Screened Probe Measurements in the Helium Negative Glow

Detailed examination of the electron energy and density distribution in the negative glow region of a low pressure helium discharge has been made with the aid of a screened probe. This structure eliminates much of the inaccuracy inherent in the use of simple Langmuir probes. Earlier results by Emeleus indicating the existence of three discrete electron groups, have been confirmed and extended and a detailed picture obtained of the conditions near the cathode dark space edge. Spectrophotometric measurements of the intensities of the helium spectral lines confirm the screened probe measurements.