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SIS18 upgrade
Subproject coordinator: Peter SpillerThe aim of the SIS18 upgrade project is to prepare the booster operation with high intensity heavy ion beams for the new FAIR facility. The majority of the upgrade tasks is focused on the specific problems arising from the low charge state operation with significantly enhanced cross sections for projectile ionization. The combination of the enhanced cross sections with beam loss driven desorption processes leads to a strongly dynamic and increased residual gas pressure, which consequently cause significant beam loss. The following counter measures are assumed to stabilize the residual gas pressure dynamics and minimize the ionization beam loss per SIS18 cycle:
- SIS18-1 / task 2
- measures: Fast acceleration with maximum ramp rate and thereby short cycle time and fast drop of the ionization cross section by the gain of kinetic energy. Minimization of RF capture loss driven pressure bumps by the generation of a sufficiently high bucket area.
- goal: Development and installation of a new MA loaded acceleration cavity.
- SIS18-2 / task 3
- measures: Increased average pumping speed of the UHV system.
- goal: Replacement of all dipole- and quadrupole chambers by new, NEG coated chambers. Increased bake out temperature.
- SIS18-3 / task 4
- measures: Minimization of gas desorption and inhibiting the beam interaction with the produced gas cloud. Increased local pumping speed at the beam impact positions.
- goal: Development and installation of a collimator system with optimized geometry and application of low desorption yield materials.
- SIS18-4 / task 5
- measures: Minimization of beam loss during multi-turn injection, especially in the injection channel and injection at higher energy.
- goal: Replacement of the acceptance limiting devices, e.g. the inflector magnet and the electrostatic septum by new devices which provide larger acceptances and higher fields.
- SIS18-5 / task 6
- measures: Optimization of the injection matching and minimization of emittance blow-up. Observation of the transverse beam profile during the first turns after injection and during the full acceleration process.
- goal: Development and installation of a fast residual gas profile monitor.
- SIS18-6 / task 7
- measures: Minimization of emittance blow-up in the transfer channel charge stripper and optimum separation of the desired charge state for injection into SIS18.
- goal: Development of a dedicated charge separator with enhanced resolving power and short space charge dominated transport section.
The described measures are accompanied by the installation of a new GSI pulse power connection which was completed in June 2006 enabling a fast cycled synchrotron operation. Furthermore a world wide unique simulation tool for the dynamic vacuum induced beam losses has been developed and benchmarked. With the aim to prepare the high space charge and high current operation and to optimize the transverse and longitudinal beam dynamics machine experiments are conducted regularly.
General status - Sep 2006All tasks could be started successfully without delay. Most of the planned and required personnel was hired. For all tasks the conceptual phase has been completed and the design- or even production phase has been reached. Production was started in the tasks SIS18-4, SIS18-5 and SIS18-6. For the tasks SIS18-1 and SIS18-3, design work is being ongoing, while for task SIS18-2 negotiations with possible deliverers and CNI partner institutes are ongoing in terms of manufacturing. An unexpected situation appeared in task SIS18-1 due to specific patents rights for the use of magnetic alloy ring cores in RF cavities and an underestimation of the technical effort. However, technical solutions were developed but still need to be optimized. For task SIS18-3, the design phase has been just finished and call for tender for a prototype collimator is planned for the coming month. A required R&D effort for task SIS18-5 has been funded by GSI – the model built will be tested in the ESR and consequently the RGM for SIS18 will be built.
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