On parametrization and mixture laws for electron ionization coefficients
Institute of Physics, POB 68, 11080 Belgrade, Serbia
Revised: 25 May 2005
Published online: 28 June 2005
In this paper we discuss the methods of calculation of electron ionization coefficient data. First we give a summary of the data for analytic parametrization of ionization coefficients. Such data may be useful for particle and radiation detectors and for studies of breakdown voltages in gas dielectrics. We have applied extended Townsend formula to fit the experimental data for a number of gases and shown that it provides excellent fits for the entire range of E/N where data are available. We also tested the application of the common E/N and the common mean energy combination of data for pure gases to obtain ionization coefficients for mixtures. The standard combination procedure gives poor results in general but the common mean energy procedure provides an extended region of reasonable usefulness. Test calculations were made for Ar–CH4 mixtures which were found to be the most difficult combination of the selected gases for the application of the mixture law.
PACS: 29.40.Cs – Gas-filled counters: ionization chambers, proportional, and avalanche counters / 34.50.Fa – Electronic excitation and ionization of atoms (including beam-foil excitation and ionization) / 34.50.Gb – Electronic excitation and ionization of molecules; intermediate molecular states (including lifetimes, state mixing, etc.) / 51.50.+v – Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005