Merging beam experiment of intense negative ions for advanced compact neutral beam injectors

A test of intense beam production with a JAERI negative ion source and an ESQ accelerator is in progress under US-JAPAN collaborative program between JAERI and LBL. In the first series of the experiments, a merging beam system with an extractor composed of spherical shaped curved grids are used to merge multiple-beams into a single high current beam to be accelerated by an ESQ accelerator. The H/sup -/ ions of 104 mA were extracted from nineteen apertures (10 mm dia.) drilled in an area of 80 mm/spl phi/. Using the merging beam system with a focal length of 150 mm, the beamlets were successfully focused and the beam envelope diameter was compressed to 23 mm. Focusing angle of the merging beam envelope at the entrance of the accelerator could be reduced within the range of -30 (converging)/spl sim/+30 (diverging) mrad, which is acceptable in the ESQ accelerator to obtain a high energy beam.