H- AND D- SCALING LAWS FOR PENNING SURFACE-PLASMA SOURCES

The small-angle source (SAS), 4X source, and 8X source are Penning sur face-plasma sources that produce high-current, high-brightness H ion b eams for accelerator applications. The scaling from the SAS (1X source ) to the 4X source, and from the 4X source to the 8X source is at leas t as good as predicted by the scaling laws. In many instances, the sca ling is better than predicted, particularly in the critical area of th e efficiency with which H- ions are produced per unit of discharge pow er. Using zeta=j(H-)/F(C), where F(C) is the cathode power density loa d, zeta4X almost-equal-to 2zeta(SAS) and zeta8X almost-equal-to 1.5zet a4X. The J(H-) scaling is at least as good as predicted by the scaling laws-we have been able to produce the predicted H- current in both th e 4X and the 8X sources. The SAS was scaled up in size to the 4X sourc e, and the 4X source was scaled up in size to the 8X source, on the as sumption that the effective kT(H-) = 5 eV. We also assume that the eff ective kT(H-) = the effective kT(D-). These temperature scalings appea r to be obeyed. The D-current scaling appears to be even better than a ssumed, namely, j(D-) almost-equal-to j(H-).