Irradiation of small sphere gaps for voltage measurement

Impulse and direct voltage calibrations are presented for 2-cm (centimeter)-and 6.25-cm-diameter sphere gaps, and the calibrations for a 1-mg (milligram) radium pellet inside the top sphere are compared with those for ultraviolet irradiation. The rate of production of electrons in the gap was measured for both irradiation sources with an electrometer amplifier. Impulse sparkover voltages are consistent when plotted as a function of electron production rate, but there are appreciable differences between 1 1/2×40- and 1×50-microsecond wave calibrations.