attended the workshops with various presentations.

The consortium has developed and characterized the world record current density YBCO tape. This has been the fruit of a specific optimization for high field-low temperature range. Before EuCARD-2, all optimization and comparison were carried out at 77 K self-field, because of the easiness of measurements and perspective use for energy application. However, the goals dictated by EuCARD-2 have now become a new standard. Figure 11 (a) shows the value of critical current density at 19T, 4.2 K vs. the value in self field, 77 K. The EuCARD-2 tapes made by Bruker, a partner in the project, despite their lower value at 77K self-field, are much better than any other tape at 19T, 4.2k (apart one single measurement on a US non-industrial tape). The success of the EuCARD-2 development has been possible thanks to the very advanced process of Bruker HTS: substrate in stainless steel, buffer layers deposited in alternate beam assisted deposition and YBCO layer deposited via plasma laser deposition and to a new dedicated line at Bruker, called PLD300. After various optimization steps, the results have been quite positive, even beyond the most optimistic target of EuCARD-2, see Figure 11 (b). In this figure, where the engineering current density Je is reported for various production run, the red line goal 1 is the initial goal of EuCARD-2, so the reference goal in terms of reaching the objectives of the program. The blue line goal 2 indicates the enhanced goal set after the first success, to push performance beyond initial targets. The values of Je obtained with the last production carried out with the line PLD300 are steadily above goal 2. Thanks to the developments in EuCARD-2 WP10, Europe has gained a prominent position in this technology.
The Roebel cable has been deeply investigated and characterized. Basic work on topology has allowed identifying the criteria to optimize the cable vs. the number of strands (tapes in this case). A noticeable difference between even and odd numbers of strands was observed and subtle optimization in terms of angle of punching and filling factor in various direction established. KIT, with the support of CERN has set up a better line for punching and cable formation, which has resulted in a faster and more uniform cabling. In Figure 12 the first Roebel cable produced for EuCARD2 is shown. This cable has been used for winding the magnets Feather_M0, the first HTS coil for accelerator and successfully tested until 12 kA. The cable has been extensively tested under pressure and found that, if impregnated, it does not degrade until a pressure of more 400 MPa. This value has to be compared with the 150 MPa normally considered the maximum pressure admissible for Nb3Sn conductor.
The three configurations of magnet, which have been studied, are described below.
1) The classical race-track, based on rectangular conductor blocks with flare ends that are bent in the non-easy direction. However, the race track was special in the sense that a new design aligning the cable along the magnetic field lines was developed. This has increased the usable critical density (YBCO is highly anisotropic, Jc being maximum when the wide face of the tape is parallel to field lines), making the best use of the material and minimizing the superconductor quantity, which is a great advantage given the prohibitively high cost. This layout is called Aligned Block Coil. The Magnet is called Feather_M2 and the first one is specifically the Feather_M2.1-2.2. Before this complete dipole, a shorted and smaller version with only one coil and few turn, called Feather_M0, was produced. The first with HTS, after a few with dummy cable, was Feather_M0.4. Both F-M0.4 and F-M2.1-2.2 were designed, manufactured and tested. The latter is the magnet of reference and the main deliverable of the program, together with the first piece length of Roebel cable.
2) The second type of magnet was a classical Cosϑ dipole layout but adapted to Roebel cable. Various studies demonstrated that the end needed to be optimized. Despite the fact that the field is intrinsically lower than in the Aligned Block Coil (because here the anisotropic behaviour plays against with field line perpendicular to the conductor wide face) the study is very interesting because cosϑ is a well- known technology and there is easy benchmark with Nb-Ti and Nb3Sn dipole. The cosϑ magnet designed within EuCARD-2 is now under construction with the direct support of the participating laboratories.
3) The third layout that has been studied is the stacked tape cable. It is based on smaller, 4 mm tapes that are simply stacked without transposition. The coil is basically a race track of rectangular block coil, with flare ends. To avoid huge unbalance due to lack of transposition, the cable is twisted once per turn, near the ends. The conceptual design has been carried out.
The results of the test of F-M0.4 and F_M2.2-2.2 the latter being the main deliverable of the whole program, and the test that validate the use of 5-10 kA Roebel cable in an accelerator magnet are shown in the figures below.

WP11: COLLIMATOR MATERIALS (COMA-HDED)
The Joint Research Activity on Collimator Materials has:
1. Selected two families of advanced materials as best candidates for the new generation of beam collimators at HL-LHC (CERN) and at the FAIR project (GSI, Germany): copper-diamond and molybdenum carbide-graphite composites.
2. For each family, analysed and tested different composition and grades narrowing the choice to few materials presenting the required characteristics.
3. Introduced in the landscape of new materials and thoroughly analysed, boosting their production capability in industry, two new families of materials with potential applications in industry, e.g. aerospace, thermal management and automotive.

