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# Topic: Langmuir probe

 PLASMA APPLICATIONS LABORATORY We have sophisticated Langmuir probes, B-dot probes, microwave interferometers, an energy analyzing mass spectrometer and an ICCD camera with imaging spectrometer. The probe system can give us information on the spatially resolved electron and ion density, the plasma potential, floating potential, and electron temperature, while the microwave interferometer gives us information on the spatially averaged electron concentration and acts as a check for the Langmuir probe. This is generally not obvious from the Langmuir probe IV curve by itself. www.utdallas.edu /~overzet/PALab.html   (1249 words)

 Langmuir probe -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-10) The beginning of Langmuir probe theory is the I-V (A distinguishing quality) characteristic of the (Click link for more info and facts about Debye sheath) Debye sheath, that is, the current density flowing to a surface in a plasma as a function of the voltage drop across the sheath. A point of contention is whether it is better to use proud probes, where the angle between the magnetic field and the surface at least 15°, or flush-mounted probes, which are imbedded in the plasma-facing components and generally have an angle of 1 to 5 °. Knowledge of the field angle is necessary with proud probes to determine the fluxes to the wall, whereas it is necessary with flush-mounted probes to determine the density. www.absoluteastronomy.com /encyclopedia/l/la/langmuir_probe.htm   (3012 words)

 Langmuir probe - Wikipedia, the free encyclopedia A Langmuir probe is a device named after Nobel Prize winning physicist Irving Langmuir which is used to determine the electron temperature, electron density, and plasma potential. The beginning of Langmuir probe theory is the I-V characteristic of the Debye sheath, that is, the current density flowing to a surface in a plasma as a function of the voltage drop across the sheath. Although this is the expression usually given in theoretical discussions of Langmuir probes, the derivation is not rigorous and the experimental basis is weak. en.wikipedia.org /wiki/Langmuir_probe   (3222 words)

 Irving Langmuir - Wikipedia, the free encyclopedia While at G.E., from 1909-1950, Langmuir advanced several basic fields of physics and chemistry, invented the gas filled incandescent lamp, the hydrogen welding technique, and was awarded the 1932 Nobel Prize for Chemistry for his work in surface chemistry. Irving Langmuir was born in Brooklyn, New York on January 31, 1881. In 1938, Langmuir refuted the claim of entomologist Charles H. Townsend that the deer botfly flew at speeds in excess of 800 miles per hour. en.wikipedia.org /wiki/Irving_Langmuir   (804 words)

 Proposal for a Langmuir probe instrument for ROCSAT-3   (Site not responding. Last check: 2007-10-10) Langmuir probes are commonly used for measuring plasma parameters in laboratory and space plasmas. Langmuir probes were flown on the Swedish scientific satellites Viking, Freja and Astrid-2, and on the NASA/ESA mission Cassini. The probe is biased to a constant voltage (0...+10V relative to the satellite), preset either from the ground or by the unit onboard. www.plasma.kth.se /~ivchenko/prop0809.html   (962 words)

 Temperature Probe   (Site not responding. Last check: 2007-10-10) A robotic probe is a device that uses onboard instruments to gather and relay a variety of telemetry to controllers from remote, hazardous or otherwise difficult to reach locations. Probes may return their data over radio links or be physically tethered to controllers or another device, or to collect and return physical samples. The word probe is also used to descibe medical instruments, such as a laparoscope, a device that assists with surgery on the human body by allowing doctors to see and manipulate organs without making large incisions. www.blownspeakers.com /pages3/87/temperature-probe.html   (1613 words)

 Medical Diagnostics -- Recommendations and Resources   (Site not responding. Last check: 2007-10-10) Langmuir probe measurements are based on the estimation of current versus voltage characteristics of a circuit consisting of two metallic electrodes that are both immersed in the plasma under study. This means that the electric field caused by the difference between the potential of the probe and the plasma potential at the place where the probe is located is limited to the volume inside the probe sheath boundary. The general theoretical description of a Langmuir probe measurement requires the simultaneous solution of the Poisson equation, the collision-free Boltzmann equation, and the continuity equation with regard to the boundary condition at the probe surface and requiring that, at large distances from the probe, the solution approaches that expected in an undisturbed plasma. www.becomingapediatrician.com /health/93/medical-diagnostics.html   (462 words)

 strele   (Site not responding. Last check: 2007-10-10) Probe diagnostics in Q-machines face the problem that the probe collector is with the time contaminated by the ionic material (K in the IQ). The probe wire, a Ta-wire of 0.12 mm diam., is first inserted into one of the bores of the vertical tube and then drawn through the horizontal tube. Starting with a heavily contaminated probe that was left for several hours in the K-plasma with no heating, the first calculated value of Te = 0.41 eV, which is about two times the expected value, and Phi_pl = +0.80 V which is also too high. www.ipp.mpg.de /BB/workshop/strele.html   (626 words)

