Beam power transmission and grid loading characteristics of a twohyphen;stage neutral beam source are presented. The dependence of power deposition on the target, the grids, and the gas cell was studied over a wide range of extraction perveance values with the accelhyphen;tohyphen;extraction gap field ratio as the other parameter. The results show that the power transmission improves remarkably with increasing field ratio. For sufficiently large field ratios (ap;2.5), more than 80percnt; of the input IV power was collected on a target located 4 m downstream and subtending 2thinsp;deg; half angle to the source. The sum of the grid loading is approximately double that of singlehyphen;stage accelerators; the plasma grid loading is the highest, followed by ground grid, accel grid, and extraction grid in that order.
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