The concept of space charge neutralization of positive ion beams is well documented but the theory has only been applied marginally to negative ion beams. The two systems differe primarily in the relative masses of the beam ions and the neutralizing ions and this gives rise to observable differences in the particle distribution within the two beam systems. Results presented here show that for negtive hydrogen beams circumstances can pertain which lead to non-gaussian beam particle distributions which can be described in terms of a Bennett-like distribution function as often seen in self pinched electron beams. The origins of this distribution are discussed in terms in of the space charge neutralization model of Holmes and its consequences for beam optic calculations and measurement are explored.
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