DIFFER
DIFFER Publication

Plasma temperature rise toward the plasma-facing surface

Author
Abstract

Detailed measurements of axial electron temperature, Te, profiles in the presheath region were carried out using a Langmuir probe and the line intensity ratio technique for both He I (728.1 nm/706.5 nm) and Be II (467.3 nm/313.1 nm). The results show that Te increases toward the material surface, which contradicts the standard picture that Te is constant along the magnetic field in the sheath-limited regime. While no target bias voltage, Vb, dependence is seen, the Te rise becomes more prominent with decreasing neutral pressure. Similarly, the ion temperature, Ti, evaluated from Doppler broadening of a He II line emission at 468.6 nm is found to increase toward the surface, but also does not depend on Vb. Possible mechanisms of the Te and Ti rise as well as validity of the line intensity ratio technique near the material surface are discussed.

Year of Publication
2015
Journal
Journal of Nuclear Materials
Volume
463
Issue
Aug
Number of Pages
440 - 444
DOI
10.1016/j.jnucmat.2014.10.083
PId
4a740a3caccb4311b0a5a70db1dd5342
Alternate Journal
J. Nucl. Mater.
Journal Article
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