Arc generator for an emission spectrometer

Claim 2

An arc generator for an emission spectrometer comprising, a pair of spaced electrodes defining an arc gap therebetween, an ignition circuit for generating a voltage capable of igniting an arc across said pair of electrodes, said ignition circuit comprising a capacitor, a charge circuit for the capacitor that includes a first source of DC voltage and a capacitor discharge circuit that includes a controlled rectifier device for selectively coupling the capacitor to said electrodes, and a lowvoltage circuit including only reactive circuit elements for maintaining the discharge across the electrodes and comprising, a second capacitor and an inductor coupling the second capacitor to the pair of electrodes to provide a discharge path for the second capacitor across the electrodes and via said inductor, and a control circuit for controlling an energy current for the discharge across said pair of electrodes, said control circuit comprising a thyristor and a coil in series with the second capacitor across a source of DC voltage, and a further thyristor controlled by a level-detection circuit with input terminals coupled across the second capacitor.

Claim 3

An arc generator as claimed in claim 1 wherein the low-voltage circuit further comprises a supervision circuit coupled to the second capacitor for checking the end of a one-pole discharge, a variable coil, a diode, and means connecting the variable coil and the diode in series with the second capacitor to allow selective passage of half current periods.

Claim 4

An arc generator as claimed in claim 1 wherein said low-voltage circuit includes a diode coupling the second capacitor to the pair of electrodes and means for selectively providing one-pole or oscillating discharges by means of a selection system provided with a contactor for short-circuiting said diode so as to obtain an oscillating discharge.

Claim 5

Apparatus for generating an arc discharge across a pair of spaced electrodes comprising, an ignition circuit for initiating an arc discharge and a low-voltage circuit for maintaining said arc discharge and including only reactive passive components, said ignition circuit comprising, a first source of DC voltage, a first capacitor, means for selectively charging said first capacitor from said first DC voltage source and discharging said first capacitor across said pair of electrodes, and means controlled by the first capacitor voltage for terminating the capacitor charge cycle at a given capacitor voltage level and for initiating the start of the discharge cycle, and said low-voltage circuit comprises a second capacitor, a second DC voltage source, a charge circuit for selectively coupling the second capacitor to the second DC voltage source and including a first controlled rectifier device, a discharge circuit for selectively coupling the second capacitor to said pair of electrodes and including an inductor, and a second means controlled by the second capacitor voltage for terminating the second capacitor charge cycle at a given capacitor voltage level and for initiating the start of the second capacitor discharge cycle.

Claim 6

Apparatus for generating an arc discharge across a pair of spaced electrodes comprising, an ignition circuit for initiating an arc discharge and a low-voltage circuit for maintaining said arc discharge and including only reactive passive components, said ignition circuit comprising, a first source of DC voltage, a first capacitor, means for selectively charging said first capacitor from said first DC voltage source and discharging said first capacitor across said pair of electrodes, and means controlled by the first capacitor voltage for terminating the capacitor charge cycle at a given capacitor voltage level and for initiating the start of the discharge cycle, and said low-voltage circuit comprises a second capacitor, a second DC voltage source, a charge circuit for selectively coupling the second capacitor to the second DC voltage source and including a first controlled rectifier device, a discharge circuit for selectively coupling the second capacitor to said pair of electrodes and including an inductor, and a second means controlled by the second capacitor voltage for terminating the second capacitor charge cycle at a given capacitor voltage level and for initiating the start of the second capacitor discharge cycle.

Claim 7

Apparatus as claimed in claim 4 further comprising a diode connected in series with said inductor in the second capacitor discharge circuit, and means for selectively short-circuiting said diode to provide an oscillatory mode of discharge cycle.

Claim 8

Apparatus as claimed in claim 4 wherein said low-voltage circuit further comprises a second controlled rectifier device connected to form a closed loop circuit with said second capacitor and said inductor and being triggered into conduction at a different time than said first controlled rectifier.

Claim 9

Apparatus as claimed in claim 6 wherein the discharge circuit of said low-voltage circuit further comprises a diode connected in series with the second capacitor, a part of said inDuctor and said part of spaced electrodes.

Claim 10

Apparatus as claimed in claim 4 wherein said ignition circuit further comprises, an auxiliary DC voltage source, a second controlled rectifier for selectively coupling the first capacitor to said auxiliary voltage source for charging the first capacitor with a voltage of reverse polarity to that provided by the first voltage source.

Claim 11

Apparatus as claimed in claim 8 wherein said means for selectively charging and discharging the first capacitor comprises third and fourth controlled rectifiers, and means for triggering said second, third and fourth controlled rectifiers into conduction at different times.