EVOLUTION OF ION AND ELECTRON-ENERGY DISTRIBUTIONS IN PULSED HELICON PLASMA DISCHARGES

The temporal evolutions of the ion and electron energy distributions o f pulsed helicon diffusion plasmas are measured. High power(tl kW) mod erate length (10 ms pulses, 10% duty cycle) 13.56 MHz RF discharges sh ow three distinct pulse phases: (a) breakdown (the first 250 mu s), ch aracterized by high electron temperatures (>8 eV) and high ion energie s (>40 eV) (b) a mid-pulse phase, which is identical to CW operation, and (c) the termination and afterglow which displays a collapsing plas ma potential, splitting in ion energy peaks and a transient hot electr on component (>11 eV). The hot electrons in the breakdown and terminat ion phases are characteristic of a capacitive antenna coupling mode, w hile high densities and low plasma potentials of the steady-state mid- pulse phase are characteristic of an inductive/helicon wave coupling m ode.