An Optical-radiation Quenching Effect following a Current Pulse superimposed on a Background Arc Plasma in a Low-pressure Mercury Vapour Valve

Abstract

AN experimental single-anode mercury pool valve with a saturated-vapour pressure of about 5 µm mercury was operated in a single-phase single-way rectifier circuit with resistance load to pass at a frequency of 50 c/s half-sinusoidal current pulses with a crest value of 20 amp, and superimposed on each of these basic pulses was a further pulse of half-sinusoidal wave-shape with a crest value of 80 amp and a duration of 14 µsec at the base, the superimposed pulses being produced in synchronism with the basic pulses by periodically discharging through an appropriate circuit arrangement a capacitor which was continuously being charged through a high resistance from a d.c. source. The phase difference between basic and superimposed pulses was adjustable and was set at 60° in respect of the starting instants. An electron multiplier photovalve with quartz window was used in combination with a high-speed cathode-ray oscillograph to obtain and to record the wave-shape of optical radiation intensity from the plasma in the valve as follows; (a) in the anode region; (b) in the region between anode and cathode; (c) in the same region but with the radiation passing through a quartz window attached at an appropriately placed outlet port in the glass envelope of the valve; (d) in the cathode region. Fig. 1 shows the oscillograms which for clarity of demonstration of some effects were obtained at two different speeds of the time base.