Alcator C-Mod Weekly Highlights April 28, 2001 All C-Mod invessel work was completed on Friday evening, 4/27. Following inspections, documentation, completion of the invessel checklist, and a final wipe down of the chamber, one of the two access port flanges was installed. On Saturday, 4/28, the final access port was sealed and Alcator C-Mod was pumped down. The cryostat is being purged with nitrogen gas in preparation for liquid nitrogen cooldown of the magnets. Approximately the next three weeks will be devoted to baking the vacuum vessel, ECDC wall conditioning, vacuum conditioning of the rf antennas, and bringing power systems and diagnostics back online. Work this week was focused on completing installation of the J-Port antenna and preparing the vessel for pumpdown. Progress was also made on DNB related diagnostics, the Lower Hybrid MIE Project, and preparations for operation of the ICRF transmitters. Physics ------- Stewart Zweben was on-site for the entire week, analyzing data from the turbulence imaging diagnostic. This diagnostic has successfully acquired many ~1 microsecond snapshots of the edge emission. He also discussed future plans for this diagnostic and our plans for comparing the experimental results with turbulence modelling. ICRF Systems ------------ Installation of the J-Port antenna was completed late this week. Careful measurements have been made of the positions of major antenna components. The B-dot probes located in the antenna boron nitride protection tiles are installed and calibrated. A picture of the antenna can be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/INVESSEL/2001/Close_Up_Survey/P0001531.JPG Note the new boron nitride septum at the middle of the antenna added to break up field line connection paths along the face of the antenna. New boron nitride tiles have also been added to completely cover moly surfaces that showed arc damage during the last run period. The FMIT#3 and FMIT#4 ICRF transmitters have been re-tuned for operation at 78 MHz. At least 2 MW of power has been delivered to the dummy load from each transmitter. PPPL has supplied us with spreadsheet models for more easily tuning these transmitters, as well as more up-to-date drawings of the cavities. The testing of all phase balance boards and their associated arc phase modules has been completed. Lower Hybrid MIE Project ------------------------ The Lower Hybrid launcher design is continuing to proceed smoothly at PPPL. Procurements have been placed for copper plating of the prototype coupler and for fabrication of larger corner radius ceramic windows. An RFQ is being generated for the large oval shaped bellows which allows radial coupler motion with respect to the plasma. Brazing of additional coupler prototypes for testing and optimization is scheduled for the upcoming week. Mechanical drawings have been generated and released for fabrication of the transmitter protection system racks. Requisitions for electrical, mechanical, and PC board components are being issued. The transmitter key-inlock configuration drawing has been generated and is undergoing the review process. A dialog with the key manufacturer, the high voltage power supply vendor, and MIT is ongoing to ensure a seamless key-interlock system. Tests of the SFOLs and the active feedback loop continue. A clock synchronization problem is being resolved. DNB --- The DNB duct is fully installed with the new pressure gauges, and windows for the H-alpha monitors have been attached. The external H-alpha monitors are tested and ready for installation as needed. A DNB cryopump compressor failed, but has been replaced, tested, and is ready for operation. The beamline is again under vacuum. Inner Divertor -------------- All inconel 718 bolts needed to secure the inner divertor tiles are now in house, and undergoing the QA process. Vendors indicate that all girdle plates will be in house by the end of next month. We are proceeding with fabrication of a very accurate inner wall mockup that will be used to test inner divertor components before installation. Power Systems ------------- Work continues updating power system and alternator documentation to reflect upgrades to the commutation banks and hi-yard instrumentation we have made over the last few weeks. Diagnostics ----------- At PPPL, Larry Guttadora has started checkout and adjustment of power supply modules for the two higher frequency mm-wave channels that are to be added to the C-Mod reflectometer for density and fluctuation measurements farther up the edge pedestal. The installation of the new CXRS shutters was completed this week. A picture of the shutters invessel can be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/INVESSEL/2001/Close_Up_Survey/P0001558.JPG Travel and Visits ----------------- Miklos Porkolab attended the Memorial Service in Princeton on April 23 in honor of Tom Stix, who passed away last week. He was the pioneer in wave propagation and RF heating in magnetically confined plasmas. His passing is a great loss to the whole fusion community. We had several visitors from PPPL at MIT this week. Chris Brunkhorst visited from Monday to Wednesday and was a great help in completing the final tune up of the FMIT#3 and FMIT#4 transmitters. Martha Redi was here on 4/24, and discussed various aspects of the new ITB discharges and modeling of C-Mod transport with Catherine Fiore, Tunde Fulop, John Rice, Paul Bonoli, and Steve Wolfe. Stewart Zweben also visited as noted above. Yves Peysson (Cadarache) visited this week to discuss a collaboration to develop an x-ray camera for C-Mod. He also gave a seminar on recent lower hybrid current drive results on Tore Supra. Amanda Hubbard attended the International Workshop on Physics of Internal Transport Barriers, Edge Pedestal, and Steady State Operation in Tokamaks, in Garching, Germany. She gave talks on C-mod pedestal and ITB results, and also made plans for a comparison experiment with ASDEX-Upgrade on Type II elms and EDA modes.