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Solid-State Neutron Detector - A new Neutron Detector for High-Flux Applications

Periodic Reporting for period 3 - SoNDe (Solid-State Neutron Detector - A new Neutron Detector for High-Flux Applications)

Reporting period: 2018-05-01 to 2019-10-31

The Solid-State Neutron Detector – SoNDe – project aimed to develop a high-resolution neutron detector technique that will enable the construction of position-sensitive neutron detectors for high-flux sources, such as the upcoming European Spallation Source (ESS). This includes also the construction of a full-scale prototype as a research and innovation action. Moreover, by avoiding the use of 3He in this detector the 3He-shortage, which might otherwise impede the construction of such large-scale facilities, can be alleviated. The main features of the SoNDe type detector are:

• high-flux capability (up to 100 MHz on a 1x1 m2 detector)
• high-resolution of 3 mm by single-pixel technique, below by interpolation
• neutron detection efficiency >= 90 %
• no beam stop necessary, thus enabling investigations with direct beam intensity
• strategic independence of 3He using scintillator technology
• time-of-flight (TOF) capability, necessary to exploit maximum flux, time resolution better than 100 ns
• modularity, improving maintenance characteristics of today’s neutron detectors

Compared to previous neutron detectors this is a huge step forward in terms of count-rate and efficiency. Such gain factors will be needed to make the best possible use of sources such as the European Spallation Source (Sweden), the Institut Laue-Langevin (France) and the Maier-Leibnitz Zentrum (Germany), which are detailed in the European Strategy Forum on Research Infrastructures (ESFRI) roadmap. Benefiting instruments at such a facility, among others, would be Small-Angle Neutron Scattering (SANS) instruments such as SKADI at the upcoming ESS, which was recently approved by the scientific advisory committee, neutron reflectometers and any instrument needing to detect neutrons with a millimetre accuracy on a large detector area.

Detectors of this kind will be capable of usage in a wide array of neutron instruments at facilities of European interest, which use neutrons to conduct their research, among them the Institute Laue-Langevin (ILL) in France, the Maier-Leibnitz-Zentrum (MLZ, former FRMII) in Germany, Laboratoire Léon-Brillouin (LLB) in France and ISIS in the United Kingdom which are in operation at the moment and the upcoming ESS. At these facilities neutrons are used as a probe in a wide array of fields, ranging from material science to develop new and smart materials, chemical and biological science to develop new drugs for improved treatment of a wide range of medical conditions, magnetic studies for the development of future information storage technology to archaeology, probing historical artefacts on a molecular level without physically destroying them.

In addition to the application of the SoNDe technology its modularity also allows applications in material testing, border control or teaching and research on a laboratory scale. Those additional applications create an even wider impact than the originally projected use in large scale facilties. It also illustrates the benefit of technical developments in research environments as the trickle down to other applications in most cases potentiates the cost-benefit ratio.
Since the start of the project we have created two technical demonstrators. The first of those was a technical demonstrator to test the technical feasibility of the project and design decisions in hardware. As a single module it served for tests such as radiation hardness of the electronics, count rate capabilities and interplay between neutron detection, scintillation material and electronics. The results and experience gained from that first demonstrator were used in order to create the second demonstrator, that already establishes key parameters of the final product, mainly the modularity (being a 2x2 module setup) and communication between the single modules. This demonstrator is being tested at the moment in order to allow to check the design before going into upscaling to a large 1x1 m2 array. Before that can be done, issues such as heat production and power consumption, as well as communication with and between the single modules have to be adressed.

As a measure to communicate the results to the wider public, we published a short video (

Finally all issues of concerning the integration of the SoNDe detector technology into a large-scale facility environment were considered. This includes cooling, signalling and mechanical integration. The project culminated in the creation of a large-scale prototype, which is now being evaluated at large-scale neutron scattering facilities all over the world.
At the end of the project a fully functioning large-scale (1x1 m2) prototype of a neutron detector was delivered, using the proposed pixelated scintillation technique. This prototype is proving the feasibility of the technology as well as its excellent performance at a large-scale neutron research facility like the upcoming ESS, preferably in a small-angle neutron scattering instrument such as SKADI. Also additional applications are possible and being tested with the now available prototype.

The developed detector is 15% cheaper than current 3He detectors, while having an approximately seven times higher rate capability and resolution (actual price difference strongly depends on the area purchased as well as the exact details of the 3He purchase). One of the main advantages that remains here is that, without the use of 3He facilities or a specialized electronics laboratory, also smaller facilities can use very small assemblies that are tailored to their needs. Such applications could be:

- Positron emission tomography (PET) in nuclear medicine
- non-destructive testing with neutrons in industry (mining, construction, food processing, extrusion production)
- mobile and stationaory scanning at border controls

Elaborating on the example of food or medicine processing here we want to discuss in-line moisture measurement of extended volumes in an extrusion process (non-transparent organic compunts, such as noodles). Controlling the absolute moisture content is a major issue is and currently simply done by over-drying and removing as much moisture as possible or off-line methods were single batches are tested after being taken out of the production. These methods either use more energy than strictly necessary to achieve the desired product or they interrupt processing. Having a good control over the moisture content is important for a wide array of things, such as shelf-life (dried food, medicine), sensory effect (coffee), of even functionality (cremes for medical application). Optical methods are not feasible, since most of the organic compounts are opaque.

SoNDe now offers the possibility to use a weak fast neutron source and measure backscattered neutrons from the sample. Since most of the content is carbon and hydrogen for the materials in question, backscattered neutrons will show a characteristic speed after interaction with the water. Similar approaches have already been used for soil measurements, but always with very specialized detectors. This would now be open to a wider application. Not interrupting the production process or extending only the exact amount of energy necessary can be both used to reduce cost, improve environmental impact and speed up the processing.