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Progress in negative ion beam development

In recent years there has been a change in direction in the development of H-, D- ion sources from those based on charge exchange to those based on collision processes in the volume of a hydrogen discharge (so-called volume sources). Data have been obtained which show that significant densities of negative ions exist and that they can be extracted to form ion beams so giving impetus to the application of H- ion sources. The optimisation of performance in all aspects of design still requires resolution of a range of physics issues:- atomic and plasma physics in the source, accelerator design for H- ions with adequate suppression of electrons and ultimately beam transport. The paper discusses the status of the investigation of these issues.