CORDIS proporciona enlaces a los documentos públicos y las publicaciones de los proyectos de los programas marco HORIZONTE.
Los enlaces a los documentos y las publicaciones de los proyectos del Séptimo Programa Marco, así como los enlaces a algunos tipos de resultados específicos, como conjuntos de datos y «software», se obtienen dinámicamente de OpenAIRE .
Resultado final
A multi-wire proportional chamber (MWPC) for the Cerenkov detector RICH was set up and tested together with its final pad cathode covered with solid CsI photo converter. The design and construction of the gas supply system is finished.
The RICH detector has been moved from TU München to GSI and installed there in the experimental hall, together with the ALADIN dipole magnet and ancillary (tracking) detectors. The RICH readout has been integrated successfully into the standard GSI data-acquisition system MBS. In addition, routines for on- and offline-analysis of the data were written or modified within the ROOT environment. Beams of 86Kr and 58Ni at various energies were used to test the performance of the detector.
The results have been presented e.g. at the Krakow and Munich R3B meetings (see web page http://www.e12.physik.tu -muenchen.de/~mboehmer->Talks ). The velocity resolution in the region 750 MeV/u < Ekin < 900 MeV/u was investigated systematically for Ni ions and shows the expected performance 3*10-3 < delta-beta/beta < 6*10-4. For Kr the velocity resolution is about 20% higher and is thus already better than needed for unique mass identification in the mass range A~100. The performance for the heaviest masses and with large-emittance secondary beams needs still to be proven.
The geometry and technical parameters of the LH2 target to be used in conjunction with the R3B reaction set-up were defined. Constructing and mounting of the target is finished. Two experiments using this target were successfully performed in 2001, one aiming for proton-elastic scattering off exotic nuclei, and one experiment with the LH2 target implemented in the R3B reaction set-up. Here the aim is the investigation of break-up reactions of light neutron-rich nuclei including knockout reactions of single nucleons but also cluster. The technical performance of the target is excellent.
A zero-degree super-conducting dipole magnet was designed within the R3B project, which fulfils all requirements dictated by the various types of experiments. The main parameters of the spectrometer are: (i) A large vertical gap allowing a cone with an angular range of +/-80mrad for neutrons to be covered. (ii) A horizontal acceptance, which allows a maximum bending angle of 40 degrees. This ensures an acceptance close to 100% even for experiments involving proton emission, or in general for experiments with very different magnetic rigidities of the beam and the fragments. (iii) A high field integral of about 5Tm is required, which allows a bending angle of 18 degrees; for a 15Tm beam (e.g. 1 GeV/u 132Sn or 500 MeV/u 8He). The required momentum resolution of up to 10-3 can be achieved by tracking the particles with high resolution. The design includes four super-conducting coils, which are tilted to match the required acceptance angle for the particles of interest. The side coils are optimised to reduce the fringe field, and guarantee a low magnetic field in the target region, where detectors have to be placed.
After the careful consideration of several solutions, the concept of a super-conducting magnet with race-track coils in conjunction with active shielding, is considered to be the best solution. The detailed technical design report was reviewed positively by a committee of international experts. The quench protection system has been meanwhile redesigned according to the recommendations of the expert committee. Now, a more classic energy extraction system with active heaters in case of failure is foreseen. The more conservative solution for the protection design led to new super-conducting-cable specifications described in the document: "Technical Specifications of R3B Model Magnet Conductor."
A preliminary cost estimate as well as a time schedule for a realization of such a magnet has been worked out. As a first step the construction and test of a model coil is foreseen, in order to verify the design parameters, to test the superconductor, the mechanical stress as well as the quench-protection system. A programme has been developed which would take about 24 months for construction and performing all tests. The estimated costs for this model coil including the test programme amounts to about 0.7 M¿, while a preliminary cost estimate for the full-size magnet results in about 3 M¿. The final technical design report is available on the R3B web page (http://www-land.gsi.de/r3b/).
The requirements of the different detector systems of the R3B setup have been summarized in a report prepared by J.U. Krakow for the March 2002 Krakow R3B meeting (see http://www-land.gsi.de/r3b/ ). This report also contains the modified trigger scheme.
A careful assessment of the available technology, together with the need to have on-site expertise and maintenance support available, led to the decision that the individual detectors should be read out using SAM3 VME modules developed at GSI. Their data are subsequently concentrated via RIO3 VME processors linked to the PC-based event builder(s) via Fast Ethernet. The software chosen is the GSI Multi-Branch System (MBS), which already contains the complete framework for such architecture. Some of the essential components (RIO3 processors, VME crates, Fast Ethernet switch, PC for event building) have been purchased und successfully tested. Up to 12Mbyte/s data transfer rate have been achieved.
In addition to designing and testing the digital part of the data acquisition, new front-end modules for analog-to-digital conversion of the detector signals had to be designed. It has been stressed before that we have underestimated the complexity of this task. During the R3B project, two parallel developments were followed: one at J.U. Krakow aiming at digitising the energy and time information from the LAND photomultiplier signals from the neutron, gamma-ray, time-of-flight, and fibre tracking detectors. A prototype of the front-end board was manufactured and the operation of the time-to-digital converter has been tested successfully. The layout of the system and the test results can be found in a summary report on this subject (http://www-land.gsi.de/r3b/).
The other development aims to read out the strip and pad detectors (RICH, Si strip) and is carried out at TU München. Within the R3B frame the concept and design of the digitising bridge boards that interfaces existing analog boards to the GTB-bus was finished. First prototypes were built and tested. Details of the designs and the status of the developments can be found in the reports (http://www-land.gsi.de/r3b/).
