Measurement of Radiation Power from the JIPP T-IIU Tokamak Plasma

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概要

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• Characteristics of a pyroelectric detector, a metal-film bolometer and a thermistor are investigated in order to attain high reliability of the bolometric measurement. The spurious signal which appears on a pyroelectric detector is efficiently eliminated by setting a mask close to the detector, which has a function of avoiding the direct incidence of photons on its electrode. This is verified with the consistency of integrated value of the signal. The detector is calibrated with a HeNe laser taking the reflection on the detector surface into account. No temporal change has been seen on the sensitivity of the detector calibrated by this method. We also developed a thin metal-film bolometer with high sensitivity (12.9Ω/mJ), high time response (3μs) and well defined thermal characteristics. The calibration of this detector was performed by supplying a bias current through its resistor. We constructed a bolometric system with high time response and high spatial resolution, which consisted of twelve pyroelectric detectors and a metal-film bolometer. The radiation power measured with the pyroelectric detector agrees with that measured with the calibrated metal-film bolometer within 10%. Spectroscopic and bolometric measurements with spatial and temporal resolution show that large radiation loss brings about the decrease in electron and ion temperatures and plasma energy. Carbon limiters have an effect to suppress the radiation power for ohmic plasma, but are insufficient for ICRF heated plasma. The main contribution to radiation power may be attributed to Fe impurity released from the ICRF antennae, the Faraday shield and vacuum vessel. By making carbonization of the wall and in-vessel components, the Fe impurity is suppressed to a low level (n_<Fe>/n_e∿0.04%) and the radiation power is reduced to P_<rad>/(P_<OH>+P_<rf>)∿20% and emissivity throughout the plasma region is reduced. This is clearly supported by the observation of Z_<eff> reduction (3.9⟶1.2).

• 核融合科学研究所の論文

著者

• Ogawa Isamu

  Research Center For Development Of Far Infrared Region Fukui University

• Ogawa Isamu

  Research Information Center Institute Of Plasma Physics Research Information Center Nagoya Universit

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