Beam collimators are an essential component of modern high-energy, high-intensity accelerators, which have to absorb on small surfaces the large amounts of power carried by particles that are outside of the main beam volume. This JRA focused towards gaining a deeper understanding of collimators and of their materials under high-energy particle impact and irradiation. The composite materials studied within this project were designed and processed in collaboration with industrial partners exploring a broad set of sintering, heat treatment and machining processes. Their potentialities and the optimal parameters combinations were extensively studied. New collimation schemes relying on these materials were implemented and simulated with different tracking codes and in the different laboratories participating in the JRA.
WP11 selected two families of materials for the new generation of collimators, and for both it has furthered the analysis and selected specific grades. The first family is that of Copper – Diamond composites (CuCD). Maximization of properties such as thermal conductivity, mechanical resistance and stability after repeated thermal cycles was pursued, acting on the initial binder type and content, as well as on the heating ramps and dwell time at the sintering temperature. The second family is that of Molybdenum Carbide-Graphite composite (MoGr). Their electrical resistivity, thermal stability and radiation hardness were optimized working on the processing temperatures and composition, with the addition of other carbide formers such as Titanium, leading to additional improvements of the mechanical strength. Five different generations of MoGr, each one including several material grades, were conceived and produced in the course of the project, varying their composition (molybdenum, graphite, carbon fibres and dopants) and several processing parameters, such as temperature, pressure, time and post-sintering heat treatments.
The experimental work included extensive thermo-physical and mechanical characterizations of the novel materials, including a large number of tests under beam or under irradiation, at CERN, GSI, Kurchatov Institute, BNL and POLITO. Results were used to upgrade composition and production parameters for further grades and, in parallel, to update constitutive models implemented in advanced simulations to predict the response of the materials in nominal and accidental operating conditions. Measured data were also exploited to redefine a set of figures of merit to rank relevant materials in the preliminary design phase of collimators and other beam intercepting devices.
Two components (jaws) of the new collimator design, embarking respectively CuCD and MoGr from last generations, were tested at CERN for qualifying the new collimator design and materials against the nominal and accidental scenarios defined for HL-LHC and for benchmarking the numerical models against experimental measurements for beam impact. A good response of both materials to beam impacts was ascertained. Several complex finite elements models simulations were run to mimic the behaviour of the jaws: a particularly interesting behaviour was observed with CuCD, which exhibited a higher than expected damping ratio against beam-induced pressure waves, possibly because of the strongly non-linear constitutive model.
Radiation resistance of different grades of MoGr was tested using swift ions at GSI and high-energy protons and fast neutrons at BNL. GSI irradiations were used for optimization of the MoGr processing and composition, to improve radiation stability (Figure 15, left). High temperature sintering, annealing and Ti addition are shown to reduce the deformation of the material at high doses. To reduce the radiation-induced hardening and the degradation of electrical and thermal conductivity, addition of short pitch-derived carbon fibres seems to be a good compromise solution (Figure 15, right).
The grade MG6451 from the 7th (latest) generation of optimized MoGr batches is one of the favourites; irradiation experiments confirmed the improved radiation resistance of these composites.
CuCD composites were exposed to 30 MeV protons at Kurchatov Institute. A good stability of material density, 10% increase of electrical resistivity, 30 – 40% increase of the coefficient of thermal expansion and a 20-30% reduction of thermal conductivity for doses up to 1018 p/cm2 indicate that the composite has a good stability in radiation fields.

WP12: INNOVATIVE RADIO FREQUENCY (RF) TECHNOLOGIES
The Joint Research Activity on Innovative Radio Frequency Technologies has:
1. Developed a novel deposition scheme for Niobium on Copper with performance similar to Niobium at lower cost, and has advanced the studies on other types of coating techniques and high temperature materials.
2. Developed the principle of a new type of high-efficiency klystron and attracted industrial interest in furthering the development.
3. Advanced knowledge on High Order Modes, for their suppression and their use for diagnostics, on wakefield monitors, on crab cavities, and on RF photocathodes.
4. Established a platform for exchange of information and identification of synergies between the superconducting and normal conducting RF communities.

