Bunching and Cooling of Radioactive Ions with REXTRAP.

摘要

The properties of radioactive ion beams produced by the present on- line target ion source technology are often not suitable for direct post acceleration. For that purpose pulsed and cooled beams of higher charged ions are required. In the case of REX-ISOLDE, the post accelerator at the CERN-ISOLDE radioactive beam facility, a unique system for beam preparation is used. It consists of a gas-filled cylindrical Penning trap (REXTRAP) for bunching and cooling followed by an electron beam ion source for charge state breeding. The Penning trap has been successfully operated with an efficiency of up to 40% and a total number of up to 10(exp 7) ions stored. Buffer-gas sideband cooling at the ions' cyclotron frequency is employed for centering of the ions in the trap. Space charge effects have been observed if more than 1O(exp5) ions are stored. The main effects are frequency shifts for the centering frequency. They can not be explained by simple single ion trap theory, hut can be reproduced in simulations.