title: Absolute densities of energetic hydrogen ion species in an abnormal hollow cathode discharge.
abstract: We develop an optical measurement for densities of fast (units to tens of keV) hydrogen ions in an abnormal hollow cathode discharge in units to tens of mTorr pressure range. This method combines results from previous collisional-radiative models, comparing the intensity of Balmer H_{alpha} due to dissociative excitation of H2 by fast electrons to Doppler-shifted emission arising from charge exchange of energetic ions. The method requires only two inputs: the current density due to fast electrons and a single H_{alpha} spectrum of the characteristic emission channel at the anode. We model in particular the cylindrical interelectrode discharge of an inertial electrostatic confinement device. Experimentally, we find that the density of fast ions emerging from the cathode (bias -5 kV at 20 mTorr ) is in the order 10;{14}m;{-3} , increasing approximately linearly with current in the 10-30 mA range. Calculated densities agree with values obtained in similar apparatus using Langmuir probes and analysis of dust particle motion.
authors.affiliation: School of Physics, University of Sydney, Sydney 2006, Australia. johnk@physics.usyd.edu.au
authors.forename: J
authors.initials: J
authors.lastname: Kipritidis
authors.forename: J
authors.initials: J
authors.lastname: Khachan
authors.forename: M
authors.initials: M
authors.lastname: Fitzgerald
authors.forename: O
authors.initials: O
authors.lastname: Shrier