Radio Frequency accelerating technology is at the core of accelerators. Dimensions, power efficiency and performance critically depend on the accelerating gradient, on the energy transformation efficiency and on the field quality of their RF accelerating system. EuCARD-2 has addressed a number of advanced RF technologies meant to improve performance of a large variety of accelerators.
Superconducting coatings (SRF thin films) on copper could dramatically reduce the cost of superconducting RF systems possibly achieving higher gradients or increasing power efficiency. Deposition conditions for Niobium films on copper have been explored, and favourable parameters identified. Twelve prototype cavities have been tested at CERN. The best cavities exhibit a behaviour close to bulk niobium, with much better performance than what can be obtained with the classical DC magnetron sputtering. For higher Tc materials, two processes which are able to produce crack-free dense grainy Nb3Sn layers have been developed also at CERN. Atomic Layer Deposition (ALD) has been used to study three different organometallic precursors on NbN at INP Grenoble. Thin layers with the correct crystalline structure have been produced and Chemical Vapor Deposition has also been used to produce very high Tc NbN layers (see Figure 16). Characterization tools, such as a Quadrupole Resonator with removable samples has been successfully commissioned at HZB, and systematically used to characterize superconducting properties of newly developed materials or processes. A local magnetometer has also been developed at CEA Saclay, allowing measurement of a series of Nb/MgO/NbN with different thicknesses of NbN in order to determine if there was an optimum thickness as determined by recent theoretical optimization calculations.
High-gradient normal conducting accelerating structures at high frequency are often plagued by unwanted higher-order modes that spoil beam quality. An RF design, based on long-range wakefield suppression using the Damped Detuned Structure (DDS) has been developed at Manchester University, as an alternative for the CLIC linear collider under study at CERN. The structure design and optimization process take into account the fundamental mode performance and high gradient limits along with transverse wakefields.
A new high efficiency klystron principle has been developed at CEA Saclay, the ‘kladistron’ and a collaboration formed with Thales (France) as an industrial partner. A prototype has been designed and first proof-of-concept RF cavities have been fabricated and successfully tested. These tests include a check of the tuning mechanism and a titanium coating for multi-pactor suppression. The fabrication of the full prototype is nearing completion. Modification to existing commercial solid-state modulators have also been studied at Uppsala University with Scandinova (Sweden) as an industrial partner, in order to adapt them to high-efficiency klystrons and critical issues were identified and preliminary solutions proposed.
Wake field monitors have been developed at PSI to directly measure the alignment between the beam and RF accelerating structure via the transverse higher order mode spectrum. A front end electronic system for the monitors of the multipurpose X-band structure installed at the SwissFEL at PSI has been developed. A final prototype has been fabricated and beam test evaluations completed with the PSI test linac. The first-generation prototype has been upgraded and significant improvements in sensitivity, insertion loss and noise has been verified in laboratory tests and upgraded systems now installed and awaiting tests on the SwissFEL accelerator.
A new optimised CLIC crab cavity structure has been designed at Lancaster University and STFC, fabricated and high power tested, with operating performance exceeding considerably the required deflecting gradient. The feasibility of a new CLIC crab cavity stabilization has been demonstrated by Lancaster University with an active waveguide phase stabilization system. Operation of the system showed that phase could be stabilized to the 20 milli-degree level with the feedback engaged, compensating for the phase shift induced by a heat source, thereby validating the concept.
Higher Order Modes (HOM) could be used for HOM-based beam diagnostics of SRF cavities. A procedure has been developed to use HOM signals from 1.3 GHz superconducting accelerating cavities for beam position monitoring stably over several months at the European XFEL (DESY). A setup for beam phase measurement with respect to accelerating RF field has been built and tested on the FLASH facility: a resolution below 0.12 deg rms at a charge of 0.4 nC was demonstrated, and the expected performance of the specially designed electronics defined.
For the 3.9 GHz cavities, simulations of the chain of 8 coupled cavities installed at the Eu-XFEL has been conducted. The feasibility of concatenation techniques, State-Space Concatenation (SSC) and Generalised Scattering Matrix (GSM) has been studied for such large linac structures and which have now been validated by Rostock and Manchester Universities respectively. A compendium of modes has been generated, which serves as a basis for the ongoing monitor developments. Electronics has been designed for both 1.3 and 3.9 GHz cavities. The results are of great interest to other facilities worldwide based on SC RF technologies.
Investigations for superconducting and normal conducting RF photocathodes have been undertaken, with 63.5 MV/m cathode field being reached during tests of a 1.5 cell superconducting gun at DESY with an un-coated Nb Photocathode (PC) plug, the highest ever demonstrated for a superconducting injector cavity. Various techniques have been developed at NCBJ for Pb cathodes to obtain smooth, droplet-free Pb surfaces: surface flattening with plasma pulses, post-deposition surface treatment. The influence of the roughness on electron emission has also been investigated, resulting in a stable photocurrent of ~1 µA at 100 kHz being obtained over several hours of operation at the HZDR gun.
A Diamond Amplifier Cathode (DAC) with back illuminated primary photocathodes has been developed by HZB for the TESLA-like electron gun capable of providing high peak and high average current beams (see Figure 17). A new Field Emission facility has been also commissioned at HZB. In addition, at HZDR the SRF Electron Gun II has been run in CW with a Mg photocathode on the ELBE facility without QE decrease over an extended period of time. The obtained results fundamentally demonstrate the viability of normal-conducting PC operating in SRF E-guns.
A Multiprobe System for Metal Photocathode Research has been developed and commissioned at STFC for research into metal photocathodes for NC RF photoinjectors. It uses various analytical techniques, such as X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy (AFM), Kelvin probe and Quantum Efficiency (QE) measurements. The system was used for investigation of cleaning procedures for bulk PC samples of various materials. The highest QE equal to 1 x 10 -3 has been measured for the ion sputtered Mg photocathode. A new metal Photocathode Preparation Facility and a load lock system and transport vessel for dedicated PC plug transfer has also been commissioned and implemented at the VELA accelerator at STFC Daresbury laboratory.

WP13: NOVEL ACCELERATION TECHNIQUES (ANAC2)
The Joint Research Activity on Novel Acceleration Techniques has:
1. Fostered collaboration within the wide community performing experimental activities on plasma wakefield acceleration.
2. Supported experimental work that has produced high-brightness electron beams from laser plasma accelerators.
3. Developed the beam instrumentation for the successful 1st phase of the AWAKE experiment.
4. Demonstrated femtosecond level synchronization between electron beams and lasers.

