Beam optics design of the REX-ISOLDE q/m-separator

In the radioactive beam experiment (REX) at ISOLDE/CERN radioactive singly charged ions are delivered by the online mass separator ISOLDE and are accelerated up to 2.2 MeV/u by a new concept, using a linear accelerator consisting of a RFQ accelerator, an IH-structure and three 7-gap-resonators (Habs et al., Nucl. Instr. and Meth. B 126 (1997) 218). The ions coming from ISOLDE are first accumulated, bunched and cooled in a Penning Ion Trap (REXTRAP), which is similar to ISOLTRAP (Bollen et al., Nucl. Instr. and Meth. A 368 (1996) 675). Then, in an electron beam ion source (REXEBIS) charge multiplication takes place. Finally, the highly charged ions are accelerated in the LINAC. As the ions coming out from the EBIS contain impurities coming from residual gas inside the EBIS, an accurate q/m selection is necessary before the beam is injected into the RFQ accelerator. This paper presents the design of the REX-ISOLDE separator.