Langmuir probe plasma diagnostic method based on virtual instrument

Abstract

This invention relates to a Langmuir probe plasma diagnosis method based on a virtual instrument for diagnosing spacial potential, charge density and electronic temperature of plasmer characterizing in using a quasi-DC probe bias signal to replace conventional sawtooth wave scan bias signal and utilizing a virtual instrument to replace conventional scan signal generator to generate a probe bias signal and collect and analyze its voltage and current signals, which does not need to collect voltage and current signals synchronously and increases the S/N ratio of data by multiple collections, and further changes the collection rate flexibly to overcome the interference of fluctuation of plasma.

Description

technical field [0001] The invention belongs to the field of plasma science and technology, and relates to a Langmuir probe plasma diagnosis method based on a virtual instrument, which is used for diagnosing parameters such as space potential, charge density, and electron temperature of plasma. Background technique [0002] The conventional method of diagnosing plasma parameters with a Langmuir probe is: using a computer or a trigger to trigger a signal generator to generate a sawtooth sweep voltage to bias the probe, and to adjust the probe voltage and The current signal is collected at equal time intervals, and then the collected current and voltage data are analyzed and calculated to obtain various parameters of the plasma. The disadvantages of this method are: 1. It is necessary to use a data acquisition card with synchronous acquisition function to ensure accurate synchronization of current and voltage signal acquisition, and its price is usually several times that of a...

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Problems solved by technology

The disadvantages of this method are: 1. It is necessary to use a data acquisition card with synchronous acquisition function to ensure the accurate synchronization of current and voltage signal acquisition, and its price is usually several times that of a data acquisition card that does not require strict synchronization

2. Due to the continuous change of current and voltage during the diagnosis process, only one current data can be collected at the same moment for each bias voltage, so the signal-to-noise ratio is low

3. Only stable plasma can be diagnosed, because the plasma changes and disturbances that occur during the sawtooth wave scanning cycle will cause distortion of the current and voltage characteristic curves, and the correct plasma parameters cannot be obtained

[0003] The main reason for the above problems is that the bias of the probe and the acquisition of current and voltage signals lack the necessary flexibility.

The sawtooth wave scanning bias signal of the probe is customized by the circuit hardware of the signal generator, and the bias voltage increases linearly with time during diagnosis, and cannot be changed and adjusted according to the fluctuations in the plasma and the needs of data acquisition

On the other hand, the inherent form of the sawtooth wave scan signal limits the flexibility of current and voltage signal acquisition, that is, it can only be collected at equal time intervals within the sawtooth wave scan cycle, and cannot be used for current signals under a certain bias. multiple repetitions

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