The status of ≳1 ampere H− ion source development at the Lawrence Berkeley Laboratory

This paper summarizes the effort to improve the operation of the ∼1. A surface‐production H− ion source developed by K.W. Ehlers and K.N. Leung. The plasma chamber consists of a large magnetic bucket of oval cross section (Fig. 1). A concave cylindrical ‘‘converter’’ surface is suspended in the plasma chamber to direct any surface‐produced negative ions through the exit aperture. The ion source has been mated to a tetrode accelerator for the ‘‘proof‐of‐principle’’ tests. Most of the problems discovered in the tests were associated with difficulties in controlling the production process. This paper describes the plasma chamber in greater detail and illustrates the quality of the present ion production. The acceleration difficulties have been deferred until a better test‐stand is completed.