 Langmuir Probe Response In considering the effects of the background magnetic field, the key parameter is the ratio of the probe diameter to the gyroradius of an electron with the average thermal energy. For a homogeneous (over the scale of the probe and sheath), collisionless, Maxwellian plasma for which the effects of secondary emission are negligible, the expected response for the current I from a spherical probe as a function of voltage V relative to the plasma is given by: To determine this, it is necessary to know how the current of photoelectrons which escape the probe to infinity varies as a function of the voltage of the probe with respect to the plasma. delta.physics.uiowa.edu /~cak/papers/swpfit/node2.html   (682 words)

 ECR Plasma Diagnostics with Langmuir Probe   (Site not responding. Last check: 2007-10-10) Langmuir probes were successfully used in case of other plasmas, e.g. However, the precise positioning of the probe in the plasma chamber (HV platform, strong magnetic field, RF waves) is a difficult task. Also the theory of probes is complicated: the ECR plasma is a special one because the confining magnetic field is inhomogeneous, beside hot electrons it contains cold ions with different charge states and it is heated with high frequency EM waves. www.atomki.hu /ar99/d/d06/d06.html   (418 words)

 DFS 2004 Atomic physics abstract   (Site not responding. Last check: 2007-10-10) Langmuir probe measurement is one of the easiest applicable in-situ plasma diagnostic tools: A biased electrode simply picks up the charged particles moving onto it. Since its emergence in 1922, the Langmuir probe has diversified into many different shapes, and many different circuits are attached to them to lead the current unhindered away from the electrode. The probes can be moved into the same position with an external drive in a sequence, so that the only difference between subsequent signals is size or type of the collecting probe. www.nbi.dk /dfs/abs2004/af09p.html   (302 words)

 LeSSETI Information Website - Langmuir Probe   (Site not responding. Last check: 2007-10-10) Helen Laird and James Carpenter are working on the Langmuir probe as their 3rd year project. LINDA (Langmuir Interferometer and Density instrument for Astrid-2) used two identical probes, where each probe assembly consisted of the spherical probe itself made from titanium connected to a stub made of a thin conducting brass tube. At present, we are also investigating manufacturers of Langmuir probes and organisations who may be interested in analysing the data received. www.le.ac.uk /physics/SSETI/lang.html   (235 words)

 [No title] Ion trajectories are deflected toward the negatively biased probe and the bracketed factor is proportional to the increase in the resulting current density at the probe surface. Large probe radius with high capture probability In this section we calculate the charge exchange current to a probe that is sufficiently large to capture all of the charge exchange ions created inside the sheath. Sudit and Woods,10 in their careful comparison of probe analysis techniques, find discrepancies of a factor of 10 between ion densities determined from the ion part of the probe characteristics using OML theory and the densities from microwaves or the electron part of the probe characteristic. debye.colorado.edu /Probe_PoP.doc   (3937 words)

 Langmuir probe - Encyclopedia, History, Geography and Biography The charge density of the ions depends on the charge state Z, but quasineutrality allows one to write it simply in terms of the electron density as $en_e$. If we refer to the probe area including these effects as $A_\left\{eff\right\}$ (which may be a function of the bias voltage) and make the assumptions Langmuir probe, I-V characteristic of the Debye sheath, Ion saturation current density, Exponential electron current, Floating potential, Electron saturation current, Effects of the bulk plasma, Pre-sheath, Resistivity, Sheath expansion, Magnetized plasmas, Electrode configurations, Single probe, Double probe, Triple probe, Special arrangements and Practical considerations. www.arikah.com /encyclopedia/Langmuir_probe   (3262 words)

 World Intellectual Property Organization   (Site not responding. Last check: 2007-10-10) The use of single-ended Langmuir probe diagnostic methods for monitoring plasma processing environments is also known, along with methods for operating the probes as generally needed for plasma characterization. Moreover, the use of any single-ended probe is intrusive, particularly when the probe is forward biased at or near the plasma potential, resulting in a condition that necessarily disrupts the electrical structure of the plasma body during processing. Another construct of the probe data is in an NxM matrix where M is the number of probes and N is the number of temporal data values for each of the M probes. www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=05/17937.050224&ELEMENT_SET=DECL   (8154 words)

 [No title] A Langmuir probe is nothing more than a wire that is inserted into a plasma to measure its potential. The probe voltage is swept and the resulting current vs. voltage characteristic, will yield the electron and ion currents to the probe. Experiments in a solenoidal field are described in "Behavior of a Single Langmuir Probe in a Magnetic Field" (J.T. Pytlinski, H.J. Donnert and I. Alexeff, December 1978). www.amasci.com /amateur/blljar4.txt   (2035 words)

 Experiments on Fluid Properties of Plasmas   (Site not responding. Last check: 2007-10-10) Measure the current-voltage characteristics of a Langmuir probe in a steady-state discharge plasma. This probe consists of two identical Langmuir probes which are biased with respect to each other rather than to ground. An emissive probe is a Langmuir probe whose electrode consists of a heated wire capable of emitting as many electrons as it collects from the background plasma. www.physics.ucla.edu /plasma-exp/180E-W97/Fluids.html   (462 words)

