Scrape-off layer power flux measurements in the Tore Supra tokamak

A new method to measure power flux in strongly magnetized plasmas is described, while the flaws inherent in standard Langmuir probe techniques are demonstrated. Instead of small cylindrical pins which overestimate the ion current density by several 100%, a concave probe has been developed which is i...

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Bibliographic Details
Published in:Journal of nuclear materials 2013-07, Vol.438, p.S184-S188
Main Authors: Gunn, J.P., Dejarnac, R., Devynck, P., Fedorczak, N., Fuchs, V., Gil, C., Kočan, M., Komm, M., Kubič, M., Lunt, T., Monier-Garbet, P., Pascal, J.-Y., Saint-Laurent, F.
Format: Article
Language:English
Subjects:
Analyzers
Collapse
Flux
Magnetic fields
Nuclear power generation
Sheaths
Tokamak devices
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Summary:A new method to measure power flux in strongly magnetized plasmas is described, while the flaws inherent in standard Langmuir probe techniques are demonstrated. Instead of small cylindrical pins which overestimate the ion current density by several 100%, a concave probe has been developed which is immune to sheath expansion, and which inherently provides accurate measurements. A retarding field analyzer directly measures the ion component of the power flux by means of an integral method that eliminates the need to calculate the heat transmission factor. Evidence shows that strong secondary electron emission from surfaces with non-oblique magnetic field incidence angles is ubiquitous in the scrape-off layer of the Tore Supra tokamak. This results in sheath collapse, causing the power flux to be dominated by the electrons. The radially integrated power flux measured by the probes agrees well with the power convected to the limiter.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2013.01.055