Current limitation through single-hole grids in a mercury-arc discharge

Measurements are reported on current limitations induced by single cylindrical-hole grids in mercury-vapour valves. It is shown that, over a wide range of time scales, a single equation may be used to predict the onset of `chop¿ for a variety of current waveforms. The values of the two parameters in the equation are estimated for grids of different diameters and depths. The neutral-number density under prescribed conditions of pool temperature and excitation anode current is measured so that dependence on this parameter is also determined.