Design and development of langmuir probe sensor for. Langmuirs technique involves the measurement of electron and ion currents to a small metal electrode the langmuir probe as different voltages are applied to it. This experimental arrangement produced a stable plasma discharge that was free. It is intended to serve as a helpful reminder of the technical details in analyzing the data from a swept langmuir probe and is not a complete theoretical effort. Figure 3 presents a first look at the actual iv trace.
Put one of the fastest industrial metal cutting processes right in your home garage or shop. T03003t03003 march 2016 with 97 reads how we measure reads. Langmuir probe diagnostics in the impf device and comparison with simulations. An introduction to langmuir probe diagnostics of plasmas. This is a simple example of langmuir probe analysis and the issues related to it. For low pressure plasmas it is important to record entire single or double langmuir probe characteristics. Langmuir probe was and operated to determine currentmade voltage characteristics of plasma, its electron density, ion density, temperature and other properties of the plasma. Langmuir probe diagnostic for local parameter measurement. The system has a base pressure of 1026 mbar while langmuir probe experiments were conducted at pressures of 10 2 mbar in a nitrogen atmosphere. Appendix a mirror langmuir probe circuit schematics.
The code uses a four parameters fitting method to deduce plasma properties including the ion and electron saturation currents, plasma potential, plasma electron temperature, the electron energy distribution function eedf. Langmuirs probe purpose the purpose of this lab is to measure some basic properties of plasmas. Langmuir spatial probe double langmuir spatial probe. Double langmuir probe with an electronic circuit for giving the bias voltage is developed for determining the currentvoltage characteristics and from these characteristics other parameters has to calculate. Euratomukaea fusion association, culham science centre, abingdon. Theoretical study of spherical langmuir probe in maxwellian. This can be done approximately by drawing a straight line through isat and extrapolating it to the electron region. The theory and application of the langmuir probe for measurements in the ionosphere is described in this manual for the information of other scientists who may wish to compare their measuring techniques with this one. It is not possible to discuss in detail the many variations of the probes based on the. Langmuir probe diagnostic for local parameter measurement in. Langmuir probe electronics upgrade on the tokamak a configuration.
The plasma is produced by electron impact ionization of argon atoms by electrons that are thermionically emitted and accelerated. The probe is immersed into the plasma and polarized to the potential v p by anexternal circuit. Determining accurately the end point of a plasmaetching process is extremely important for integrated circuit fabrication, as overetching can result in the removal of part of the film, or substrate lying under the film to be etched, andor in extra undercut of the film. While the algorithm to estimate the temperature and number density of thermal electrons from langmuir probe measurements is relatively simple, a number of factors, such as the position of probe installation, probe surface contamination. Jul 20, 2011 today i began fabricating the langmuir probe. Langmuir probe rf source matching circuit stainless steel glass electrodes tube fig. Langmuir probe data analysis code file exchange matlab. A langmuir probe system for high power rfdriven negative ion.
Probe 1 probe 2 schematic of potential distribution between the probes of a double. Introduction when you think of electrical conductors, you probably think. The langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. The langmuir probe is used to establish plasma process repeatability and uniformity. The langmuir probe is the key plasma diagnostic used by scientists interested in plasma characterization to measure the internal parameters of the bulk of the plasma. Langmuir probe diagnostics of dc cylindrical magnetron. A computer code for plasma langmuir probe analysis is presented here. Mass spectrometers for vacuum, gas, plasma and surface science owners area. A langmuir probe is a device used to determine the electron temperature, electron density, and electric potential of a plasma. Comsol and jmag software were employed to characterize the electron density and identifying the set up effect in. I believe that the main components of the instrument have been successfully identified. Small amounts of dust particles are used as a novel. Plasma potential and langmuir probe measurements in the. Kinema software is made, which yields good overall agreement.
I am using a tungsten light bulb filament as the probe tip. The design includes the probe and boom development, as well as the onboard electronics. Langmuir probe method tpm 8 consisting of three metallic tips exposed to the same plasma conditions as shown in the figure 3. I built a second cabinet so that i do not have to modify the one that came with my crossfire. Thc installation step by step langmuir systems forum. Building the langmuir probe prometheus fusion perfection. Probe construction a compensated langmuir probe is used to obtain the iv characteristic, 2. Using a laptop computer renders the main component of the system portable. Schematic diagram of the cylindrical magnetron apparatus. A compensated probe insures the suppression of the rf interference. Triple langmuir probe a langmuir probe triple provides an advantage over single and double probes, allowing simultaneous measurement of plasma parameters without the need to sweep a voltage bias, which are a limiting factor in the environment of pulsed plasma. Now you can create projects with some of the worlds strongest and most durable materials. How to measure probe current using single langmuir probe. So i have seen several great threads about z axis and torch height control, but no step by step, or wiring diagrams.
