H_βprofiles at high electron densities from optical discharges

Abstract

In continuous optical discharges, plasmas with temperatures of about 10 4 K and with electron densities of the order of 10 24 m -3 can be produced. The discharge is generated by a 5 kW CW CO 2 laser focused into a chamber filled with hydrogen at a pressure of several MPa. The calibrated line intensity of H beta was monitored by means of an OMA system with spatial and frequency resolution. The measurements yield Stark-broadened H beta profiles from which, using Saha's equation, the electron temperature and density can be derived. The asymmetry of the H beta line increases from 8% at n e =4*10 23 m -3 to 14% at n e =1.2*10 24 m -3 , in rough agreement with theoretical predictions, whilst the half width of the line is in good agreement with theory in the same electron density interval.