LONG-PULSE NEUTRAL INJECTOR DEVELOPMENT AT THE LAWRENCE BERKELEY LABORATORY*

ABSTRACT The program elements for the development of long-pulse deuterium accelerators for neutral-beam injection into fusion plasmas are described. Operational characteristics of a 4-grid, 80-kV, 40-A accelerator, designed for 30-sec operation but limited to 800 msec operation by the test facility, are presented. These pulses are long enough to establish thermal equilibrium of the accelerator grids. Beam divergences of 1.0° × 0.4° have been achieved at 80 kV, 36 A for deuterium; 0.44° × 1.0° at 80 kV, 47 A for hydrogen. Measured heat loads on each grid are of the order of 0.5% of the beam power.