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Apparatus for controlling a plasma

  • US 4,609,810 A
  • Filed: 06/25/1984
  • Issued: 09/02/1986
  • Est. Priority Date: 06/25/1984
  • Status: Expired due to Fees
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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