Study Of Labview-Based Langmuir Probe Plasma Diagnostic System

In order to effectively control the pollution of the Hall thruster and improve its performance, it is necessary to accurately measure its plume plasma parameters. Langmuir probe method is a common method for low-temperature plasma diagnosis in the study of electric propulsion. This method uses only simple devices and is easy to operate. Traditional Langmuir probe systems, however, are time-consuming and complex in operation, and have low testing precision. Therefore, the development of a fully automatic, high accuracy and anti-jamming Langmuir diagnostic system is very necessary.A new kind of electric propulsion plume diagnosis system based on the LabVIEW virtual instrument technology is proposed in this dissertation. Three subsystems were included in the plasma diagnostic system, the probe positioning subsystem, power supply and data acquisition subsystem and data processing subsystem. A probe positioning hardware platform was constructed in the probe positioning subsystem, which can rapidly and accurately move the Langmuir probe to its target position. The plasma data in the target position were acquired in the power supply and data acquisition subsystem and uploaded to the computer. The data processing method was studied in the dissertation. Physical parameters of the plasma were calculated based on the testing data. The results can be displayed in real time and be saved in the hard disk. Furthermore, this system joins S-G filter to smooth the I-V curve and to improve the anti-interference ability of the system.Compared with traditional diagnosis methods, the proposed plasma diagnosis system obviously increased the operating speed and precision of plasma plume diagnosis in the experiments. In addition, the plasma parameters calculated from the testing data coincide with the experimental results of Shanghai Institute of space propulsion. The langmuir probe plasma automatic diagnosis system is proved to be feasible and effective.