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US 5,383,019 AGranted
Inductively coupled plasma spectrometers and radio-frequency power supply therefor
AssigneeFisons Limited
InventorsRegis C. Farrell, James J. Hornsby
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AssigneeFisons Limited
InventorsRegis C. Farrell, James J. Hornsby
Estimating the term…
The invention provides methods and apparatus for atomic emission spectroscopy and for mass spectrometry which make use of an inductively coupled radio-frequency plasma torch. A radio-frequency power supply supplies energy to a plasma induction coil via reflectometer means and a matching network. A signal indicative of reflected power generated by the reflectometer is used to set the frequency of the power supply to the resonant frequency of the matching network and plasma induction coil, thereby ensuring the maximum efficiency of power transfer irrespective of the state of the plasma. Preferably a solid state power amplifier is employed in conjunction with a lower power variable frequency oscillator. Means for ensuring proper ignition of the plasma while maintaining the frequency of the power generator within a governmentally specified frequency band are also provided.
An inductively-coupled plasma mass or emission spectrometer having a plasma induction coil, a radio-frequency power generator whose frequency is determined by an analogue frequency control signal and a matching network comprising only fixed-value electrical components for efficiently transferring power from said generator to said plasma induction coil, said spectrometer characterized by reflectometer means disposed between said generator and said matching network for generating a signal indicative of the reflected power at the output of said generator and frequency control loop means for generating said control signal in response to said signal indicative of the reflected power whereby the frequency of said RF power generator is adjusted to maintain said reflected power at a minimum.
A method generating an inductively coupled plasma for use in a mass or emission spectrometer, said method comprising generating radio-frequency power at a frequency determined by an analogue frequency control signal, transmitting said power to a plasma induction coil via a matching network comprising only fixed value electrical components, generating a signal indicative of the reflected power at the input of said matching network, and generating said analogue frequency control signal in response to said signal indicative of reflected power to minimize said signal indicative of reflected power.
An inductively coupled RF plasma torch, comprising
An optical emission spectrometer comprising
Dependencies are inferred from the claim text.