Conceptual Design of the Collector Ring Rf System

Requirements The CR is designed for fast precooling of rare isotopes and antiproton beams. Prior to stochastic cooling the relative momentum spreads of the incoming beams have to be reduced from 3% (antiprotons) and 1.5% (rare isotopes) down to 0.7% (antiprotons) or 0.4% (rare isotopes) respectively. This is achieved by means of a two step process. First, the bunch is rotated in phase space by a quarter of a synchrotron period in a mismatched bucket; afterwards it is adiabatically debunched. Additionally, the RF system at hand will also be used to rebunch the beam to allow a bunch to bucket transfer from CR to a subsequent ring. According to single particle beam dynamic simulations [4] the CR debuncher RF system has to operate between 1.18 MHz and 1.38 MHz. At 1.18 MHz it has to provide a total voltage of 400 kV in pulsed and 20 kV in continuous operation. All changes in the operational frequency will be slow (timescale 5 min). No in situ vacuum system baking is needed. The total installation length amounts to five times 2 m. The beam pipe of the cavities must have a cylindrical diameter of at least 150 mm. The RF system will be installed in a two stage process, the first stage only accounts for half of the cavities (200 kV pulsed, 10 kV continuous), resulting in a reduced capture range of the RF system.