• P. Hülsmann, R. Balss, H. Klingbeil, U. Laier
  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.