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The infrared imaging video bolometer (IRVB) in JT-60U includes a single graphite-coated gold foil with an effective area of 9 × 7 cm 2 and a thickness of 2.5 μ m . The thermal images of the foil resulting from the plasma radiation are provided by an IR camera. The calibration technique of the IRVB gives confidence in the absolute levels of the measured values of the plasma radiation. The in situ calibration is carried out in order to obtain local foil properties such as the thermal diffusivity κ and the product of the thermal conductivity k and the thickness t f of the foil. These quantities are necessary for solving the two-dimensional heat diffusion equation of the foil which is used in the experiments. These parameters are determined by comparing the measured temperature profiles (for k t f ) and their decays (for κ ) with the corresponding results of a finite element model using the measured HeNe laser power profile as a known radiation power source. The infrared camera (Indigo/Omega) is calibrated by...

In order to measure the ion temperature of the JT‐60 tokamak, we have developed a Rutherford scattering system using a helium atom beam. A positive‐ion beam generated by an ion source which has a capability of beam energy 200 keV and drain current 3.5 A is converted to a helium atom beam by collision with cold helium gas. The He atom beam, equivalent to 0.6 A, reaches the center of the vacuum chamber of the JT‐60 tokamak. The scattering angle is 7.0°. Scattered helium atoms are analyzed by an E∥B‐type neutral particle energy analyzer with a gas stripping cell. This scattering system has been applied to investigate additionally heated plasmas by the method of neutral beam injection (NBI), ion cyclotron wave (ICRH), lower hybrid wave (LHRH), and combined heating of NBI+LHRH or ICRH in a parameter range of Bt=4.0 to 4.5 T, Ip=1.0 to 3.2 MA, and ne≲1×1020 m−3. The ion temperatures obtained by the system are consistent with those measured by Doppler broadenings of Ti xxi and Ti xxii resonance lines. To invest...

Radiation losses from the main plasma of the JAERI Tokamak‐60 (JT‐60) were measured by a 15‐channel bolometer array and those from divertor chambers in the ion and electron drift sides were each measured by two bolometers. The bolometric detector consisting of three layers (5‐μm‐thick gold absorber, 7‐μm‐thick polyimide foil, and 0.1‐μm‐thick gold resistor grid) was developed for this measurement. In typical diverted discharges with NB heating, the ratios of power radiated from the main and divertor chambers to the absorbed power were approximately 10% and 20%, respectively. Intense poloidal asymmetries of radiated power localized near the X point outside the torus were observed in diverted discharges. The profiles of the radiated power were reconstructed by an Abel inversion with an asymmetric term. On the other hand, a poloidally asymmetric radiation band localized near the inner wall, ‘‘marfe,’’ was observed for dense plasmas in limiter discharges with neutral beam heating.