Metastable helium density probe for remote plasmas.
Helium metastable atom density was spatially determined by a modified electrostatic probe in a remote plasma. The probe structure was similar to that of a guard ring probe. Opposite polarity voltages were applied to the inner probe and the guard ring to shield both electrons and ions from the vicinity of the inner probe. Therefore, the inner probe current is due to secondary electrons generated by the de-exciting helium metastable atom flux. The photoelectron current was removed by shielding and orienting the probe 90 degrees to the direction of the plasma-generated photon flux. Helium metastable atom density on the order of 10(7) cm(-3) was measured. Limitations on the use of this technique are revealed by comparisons with simulated metastable distributions.
Miura
Naoto
N
Department of Electrical and Computer Engineering, Tufts University, 161 College Ave., Medford, Massachusetts 02155, USA.
Hopwood
Jeffrey
J