Dynamic vacuum in synchrotrons as intensity limitation and counter measures

In order to produce high intensity heavy ion beams, intermediate charge states are used for acceleration. Such ions are exposed to a high probability of charge exchange due to interactions with residual gas particles. Ions which underwent a charge change are separated from the circulating beam in dispersive elements and hit the beam pipe at acceptance limiting devices. At the point of impact an energy-dependent gas desorption takes place which increases the local pressure and the probability for further charge exchange. Thereby, the pressure rise in the machine becomes dependent on the intensity of the ion beam and is referred to as dynamic vacuum. The amount of desorbed gases and thus the beam loss can be reduced drastically by providing special low desorption ion catcher, which reduce the pressure rise compared to standard vacuum chambers. A warm ion catcher system has been successfully installed in the existing SIS18 at GSI stabilizing the residual gas pressure during operation with intermediate charge state uranium. A cold system is also foreseen for the planned superconducting SIS100 at FAIR. A prototype of a cryo-ion-catcher is presently under construction and will be tested soon.