Method for acquiring voltage-current characteristic curve of plasma

Abstract

The invention relates to a method for acquiring a voltage-current characteristic curve of plasma. The method is characterized in that plasma parameters are probed by using a Langmuir probe under the condition of radio-frequency discharge mode; a point to be probed is probed by the Langmuir probe under the control of a scanning voltage to acquire sampling values of the parameters, thereby, the voltage-current characteristic curve of the plasma is acquired, wherein one-time probe working time comprises a plurality of discharge cycles; the stable scanning voltage is applied to the Langmuir probe during the same discharge cycle; and each discharge cycle corresponds to one different scanning voltage.

Description

technical field [0001] The invention relates to the plasma field, in particular to a method for obtaining a plasma volt-ampere characteristic curve. Background technique [0002] Such as figure 1 as shown, figure 1 Schematic diagram of how a conventional Langmuir probe works. The average thermal velocity of electrons in the plasma is much greater than the velocity of ions. Therefore, when the probe first enters the plasma, the number of electrons hitting the surface of the probe per unit time is much greater than the number of ions. When the probe is at a certain negative potential V F When the electrons are repelled and the ions are attracted, the probe current is zero, and the potential V F called the floating potential. In the actual test, the probe and the plasma space potential V S The difference V P It is difficult to obtain directly, usually the potential difference V between the measuring probe and a reference electrode in the discharge system. Let the potenti...

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Problems solved by technology

Practical technical difficulties encountered in adopting this approach

First of all, under the condition of such a high frequency, the ion saturation current terminal is difficult to meet the test requirements due to the small current of the differential circuit; secondly, the interference signal brought by the high-voltage pulse discharge process can easily overwhelm the test signal

Again, when the frequency of the scanning voltage is too high, the power amplifier is prone to signal distortion during the process of amplifying the voltage signal generated by the signal generator, resulting in distortion of the scanning voltage signal

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