Electrical Conduction through Radiation-Produced Plasmas in Inert Gas Thermionic Diodes

Properties of thermionic diodes containing inert gases at pressures from 1 to 600 Torr have been determined during irradiation with gamma rays and 1-MeV electrons at dose rates to 3×${10}^8$ rads/h. Anode current maxima were observed at applied potential less than 4 V in tubes containing argon, krypton, or xenon, the gases having Ramsauer minima in their scattering cross sections. Negative resistance in the tube characteristics was not observed with helium, neon, or nitrogen which do not have scattering cross-section minima. Negative resistance was observed in diodes having both planar and cylindrical geometry. With all of the rare gases, initiation of breakdown occurred during irradiation at applied potentials less than the ionization potentials of the gases. The diode current at a constant anode voltage increased linearly with dose rate at low radiation intensities and approximately as the square root of dose rates at higher intensities.