Development And Application Of Langmuir Probe Diagnostic System Based On LabVIEW

Recently, technology of low-temperature plasma has been more widely used in industry. In all of these, people have concerned a lot about the technology of plasma discharged by microwave. So it becomes more important to know how to control the parameters of plasma in practical application. One of the essential prerequisites to control the plasma parameters is to obtain them accurately. Among all kinds of diagnostic tools used to measure plasma, Langmuir probe is one of the most important method because of its simple structure, convenient operating method and wide applicable scope. Also Langmuir probe can get more information than most of the other method. In the past, we used Langmuir probe to measure plasma parameters by manual operation in our laboratory. It needs a lot of time and is hard to control. Also its precision can't need our requirement, and its anti-interference ability is not so satisfactory. So we need to design a kind of Langmuir probe system to improve our laboratory's experiment efficiency, and we hope the system is high-efficiency, accurate and good to shield interference.In this article, I will introduce the automatic Langmuir probe system we designed to diagnose the plasma discharged by microwave. This system is composed by the Langmuir probe, hardware and software. The core component of the system's hardware is an acquisition card, and it includes the part to output scanning voltage and the part to collect the signal of voltage and current. In the software part, we choose LabVIEW as the application programming software in this program. This part includes the control program for the data acquisition part and the data analysis program. It will give details of operating principle of hardware and programming thread of software in this article.The automatic Langmuir probe system introduced in this article has been used in the laboratory's experiment work. It can be used to measure the large area surface-wave plasma discharged by microwave, and achieved satisfactory results. It will introduce each part of the experiment's operation and the result that each part can obtain. To analysis the influence on the plasma parameters when changing the discharge conditions, we will change the experiment conditions to measure multiple sets of experimental data, and calculate the plasma parameters from these data. After that, compare the results of the calculation to analysis them and give conclusion.