Microcomputer-Based Langmuir Probe System

2016

The paper deals with the design of a new plasma diagnostic system consisting of a microcontroller based power supply for automatic control of the measurement using Langmuir probe, the communication interface of the power supply and the signal processing program. The utility of the designed plasma diagnostic system is presented through measured U-I curves and a method to measure the relaxation time of the plasma. The main motivation for the design of the automated plasma diagnostic system was given by our research in different methods of plasma nitriding of steels. During the nitriding process, it is important to get information about the plasma, which is the medium where the heat-treatment process is going on. The new diagnostic system is able to perform measurements during the nitriding process, thus we can analyze the plasma at different temperatures and gas mixtures. The obtained voltage-current curves are recorded and transmitted to the computer, where further signal processing ...

IEEE Transactions on Nuclear Science, 1996

A bs t ra c t Experimental fusion machines are devices which require many sensors to study plasma formation and evolution, information that basically relies on the time behavior of the signals produced by those probes. The complexity inherent in this kind of experiments requires a powerful treatment for a great variety of electric inputs, both at analog and digital stages. Here, a VXI module that incorporates a digital filter to analyze signals whose spectral contributions are limited to 500 KHz, is presented. Its main features are commented, showing and discussing the substantial improvements in the enhancement of noise rejection and digitation resolution. The filter characteristics only can be modified by fetching new coefficients through software, thus making this approach particularly attractive for experimental data analysis.

pupr.edu

The design of a computer application to perform plasma diagnostics at the Plasma Engineering Laboratory of the Polytechnic University of Puerto Rico is described. The application provides undergraduate and graduate students working at the Plasma Engineering Laboratory with a tool to speed up their experimental work. The application is able to control the data acquisition from various electrostatic probes, analyze the data acquired and perform the computations to obtain plasma parameters, store both raw data and parameters into a database, communicate with the control software used at the laboratory, and be accessed remotely. With this application, students and professors at the Plasma Engineering Laboratory are now able to perform experiments in a faster fashion and needing minimum training.

2002

Plasma is the fourth and least understood state of matter. A more complete understanding of this state of matter has numerous practical applications, including fusion energy, space travel, materials synthesis, and thin film deposition. As such, there is an obvious motivation to study this state. To do this, we have constructed a radio-frequency plasma device at Illinois Wesleyan University. I

1975

Significant progress has been made in the development of heavy ion beam probing techniques for making space and time resolved measurements in magnetically confined plasmas. The present analyzer/detector system has been calibrated for amplitude and phase measurements out to 100 KHz. A new amplifier system has been designed to extend the frequency range of the measurements and the concept of coupling the feedback signal to the bottom plate of the analyzer has been explored. In addition, a dual-gain analyzer for making current density measurements has been designed and constructed. An investigation of a Kelvin-Helmholtz instability has been performed, leading to an unambiguous identification of the mode. A parametric study shows that the instability characteristics are mainly determined by the internal electric fields of the plasma. A normal mode analysis for comparing theoretical and experimental results is in progress. Data handling capabilities have been improved with the installation of a dedicated minicomputer, further work on a buffer storage system, and the design of an interface system for direct access to the computer. The measurements required for determining current density distributions are now well understood and work is continuing on the extraction procedure. A plasma system with sufficient current to make the measurements practical is required. Finally, a small Tokamak facility is being designed for the continued development of beam probing techniques. •>

Review of Scientific Instruments, 1999

A ''test function'' sensitive to the electron distribution function is used to determine the plasma parameters by Langmuir probes. It was successfully applied to determine the parameters of the hot-electron group in a multipolar, magnetically confined Ar plasma, even when the ratio of bulk to hot-electron densities is greater than 50. The method can also be used to measure the positive-ion density from a probe potential slightly below the plasma potential, and to estimate the electron and negative-ion density and temperature in an Ar/SF 6 plasma. A characteristic plasma potential is also introduced and is correlated with the plasma parameters.

AIP Conference Proceedings, 2008

ABSTRACT We have constructed a high resolution I-V Probes including a high voltage and current probes to measure the current and the tension at the entry of the electrode excitation in reactor plasma RF argon. The I-V Probes is no intrusive, therefore it can be transposable in another surface treatment reactor, and it is what is required in the industrial applications. Because of capacitive aspect of the coupling and the presence of parasitic electrical elements in the chamber plasma reactor and the connection circuits, the measured signals are largely different from the signals at the RF electrode in contact with plasma. A phase angle error of 1° between i(t) and v(t) introduce a large error in the calculated parameters. The objective of this work is the calibration of the I-V Probes and the whole system of measurement, and the characterization of the parasitic elements of the reactor. The characterization of the I-V Probes required the realization of several reactive loads (capacitive) measured with a network analyzer HP8753ES. The signals Vi(t) and Vv(t), resulting from the I-V Probes and collected by a DPO (TDS4054 numerical oscilloscope of very high performance), are transferred towards the computer for a digital processing. The elimination of the offsets voltage present at the entries of the DPO and the smoothing by a powerful method of least squares, make it possible to increase precision.