Pulsed plasma probe
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsEdward P. Szuszczewicz, Julian C. Holmes
Life of this patent
Estimating the term…
Abstract
Method and apparatus for Langmuir probe plasma diagnostics employing an etronically controlled, discontinuous, modulated sweep of pulses in which the pulse amplitude follows a sawtooth envelope. The pulse organization procedure is such that the probe rests at a baseline potential for a period which is much longer than the pulse width and current-voltage data points are generated by each pulse. The distortions that can result when probe surface conditions change within the measurement period are eliminated by maintaining a single probe surface condition throughout the collection period of the current-voltage characteristic.
Claims12
A device for plasma investigation for applying a voltage to a probe and measuring the current collected by said probe comprising:
- generator means for providing a sweep voltage;
- modulator means coupled to said generator means to provide a pulse-modulated voltage for application to said probe, the output of said modulator means being coupled to said probe;
- and
- measuring means coupled to said probe to measure current collected by said probe.
A device for plasma investigation for applying a voltage to a probe and measuring the probe current collected by said probe comprising:
- generator means for providing a sweep voltage;
- modulator means coupled to said generator means to provide a pulse-modulated voltage for application to said probe, the output of said modulator means being coupled to said probe;
- a plurality of electrometers having different sensitivities for measuring said probe current, said modulator output being coupled to said plurality of electrometers;
- first switching means coupled between said plurality of electrometers and said probe;
- differential amplifier means coupled to output of said modulator means;
- second switching means coupled between said plurality of electrometers and said differential amplifier means;
- and
- logic means responsive to said probe current to actuate said first and second switching means to connect the appropriate electrometer between said probe and said differential amplifier means.
A method for plasma investigation for use with a Langmuir probe comprising:
- applying a series of voltage pulses to said probe, each pulse having a duration sufficient to allow the plasma to establish a steady-state condition but less than the period within which the probe surface conditions can change in response to said voltage pulse;
- applying a constant baseline voltage to said probe during the period between said voltage pulses;
- varying the amplitude of said voltage pulses so that pulses of different amplitudes will be applied to said probe;
- and
- measuring the current collected by said probe to obtain a relationship between said applied voltage and said current collected.
Dependencies are inferred from the claim text.