ELECTRIC-FIELD AND DOPPLER EMISSION PROFILE MEASUREMENTS IN AN OBSTRUCTED HYDROGEN DISCHARGE

Spatially resolved electric field, emission intensity, and l linewidth profiles have been measured in a dc low current, low pressure obstructed hydrogen discharge with a planar electrode configuration. The polarization-dependent Stark splitting of the H-beta line has been used to measure the electric field. The axial electric field was high over the entire interelectrode space. The radial variations of electric field and emission intensity show that the discharge is almost annular. The H-alpha spectra indicate that, except in a plasma region at an edge of the anode, heavy-particle excitations exceed electron-impact excitation and that the kinetic energy of much of the excited atomic hydrogen was as high as 450 eV. This dc discharge exhibits current-voltage oscillations which appear to be caused by the periodic collapse of the wall sheath. For these discharge conditions, the H-beta Stark spectrum yields electric field measurements with an accuracy of better than 5%.