BEAM OPTICAL DESIGN OF A MULTI CHARGE ION RECIRCULATOR FOR CHARGE BREEDERS

Ions of high charge states as required for both stable and radioactive beams in order to optimally profit from the accelerating voltage provided can be produced by means of charge state breeders. However, the energy increase obtained is accompanied by an intensity decrease due to the low efficiency of the charge breeding process itself. With respect to the production of radioactive beams an enhancement of the breeding efficiency would be most desirable to avoid a high power primary beam as yet inevitable to counteract the loss in intensity. For this purpose the beam optics of an ion recirculation capable to separate the desired charge state and to reinject the remaining charge spectrum has been designed. The ions, potentially extracted from both sides of the charge breeder, are focused by means of electrostatic quadrupole doublets and bent by two 180 ◦ dipole magnets resulting in a racetrack-like shape. After one revolution the optics realises horizontally and vertically a point-to-point image independent from the charge state of the ions. The second order geometric aberrations as well as most of the chromatic aberrations vanish. The non-zeroenergydependantaberrationsare compensatedby the charge dependant aberrations leading to an effectively achromatic system up to the second order. The beam optical calculations have been carried out with the arbitrary order beam physics code COSY INFINITY and been validated with the beam envelope code TRANSPORT.