Wisconsin Alumni Research Foundation

David M Coleman

John P Walters

The disclosed spark source is adapted to generate electrical sparks to produce light for spectroscopic analysis of materials placed on the spark gap electrodes or introduced into the sparks. The disclosed spark source comprises a high voltage transformer having a secondary winding for supplying alternating current at a high voltage, a storage capacitor, a charging circuit including a rectifier connected between the secondary winding and the capacitor for charging the capacitor, spark gap electrodes having a spark gap therebetween, a discharge circuit including an electronic switching device connected between the capacitor and the spark gap electrodes for discharging the capacitor across the spark gap and control means for supplying a sequence of variably spaced triggering pulses to the input means of the electronic switching device for producing a sequence of spark cycles in which the capacitor is charged to substantially the same voltage for all of the spark cycles. During the intervals between sparks, the capacitor is recharged by the transformer and the rectifier. The timing of the sparks is varied, with reference to the phase angle of the alternating current, so that the capacitor is charged to the same voltage during each of the intervals between sparks. The timing of the sparks is computed to accommodate the variation in the instantaneous voltage developed by the transformer during such intervals. By varying the timing of the sparks, it is possible to vary the voltage to which the capacitor is charged, over a wide range. The electronic switching device may comprise a thyratron in parallel with a shunting diode, to carry the oppositely polarized half-cycles of the oscillatory capacitor discharge current. An inductance element may be connected in series with the thyratron to improve the commutation between the thyratron and the shunting diode. It is also advantageous to insert an inductance element in series with the shunting diode to bring about a further improvement in such commutation.

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Madison, WI, United States of America

David M Coleman