Light Ion Sources for ICF

Abstract

PBFA II, Sandia National Laboratories' (SNLA) advanced light-ion accelerator [1] (now under construction), will deliver a 30-MV, 5 MA lithium ion beam to an Inertial Confinement Fusion (ICF) target. Although most ICF experiments have been performed with proton beams, lithium ions were selected for PBFA II for several reasons. The use of lithium enables a large anode-cathode spacing, resulting in less impedance change during the pulse. Lithium ions have less magnetic deflection in the diode, so they can be focused for a longer period of time. Also, since the ionization potential of Li+ is low, while that of L++ is very large, a Li+ source should be achievable without significant contamination from Li++ Ions heavier than Li+ would require operating voltages greater than 30 MV, or the ions would have to be accelerated in a multiple charged state. The selection of the lithium option for PBFA II has made the development of a suitable lithium source one of the highest priority areas in the light-ion ICF program. Following that decision in the fall of 1983, SNLA organized a comprehensive ion source program to develop an optimum lithium source for PBFA II and to understand near-term sources.