Use of the Hot-Electron Mirror Machine Interem as a High-Z Ion Source

Production of the high-Z charge states in helium, nitrogen, and argon has been measured in the INTEREM device at the Oak Ridge National Laboratory. The INTEREM device contains a hot electron (~500 keV) plasma trapped in a minimum B geometry. The device is of interest because its parameters, electron density and energy, and ion lifetime are consistent with those required for the production of highly charged ions. Ion charge and ion energy spectra were measured independently using an einzel lens type energy analyzer combined with a quadrupole mass filter. For helium, most of the ions were doubly charged under proper operating conditions. For nitrogen, we found the ion yield to be peaked at Q = 4, and under these conditions the yield at Q = 6 was down by a factor of about 20. Energy distribution curves for different charge states show interesting features, from which important information may be inferred about the plasma in INTEREM. Although discrepancies exist in the ion yields we conclude that an INTEREM-like device employing a minimum B geometry and electron cyclotron resonance heating may be expected to be a good high-Z ion source.