New Developments in Atomic Beam Polarized Ion Sources at ETH-Zurich

Abstract

The most powerful polarized ion sources presently in operation at particle accelerators are based on the ground state atomic beam scheme. The ionization of the polarized atoms is carried out by electron impact in order to produce positive hydrogen ions for injection in conventional cyclotrons. For the production of negative ions, which are particularly interesting for tandem accelerators and for use in high energy machines by application of charge exchange and multiturn injection, either a double charge exchange in a alkali vapour or the direct ionization of the atoms by a neutral Cs beam is used. In the last few years substantial progress on the performance of the electronimpact ionizer and the double charge exchanger has been made in our laboratory. A proton or deuteron beam intensity of over 100 μA has been observed in the positive stage of the source. A polarized negative ion intensity of 6 μA was obtained after the charge exchange. After acceleration in the ETH EN-tandem accelerator 2 to 3 μA of polarized deuterons with 90% polarization could be focussed through a 3 mm diameter collimator on a target. This is the highest value ever reported for an accelerated beam. At present we investigate improvements of the atomic beam stage. Presently available techniques suggest that it is possible to obtain 50 ÷ 100 μA of polarized H- and D- ions with this type of source. The problems involved are discussed and new progress will be reported.