Penning ionization ternary gas mixtures for diffuse discharge switching applications

Abstract

The increase in the total ionization produced by high-energy α particles in Ar/C2F6 mixtures, which have conduction and insulation properties appropriate for use in diffuse discharge switching applications by addition of low ionization energy additives has been quantitatively studied. The energy to produce an electron-positive ion pair (ip) W in C2F6 was found to be 34.7 eV/ip; this rather high value is attributed to the large cross section for electron impact-induced dissociation of C2F6. The W values of Ar/C2F6 mixtures have also been measured and are reported; they increase with increasing C2F6 content. The W values of Ar/C2F6 binary gas mixtures have been found to decrease by addition of C2H2 or 2-C4H8. Quantitative measurements of the W values of the ternary gas mixtures are reported. The amounts of C2H2 or 2-C4H8 in Ar/C2F6, which maximize the increase in total ionization have been estimated; some of these ternary gas mixtures may be useful for diffuse discharge switches sustained by external electron beams. The experimental results on the W values for the binary and ternary gas mixtures studied have been modeled and good agreement has been found between the experimental and the calculated results. From an analysis of the data it has been found that the α-particle energy is partitioned between C2F6 and Ar approximately in the ratio 4.2:1. It has also been found that at the argon pressures employed, the probability of deexcitation of excited argon atoms by C2F6 (or C2H2 or 2-C4H8) molecules is more than three orders of magnitude larger than the probability of radiative deexcitation of the excited argon atoms.