Wisconsin Alumni Research Foundation

Fisher Scientific Company

John P Walters

John A Bernier

David M Coleman

Steven G Barnhart

An electric spark type light source for producing light for spectroscopic analysis, comprising an analytical spark gap, an energy storage capacitor, a charging and discharging circuit for alternately charging the capacitor and causing the capacitor to discharge across the spark gap to generate sparks which produce light for spectroscopic analysis, such circuit including at least one inductance coil for causing the discharge current through the spark gap to be oscillatory and pulsating in waveform, the circuit including rectifier means for causing the discharge current through the spark gap to have at least a unidirectional component, and time gate pulse generating means for deriving time gate pulses from the circuit in synchronized relation with the oscillatory pulsating spark gap current for use in selecting repetitive segments of the light from the sparks for spectroscopic analysis. The time gate pulses may be derived from the rectifier current, the capacitor discharge current or the spark gap current. A current transformer, a threshold detector and variable delay means may be employed to generate the time gate pulses. The circuit may comprise a capacitor path including a first inductance coil, a spark gap path across the capacitor path and including a second inductance coil, and a rectifier path in parallel with the spark gap path and including a third inductance coil. The spark gap path may include electronic switching means for initiating the discharge of the capacitor across the spark gap. The rectifier means may take the form of a bridge rectifier having its alternating current input terminals connected to an alternating current power supply for charging the capacitor. The direct current output terminals of the bridge rectifier may be connected into the rectifier path for producing a unidirectional pulsating oscillatory current in the rectifier path, while also causing the oscillatory pulsating spark gap current to have at least a unidirectional component.

Electric spark type light source for producing light for spectroscopic

A device is disclosed for producing an electrical arc which is stabilized by a stream of metastable argon, or some other stabilizing gas. The arc may be employed to vaporize a sample material so as to produce light for spectroscopic analysis. The vaporization is rapid so that the constituents of the sample material can be determined very quickly and accurately. The arc is highly stable so that it operates without sputtering, dancing or showing other signs of instability. Thus, the results obtained with the arc are highly accurate and repeatable. The arc is produced between a cathode in one end of an arc chamber and an anode outside the opposite end of the chamber. The arc passes out of the chamber through an orifice in a gas shaping nozzle. Argon gas is supplied to the chamber through a plurality of gas inlets, which preferably are directed at angles having peripheral components so that a whirling motion is imparted to the gas as it enters the chamber. The gas is discharged steadily out of the chamber through the nozzle and toward the anode in a restricted, shaped and controlled amount, so that the gas plays in a sloped beam over the anode. The sample material to be analyzed is preferably contained within a cavity in the anode, which is heated to a high temperature by the arc, so that the sample material will be vaporized.

Metastable argon stabilized arc devices for spectroscopic analysis

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.

Spark source with regulation of spark magnitude by control of spark

A spark source is disclosed having an analytical spark gap, a capacitor, a power supply for charging the capacitor, and an electronic switching tube connected in a series circuit between the capacitor and the spark gap. When the tube is rendered conductive by a triggering pulse or other signal, the capacitor is discharged through the spark gap and the switching tube, which carries the entire discharge current.

Growing community of inventors

Madison, WI, United States of America

John P Walters