LIZ-MeV a Novel High Current High Charge State Heavy Ion Source
 

Ady Hershcovitch and Brant Johnson

Abstract

Existing heavy-ion sources can produce either high beam currents, but low charge states (e.g., the Metal-Vapor Vacuum Arc [MEVVA]) or high charge states, but low beam currents (e.g., the Electron Beam Ion Source [EBIS]). For heavy ion beam injection (accelerators and ion implanters) our goal is to develop an ion source that produces both high charge states and high beam currents. With sufficiently large electron impact energies, electron current densities, and confinement times for high charge state generation, coupled with minimizing charge state reducing processes, we hope to eventually produce several mA of highly ionized heavy metal ions (Au and U with charge state exceeding 20+). Our approach is based on utilizing proven plasma configurations and technologies that have the desired parameters, while minimizing the necessity for any complicated technologies, or to explore unknown physics. Previous efforts at LBNL:  http://www.triumf.ca/pac97/papers/S2html#Sess2C  resulted in a Z-MEVVA ion source (Z-Discharge MEVVA) which produced higher charge states than a conventional MEVVA (Au 3+). However, results were limited to Au 6+, because the relatively high impedance (about 2 ohms) of the power supply circuit limited the Voltage drop across the discharge and therefore the electron-impact energy. We embarked on an effort to develop a two-stage, low inductance ion source. The first stage of the novel ion source is the low inductance circuitry LIZ-MEV (Low Impedance Z-discharge Metal Vapor). Our preliminary results indicate that LIZ-MEV has generated very large heavy ion currents with considerably higher charge states than MEVVA.