Measurement of grid heat loading in a negative ion source for producing intense H- ion beams by aperture displacement focusing technique

Heat loading of acceleration grids has been investigated using a JAERI 400 keV negative hydrogen ion source, which has a three-stage multiaperture acc elerator. To investigate the effect of beamlet steering on the heat loading , the apertures in the grounded grid were displaced up to 5 mm. The steerin g angle increased linearly with the displacement distance of the grid. The obtained steering angle was 7.5 mrad at the displacement distance of 5 mm. It was confirmed that the steering angle agrees well with the thin lens the ory. Degradation of beam optics due to the steering was not observed. The h eat load of the grounded grid was scarcely changed up to the displacement d istance of 2 mm and then increased from 2.5% to 8% of the total input power when the grid was displaced from 2.5 to 5 mm. Heat loads of the other unst eered grids were not changed. (C) 2001 American Institute of Physics.