POWER REQUIRED TO MAINTAIN AN ELECTRON IN A DISCHARGE - ITS USE AS A REFERENCE PARAMETER IN MAGNETIZED HIGH-FREQUENCY PLASMAS

Earlier works on discharges sustained by electromagnetic surface waves in absence of a magnetic field have revealed the central role played by the power balance per electron. This balance relation stated that, provided energy transport is negligible, the power theta(L) lost by th e electron an the average in collisions with heavy particles is exactl y compensated under steady-state conditions by the power theta(A) take n by the electron on the average from the high frequency (hf) field, t heir common value being the parameter theta. Then, because theta(L) is to a first approximation the same in all hf discharges under given di scharge conditions and power density, a simple discharge model valid f or all hf plasmas was used. The present article is an extension of thi s approach to hf magnetized plasmas, using surface-wave plasma columns placed in an axially directed static magnetic field as a means of inv estigation. We observe that theta decreases monotonously when increasi ng the magnetic field intensity B-o, showing no extremum at or close t o the electron cyclotron resonance frequency match over the gas pressu re range (5-100 mTorr) investigated. We show that theta is controlled either by classical ambipolar diffusion or anomalous diffusion, the ac tual diffusion regime depending on whether the novel parameter B(o)p ( p is gas pressure) is small or large. Our measured theta values are fu rther used to estimate the average electron density in helicon sources given the power density, showing fair agreement with the reported val ues. (C) 1995 American Vacuum Society.