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Title: Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

Abstract

Here we present a method to calculate the ion saturation current, I sat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.

Authors:
ORCiD logo [1];  [1]
  1. Univ. of California, San Diego, CA (United States). Center for Energy Research
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1374808
Alternate Identifier(s):
OSTI ID: 1373967
Grant/Contract Number:  
FC02-04ER54698; FG02-07ER54917
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 88; Journal Issue: 3; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Electric measurements; Plasma temperature; Probe plasma diagnostics; ECR heating; Tokamaks

Citation Formats

Boedo, J. A., and Rudakov, D. L. Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics. United States: N. p., 2017. Web. doi:10.1063/1.4978453.
Boedo, J. A., & Rudakov, D. L. Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics. United States. doi:10.1063/1.4978453.
Boedo, J. A., and Rudakov, D. L. Mon . "Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics". United States. doi:10.1063/1.4978453. https://www.osti.gov/servlets/purl/1374808.
@article{osti_1374808,
title = {Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics},
author = {Boedo, J. A. and Rudakov, D. L.},
abstractNote = {Here we present a method to calculate the ion saturation current, Isat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of Isat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating Te. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.},
doi = {10.1063/1.4978453},
journal = {Review of Scientific Instruments},
number = 3,
volume = 88,
place = {United States},
year = {Mon Mar 20 00:00:00 EDT 2017},
month = {Mon Mar 20 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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