Beamlet–beamlet interaction in a multi-aperture negative ion source

Beamlet–beamlet interaction in an acceleration region of a multi-aperture hydrogen negative ion source was experimentally studied. Deflection angle of beamlets was measured in the case of both five-row beamlets and three-row beamlets at the beam energy ranging from 86 to 178 keV. The deflection angle of beamlets at the edge of a beam was about 3 mrad larger than that at the center of the beam. The deflection angle was independent of beam energy at the same perveance. Repulsive force due to the beamlet–beamlet interaction proved to be inversely proportional to the square of distance approximately. From a beam trajectory calculation, shaping of a grid was confirmed to be effective to compensate the beamlet–beamlet interaction.