The first challenge of this WP was the achievements of high brightness electron beams with laser plasma accelerators. High quality and stable beams have been successfully produced at LOA resulting from the interaction of a single laser pulse with a sharp density gradient produced by placing a solid obstacle, a blade, in the path of a supersonic gas jet. Another approach performed at Lund Laser Centre was to inject a small jet at 90 degrees of a longer gas jet. Since the position of the first gas jet, the gas density and/or gas composition of each gas jet can be changed independently, this approach offered more flexibility. Electrons were first injected and accelerated in a target where gas was supplied only from a 2 mm gas nozzle. The observed beams of electrons had the typical characteristics of self-injection in gas jets, with limited reproducibility and a bunch charge of the order of 30 pC with a standard deviation higher than 50%. When adding gas also from the narrow tube, beams of accelerated electrons were observed for 100% of the laser pulses sent onto the target. In addition to improving the stability, this scheme also allows precise control of the electron beam charge and peak energy. At STRATH, experimental and theoretical investigations into the properties of wide-angle electron beams, in the forward and backward directions, were performed. Beams with 1–2 MeV energy and nC level charge are emitted in a forward cone with aperture angle of about 30º–50º from the laser propagation axis. This cone is hollow when plasma electrons are not injected into the bubble and fills in with more energetic electrons when injection occurs and high-energy forward beams are produced. Oblique electrons therefore appear as a high-charge background halo around the high-energy short bunches accelerated inside the bubble. Because of the high charge, wide-angle beams can generate a significant amount of bremsstrahlung radiation and cause damage to equipment, which is a particular concern for laser-plasma accelerators based on capillaries. Wide-angle electron beams can also carry a significant fraction of laser energy out of the plasma, limiting the efficiency of the accelerator, which could have an impact on the use of the LWFA as stages for a linear collider.
As a first achievement of the LWFA with external injection, at INFN electron beams of charge as low as 20 pC and rms lengths down to 20 fs have been produced and measured. The procedure started with the photo-generation of a sub-ps electron beam, obtained by illuminating the cathode with a 200 fs laser pulse at 266 nm. A value of 20 pC of charge was measured with a beam current monitor. The extracted electrons were then propagated along a linac and compressed by velocity bunching, injecting the electrons into the first accelerating structure close to the zero crossing phase. At maximum compression, corresponding to about 20 fs, the electron bunch mean energy was 114 MeV and the projected energy spread was evaluated at less than 0.36 MeV. At HZDR, in order to control the timing of injection, the ELBE accelerator and the DRACO laser system were synchronized by phase locking the laser oscillator repetition rate to the 6th harmonic of the ELBE RF master oscillator. A time jitter of better than 100 fs was electronically realized. However, shot-to-shot variations of the electron beam energy as well as pointing jitter of laser beams can lead to variations of the bunch arrival time, which limits the absolute time resolution. A single-shot beam arrival time monitor has been successfully installed and a balanced detection scheme was implemented. The time resolution of better than 200 fs was successfully demonstrated.
The second wakefield accelerator explored by the WP was proton beam driven, in the context of the AWAKE project at CERN. This is a proof-of-principle experiment to demonstrate proton-driven plasma wakefield acceleration, which relies on the use of protons of energy 400 GeV and high charge, about 3 × 1011 protons. As the proton bunches are long, in order to attain high electric fields, the experiment relies on an effect known as the self-modulation instability (SMI), leading to the microbunching of the long proton bunch in the plasma that is seeded by a high-power laser. The much shorter and denser microbunches are then expected to constructively interfere and so produce fields of the order of 1 GeV/m. Theoretical works have been performed to study the transverse stability of a pre-modulated bunch train in the plasma. The result shows that to excite focusing fields of the same intensity for increasing propagation distances, it is required a longer section of the bunch, due to the decreasing density of the front. On the experimental side, a plasma with challenging requirements (length ~10 m, plasma electron density ne = 1-10 ×1014 cm−3, radius r ≥ 1 mm and with a density uniformity δne/ne ~ 0.2%) has been developed in a plasma cell of Rubidium (Rb) vapour ionised by a laser pulse. During the EuCARD-2 project, the AWAKE experiment has gone through development, preparation, installation and commissioning phases. A suite of diagnostics to measure the modulation of the proton beam was installed and commissioned. An indirect measurement of the SMI relies on observing the transverse blow-up of the proton beam by using two screens downstream of the proton beam and comparing the distributions when there is no plasma and when there is a plasma. The measurement results are shown in Figure 19. Where there is no plasma (left), the proton beam has a faint halo, whereas where the plasma is on (right) the proton beam has a distinct halo and demonstrates that there is transverse blow-up of the proton beam. This result indicates a strong transverse electric fields, as would be expected if the proton beam has undergone SMI.
A direct method to measure modulation of the proton bunch relies on optical and coherent transition radiation. Figure 20 shows images of the proton beam measured with a streak camera for where there is no plasma (left) and when there is plasma (right). When there is plasma, the image shows a clear modulation of the proton beam, with microbunching on the scales expected.
Present-day and future accelerator facilities require femtosecond precision synchronization between the electron beam and external laser systems. This challenging task is crucial for the studies of ultra-fast phenomena in domains such as chemistry, biology or physics. A fast beam-based feedback was planned at FLASH, the Free Electron Laser (FEL) in Hamburg. Arrival time fluctuations of the electron beam were correctable by introducing small energy modulations prior to the magnetic bunch compressor. Design, characterization and the later tunnel integration of an ultra-fast actuator (NRF cavity) with large bandwidth, mandatory to correct fast arrival time fluctuations were achieved. The design and measurements on the ultra-fast normal conducting corrector cavity were achieved. Additional high frequency components needed for cavity operation and its digital low-level radio frequency regulation system were successfully characterized to reach arrival time stabilization towards one femtosecond range.

Potential Impact:
IMPACT

Improving performance of existing and future accelerators

EuCARD-2 primarily focused on improving the present and future European accelerator-based Research Infrastructures. This has been achieved by acting at three levels. The first level consisted in improvements applicable at short-term and consisting in the development of specific technologies or instrumentations for accelerator infrastructures currently in operation or in construction, which present an added value from cooperative multi-laboratory developments. The second level was focused on the medium-term and consisted in the definition of new designs and in the contribution to existing design studies aimed at future accelerator infrastructures. The third level is long-term, where collaborative generic R&D that cannot be carried out by individual institutions may have the potential to open new horizons for the accelerator field.

