Liquid-anode lithium ion-source experiments on PBFA II

Summary form only given. Anodes are being developed to test the electrohydrodynamic (END) instability as a means of producing an intense lithium beam on the Particle Beam Fusion Accelerator II. In a strong electric field (~10 MV/cm) a molten lithium or lithium nitrate surface is predicted to become EHD unstable and deform into a dense array of cusps with submicron spacing. Ions field-evaporated from the cusp tips form the ion beam. A number of problems in fielding these liquid sources in PBFA II have been dealt with. The vertical liquid anode surface required has been formed by suspending the molten anode material in a porous metal frit. In order to attain the high electric fields required to turn on the END source, 5-T B-fields must be impressed in the A-K gap of the applied-B ion diode. Applying the 5-T B -fields on the diode has required peak currents in the diode B -field coils of 70-100 kA. Recent developments include a new diode design which has made it possible to achieve a uniform 5-T B-field on the anode surface, fast heating of the anode, which melts the lithium and allows it to wick up into the anode frit just before the accelerator shot, and development of reflectance-based monitors of molten anode surface quality