Tandem electric discharges for exciting lasers

Apparatus for producing an electrical discharge within each of two glow discharge devices, comprising:

• two glow discharge devices, each discharge device having two opposing electrodes within an envelope filled with gas such that applying a voltage to the electrodes in excess of a characteristic firing voltage causes a glow discharge in the gas that persists as long as the applied voltage exceeds a characteristic sustaining voltage which is less than the firing voltage, the two discharge devices being electrically connected in series to form a series circuit, and the electrical connection point between the two discharge devices being termed a node;
• a main power supply, electrically connected across said series circuit, for producing a voltage greater than or equal to the sum of the respective sustaining voltages of the two discharge devices, so that the main power supply voltage sustains the glow discharge in both discharge devices after the prepulse power supply initiates the glow discharge;
• and
• a prepulse power supply, electrically connected to said node, for applying respective voltages across each of the two discharge devices greater than the respective firing voltages of the discharge devices, the voltages applied to each discharge device being sustained long enough to initiate a glow discharge in that device, and the voltages being applied to the two devices within a short enough time interval of each other so that the glow discharge in one device begins while the glow discharge in the other device is continuing.