Alcator C-Mod Weekly Highlights Sept 29, 1997 The maintenance period continued at Alcator C-Mod last week. The alternator repair, DNB, and RF upgrades are progressing. Analysis from the last run campaign continues. All coils have been installed on the alternator rotor and hi-potted to 6000 V. Jumpers were brazed into position, the connections were made to the bore copper, and the rotor was baked at 130C to set the epoxy impregnating the insulation. Both megaohm and hi-pot tests of the full rotor have been performed. In addition, a turn-to-turn AC test was performed to guarantee proper turn-to-turn insulation. These tests have insured the electrical integrity of coils, jumpers, and bore copper. Installation of the wedges has begun. A review of the design for the high voltage transmission line for the DNB was held and materials for the support structure have already begun to arrive. Construction will begin next week. Terminal connectors for the transmission line were completed. Relocation of the air, water, and process gas systems for the DNB continued. Work continues on assembly of the vacuum system controls and layout of the beamline in the cell. Calibration and testing on FMIT#1 and #2 interlock system has been completed. The final step was to check the optical links with the transmitters and the receivers in the power room. The position feedback was also bench tested. Work has been started on modifying the power feedback circuit to allow for faster modulation of the RF power for physics experiments. Randy Wilson from PPPL visited with the RF group last week. The coax for the new PPPL antenna, due to arrive in spring '98, was discussed. The resonant loops will be smaller than the present loops on D and E-port which are two wavelengths long. The new ones will be 1.5 wavelengths long and the decoupling will be a simple short stub. Also discussed were the power supply options and general layout for a proposed lower hybrid RF system. We also discussed D(He3) heating on C-Mod, and past discharges and data were made available for analysis. In particular, the calculation of the single pass absorption is of interest. First measurements of "radiated" power through escaping neutral particles were obtained during our last campaign. Preliminary analysis made by comparing two measurements, one by normal foil bolometers, the other by the newly installed AXUV diodes, which measures photon radiation only, indicates a significant source of radiation carried by neutrals immediately inside the separatrix. Effects are being quantified for different conditions such as L vs H mode discharges. Brian LaBombard visited the Tokamak de Varennes facility at the CCFM (Centre Canadien de Fusion Magnetique) and the INRS (Institut National de la Recherche Scientifique) in Quebec last week. At the CCFM, he gave a talk on C-Mod divertor transport physics and discussed C-Mod results with members of the T de V edge physics group. At the INRS, he participated in a thesis defense for a University of Quebec student (James Gunn) as an external examiner. Rejean Bovin was at North Carolina State University last week and gave a talk on the role of neutral particles in a fusion reactor. He also discussed possible collaborations with faculty and students there. Four members of the C-Mod team attended the H-mode Workshop in Kloster Seeon, Germany, Sept. 22-24. Presentations were made by Martin Greenwald on H-mode confinement, John Rice on toroidal rotation in RF heated H-modes, Amanda Hubbard on local variables affecting the H-mode threshold, and Thomas Pedersen on ELMs and Enhanced D-alpha H-mode. Following the workshop, Amanda Hubbard attended the first informal meeting of the working group on the ITER edge pedestal database, which was held at Garching. Part of this discussion, concerning the H-mode threshold, was held jointly with an ITER confinement and database meeting. John Rice is currently visiting Asdex-Upgrade as part of a collaboration concerning spectroscopy of high-Z materials. Miklos Porkolab travelled to Washington DC last week. He attended a meeting with Martha Krebs and other Lab Directors to discuss the White Paper the Lab Directors and UFA Chair Mike Mauel prepared for the post ITER EDA period. He also participated in a panel discussion with the Grunder Panel on the post-EDA proposal.