Ion temperature measurements in a tokamak by collective Thomson scattering

Collective Thomson scattering, using a high-power pulsed D2O laser at 385 μm and a heterodyne receiver system, has provided local ion temperature (Ti) measurements of the plasma in the tokamak chauffage Alfvén (TCA) tokamak. Recent improvements in the noise-equivalent power of the Schottky barrier d...

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Bibliographic Details
Published in:Journal of applied physics 1991-02, Vol.69 (4), p.1993-1998
Main Authors: SIEGRIST, M. R, BEHN, R, YUAN, D. C, DICKEN, D, DUVAL, B. P, HACKMANN, J, JOYE, B, LISTER, J, NIESWAND, C, POCHELON, A, SOUMAGNE, G
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102 - Fusion Energy- Plasma Research- Diagnostics
CLOSED PLASMA DEVICES
COMPUTER CODES
ELECTROMAGNETIC RADIATION
ELECTRON TEMPERATURE
Exact sciences and technology
HEAVY WATER
HYDROGEN COMPOUNDS
INELASTIC SCATTERING
INTERFEROMETERS
ION TEMPERATURE
LASER RADIATION
MEASURING INSTRUMENTS
OXYGEN COMPOUNDS
Physics
Physics of gases, plasmas and electric discharges
Physics of plasmas and electric discharges
PLASMA DIAGNOSTICS
PULSES
RADIATIONS
SCATTERING
SCHOTTKY BARRIER DIODES
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
SIMULATION
TCA TOKAMAK
THERMONUCLEAR DEVICES
THOMSON SCATTERING
TOKAMAK DEVICES
WATER
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Summary:Collective Thomson scattering, using a high-power pulsed D2O laser at 385 μm and a heterodyne receiver system, has provided local ion temperature (Ti) measurements of the plasma in the tokamak chauffage Alfvén (TCA) tokamak. Recent improvements in the noise-equivalent power of the Schottky barrier diode mixers permitted us to achieve a typical precision of ±12% for a single shot measurement at densities above 1020 m−3. Even at densities of standard TCA discharges (5×1019 m−3) the uncertainty is better than ±25%. For the interpretation of the measured spectra and the evaluation of Ti the local value of the electron temperature (Te) is an important parameter. Therefore, Te was measured simultaneously by incoherent Thomson scattering at 0.694 μm during a series of shots. The density was obtained from a far-infrared interferometer. An independent measurement of Ti on TCA can be obtained from a neutral particle analyzer. Comparison of the results from the two methods showed good agreement. The precision of a Ti measurement depends strongly on the plasma density. Since an uncertainty of ±25% at standard densities may still not be regarded as satisfactory, further investigations using a numerical simulation code have been carried out to find ways of improvement.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.348772