Various types of reactions are identified as key experiments to be performed at the R3B reaction set-up. These reactions were also considered in defining the key parameters for the magnetic spectrometer. A simulation program based on GEANT 3.21 was developed, which includes:
- Full description of the geometry and materials of the R3B set-up.
- Description of the magnetic field of the dipole based on realistic OPERA calculations.
- Tracking of the ions through the set-up.
- Realistic description of the atomic and nuclear interactions of the ions inside the set-up.
- Full description of the Cerenkov detector.
The program was used to investigate the determination of the magnetic rigidity Brho of the ions passing through the dipole by using a ray-tracing procedure. This allows the comparison of the Brho¿nresolution achievable with different magnets, e.g. the existing ALADIN magnet and the new designed dipole. The intrinsic resolution of the tracking procedure has been studied and several options to improve it will be considered in the future. The Monte-Carlo code was additionally coupled to different event generators describing the reaction mechanisms of some key experiments (Coulomb dissociation and fission). The simulation has been applied to investigate the achievable mass resolution for a realistic case (e.g. fragmentation of 136Xe on Be at 1 GeV/u).
This full simulation is the basis to define the requirements of the experimental setup, as e.g. the optimum Cerenkov radiator or the required position resolution of the tracking detectors. A more detailed description of the subject can be found in three reports available at http://www-land.gsi.de .
The ion-optical concept of a super-conducting fragment separator (Super-FRS) that fulfills the acceptance and resolution requirements needed for efficient separation of high-energy fission fragments was developed.
The separation quality was verified in Monte-Carlo simulations. The procedure was tested by a comparison with the performance of the present Fragment Separator FRS at GSI. The ion-optical layout includes higher-order corrections as well as an efficient beam transport to three experimental areas, which comprises a reaction set-up (which will be very similar to the R3B set-up), storage rings, and experiments for decay studies and trapping of ions. The resulting separation efficiency for secondary beams produced via fission of 238U with an energy of about 1 GeV/u surpasses that of the present facility by more than one order of magnitude.
Different ion-optical solutions were studied in detail including a standard achromatic mode, as well as settings optimised for high transmission or high resolution. In the high-transmission mode the separator has an increased momentum acceptance compared to the standard achromatic mode, while in the spectrometer mode the separator is tuned such that the momentum dispersion of pre- and main-separator will sum up. In this mode, a resolving power of 4400 is reached in first order. In addition, a focussing system in front of the Super-FRS was designed, which is able to handle primary beams with a magnetic rigidity up to 100 Tm.
The developed design is an integral part of the proposed new GSI radioactive beam facility, as described in the Conceptual Design Report ("An International Accelerator Facility for Beams of Ions and Antiprotons", http://www.gsi.de/GSI-Future/cdr/ ). Details can be found there, in three reports (http://www-land.gsi.de/r3b/ ) and in the EMIS14 proceedings (H. Geissel et al., GSI Preprint 2002 - 23, accepted for publication in Nuclear Instruments and Methods B, in press).
Detailed calculations of temperature profiles were performed for the different extraction modes foreseen for the future high-intensity accelerator, which are a fast (~ 1 microsec) and a slow (~ 1 sec) extraction mode. These simulations concerning the heat profiles were performed for the most extreme case of energy deposition, that is a uranium beam with an intensity of about 1012 ions/pulse at 1 GeV/u, loosing 25% of its energy inside the target (10 kJ).
For the slow extraction mode, rotating solid targets seem to be feasible even for a beam spot size in the order of 1 mm². A target similar to the SISSi target was proposed. The SISSI target has been used at GANIL since 8 years with good reliability, for lower power deposition (<1 kW), but concentrated on a smaller beam spot and smaller depth. The target proposed for R3B is a fast rotating disk, of 10cm radius, and can be made of different materials such as C or Ta. Considering the large thickness needed for the high energy-beams available at GSI, the thickness can be decreased in the central part of the target in order to reduce the weight of the target and the requirements on ball bearings.
The situation becomes more dramatic in the case of fast-extracted beam pulses containing 1012 uranium ions. In this case the beam energy will be deposited in very short beam pulses, thus corresponding to huge instantaneous power and leading to explosion of the target material. Possible solutions were evaluated and the possibilities for experimental tests to simulate the stress acting on the target were considered. Calculations of the hydro-dynamical response of the target point towards a possible solution, which would be a combination of sufficiently short beam pulses (shorter than the hydro-dynamical time scale, about 50ns) and a liquid target guaranteeing a continuous replacement of target material. Calculations for different beam parameters show that even for the fast extraction mode, some target materials may stay below the melting temperature while exposed to 1012 uranium ions in a short time period, if the beam spot is sufficiently large. The beam size, however, has critical influence on the performance of the separator. The results of the simulations and the proposed target solutions are described in six reports (http://www-land.gsi.de/r3b/).
As an alternative to short beam pulses, the possibility of cooling of individual ions before the injection into a storage ring was investigated. Thereby, the particle characteristics are corrected to a nominal value by individual trajectory correction applied after measurements of these characteristics in the fragment separator. This measurement is possible in the case of very exotic nuclei where the production rate after selection is less than 106 ions/s. Therefore GANIL established a contract with JINR Dubna, where a strong expertise exists in the field of storage rings and cooling, in order to study the possibilities and limitations of such a scheme. The report describing the results of this investigation and the proposed scheme can be found in http://www-land.gsi.de/r3b/.
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