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Title: Overestimation of Mach number due to probe shadow

Abstract

Comparisons of the plasma ion flow speed measurements from Mach probes and laser induced fluorescence were performed in the Controlled Shear Decorrelation Experiment. We show the presence of the probe causes a low density geometric shadow downstream of the probe that affects the current density collected by the probe in collisional plasmas if the ion-neutral mean free path is shorter than the probe shadow length, L g = w 2 V drift/D , resulting in erroneous Mach numbers. We also present a simple correction term that provides the corrected Mach number from probe data when the sound speed, ion-neutral mean free path, and perpendicular diffusion coefficient of the plasma are known. The probe shadow effect must be taken into account whenever the ion-neutral mean free path is on the order of the probe shadow length in linear devices and the open-field line region of fusion devices.

Authors:
ORCiD logo [1]; ORCiD logo [1];  [2];  [3];  [3];  [1]
  1. Univ. of California, San Diego, CA (United States). Center for Energy Research
  2. Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics
  3. West Virginia Univ., Morgantown, WV (United States). Dept. of Physics
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1467827
Alternate Identifier(s):
OSTI ID: 1274825
Grant/Contract Number:  
FG02-07ER54912
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 7; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; diffusion; plasma flows; velocity measurement; laser induced fluorescence; Doppler effect; Zeeman effect; plasma diagnostics; plasma density; magnetic fields; Mach numbers

Citation Formats

Gosselin, J. J., Thakur, S. C., Sears, S. H., McKee, J. S., Scime, E. E., and Tynan, G. R.. Overestimation of Mach number due to probe shadow. United States: N. p., 2016. Web. doi:10.1063/1.4954820.
Gosselin, J. J., Thakur, S. C., Sears, S. H., McKee, J. S., Scime, E. E., & Tynan, G. R.. Overestimation of Mach number due to probe shadow. United States. doi:10.1063/1.4954820.
Gosselin, J. J., Thakur, S. C., Sears, S. H., McKee, J. S., Scime, E. E., and Tynan, G. R.. Thu . "Overestimation of Mach number due to probe shadow". United States. doi:10.1063/1.4954820. https://www.osti.gov/servlets/purl/1467827.
@article{osti_1467827,
title = {Overestimation of Mach number due to probe shadow},
author = {Gosselin, J. J. and Thakur, S. C. and Sears, S. H. and McKee, J. S. and Scime, E. E. and Tynan, G. R.},
abstractNote = {Comparisons of the plasma ion flow speed measurements from Mach probes and laser induced fluorescence were performed in the Controlled Shear Decorrelation Experiment. We show the presence of the probe causes a low density geometric shadow downstream of the probe that affects the current density collected by the probe in collisional plasmas if the ion-neutral mean free path is shorter than the probe shadow length, Lg = w2 Vdrift/D⊥, resulting in erroneous Mach numbers. We also present a simple correction term that provides the corrected Mach number from probe data when the sound speed, ion-neutral mean free path, and perpendicular diffusion coefficient of the plasma are known. The probe shadow effect must be taken into account whenever the ion-neutral mean free path is on the order of the probe shadow length in linear devices and the open-field line region of fusion devices.},
doi = {10.1063/1.4954820},
journal = {Physics of Plasmas},
number = 7,
volume = 23,
place = {United States},
year = {Thu Jul 28 00:00:00 EDT 2016},
month = {Thu Jul 28 00:00:00 EDT 2016}
}

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Cited by: 2 works
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