Apr 22, 2017 the langmuir probe is the key plasma diagnostic used by scientists interested in plasma characterization to measure the internal parameters of the bulk of the plasma. Electrostatic langmuir probe measurements in rf driven he. Figure 3 shows a schematic of the probe tip used in this study. The ability to measure local plasma parameter using langmuir probe. Endpoint detection of polymer etching using langmuir probes abstract. A detailed description of the langmuir probe electronics upgrade for tcv tokamak. Electrostatic langmuir probe measurements in rf driven he, n2, bcl3, and bcl3n2 plasmas by bogdan amaru pathak cbn 2008 submitted to the graduate degree program in electrical engineering and the graduate faculty of the university of kansas in partial fulfillment of the requirements for the degree of master of science in electrical engineering. This document describes the langmuir probe spacecraft potential lpsp investigation of the plasma environment in the vicinity of the proseds delta ii spacecraft. Langmuir probe measurements in the plume of a pulsed plasma.
The scheme of the spherical langmuir probe construction. Atomic energy commission aec initiated the program for magnetic. A single langmuir probe was used to measure the floating potential and electron temperature in the nearfield plume of the nasa457mv2. However, it is an intrusive, not remote, technique. Determining accurately the end point of a plasmaetching process is extremely important for integrated circuit fabrication, as overetching can result in the removal of part of the film, or substrate lying under the film to be etched, andor in extra. It is useful to note that about 500 technical papers describing langmuir probe applications were published from 2000 to 2007 alone, in leading scientific journals. I believe i have a diagram that possibly works, but would love some confirmation.
Of all the ways to measure a plasma, the langmuir probe is probably the simplest, since it consists of sticking a wire into the plasma and measuring the current to it at various applied voltages. Plasma sensors plasma probe diagnostics, langmuir probe. According to the model, adsorption and desorption are reversible processes. At its simplest, a langmuir probe is just a wire stuck into the plasma. This investigation will employ a group of three 3 langmuir probe assemblies, lpas, mounted on the delta ii. Never seen i sat v f ideal probe curve distribution functions. The schematic set up of langmuir probe in plasma system malaysian journal of science 38 special issue 3.
Calibration of langmuir probes against microwaves and plasma. To probe circuit choke capacitor 5nf compensation winding. Langmuir systems no rnr motion controller found mach3 youtube. Computerized langmuir probe measurements in a capacitively.
Langmuir probe fabrication procedures, and materials. This is the potential that an insulator would reach. The detail about the langmuir probe, its circuit and other information can be. Langmuir systems no rnr motion controller found mach3. Im currently in the process of installing a thc, but im stuck at how to wire it. Langmuir probe is one of the most frequently installed scienti. A system of automated computerized langmuir probe measurements is used in order to determine the plasma parameters in a plasma reactor constructed for cleaning of metallic artifacts by rf discharge. The langmuir probe is the hiden esp mk2 system consisting of a probe, a voltage sweep circuit and software espsoft hal iv to collect and analyze the data. Spherical langmuir probes have been installed on satellites and sounding rockets to observe the general characteristics of thermal plasma in the ionosphere for more than five decades. It is known that probe geometry cylindrical, spherical, planar. Because of its simplicity and convenience, the langmuir probe is one of the most frequently installed scienti. Constructional view and experimental results are given in this paper.
The requirements on the langmuir probe and its controlanalysis system are anything but trivial. Carnegie department of physics and electronic engineering, university of waikato, hamilton, new zealand 2001 received 27 december 2002. Specific lines are then connected to the probe driver circuit shown in fig. Langmuir probe diagnostics the schematic pictures of the cylindrical and spherical probe are in figure 2 and 3. The langmuir probe technique involves applying a voltage to a metallic conductor immersed in plasma and observing the collected current. A computerized langmuir probe system research commons. Measurement of the electron energy distribution function. Langmuir probes have been installed on satellites and sounding rockets to observe the general characteristics of thermal plasma in the ionosphere for more than. The probe is cylindrical and sized using orbitalmotionlimited theory.
