Ion temperature measurements in the TCA tokamak by collective Thomson scattering
The feasibility of using collective Thomson scattering for ion temperature measurements in tokamak plasmas was demonstrated in 1988 at CRPP, using a high-power pulsed D(2)O laser at 385 micron and a heterodyne receiver system. The technique provides very good spatial and temporal resolution and is particularly suited to the determination of spatial profiles. Recent improvements in the noise-equivalent power of the Schottky barrier diode mixers resulted in a typical precision of +/-12% for a single shot measurement at densities above 1.0 E20/m3. Even at densities of standard TCA discharges (5 x 1.0 E19/m3) the uncertainty is better than +/-25%. For the interpretation of the measured spectra and the evaluation of T(i), the local value of the electron temperature is an important parameter. Therefore, T(e) was measured simultaneously by incoherent Thomson scattering at 0.694 micron during a series of shots. The density was obtained from a far-infrared interferometer. An independent measurement of T(i) on TCA can be obtained from a neutral particle analyser. The results from the two methods show good agreement. The collective Thomson scattering system on TCA has recently been modified to allow measurements of the spatial ion temperature profile in the central part of the plasma. The results are reviewed and future improvements of the method described. The potential of this method to determine the alpha-particle density and slow-down distribution are also discussed.
Bibliographic Reference: Article: Proceedings of the Workshop on Diagnostics for Contemporary Fusion Experiments, Varenna (1991) pp. 283-303
Record Number: 199210479 / Last updated on: 1994-12-02
Original language: en
Available languages: en