Betts, Brian Philip (1965) Formative time lags in hydrogen. Doctoral thesis, Keele University.

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Abstract

Formative time lags (FTL's) have been measured in low pressure hydrogen discharges under both low and high overvoltages.
The low overvoltage experiments were conducted in the range 40 (E/p t( 250 V(cm.mm Hg)-1 and were designed to investigate the relative importance of the secondary processes which could be active in the considered discharges. Results from four experimental tubes are presented, the later tubes having evaporated gold electrodes and a variable inter-electrode distance. The hydrogen was prepared by the electrolysis of barium hydroxide solution, and was purified by passing it through two palladium osmosis tubes in series. Davidson's approximate theory of the temporal growth of discharges was used to analyse the experimental results, and it was found that the cathodic photon process was the predominant secondary process under all the experimental conditions considered, accounting for at least 60% of the secondary action. A preliminary curve of the FTL vs. inter-electrode distance, for constant E/p, pd and overvoltage was obtained for one of the tubes.
The high overvoltage experiments were quite distinct from the lower overvoltage experiments, FTL's being obtained of the order of nano-seconds, about two orders of magnitude lower than in the lower overvoltage experiments. The primary ionization process is sufficient to explain some very short FTL's but some secondary processes have also to be considered to explain others. The high space charges developed in the initial avalanche was seen, in general, to retard the avalanche growth, and to make the value of the primary ionization coefficient within the gap less certain. Using three experimental tubes having different inter-electrode distances, the effects of varying pressure and inter-electrode distance on the growth of the discharge could be studied at a given E/p; also, the effect of a change in E/p at constant pressure was studied for the three inter-electrode distances.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QC Physics
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Lisa Bailey
Date Deposited: 19 Mar 2018 15:17
Last Modified: 19 Mar 2018 15:17
URI: http://eprints.keele.ac.uk/id/eprint/4611

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