INVESTIGATION OF CATHODE PHENOMENA IN THE MERCURY ARC.
Abstract
An experimental and analytical study is made of the emission mechanisms of the mercury arc and it is concluded that the cathode spot temperatures are too low to operate predominately by thermionic emission. Various physical processes to reduce work function are discussed, and shown to be probably not significant. An emission model involving ion microfield emission is proposed and shown to be feasable. The related problem of retrograde arc motion is studied and a model involving plasma growth into large magnetic field regions is proposed. The retrograde arc speed is measured as a function of magnetic field and arc current. The variation of spot size with arc current, magnetic field, and vapor pressure is measured and is compared with a theoretical model based upon low pressure energy balance considerations. Spectrographic measurements show the absence of continuum radiation from the Mo notch cathode and the absence of Mo spectral lines. This suggests that the refractory cathode spot operates at low pressures with little electrode evaporation for the conditions studied. The increase of arc votage with magnetic field was measured and was interpreted as being predominately due to the cathode sheath. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1966
- Accession Number
- AD0629869
Entities
People
- C. G. Smith
- S. Aisenberg
- S. B. Afshartous
- V. Rohatgi