Secondary Ionization Processes in Hydrogen at High Gas Pressures

Autor: D K Davies, J. Dutton, F Llewellyn Jones
Rok vydání: 1958
Předmět:
Zdroj: Proceedings of the Physical Society. 72:1061-1073
ISSN: 0370-1328
DOI: 10.1088/0370-1328/72/6/315
Popis: This paper describes accurate experimental measurements of the spatial growth of ionization in steady state conditions in hydrogen at high pressures (100 to 450 mm Hg) using an apparatus and procedure previously described (Crompton, Dutton and Haydon 1956). The values of the secondary ionization coefficient ω/α obtained from these measurements by means of the method of analysis developed in that paper show that, at a constant value of E/p (E the field, p the gas pressure), the value of ω/α is dependent both on the nature of the cathode and on the pressure of the gas. The variation in the value of ω/α with the material of the cathode shows that the predominant secondary ionization processes in hydrogen at high pressures are cathode dependent processes, thus confirming the previous work. A theoretical investigation of the possible cathode-dependent processes in hydrogen shows that the variation in the value of ω/α with gas pressure may be satisfactorily explained on the assumption that the photo-electric process is predominant and that excited molecules undergo collisions of the second kind with neutral gas molecules, so that the molecular collision frequency affects the rate of production of photons. Theoretical computations of the value of ω/α based on the assumption that the photo-electric process at the cathode is the predominant secondary ionization process, and using previously measured values of the atomic constants involved, give good agreement with experiment. Measurements of sparking potentials to within 1% show, in agreement with theory, that such measurements are not sufficiently precise to detect the departures from Paschen's law consequent on the observed dependence of the value of ω/α on gas pressure.
Databáze: OpenAIRE