Use of Radioactive Cobalt for Sphere Gap Irradiation

Abstract

IN many cases where sphere gaps are used for voltage measurement, and particularly where the impressed voltage wave is a short impulse, it is important to provide adequate external irradiation, or the behaviour of the test gap may be erratic and the measurements accordingly inaccurate. If a sufficient supply of initiating electrons is provided, the statistical time-lags of the test gaps are reduced, so that accurate measurement of rapidly changing voltages (lasting some microseconds or less) is possible. Irradiation of sphere gaps (a) by an ultraviolet lamp (for example, mercury in quartz^1-), (b) by radium (usually inserted in a metal capsule and placed inside one of the spheres^{1,3 4}), or (c) by polonium (deposited as a very thin layer on one of the electrodes^3,6) has been successfully used by many workers.