Short term

The EuCARD-2 activities have contributed to almost all ongoing particle accelerator projects in the ESFRI roadmap and beyond.
The HL-LHC (High-Luminosity upgrade of the LHC) at CERN is the largest ongoing particle physics project in Europe. EuCARD-2 has contributed through WP11 to the development of new material composites based on copper-diamond and on molybdenum carbide-graphite that will equip the HL-LHC collimation system, a critical item to cope with the huge beam densities that will be achieved in this high-luminosity collider. These new materials were tested at the HiRadMat TNA facility (WP9).
The same materials are being considered for the different collimation systems of the FAIR project at GSI (Germany), which will accelerate unprecedented ion intensities.
In Europe, there are currently 12 synchrotron radiation facilities in operation, generating an enormous and growing research output across different scientific disciplines; many more are now under study. The EuCARD-2 low emittance ring network (WP6) has addressed one the most important challenges in the upgrade of the existing and in the design of the next generation light sources, the generation and control of extremely bright and small particle beams, with emittances down a factor 100 compared to the accelerators currently in operation. This reduction will drastically increase the brilliance of the beam available to users. The exchange of information between accelerators for fundamental research and synchrotron light facilities has paved the way for the ongoing transition from the 3rd generation to a new 4th generation of light sources.
In recent decades, there have been major advances in the development and construction of light sources based on electrons accelerated in linacs. Free-Electron Laser (FEL) light sources can provide a highly coherent X-ray beam with considerably increased scientific range. EuCARD-2 has contributed to two FEL projects commissioned during its lifetime, the European XFEL at DESY (Hamburg) and the SwissFEL project at PSI (Switzerland), via its innovative Radio-Frequency WP12. Higher-Order-Mode and wakefield monitor diagnostics systems were established and tested with beam and they will provide a new cost-effective and high-performance diagnostic capability for advanced FEL accelerators.
The design of the European Spallation Source (ESS) at Lund (Sweden) has profited from the interaction with the Accelerator Driven Systems community via workshops organised by WP5. Smaller linac-based facilities like CLARA and VELA (STFC, UK) and ELBE (HZDR, Germany) have profited from the developments of cathode materials and deposition processes for RF photocathodes carried out in WP12.

Medium term

The concept of the Future Circular Collider (FCC) study at CERN for a 100 TeV circular collider in the Geneva area, is the result of a series of workshops and discussions that took place in EuCARD, the project which preceded EuCARD-2. In EuCARD-2 WP5, the FCC basic parameters were discussed and compared to other ongoing studies.
The design of the Compact Linear Collider (CLIC) at CERN aiming at a 3 TeV electron linear collider is at an advanced stage of maturity. WP12 contributed to the design and optimization of key CLIC RF components as the high field accelerating and deflecting RF structures, including significant suppression of higher-order modes and wakefields. One of the main challenges for CLIC consists in reducing its power consumption; EuCARD-2 has contributed with ideas and technologies originating from WP3 Energy Efficiency. In particular, WP3 and WP12 have participated in the development of new high-efficiency klystrons that are crucial in reducing the power consumption of a normal-conducting collider.
A promising option to extend the energy reach of present accelerators without large investments in tunnels or infrastructure is the upgrade in energy of the Large Hadron Collider, consisting in the replacement of all its magnets with higher magnetic field units. A very promising long-term alternative for this High-Energy LHC (HE-LHC) relies on the development of a third generation of superconducting accelerator magnets based on High-Temperature Superconductors (HTS) reaching a magnetic field of 20 T, 2.5 times the limit of the present LHC magnets. The HTS development was the subject of EuCARD-2 WP10. Thanks to this WP, a new cable in HTS respecting the requirements for HE-LHC together with a compatible magnet design, were developed. Only this technology can today allow a goal of >30 TeV in the HE-LHC (20 T dipole with 33 TeV in the centre of mass).
EuCARD-2 WP7 has been at the origin of EuPRAXIA, a seminal Design Study recently approved under the Horizon 2020 program. This concerns an ultra-compact, multi-GeV accelerator and photon source as a user facility based on plasma wakefield acceleration.
Muon colliders represent another alternative to, or possible future extension of, high-energy proton and electron colliders. EuCARD-2 contributed in two directions to improving their design. The Transnational Access to ICTF (WP8) supported several experiments related to the Muon Ion Cooling Experiment (MICE) in the UK, contributing to its recent success in demonstrating ion cooling. Two WP5 workshops revealed the possibility of new, more compact muon-collider designs relying on novel sources of cold muons, either based on the annihilation of positrons from a storage ring with internal target, or through the production of pions in collisions of a high-energy proton beam with repetitive laser pulses.
Reaching higher beam power from the ESS linac was the subject of a WP5 workshop that contributed to the design of a neutrino production facility using the ESS linac. This activity supported the ESS-nu-SB Design Study proposal submitted to the Horizon 2020 programme in 2017.

Long term

EuCARD-2 WP5 helped shaping the future generation of accelerator facilities, by defining a global accelerator roadmap for colliders, hadron storage rings, hadron linacs and beam polarization, and by guiding pertinent R&D efforts. More specifically, WP5 developed several attractive roadmaps for the medium and long-term future, identified promising novel approaches, and singled out specific key areas requiring further effort to optimize the performance of accelerator facilities presently under construction or to improve the design of proposed future machines.
In an effort to determine how to make a 100 TeV hadron collider more affordable, WP5 identified three key factors for consideration: site selection, staging possibilities, and targeted superconductor/magnet development. For the long-term future, WP5 supported studies on novel production concepts for low-emittance muon beams, the exploration of advanced acceleration schemes based on crystals or nanotubes, and the use of large hadron storage rings for new types of physics, e.g. the generation of X-ray bursts and the excitation or detection of gravitational waves.
Other results from WP5 include the validation of the ILC positron target with a beam test and the demonstration that polarized hadron beams at energies of tens of TeV may be more possible than previously thought. A commissioning strategy for ESS was also worked out, as were polarization requirements needs for the MESA facility at Mainz.
Reducing the size and cost of particle accelerators is one of the main drivers of present day particle accelerator research. One road to be followed consists in improving the present accelerator schemes, whilst another important approach consists of finding disruptive technologies that require R&D investment but have a strong potential for the long-term future. In EuCARD-2, WP7 has promoted novel acceleration methods that have the potential to overcome many practical limitations. Novel accelerators may provide accelerating fields of several orders of magnitudes higher than is currently possible. Once the required beam quality can be guaranteed, a new and revolutionary generation of particle accelerators will provide unique beam parameters (ultra-short pulses) with significantly reduced cost and size. WP7 contributed with the development of new concepts for a plasma-based high energy physics collider that will be presented at the European Strategy on Particle Physics that will take place in 2019-2020.
On the experimental side, WP13 contributed to overcoming the technical challenges of novel laser plasma accelerators, demonstrating that they can now deliver high quality electron beam in the 100 MeV to a few GeV energy range in a compact distance. The advances in two-stage plasma accelerators are very promising and they will pave the way for multi-stage plasma accelerators based on external injection and/or on all optical injection for delivering higher energy electron beams. Thanks to the progress in reducing the jitter between the laser and the electron beams, the multi-stage approach made significant progress. The plasma wakefield driven by a proton beam, with the results obtained during the course of the EuCARD-2 project, open new horizons for high energy physics.
The impact of the WP3 Network on Energy Efficiency, ranges across short, medium and long terms. New potential facilities will be more powerful, yet this often comes hand in hand with higher energy consumption. The efforts of this Network were aimed at improving sustainability and the energy efficiency of concepts and subsystems for particle accelerators. This is an important and necessary activity for the development of future research infrastructures.

