Sadao Sawada

Boltzmann equation analyses of electron swarm parameters in Ar/Ne, Kr/Ne, Xe/Ne, Hg/Ar and Hg/Kr mixtures and derived effective excitation cross sections for metastable states of rare atoms

The steady-state electron swarm parameters in a series of Penning gases, Ar/Ne, Kr/Ne, Xe/Ne, Hg/Ar and Hg/Kr mixtures, were analysed using a Boltzmann equation in which generation of secondary electrons through Penning ionization and ionization collision between two metastable Hg atoms, as well as electron-impact ionization, are property considered. The ratios of the Townsend first ionization coefficient to the field strength, alpha /E, calculated using the present equation in Ne gas with admixtures of Ar, Kr and Xe, were strongly influenced by Penning electrons. On the other hand, in Ar and Kr gases with Hg vapour, the ionization between two metastable Hg atoms was found to be the dominant ionization process at low E/N. The present alpha /E in every gas agrees well with experimental values over a wide range of alpha /E. The effective cross section of excitation for the metastable states of the rare atoms was derived by comparing the present alpha /E with the experimental values.

Boltzmann equation analyses of electron swarm parameters in Hg/Ar gas mixtures: effect of metastable Hg and Ar atoms

The steady-state electron swarm parameters in Hg/Ar mixtures are analysed using a Boltzmann equation in which the collision terms providing generation of secondary electrons via metastable Hg and Ar atoms presented in the preceding paper (see Y. Sakai et al., ibid., vol.22, p.276, 1989) are taken into consideration. The ratio of the Townsend first ionisation coefficient to the electric field strength, alpha /SiE, calculated using the present equation for E/N values from 5 to 1412 Td in Ar with various admixtures of Hg vapour (K=ratio of Hg to total gas atom concentrations from 2*10-4 to 2*10-2) is in good agreement with the experimental values of Burgmans and Smeets (1983). For E/N below 100 Td and K above 6*10-3 ionisation collision between two metastable Hg atoms is found to be the dominant process for electron multiplication. The influence of electron concentration on the swarm behaviour is discussed quantitatively.

Boltzmann equation analyses of electron swarm parameters in Hg vapour: effect of metastable Hg atoms

A Boltzmann equation, in which the generation of secondary electrons through cumulative ionisation and collisions between two metastable atoms (electron-concentration-dependent processes) is taken properly into consideration, is presented for the first time. This equation is applied to an analysis of the steady-state electron swarm parameters in Hg vapour. The ratio of the Townsend first ionisation coefficient to the electric field strength, alpha /E, for E/N values from 50 to 1412 Td is compared with experimental values. The effect of metastable Hg atoms on the swarm parameters is discussed. It is found that secondary electrons generated through collisions between two metastable Hg atoms are much larger than those generated through cumulative ionisation in a low range of electron concentrations such as is given in Townsend discharges.

Effect of Penning ionisation on an electron swarm in Ar/Ne mixtures: Boltzmann equation analysis

The steady-state electron swarm parameters in Ar/Ne mixtures are analysed using a Boltzmann equation in which the influence of generation of secondary electrons through Penning ionisation in a discharge is taken properly into consideration. The ratios of the Townsend first ionisation coefficient to the electric field strength, alpha /E, calculated using the present equation for E/N values from 1.7 to 565 Td in neon with various admixtures of argon (ratio of the Ar to total concentrations from 10-6 to 10-1) agree well with the experimental values of Kruithof and Penning. It is found that generation of Penning electrons in an electron swarm lowers the mean electron energy appreciably, but influences the drift velocity very little. The values and shape of the effective excitation cross section of the metastable neon, which plays an important role in the determination of the amount of Penning electrons, are discussed.

Effect of Penning ionisation on the Townsend first ionisation coefficient of pulsed and steady-state Townsend experiments in Ar/Ne mixtures

The Townsend first ionisation coefficient alpha defined in pulsed Townsend (PT) experiments in Ar/Ne mixtures are analysed using a Boltzmann equation in which the influence of generation of secondary electrons through Penning ionisation in a discharge is taken properly into consideration. It is found that the values of alpha /E, where E is the electric field strength, for PT experiments differ considerably from those for steady-state Townsend (SST) experiments especially in the E/N range, where N is the gas atom concentration, in which Penning ionisation affects the SST values of alpha /E considerably (Sakai et al. 1986). This difference of the alpha /E is shown to be a peculiar phenomenon in Penning gases and to occur due to difference between the observation method for the metastable Ne and the electron concentrations in a swarm of PT and SST experiments.

The Effective Ionization Coefficient in SF6/Xe-Mixtures

The effective ionization coefficient, {α}/p was measured for mixtures of sulphur hexafluoride and xenon over a wide range of compositions. A charge collection method was employed the basic features of which are discussed. The data were analyzed by numerical solution of the Boltzmann-Equation with proper cross sections.