• Electrical & Electronic Materials
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• v.9 no.5
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• pp.506-511
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• 1996

This paper deals with an inexpensive, simple and fast Langmuir probe sweeping circuit and its application. This sweeper completes a probe trace in a 1 ms order. Futhermore, the circuit drives a maximum probe voltage of $\pm$30V and has a maximum probe current capability of a few amperes. The plasma parameters are successfully determined using the fast Langmuir probe method.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.576-576
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• 2013

Recently, diagnostics of plasma becomes more important due to requirement of precise control of plasma processing based on measurement of plasma characteristics. The Langmuir probe has been used for the diagnostics but it has an inevitable uncertainty and error sources such as incorrect tip length and RF noise. Instead of the Langmuir probe, various diagnostic methods have been developed and researched. The cutoff probe is promising one for plasma density using microwaves and resonance phenomenon at the plasma frequency. The cutoff probe has various advantages as follows; (i) it is simple and robust, (ii) it uses few assumptions, and (iii) it is free from deposition by reactive gas. However, the cutoff probe also has uncertainty and error sources such as gap between tips, tip length, direction of tip plane, and RF noise. In this study, the uncertainty and error sources in manufacturing both probes and in diagnostics process were analyzed via comparative experiment at various discharge conditions. Furthermore, to reveal the user dependence of both probes, three well trained Ph. D students made the Langmuir probe and the cutoff probe, respectively, and it were analyzed. Thought this study, it is established that reliability and validity of the Langmuir probe and the cutoff probe related with not only the intrinsic characteristics of probes but also probe user.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1111-1114
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• 2003

In this paper, electrical characteristics of inductively coupled plasma in an electrodeless fluorescent lamp were investigated using a Langmuir probe with a variation of argon gas pressure. The RF output was applied in the range of $5{\sim}50W$ at 13.56MHz. The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of $-100V{\sim}+100V$. When the pressure of argon gas was increased, electric current was decreased. There was a significant electric current increase from l0W to 30W. Also, when the RF power was increased, electron density was increase. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.391-395
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• 1999

In this paper, we have obtained the Electron Energy Distribution Function(EEDF) in plasma by using two differentiators and investigated the EEDFs by sawtooth and triangle waveform voltages with the working pressures and the positions of single probe. It is found that as the working pressure is decreased, the EEDFs approach to theMaxwellian distribution independent of the waveforms of probe voltage. On the otherhand, as the position of probe is moved from the center of the plasma to its edge, the EEDF of sawtooth waveform probe voltage approaches to the Maxwellian distribution, but the EEDF of triangle waveform probe voltage deviates from the Maxwellian distribution.

• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.145-148
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• 1989

Plasma diagnostics using Langmuir Probe is of wide application because of its simplicity in measurement of electron temperatures and densities. Current methods using simple circuit and analog meters, however, have troubles when they are applied to time-varying or thermal plasmas. To overcome these problems and expand the area of applicability, we have designed fast electronic voltage sweeping circuit in which we can detect digital data. Diagnostics using our digital Langmuir Probe is performed in various kinds of plasmas and the results are shown. Our method can be applied to measuring electron temperature and density of high temperature or time-varying plasmas. And we expect further knowledge of each state of plasma.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1609-1611
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• 1994

In ECR and helicon reactors for plasma processing, a high density plasma is generated in a source region which is connected to a diffusion region where the processing takes place. Large density and potential gradients can develop at the orifice of the source which drive ion currents into the diffusion region. The average ion velocity may become the order of the sound velocity. Measurements of the ion saturation current to a Langmuir probe are used as a standard method of determining the plasma density in laboratory discharges. However, the analysis becomes difficult in a steaming plasma. We have used the HAMLET plasma simulator to simulate the ion flow to a large langmuir probe in an ECR plasma. The collection surface was aligned with the Held upstream, normal to the field, and downstream. ion trajectories through the electric and magnetic fields were calculated including ion-neutral collisions. We examines the ratio of ion current density to plasma density as a function of magnetic field and pressure.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.167-180
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• 2015

Herein, we discuss the in situ measurement of the electron temperature in the ionosphere/plasmasphere by means of DC Langmuir probes. Major instruments which have been reported are a conventional DC Langmuir probe, whose probe voltage is swept; a pulsed probe, which uses pulsed bias voltage; a rectification probe, which uses sinusoidal signal; and a resonance cone probe, which uses radio wave propagation. The content reviews past observations made with the instruments above. We also discuss technical factors that should be taken into account for reliable measurement, such as problems related to the contamination of electrodes and the satellite surface. Finally, we discuss research topics to be studied in the near future.

• Journal of Astronomy and Space Sciences
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• v.18 no.3
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• pp.249-256
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• 2001

KARI(Ko.ea Aerospace Research Institute) has measured the ionospheric electron temperature and density over the Korean Peninsular with the Langmuir and Electron Probe(LEP) onboard the Korean Sounding Rocket-II(KSR-II) In 1998. The purpose of LEP is to measure the electron density and temperature profile in the ionosphere. LEP consists of the Langmuir probe(LP) and the Electron temperature Probe(ETP) which are widely used for the measurement of the ionospheric plazma environment . We discuss the development of the Langmuir and Electron Probe which will be onboard the KSR-III and some test results in a simulated space plasma environment with the plasma chamber at the ISAS in Japan. These measurements could contribute to the basic study of ionospheric environment which also can be compared with other reference models such as IRI and PIM.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1719-1721
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• 2003

In this paper, electrical characteristics of inductively coupled plasma in an electrodeless fluorescent lamp were investigated using a Langmuir probe with a variation of Ar gas pressure. The RF output was applied in the range of 5-50W at 13.56MHz. The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of -100V ${\sim}$ +100V. When the pressure of Ar gas was increased, electric current was decreased. There was a significant electric current increase when the applied RF power was increased from 10 W to 30 W. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.189-194
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• 2008

Measurements with a Langmuir probe, which are the most often used procedures of plasma diagnostics, can disturb plasma flows and change its characteristics quite a little because the probe should be inserted into thermal flowing plasmas. In this study, we calculated the characteristics of thermal plasmas with and without the probe into an atmospheric argon free-burning arc numerically, and investigated aerodynamic and thermal disturbances with temperature and axial velocity distributions. For the modelling of thermal plasmas, we have made two governing equations, which are on the thermal-flow and electromagnetic fields, coupled together with a commercial CFD package and user-coded subroutines. It was found that thermal disturbances happened to both sides of the probe, before and behind, seriously. Due to the aerodynamic disturbance, we could find that there were the stagnation point in front of the probe and the wake behind it. Therefore, aerodynamic and thermal disturbances caused by the probe insertion should be considered to increase the reliability of the probe diagnostics.