Innovation potential of accelerators and accelerator technologies

Potential for accelerator applications

More than 30,000 particle accelerators are nowadays in operation worldwide, the large majority being used in industry or medicine. The EuCARD-2 ambition was to have an impact on this large inventory of accelerators responding to societal needs, by transferring the competences and experience from research accelerators to this field.
In this respect, a fundamental step was the publication of the Applications of Particle Accelerators in Europe (APAE) document, prepared by WP4. This 113-page reference document includes the direct contributions of 20 experts in the field, with many more contributing to the preparatory meetings. The report describes the current applications of accelerators, achievable improvements in cost and performance via the exploitation of technology from RIs, possible new applications and actions necessary to achieve these applications. It is expected that this document will break the ground towards many further developments in accelerator applications. To complement the extended version, a 6-page summary brochure for the general public and policy-makers has been produced and will be circulated and translated into multiple European languages.
More in detail, WP4 identified many existing and new accelerator applications which could benefit from technology developed for RIs. Examples include:
• New environmental applications of low energy electron beams.
• Industrial applications of low energy electron beams.
• Implantation of ions with a range of energies (1 keV to 10 MeV) at different depths (detailed circuit printing or etching, or gross material modifications, curing, hardening).
• Low energy neutron production (for BNCT, material inspection, material tests).
• Use of ion beams for fusion and for satellite propulsion.
• Radioisotope production.
• New accelerator technologies for cancer therapy with ion beams.
• Cancer therapy with high electron beams.
• New accelerator technologies for ADS.
In the medical field, EuCARD-2 has contributed to a coordinated effort to develop accelerators for medical isotope production, based on linacs or on compact cyclotrons. The AMIT superconducting cyclotron of CIEMAT (Spain) has been presented within WP4, selected for further support under ARIES, and supported by an experiment in the WP9 Transnational Access. Further progress could be brought into the field of compact medical cyclotrons by the use of high-temperature superconductivity technology developed in WP10. With HTS, the magnet can be more compact and /or work comfortably at 30 K, which makes cryogenics much easier, by using a simple cryo-cooler. The HTS could also be applied to high field magnets for NMR. HTS using YBCO superconductor is the only way to go beyond the 23 T at 1.9 K given by Nb3Sn technology. The developments of high current density coils for high field in WP10 has a big impact in this area.
The studies of applications for low-energy electron accelerators have indicated that these accelerators have large potential in the treatment of wastewater, sludge, and flue gases. Here accelerators would not only have a major economic impact, but would also carry extensive environmental and health-related socio-economic impact. A prospective collaboration was formed, which will continue this activity as part of the new ARIES project.
Finally, the longer-term development of plasma-based acceleration techniques (WP7 and 13) could potentially lead to table-top accelerators capable of moving accelerator technologies into unexplored territories.

Potential for other technologies

The material studies on Molybdenum carbide– Graphite composites and other thermal-management materials in WP11 is of strong relevance to high-performance industries. This type of novel material with low density and high thermal conductivity may potentially be appealing to a range of domains, as high-end thermal management applications in power electronics, avionics and aerospace, advanced braking systems for automotive and aerospace and hot components in gas turbines.
The development of laser-based plasma wakefield acceleration (via WP7 Network and WP13 Joint Research Activity) has a strong impact on the European laser industry. High power lasers are the drivers for one of the most promising classes of novel accelerators, which requires high performance and is already a new test bench for future laser developments. EuCARD-2 WP7 has worked in close connection with the European laser industry, the leading global manufacturer for lasers with high peak power.
As large energy consumers, accelerators actively participate in the global effort to optimise electric power generation, distribution and consumption. The dynamic regulation strategies including virtual power plant technologies and the large energy storage system analysed in WP3 are meant at managing the fluctuations of power generation on the grid coming from a larger contribution of sustainable energy sources as wind and solar power. In the energy production field, there may be a significant impact of the WP10 HTS technology for eolic systems for renewable energy production. Windmills of large power (>10 MW) require a superconducting generator, to avoid excessive size and weight; here the possibilities opened by the HTS conductor are certainly significant.

