First results from EBW emission diagnostics on COMPASS

COMPASS tokamak shots at low magnetic field feature overdense plasmas during the extended current flat-top phase. The first harmonic of the electron cyclotron emission is completely cutoff for O and X modes and so the emission caused by electron Bernstein waves (EBWs) propagating obliquely with resp...

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Bibliographic Details
Published in:Review of scientific instruments 2012-10, Vol.83 (10), p.10E327-10E327
Main Authors: Zajac, J, Preinhaelter, J, Urban, J, Aftanas, M, Bílková, P, Böhm, P, Fuchs, V, Nanobashvili, S, Weinzettl, V, Zácek, F
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Antennas
BERNSTEIN MODE
CARBON MONOXIDE
COMPASS-D TOKAMAK
Conversion
CYCLOTRONS
Electron beam welding
ELECTRON TEMPERATURE
ELECTRONS
EMISSION
INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
MAGNETIC FIELDS
MODE CONVERSION
PLASMA
PLASMA WAVES
RADIOMETERS
REFLECTION
Shot
TEMPERATURE MEASUREMENT
THOMSON SCATTERING
Wave propagation
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Summary:COMPASS tokamak shots at low magnetic field feature overdense plasmas during the extended current flat-top phase. The first harmonic of the electron cyclotron emission is completely cutoff for O and X modes and so the emission caused by electron Bernstein waves (EBWs) propagating obliquely with respect to the magnetic field and undergoing so called EBW-X-O conversion process can be observed. We perform an angular scan of the EBW emission during a set of comparable shots in order to determine the optimum antenna direction. A weak dependence of the radiative temperature on the antenna angles indicates an influence of multiple reflections from the vessel wall. The low temperature at the mode conversion region is responsible for the collisional damping of EBW, which can explain several times lower measured radiative temperature than the electron temperature measured by the Thomson scattering system.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4733530