Studies ofγ-Processes of Electron Emission Employing Pulsed Townsend Discharges on a Millisecond Time Scale

The relative amounts of electron emission from the cathode in a Townsend discharge caused by ions, photons, and metastables have been studied experimentally for several cathodes in argon, using pulsed-light stimulation of the discharge. The current initiated by metastables exhibits a slow build-up and decay, thus permitting easy separation from the faster rising effects of gas ionization and electron emission by photons and ions. Time constant studies of the slow component yielded a diffusion constant for metastable argon atoms of 45 ${\mathrm{cm}}^2$ ${\sec }^{-1\mathrm{}}$ at one millimeter pressure. The efficiencies of electron emission by metastables and ions was found to be closely the same, while the quantum yield for photon emission was found to be generally smaller.