Structuring the European Research Area

Structuring and integrating the European accelerator community

The EuCARD-2 consortium has mobilised more than 350 participants, representing major European laboratories, research institutes, universities and industries. The members operate very large or large-scale world renowned accelerator infrastructures or contribute to their construction and upgrades or to the R&D for future infrastructures.
With its four Annual Meetings, its 54 thematic Workshops, its more than 40 other events, and the common daily effort on R&D activities that took place in Networks, Transnational Access and Joint Research Activities, EuCARD-2 has created a culture of open collaboration and exchange of ideas and information, across borders and technical cultures, and between academia and industry.
While in the past, accelerator R&D and project design were predominantly carried out in individual laboratories, the partnerships at the European level created by FP6 CARE, FP7 EuCARD and now EuCARD-2, continue to enhance a culture of collaboration that is recognized at world level. This includes scientific communities outside of Europe, as testified by the appreciating remarks expressed in the reports of the EuCARD-2 Scientific Advisory Committee, where two out of the three members come from outside of Europe. The deliberate choice to favour a large number of partners, in spite of the limited budget, has been instrumental in enhancing cross-fertilization between European accelerator laboratories, including CERN, Universities, Technology Institutes and SMEs.
The impact of the EuCARD-2 strategy can be measured by the number of new collaborations formed within EuCARD-2 that will now continue inside the next project ARIES or independently.
WP4 on accelerator applications has been particularly active in creating new collaborations and supporting existing collaborations, in initiating new studies, and promoting the exchange of ideas on common specific subjects and fostering dialogue between political/official representatives from EC institutions, scientific experts and industry. Examples include collaborations to study water and biological sludge treatment, including institutes from Ghana and Uganda, and European water companies; a collaboration to study aspects of accelerator-driven BNCT; a collaboration between the scientific institutes PSI, LBNL (USA) and the company Varian to build a prototype of a SC magnet based on a canted-cosine-theta design.
WP5 greatly contributed to strengthening the synergies between previously separated communities, such as magnet developers, diagnostics experts, vacuum and surface physicists, etc. The WP5 networking effort established new discussion fora, which are enthusiastically maintained by the communities concerned.
WP6 has federated for the first time three accelerator communities sharing common problems and technologies: damping rings for electron colliders, synchrotron light sources, and advanced factories. For the developers and operators of synchrotron light facilities, a strategic setup of European Research Infrastructures, this was a unique occasion of sharing a forum for open discussion and exchange and for identifying synergies and common strategies. The emergence of this new community has already contributed to improving the performance of high-ranking synchrotron light facilities.
WP7 had a crucial role in federating all European efforts in the study of novel accelerators based on lasers and plasmas. This rather dispersed community, characterised by a large share of small universities and only few large laboratories has been boosted by the appearance of the EuroNNAc Network, first in EuCARD and then in EuCARD-2. WP7 has directed the effort towards common goals and has created a permanent coordination structure at the European level that is already moving to Europe the focus of a new technology that was basically started in the US.
The EuCARD-2 WP9 Transnational Access has operated towards not only providing service to users, but also towards creating a user community that could share ideas and resources, with the organization of dedicated user workshops as the HiRadMat Users’ day (>50 participants) and the MagNet International Workshop of the Superconducting Magnets Test Stands (>60 participants).
Particular effort within the project went into providing opportunities for employment, education and career advancement for young people, by opening positions and offering supervision of bachelor, master and PhD students. Training of the new generation of scientists was one of the project priorities, via a large number of PhD theses (18), and via special prizes and focus groups for students that were organised by the Networks WP5, 6 and 7.
Gender balance was another project priority. A large number of the students supported by the project were young women, which were constantly encouraged to pursue an education and career path related to innovative technologies. The presence in the EuCARD-2 management of a number of female colleagues as well as of a female member in the Scientific Advisory Committee has provided adequate role models of females with a successful career in science.

Development of world-class infrastructures

The activity of EuCARD-2 has contributed to keeping the European particle accelerator infrastructure at world-class level. This concerns the High-Luminosity upgrade of the LHC, the recently commissioned European XFEL and SwissFEL, the ongoing FAIR and ESS projects, and the upgrades of the many European synchrotron light facilities including the ESRF upgrade.
For the design of future infrastructure, EuCARD-2 has contributed to FCC and CLIC at CERN, to the ESS-nu-SB and EuPRAXIA Design Studies, to the high-energy upgrade of the LHC and to the design of a future muon collider.

Synergies with other European and International projects and programmes

The activities of EuCARD-2 took place in close coordination with ongoing programmes in Europe and outside. Participation to the TIARA Committee ensured the coordination with EC supported projects, as the Design Study EuPRAXIA that was structured to be complementary with WP7 and 13, and a coordination of initiatives in the field of communication, education and technology transfer. EuCARD-2 is also complementary with the EuroCirCol Design Study; the HTS magnet technology developed in WP10 is intended to constitute a valid alternative to the Nb3Sn technology adopted for FCC and EuroCirCol.
The presence in the EuCARD-2 Scientific Advisory Committee of members from Japan and from the US provided a welcome connection with similar initiatives in Japan and US.

Impact on European science and society

The exciting developments in particle physics and in fundamental science have been driving the remarkable progress of modern particle accelerators since their invention 90 years ago. While scientific discoveries related to particle accelerators, as the acclaimed Higgs boson, with their wide media coverage convey to the public opinion a positive and progressive image of European scientific research, the impact of particle accelerator technology on European science and society goes much beyond fundamental science. Accelerator technology is now rapidly moving from basic science towards applied science, represented by the multitude of accelerator-based X-ray and neutron sources, and finally to medicine and industry where accelerators have a huge and only partially exploited potential.
The priority of the EuCARD-2 project has been to accompany and favour this transition of accelerator technology, creating bridges and connexions between different accelerator communities and between academia and industry. The project has supported with similar vigour both large projects for fundamental science and smaller initiatives for applied science. At the same time, it has identified promising avenues to exploit the potential of particle accelerators to address European societal challenges, such as providing better medicine for an aging population, reducing the environmental impact related to high living standards, and increasing technological content and competitiveness of industry.
By attracting a large number of students to enter the field of accelerator research and development under the Ph.D. programmes of the participating universities and research centres, EuCARD-2 has contributed to the development of the human resource potential in accelerator science and technology in Europe. Accelerator research is largely multidisciplinary and requires, at the same time, theoretical and technical skills. Training in accelerators in a collaborative environment, has provided students with competences that will be extremely valuable in their future careers, both in science or in industry. By giving relevance to successful cases of young female researchers as role models, EuCARD-2 has contributed to the promotion of women in science and of gender diversity in working environments.
Promotion of accelerator science and outreach were other EuCARD-2 priorities. Particle accelerators represent a success story for European science, and the resonance of the project outreach events was an indication of the impact on the people of the challenges and fascination of research with and on particle accelerators. Presenting accelerator science as a way to find answers not only to fundamental scientific questions, but as well to societal challenges, addressing in particular the young public, was a way to underline the positive role of science in society.
Although the impact of the project is largely demonstrated by its scientific results including 282 publications, its four applications for patents, the support to 64 students, the more than 100 workshops and events organised, and by the large involvement of European industry, it also goes beyond these result and will be in the medium and longer terms, through its contribution to the advancement of a knowledge-based, science and technology driven European society.

