Apparatus for controlling a plasma
First Claim
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1. Apparatus for preventing damage to a plasma torch comprising:
- a plasma torch which includes a quartz tube through which an inert gas flows and a helical RF coil disposed on the outside diameter of said quartz tube substantially at one end thereof;
said RF coil being energizable so as to ignite said inert gas emanating from said one end of said quartz tube, the ignited inert gas forming a plasma discharge;
light gathering means, directed at a predetermined volume above said RF coil, for gathering a portion of the light from the plasma discharge;
detector means, remote from said light gathering means, for producing a detector signal indicative of the light intensity of the plasma discharge;
light transmitting means, coupled between said light gathering means and said detector means, to transmit light from said light gathering means to said detector means;
reference signal means for supplying two reference signals comprising a static reference signal, having a predetermined value, and a dynamic reference signal proportional to the instantaneous power to said RF coil;
comparing means for comparing the detector signal with said two reference signals; and
de-energizing means to de-energize said RF coil whenever the detector signal is below either of said two reference signals.
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Abstract
An apparatus for controlling a plasma discharge includes a light gathering tube remotely directed at the plasma discharge. The gathered light is transmitted, via a filter optic light pipe, to a detector that produces a signal that is compared with at least one reference signal. After comparing the signals the RF power to the plasma torch is either interrupted or continued.
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Citations
7 Claims
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1. Apparatus for preventing damage to a plasma torch comprising:
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a plasma torch which includes a quartz tube through which an inert gas flows and a helical RF coil disposed on the outside diameter of said quartz tube substantially at one end thereof; said RF coil being energizable so as to ignite said inert gas emanating from said one end of said quartz tube, the ignited inert gas forming a plasma discharge; light gathering means, directed at a predetermined volume above said RF coil, for gathering a portion of the light from the plasma discharge; detector means, remote from said light gathering means, for producing a detector signal indicative of the light intensity of the plasma discharge; light transmitting means, coupled between said light gathering means and said detector means, to transmit light from said light gathering means to said detector means; reference signal means for supplying two reference signals comprising a static reference signal, having a predetermined value, and a dynamic reference signal proportional to the instantaneous power to said RF coil; comparing means for comparing the detector signal with said two reference signals; and de-energizing means to de-energize said RF coil whenever the detector signal is below either of said two reference signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification