Development of a high-brightness, applied-B lithium extraction ion diode for inertial confinement fusion

Summary form only given. The light ion fusion program is pursuing the development of a high brightness lithium ion beam on the SABRE accelerator at Sandia (6 MV, 0.25 MA). This will require the integration of at least three conditions: 1) an active, pre-formed, uniform lithium plasma ion source, 2) modification of the electron sheath distribution in the AK gap, and 3) mitigation of undesired electrode plasmas. These experiments represent the first attempt to combine these three conditions in a lithium ion diode. Our primary goal is the production of a lithium beam with a microdivergence at peak ion power of /spl les/20 mad, about half the previous value achieved on SABRE. A secondary goal is reduction of the impedance collapse rate. Our primary approach is a laser-produced lithium plasma generated with 10 ns YAG laser illumination of LiAg films. Laser fluences of 0.5-1.0 J/cm/sup 2/ appear to be satisfactory to generate a dense, highly ionized, low temperature plasma. An ohmically-generated, thin-film ion source is also being developed as a backup, longer term approach. Small-scale experiments are performed to study each ion source in detail, prior to fielding on the accelerator. Pre-formed anode plasmas allow the use of high magnetic fields (Vcrit/V/spl ges/2) and limiters which slow the onset of a high.