The simplest collecting langmuir probe is a metallic electrode as those of fig. Impedans ltd langmuir probe best commercial langmuir. Langmuir probe is used to measure critical plasma parameter helps minimize development time and optimize plasma process for desire application. Langmuir probe is one of the most powerful diagnostic tool which is used to measure the low temp plasma parameter. Measurement of the electron energy distribution function by langmuir probe in an iter like hydrogen negative ion source 1b. In its conventional structure, langmuir probe is a thin. The langmuir probe is the fastest and most reliable langmuir probe in the world time resolution 12. Time resolved analysis algorithm for ramped langmuir probe. The plasma cutting process is capable of cutting nearly any metal including steel, stainless steel, aluminum, titanium, copper, and brass. Langmuir probe positive ions are collected on the tip of langmuir probe whichgives a change in voltage across the resistor is known as ion saturation current i. D rp collisionfree movement of ions and electrons in thick sheath orbital motion limit, oml langmuir theory. Langmuir probe measurements in the plume of a pulsed plasma thruster by lawrence thomas byrne a thesis submitted to the faculty of the worcester polytechnic institute in partial fulfillment of the requirements for the degree of master of science in mechanical engineering november 2002 approved.
Many students of experimental plasma physics are given the task of constructing and implementing a langmuir probe in a plasma. A langmuir probe system for high power rfdriven negative. Langmuir probe as a plasma diagnostic device has been widely used to characterize laboratory plasmas and is accepted worldwide for the measurement of plasma parameters like electron density, electron temperature, floating potential, plasma potential, and electron. It works by inserting one or more electrodes into a plasma, with a constant or timevarying electric potential between the various electrodes or between them and the surrounding vessel. Espion is an advanced langmuir probe from hiden analytical, suitable for plasma diagnostics for use in characterisation monitoring. It is however too early to declare this design as operative. The langmuir probe provides plasma parameter measurement in dc, rf, microwave, continuous and pulsed plasma. In this video i demo my schematic upgrade for the 5v isolation and estop.
Full simple instructions are given in the pdf file. The floating potential, v f, occurs where i probe 0, which appears to give v f. Our system uses the most up to date probe theory available, drawing on orbital motion limited and as the pressure regimes change, moving on to allen boyd. In this region bias voltage is kept positive and is varied up to plasma potential. The orcad suite 10 of electronic design and simulation software was used for this.
The freundlich isotherm has two parameters while langmuir s equations has only one. Construction and operation of a mirror langmuir probe diagnostic. A computerized langmuir probe system semantic scholar. Calibration of langmuir probes against microwaves and. A compact and portable pcbased gundestruplangmuir probe. Ideal currentvoltage characteristic with langmuir probe. The langmuir spatial probe is an essential plasma process diagnostic to understand the correlation between plasma inputs and the plasma state. Langmuir probe data was a thermionically enhanced dc discharge plasma.
From the probe characteristic it is possible to determine the plasma parameters. Each langmuir probe circuit board requires one analog input and output. Thus a reliable langmuir probe system complements the optical spectroscopy recently added to the source diagnostics 4, 5 and is a requirement for spatially resolved h. Iv characteristic of the probe as the applied bias voltage v b, is swept from a negative to a positive potential. The scheme of the cylindrical langmuir probe construction. The rest is just ceramic tubing to hold it in place. This is probe current plotted as a function of probe bias. Labview software for analyzing langmuir probe characteristics in magnetized plasma article in journal of instrumentation 1103. Langmuir probe with electronic circuit is given in fig. These mods improve the stability of the motion controller and software for the langmuir systems crossfire. The langmuir probe used in plasma etching applications.
Langmuir probe measurements in the plume of a pulsed. Langmuir probe, iv characteristic floating potentialno net current to the probe. V sp the probe with respect to the local space plasma potential v sp. Some examples of langmuir probe iv characteristics obtained in laboratory plasmas are presented and analyzed.
Design and development of langmuir probe sensor for electron. Abstractthe double and triple langmuir probe diagnostic systems with their necessary driving circuits are developed successfully for. Understanding langmuir probe currentvoltage characteristics. The current of each species to the langmuir probe as a function of velocity is. Labview software for analyzing langmuir probe characteristics. More testing and development of new and better software is required. National tokamak fusion program, po box 3329 islamabad. Plasma sensors is a group of highly skilled professionals in the field of plasma physics, plasma probe diagnostics and scientific instrumentation design. Langmuir probe lp is the most widely and frequently employed diagnostic technique in plasma all over the world due to its cost affective simple structure and well developed theory for analysis in a variety of plasmas extending from glow discharge to thermonuclear fusion plasmas. It helps in the understanding plasma changes and the impact on surface treatment. Plasma diagnosis has done by using langmuir probe and software modeling. Langmuir probe diagnostics continues to be one of the most popular instruments for physicists and engineers working with plasmas.
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