Stripping of ion beams by multiple passes through a plasma medium

Abstract

A method to increase the charge state of multicharged ions is explored. The method is based on stripping, during multiple passes, of an initially low charge-state ion beam through a plasma medium with energetic electrons heated at the electron cyclotron resonance. The key feature of the system is a magnetic recirculating line which has a built-in stripping chamber and a system of entrance-exit apertures. The recirculating line comprises a magnetic low-loss ion guide which delivers ions being passed through the stripping chamber to its entrance. As a stripping medium, a hydrogen plasma confined in a magnetic trap of cusp configuration is proposed. To model the conversion of initially injected ions with charge state ζ=1 to higher states, basic parameters of the stripping chamber can be estimated as follows: microwave frequency: 14.4 GHz; effective plasma length 10–30 cm; gas pressure: 1×10−5 Torr. Results of numerical calculation of the proposed stripping process show that an increase of ion charge is possible with acceptable deterioration of ion beam characteristics. Conversion efficiency, for example, for Pd103 from ζ=1 to ζ=5 for these parameters is about 80%.