The neutral beam injection system for ITER is based on negative hydrogen or deuterium ion sources. In these sources negative ions are produced by conversion of atoms and protons on a cesiated surface with low work function. Besides increasing the negative ion production yield, the low work function of the converter surface leads to a high probability of photoelectron emission. The 1d3v particle in cell code Bacon is applied to investigate the influence of the photoelectrons on the plasma sheath and the emission of negative ions. For typical parameters the production rate of photoelectrons is a factor of eight smaller than the one of surface produced negative hydrogen ions. Due to the small flux and mass of the photoelectrons, their effect on the sheath is small: the negative ion density is almost not affected and the potential is slightly reduced. The photoelectrons have a negligible influence on the negative ion flux into the plasma volume.
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