Alcator C-Mod Weekly Highlights September 7, 2004 FY 2004 weeks of operation planned: 18 weeks, completed: 18.9 weeks. The Preliminary Design Review for the proposed new 4-strap ICRF antenna was successfully completed last week. The PDR was the last task required to complete the FY2004 level 1 JOULE milestone SC6-1e, "Complete design of ICRF antenna for C-Mod." A detailed milestone completion report will be submitted shortly to the DoE OFES. We are currently up-to-air with the primary goal of installing the lower hybrid launcher. In addition, a large number of in-vessel activities are ongoing in support of ICRF and diagnostic systems. Maintenance and upgrades to diagnostic and power systems are also in progress. Physics ------- A Preliminary Design Review of the proposed 4-strap ICRF antenna was held at MIT on 8/31. The participants from ORNL were Rick Goulding, Dave Swain, Phil Ryan, and Dave Rasmussen. Peter Titus was at ORNL during the review and attended from there. Attending from PPPL were Bob Ellis, Gerd Schilling, and Randy Wilson. MIT participants included Steve Wukitch, Jim Irby, Rick Leccacorvi, David Terry, Yijun Lin, Peter Koert, Steve Wolfe, Alex Parisot, Paul Bonoli, Dave Gwinn, Earl Marmar, Amanda Hubbard, and Martin Greenwald. Rostom Dagazian represented DoE. The preliminary 4-strap ICRF antenna design was presented along with mechanical, RF, and thermal analysis. Peter Titus performed the mechanical analysis (associated with disruption forces), RF electrical analyzes were independently done by Peter Koert and Rick Goulding who made a presentation on his results, and the thermal analysis was done by Steve Wukitch with input from Riu Vieira and Dave Gwinn. David Swain presented a possible load tolerant external transmission line network. It was agreed that the overall design of the antenna is solid with no major problems or issues. It incorporates a boxed transmission line network, a solid antenna box similar to the D-Port and E-Port antennas, and folded currents straps with the same separation as the J-Port antenna. The disruption analysis indicates that the vessel currents result in the largest disruption force on the antenna structure, and an increase in the backplate thickness will be required. The RF analysis suggested modifications to the backplate feedthroughs should be made, and an increase to the clearance on the strap to ground bridge should be incorporated. Thermal analysis indicated the Faraday screen is the limiting component. A passively cooled Mo screen can be used for 5 s long, high power, high performance discharges. Operation without a screen poses no problems from a thermal standpoint. Side tiles require no active cooling for either Mo or BN tiles. For the external transmission line network, a load tolerant configuration is possible even in the presence of substantial coupling. Operations ---------- Outer divertor modules have been removed from the vessel so that preparations can be made for installation of the W-brush tiles. The vertical columns of moly tiles in the four locations specified for the new brush tiles will be removed and accurate dimensions of those tiles will be taken. This information will then be used to EDM the new brush tiles to the proper contours. Of the 20 EF1 cylindrical heat shield modules removed from the vessel, 15 have been reinstalled, and 5 are awaiting installation of molybdenum tile mounting screw keepers. Of the total of 20 ceiling modules removed from the vessel, 10 have been reinstalled, 5 are awaiting installation of molybdenum tile mounting screw keepers, and 5 are waiting machining of replacement tiles. Power Systems ------------- General maintenance work on the MIT Alternator continued last week. Control cabinets and the vapor extractor were inspected and refurbishment begun, and preparations for painting the flywheel end of the alternator were made. A low temperature bake-out of the Long Pulse DNB power transformer continued. Numerous tests of the transformer have indicated very good electrical properties of the primary and secondary windings. Conduit from the transformer into the C-Mod cell is being installed. Lower Hybrid System ------------------- The second and third PPPL couplers are being prepared for brazing. After a careful cleaning, they will be etched to fit the alumina windows, and then taken to our vendor for copper plating. We expect to be ready to braze the second coupler next week. We continued development of the new launcher rf probes. The effects of small adjustments to the probe position on directivity are being investigated. Comparisons of measurements to simulation results are being made. The patch panel that interfaces the launcher instrumentation to the data acquisition and protection electronics is being upgraded to handle more probe signals. Clean up of the WR-187 waveguides needed to bring the RF power from the klystrons to the launcher has been completed, and the guides are ready for installation in the C-Mod Cell. ICRF System ----------- EIMAC/CPI has informed us that they are having ongoing manufacturing problems, and the three new 2MW FPA tubes that we expected to be delivered 09/01/04 will be delayed. Work continues on the preparation for low power testing of the prototype fast ferrite tuner (FFT). A meeting was held last week to discuss the overall testing plan, the cell installation, and the development of the MIT FFT. Diagnostics ----------- We are currently working with two vendors to polish the polarimeter/interferometer retro-reflectors and to coat them. Six retro-reflectors will be installed in-vessel. They will be placed on the inner wall from the machine mid-plane up to a position high enough on the wall to provide a chord well outside the LCFS. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly