A lithium ion source for the production of anode plasma layers in Applied-B ion diodes

In the development of intense light ion beams for ICF, increased attention is given to the production of preformed, high density lithium anode plasmas. General requirements of the PBFA II accelerator are high purity (>90% lithium) layer, <4 mm thick, with ion densities approaching 10/sup 17/ cm/sup -3/ and steep gradients to vacuum in the A-K gap. The authors present an approach to providing such a layer. The heart of the concept is a millimeter size, capillary discharge using lithium foil as the source material. The discharge is driven by currents -- 10 kA for several microseconds to form a warm (-- 1.5 eV), high pressure (-- 1 kbar) plasma. Escaping plasma expands through a large area ratio, supersonic nozzle. In the process, the plasma cools to low temperature (-- .2 eV) and the nozzle exhaust stream will be predominantly neutral. This stream of high velocity neutrals is directed through B applied to impinge on the anode surface, accumulating as a shock heated plasma layer