Alcator C-Mod Weekly Highlights September 11, 2006 FY2006 weeks of research operations: JOULE target: 14 weeks Completed: 16.7 weeks Physics ------- Paul Bonoli, Andrea Schmidt, and Bob Harvey have analyzed the lower hybrid current in C-Mod Shot 1060728014 using the CQL3D - GENRAY codes. The EQDSK equilibrium reconstruction from a time during the ohmic discharge was used. It was foud that 1.06 MA of current could be driven using 800 kW of LH power. This result is consistent with the experimental observation that 1 MA of current was sustained with LHCD for about 160 ms, as evidenced by a zero or reversed surface loop voltage. Operations ---------- Preparations are being made for a minor alternator inspection to be made later this month. One access cover to the alternator housing has been removed and the helium has been allowed to be replaced with room air. Work continued on inspection and refurbishment of various alternator systems. CAMAC modules are being replaced with CPCI data acquisition equipment in both diagnostic and engineering systems. Work recently began to upgrade the bus instrumentation CAMAC with the CPCI equipment. The resolution, data rates, and storage capability will all be enhanced. A vent line for SF6 is being installed in the power room. Very low levels of SF6 in the air can affect CO2 laser based diagnostics. The SF6 is used to insulate ICRF coaxial lines. Lower Hybrid System ------------------- Repairs to the lower hybrid high voltage supply continued. Thermal stress analysis of the new 24-window couplers is focusing on two options. One option places the alumina windows in the middle of the 1.5" thick flange while a second option uses a thinner primary flange but adds a secondary flange with the windows placed between. We are currently working to verify the models. Changes to the couplers are required to eliminate cracking in the edge windows that required us to use only 22 of the 24 waveguide channels on each of the currently installed couplers. Cryopump -------- We continued to operate the prototype pump in the vacuum test chamber. A meeting was held last week to discuss prototype results and plan for fabrication of the C-Mod pump. Some minor changes were proposed to improve cooling of the liquid nitrogen shield. Changes to the liquid helium exhaust line will be made to allow easier escape of the helium past the level detector. ICRF Systems ------------ Work continued on the FFT system last week with improvements to protection circuitry that added a new time-out feature. Design changes are being considered for the new 4-strap antenna that may reduce rf sheath production that is likely responsible for enhanced boron erosion in the outer divertor. Work is also progressing on the incorporation of an open ended waveguide into the antenna so that density profiles local to the antenna can be measured by reflectometry. Diagnostics ----------- Work is progressing on feedback control systems for the two color interferometer and the polarimeter prototype. These systems will maintain optical alignment of these diagnostics over both long (thermal) and short (vibrational) time scales. Visitors and Travel ------------------- John Rice and Alex Ince-Cushman attended the EU-US TTF meeting in Marseille Sept. 4-7 and presented their work on 'Inter-Machine Comparison of Intrinsic Toroidal Rotation' in a talk and poster. Martin Greenwald and Joshua Stillerman attended the FY`06 US-KSTAR Collaboration Workshop via video conference. Joshua Stillerman presented a talk on the use of the MDSplus data system at KSTAR, and future collaboration possibilities. Greg Hanson and John Wilgen, both from Oak Ridge, visited last week to discuss the addition of a reflectometer to the new 4-strap antenna now being designed. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly