Status of the Design Study for 10 MHz Post-accelerated Radioactive Ion Beams at HIE-ISOLDE

A ten-fold increase in the bunch spacing of post-accelerated radioactive ion beams has been requested by several research groups at ISOLDE, CERN in order for experiments to use time-of-flight particle identification and background suppression techniques. It is proposed to bunch externally into the existing REX-ISOLDE RFQ at a sub-harmonic frequency of 10.128 MHz to produce the desired 100 ns bunch separation with minimal loss in transmission. The status of a beam dynamics design study carried out to meet this request will be presented in the framework of the HIE-ISOLDE linac upgrade at CERN.