EFFICIENT NEGATIVE-ION SOURCES FOR TANDEM INJECTION

Tandem-accelerator operation requires a source of negative ions. The e arliest negative-ion sources were based on charge exchange of positive ions from a rf or duoplasmatron source. The development of the sputte r-ion source in the 1970's produced a revolutionary change in the numb er of negative-ion beams for Tandem operation. This article will revie w operational characteristics of sputter-ion sources coupled to large Tandem accelerators. These characteristics and matching of the ion sou rce to the accelerator are determining factors for the production of u seful beam intensities for physics experiments. A new approach using a 2.45 GHz microwave ion source to produce a high-quality, positive-ion beam coupled to a charge-exchange canal is being developed at Chalk R iver Laboratories, and some results of this development program will b e presented. Plans for future development include the investigation of direct extraction of negative ions from a microwave-driven plasma. (C ) 1996 American Institute of Physics.