Electron Transfer in Spherical Vacuum Chambers

IN an effort to explain the breakdown of proportionality between ionization current and gas pressure in cavity ionization chambers, Greening1postulated the transfer of slow electrons between the chamber electrodes. Using an approximate formula for the energy distribution of these electrons, he analysed the behaviour of ‘vacuum’ chambers with planar, spherical and cylindrical geometries, and thereby accounted for the asymmetrical current-voltage characteristic reported by Taylor2. Greening noted that the characteristic is in general dependent on the directional distribution of the emitted electrons; but stated that the expressions derived for the case of spherical electrodes should be independent of this angular function. Burlin and Husain have recently adopted a spherical vacuum chamber in their experiments on electron transfer, and have compared their results with those calculated on the basis of Greening's semi-empirical theory.