Buildup of Electron Density in Neo-Argon Gas Discharges in Pulsed Microwave Fields

Abstract

The rate of increase of the electron density in a pulsed microwave field (5550 Mc/s) applied to gas mixtures of neon and argon at a fixed total pressure of 100 mmHg is calculated by taking account of various possible atomic processes and an energy distribution of electrons in the mixed gases.The electron density increases exponentially with a time constant τb in the density range smaller than 1011/cm3. The relations between τb and the relative partial pressure of argon, r, are obtained for various values of.E/p where. E/p is the ratio of the electric field strength to the total pressure of the mixed gas (in volt/cm mmHg). The value of r giving a minimum value of τb, min=9×10-7 sec is 0.01 for E/p=3, while it is 0.07 at τb, min=3.8×10-9 sec for E/p=17, A tendency is also obtained that the larger the value of E/p, the slower the inclination of τb in the τb r diagram for the range r<rm (which gives the minimum value of τb). This is explained in terms of that, with increasing E/p, the direct ionizations by collisions between electrons and neutral neon or argon atoms predominate over the ionizations by collisions between metastabe neon atoms and the neutral argon atoms, the latter process corresponding to the so-called “Penning effect”. A fairly good agreement is obtained between the calculated τ'bs and our experimental one's within a range of the experimental errors.