GSI, Darmstadt
To feed the production targets of FAIR with very short bunches (pulse durations of not more than 50 ns are envisaged) demanding rf-systems for bunch compression are required in SIS18 and SIS100. But also the opposite process, namely debunching, is required in the collector ring CR. Bunch compression as well as debunching will be done by fast bunch rotation. Due to space restrictions both rf-systems must be able to generate a very high field gradient of 50 kV/m at very low frequencies. Such high field gradients can be realised only using magnetic alloy (MA) cavities, since their saturation field strength is about ten times higher compared to NiZn-ferrites. For SIS18 a MA bunch compressor unit, which generates the required 50 kV/m at 800- and 1200 kHz, has already been realized as a forerunner for the required FAIR-systems.
GSI, Darmstadt
Funding: Project funded by the European Community under the FP6 "Structuring the European Research Area" program (SIS1002, contract number 515873)
SIS100 is a synchrotron that will be built in the scope of the FAIR (Facility for Antiproton and Ion Research) project. High intensity ion beams are required, making it necessary to damp longitudinal coupled and uncoupled bunch oscillations. For this purpose, a closed-loop control system was designed. Its processing part is based on digital signal processors (DSP) and field programmable gate arrays (FPGA) whose advantage is their adaptability to different problems by software changes. Experiments with a prototype were performed at the existing synchrotron SIS12/18 at GSI concentrating on the damping of longitudinal coupled bunch quadrupole oscillations of the lowest order. The configuration of the electronic system is described and results of the machine development experiments are reported. Finally, an outlook to the application in SIS100 is given.
TU Darmstadt, RTR, Darmstadt
GSI, Darmstadt
Funding: This work was partly supported by Deutsche Telekom Stiftung.
The effects of heavy beam loading on the RF control loops of a double-harmonic cavity system are examined. This cavity system that will be realized at the GSI Helmholtzzentrum für Schwerionenforschung in the scope of the SIS18 upgrade program consists of a main broadband cavity and a second harmonic narrowband cavity. The cavities comprise both an amplitude and a phase feedback loop. In addition, the narrowband cavity includes a feedback loop which controls its resonance frequency to follow the main RF frequency. After modelling the cavity system and the feedback loops, an analytic controller design is presented. In addition, longitudinal beam dynamics are added to the cavity model to allow a detailed simulation of the cavity-beam interaction. Realistic simulation results are given for an acceleration cycle of heavy-ions to demonstrate the performance of the RF control loops.
GSI, Darmstadt
CERN, Geneva
The FAIR storage ring complex comprises three storage rings with a magnetic rigidity of 13 m. Each of the rings, CR, RESR, and NESR, serves specific tasks in the preparation of secondary beams, rare isotopes and antiprotons, or for experiments with heavy ion beams. The CR is optimized for fast stochastic pre-cooling of secondary beams. The RESR design includes optimization of antiproton accumulation. The design of the NESR for experiments with heavy ions, deceleration of ions or antiprotons for a subsequent low energy facility, and the accumulation of rare isotope beams is proceeding. This report summarizes various new concepts conceived in the design process of this new storage ring facility.