DISSEMINATION ACTIVITIES AND EXPLOITATION OF RESULTS

The communication and dissemination activities of EuCARD-2, under WP1, Task 1.2 included both internal and external communication, ensuring information about the project reached a range of audiences: project members, the wider scientific community, members of industry and the public.

Communication inside the project

The main communication tools and activities for the project members were the internal collaborative workspace (Intranet), where the project documentation was stored and shared, the Steering Committee meetings, where the WP Coordinators provided activity reports, and the Annual Meetings, where EuCARD-2 partners met to discuss the project scientific and technical achievements (Figure 22).

Publications
EuCARD-2 publications are stored in an open access database and amount to a total of 282.
Scientific and technical results were published in peer-reviewed journals such as: IEEE Transactions on Applied Superconductivity, Physical Review Accelerators and Beams, Applied Physics Letters, Superconductor Science and Technology to name a few.
In addition, results were also presented at major international conferences including: International Particle Accelerator Conference (IPAC) or International Beam Instrumentation Conference (IBIC).

Dissemination to the scientific accelerator community

Website
The EuCARD-2 project website (http://cern.ch/eucard2) was the primary tool for communication to project members and stakeholders. The site hosted information about the EuCARD-2 work programme, participants, goals, schedule and results. Events, vacancies, outreach, and Transnational Access information were also provided. The site served as a point of access for the publication database, intranet, and project meetings.

Newsletter
The “Accelerating News” (http://acceleratingnews.eu) newsletter grew from the EuCARD quarterly newsletter to include additional accelerator projects and EuCARD-2 became a key contributor. The first issue EuCARD-2 contributed to was published in June 2013 and 15 issues have been published since, which included 30 EuCARD-2 articles. The newsletter has a core subscription base of 1,300+ and is also disseminated to FCC members, an additional ~1,500 recipients.

Network events
The project network events aimed to gather members of the particle accelerator community, including audiences far beyond EuCARD-2, to foster multidisciplinary links and investigate novel concepts and solutions in accelerator science. Across the duration of the project, 82 network events took place.

Dissemination to scientific policy-making bodies

The EuCARD-2 community was well positioned to disseminate its knowledge and results to policy-making bodies, as it represented a wide intersection of European organizations involved in particle accelerator research. EuCARD-2 progress and results were reported to key policy-making bodies through a range of media: newsletter articles, oral reports, meetings and workshops.
EuCARD-2 activity was reported to the CERN Council periodically, as well as to meetings of the European Steering Group for Accelerator R&D (ESGARD). The project also strengthened links with the European Strategy Forum on Research Infrastructures (ESFRI) as the WP7 European Network for Novel Accelerators (EuroNNAC) investigated the ability of the EuPRAXIA project to contribute to the ESFRI roadmap.
A strong and constructive relationship with the European Commission was maintained through regular meetings with the Project Officers, and via participation in consultations and workshops. As a result, EuCARD-2 was able to offer its experience in the management of Research Infrastructures, to contribute to discussions regarding strategies for the future.
In addition, WP4 Task 4.1 led the preparation of the “Applications of Particle Accelerators in Europe (APAE)” document, aimed at policy and decision makers, as well as having scope for members of the public and industry.

Dissemination to industry

A dedicated Work Package (WP2) was set up to foster links between project members, academia and industry, enhancing collaboration and establishing new partnerships.

Outreach towards the general public and media

To raise awareness and provide the most up to date information about EuCARD-2 to the public and the media, the project website was regularly updated with news and results from its work programme. In addition, dedicated articles detailing specific developments were published in Accelerating News, and via additional channels, such as the CERN Bulletin. Both the EuCARD-2 and Accelerating News websites regularly received a higher number of visitors to the site than the number of project members, and included visitors from non-member countries. As such, publicising project information via these channels allowed an audience beyond project members.
The EuCARD-2 website also included an outreach and engagement page, which collected outreach materials for school and university students, teachers, and the public. In addition, the site hosted the project video, which aimed to engage a wide range of audiences to inform them about the project, the applications of accelerators, and to inspire them to pursue accelerator science as a career.
Additional outreach activities included: providing support for accelerator schools aimed at university students, public talks, seminars, publication of articles in several outlets, and the provision of outreach and education materials.
EuCARD-2 supported the Joint University Accelerator School (JUAS) in 2015 and 2016. The project contributed funds and participants presented talks to the attendees.
The project was also featured on the Television of Malta during the 3rd Annual Meeting in 2016, where the Project Coordinator and three EuCARD-2 members were interviewed during the morning show.
Project members also presented public talks and seminars, took part in science festivals and contributed to the Interactions Collaboration (http://www.interactions.org/) comprised of particle physics communicators.
List of Websites:
http://cern.ch/eucard2

Name of the scientific representative of the project's coordinator:
Maurizio Vretenar, Scientific Coordinator CERN
Tel: +41 22 76 72925
Email: Maurizio.Vretenar@cern.ch