 Table of Contents   (Site not responding. Last check: 2007-10-10) Irving Langmuir and H. Mott-Smith, Jr., reported the use of anelectrostatic probe in a laboratory plasma in 1924. This cylindrical probe isnow referred to as the Langmuir Probe (LP), and is extensively used tocharacterize the Earth's ionosphere. The curve begins in the ionsaturation region where the probe potential is sufficiently negative to repelall the thermal electrons and allow access to the ions. utd500.utdallas.edu /www_root/documents/Spaceinstruments.htm   (1431 words)

 DavidPace.com - Example of Langmuir Probe Analysis   (Site not responding. Last check: 2007-10-10) 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. In this example I begin with the data acquired by measuring the current drawn by a Langmuir probe as the bias applied to that probe is varied. While the concept of Langmuir probe usage, digitization of the received data, and even the engineering of the diagnostic are all worthy of discussion, the following has a focus on analysis in order to limit the size of this entry. www.davidpace.com /physics/graduate-school/langmuir-analysis.htm   (552 words)

 Laser and Plasma Applications Group - Trinity College Dublin : Current Projects : Development of Langmuir Probes Langmuir probes, have been used to measure the supersonic flow and the electron temperature in laser plasma plume. The aim of this project is use a combination of experiment and theory to thoroughly investigate the behaviour of a Langmuir probe in the supersonic flow produced by the laser ablation of a solid target. The I-V characteristic of the Langmuir probe will be calculated using a particle-in-cell model to describe plasma flow around the probe and the net current to the probe. www.tcd.ie /Physics/Laser-Plasma/LANGMUIR.PHP   (235 words)

 VASIMR Plasma Diagnostics Reciprocating Langmuir and Mach probes are the primary plasma diagnostics. The Langmuir probe measures electron density and temperature profiles while the Mach probe measures flow profiles. LANL is producing an RF-compensated Langmuir probe for insertion in the helicon discharge based on past experience with this type of work [Light, 1995]. www.uh.edu /research/spg/uhdiagnostics.html   (2144 words)

 Global hybrid simulations - introduction   (Site not responding. Last check: 2007-10-10) The Segmented Langmuir Probe (SLP) instrument of DEMETER comprises two electrodes: a cylindrical electrode and a spherical electrode whose surface is divided in several sectors electrically isolated from each other. The SLP is a new concept developed in an attempt to alleviate the difficulties associated with the use of a single electrode Langmuir probe. The main expected advantage is the reduction of the Langmuir probe electrode photoemission and disentangle magnetic field and plasma drift effects. terezka.ufa.cas.cz /pt/me/plasma/slp/slp.html   (131 words)

 Title page for ETD etd-100499-214413   (Site not responding. Last check: 2007-10-10) Langmuir Probe Measurements in the Plume of a Pulsed Plasma Thruster In this thesis, a triple Langmuir probe apparatus was designed and used to obtain electron temperature and density measurements in the plume of a PPT. Triple probes have the ability to instantaneously measure electron temperature and density, and have the benefit of being relatively simple to use, compared to other methods used to measure these same properties. www.wpi.edu /Pubs/ETD/Available/etd-100499-214413   (673 words)

 Plasma Waves / Lightning on Venus - Section 4 First, each Langmuir probe sweep lasted 0.5 s, but only one sweep was transmitted to the Earth every 8 seconds. We have used the Langmuir probe anomaly data (J. Grebowsky, personal communication, 1992) for the first three nightside periapsis seasons as a basis for this determination. We have chosen this length of interval since the Langmuir probe anomaly timing is given to the nearest second. www-ssc.igpp.ucla.edu /~strange/JATP_paper/JATP_4.html   (1060 words)

 Langmuir Probe Measurement Techniques and Data Analysis for LAPPS - Storming Media Abstract: Langmuir probe diagnostics have been applied to an inductively coupled test discharge as part of the diagnostics development effort for the Large Area Plasma Processing System at NRL. The method of calculating electron energy from the EEDF derived from the probe second derivative is compared with more traditional methods of fitting the probe characteristics to a known function assuming a Maxwellian distribution. It is shown that under some circumstances the local plasma around the probe can be perturbed such that fewer electrons are sourced to the probe than theory would predict for a non- perturbing diagnostic, resulting in a higher average electron energy. www.stormingmedia.us /40/4071/A407193.html   (136 words)

 Plasma density analysis using current sweeps in Freja electric field instrument   (Site not responding. Last check: 2007-10-10) This technique was developed by Langmuir in 1924, and is often referred to as the method of Langmuir probes. Electric probes are simple devices, consisting of a small electrode inserted into the plasma and attached to a power supply capable of biasing the electrode to various potentials with respect to the plasma. In satellite-borne double-probe electric field instruments the potential of a probe in a plasma is determined by a balance of the currents flowing to the probe. spaceweb.oulu.fi /~petri/fp97abs.html   (379 words)

 IngentaConnect Short-circuited double Langmuir probe as a model of a conducting ... IngentaConnect Short-circuited double Langmuir probe as a model of a conducting... Short-circuited double Langmuir probe as a model of a conducting wafer under plasma processing The electromagnetic interaction is considered between a conducting wafer and a gas-discharge plasma under both dc and ac conditions, with emphasis on the collection of discharge current by the wafer. www.ingentaconnect.com /content/maik/rumi/2005/00000034/00000001/00000002   (152 words)

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