The power flow to the DIII-D divertor targets is routinely measured using infrared (IR) thermography. An IR television camera sensitive to radiation in the 8–12-μm range views the divertor region using a set of germanium optics. Digital signal processing is used to extract the desired surface temperature profiles from the analog data (≂12 Mbytes) stored on videotape. Inversion of these data using a simple matrix formulation of the inverse heat conduction problem then yields the incident heat flux as a function of space and time. Results from a DIII-D discharge are included.

Recent Alcator C-Mod experimental campaigns have focused upon the study of the Advanced Tokamak regimes, which includes characterization of the RF heating, the formation and dynamics of internal harriers, H-mode edge pedestal, and divertor and scrape-off physics. The ICRF system has been recently upgraded with the improved performance of the 4-strap antenna. Total ICRF power in excess of5 MW has been launched successfully into the plasma during this campaign. Due to the compact nature of C-Mod, the power feeds for the antenna are vacuum strip lines. Their orientation, to the tokamak B-field, is governed by maintaining E<15 kV/cm in locations where the RF E-field is parallel to tokamak B-field. Other modifications included improved protection tile grounding and installation of protective shields for Faraday screen ceramic isolators. The antennas also mskc use of BN protection tiles to eliminate high Z impurities from the antennas. The present empirical power limit results from arcing in a region of the antenna strap where G I 5 kV/cm and parallel to B and injections from the metallic fasteners used to attach the BN tiles to the antenna. In preparation for 2 MA plasma operation, the inner divertor is being modified to a more open design and the lower inner wall is being reinforced. For future 5-10 sec experiments, successful 3 seconds discharges were performed at the end of the last campaign. These experiments were designed to test the magnet power supplies, plasma and supply controls, divertor heat load handling, and density control. The experiments were successful in that the systems performed flawlessly and no uncontrolled density source was observed.

The DIII-D ECH system includes three launcher assemblies each of which can accommodate the rf beams from two gyrotrons. The launchers use four different designs for the mirrors which focus and direct the beams into the tokamak. The designs use molybdenum brazed to graphite, thin Glidcop or variable thichess Glidcop. A fourth design with laminated Glidcop/stainless steel construction has been operated, but no thermal data are available. All the mirrors operate without active cooling. This paper presents preliminw analyses and measurements of the thermal performance of the three designs for which data have been obtained.