Measurements of helicon wave propagation and Ar II emission

Abstract

Wavemagnetic field, optical and Langmuir probemeasurements are carried out to examine fast and thermal electron contributions to plasma ionization in a helicon plasmasource. For the optical measurements, an Ar II line (443 nm) with a particularly short lifetime (7 ns) is chosen to resolve the excitation rate within a radio frequency period (73.7 ns). Information is then obtained regarding the acceleration processes and their action on the electron distribution that caused the excitation. Spatio-temporal measurements of 443 nm peak emission show that the emission is modulated at the source frequency. The peak count phase of the modulation propagates along the plasma at a comparable speed as the local helicon wave phase velocity. Computer modeling utilizing lab data is carried out to examine wave field effects on electron acceleration and ionization contributions arising from non-Maxwellian fast electrons. Show more