HITRAP – Heavy , Highly-Charged Ions at Rest

At the GSI accelerator complex, using the universal linear accelerator UNILAC and the synchrotron SIS, highly-charged ions up to U 92+ are produced by passing a 400 MeV/u beam through a gold foil stripping off al l or nearly all electrons. The HITRAP facility is built to decelerate those ions to almost rest and to provide t hem to the experiments [1]. First, the ions are decelerate d in the experimental storage ring ESR from 400 to 4 MeV/u a ccompanied with stochastic and electron cooling to k eep the emittance small. Then, in the HITRAP linear dec elerator the deceleration is performed in two additio nal steps. An interdigital H-type (IH) structure and a radiofrequency quadrupole (RFQ) structure are operated i n inverse mode to decelerate first from 4 MeV/u to 0. 5 MeV/u and then further to 6 keV/u. For final coolin g below one meV the ions are captured in a Penning trap .