Alcator C-Mod Weekly Highlights March 12, 2012 FY2012 weeks of research operations Target: 17 Completed: 5.6 Plasma Shots: 753 Operations ---------- Alcator C-Mod is presently up-to-air for planned maintenance and upgrades. The first manned entry into the C-Mod vessel occurred on Wednesday 3/7/2012. After a careful radiation survey, a visual survey was completed, and photographs were taken to document the status of in-vessel components. ICRF Systems ------------ An inspection of the ARRA-funded field aligned antenna confirmed that the bolt that connects one of the rf feedthrough center pins to the bellows mounted on the rf strip-line had come loose. The larger gap between the bellows and the center pin at this location, together with the less compliant #2 strip-line may explain why this connection came loose while the other three did not. All four connections will be modified during the current up-to-air to improve their reliability. We continued work needed to replace the FMIT#4 driver ignitron. Two more FFT control/overload assemblies have been fitted with their power supplies, fans, power service and hardware. Alan Binus visiting our vendor's site to witness acceptance tests of the first pair of ARRA-funded FFTs. Lower Hybrid Systems -------------------- A detailed visual inspection of the LH launcher revealed evidence of tracking in the waveguides extending back ~4 cm from the plasma edge. The waveguide windows (located ~15 cm from the plasma) were not affected by the tracking. A boron film is apparent on the front of the launcher. Tests of the klystron coolant outlet temperature were conducted with a thermocouple mounted directly at the outlet of the collector. The time response of the measurement was significantly improved over measurements made earlier with the thermocouple more downstream from the collector. This information will be used to better calibrate the real-time calculations made by the Transmitter Protection System. Diagnostics ----------- On Thursday, 8 March 2012, power tests of the Shoelace antenna system were run. The purpose of the tests was to examine the survivability of the antenna and its power connections under repeated high-power loading. The tests were run at a fixed frequency of 97 kHz, and made use of the new matching network. A peak power of almost 1900 W was reached, with a steady power of over 1600 W, corresponding to peak and steady antenna currents of 83.5 A and 75 A. These levels exceed the original design specifications. During the tests, there were no detectable component failures, and the antenna should be capable of full performance operation during the next run period. Remote Participation, Travel, and Visitors ------------------------------------------ The PSFC hosted a visit by Massachusetts Governor Deval Patrick who was accompanied by Jay Inslee, a U.S. Representative from Washington State. The two took a tour of the Alcator C-Mod facility and were briefed on the current budget challenges. Governor Patrick was particularly interested in the role of the PSFC in incubating high-tech economic development in the state, and Congressman Inslee has a longstanding interest in energy and environmental issues. Later that day, we were visited by Congressman Michael Capuano, who represents the district in which MIT is located. Congressman Capuano toured the facility and met with officers of the MIT technical employees union. Paul Geelen, a student from Einhoven University has started a 3 month visit to MIT. He will be using the 3D MSE simulation code that was used to model MAST to examine the performance of the C-Mod MSE system. Last week, Robert Granetz attended an ITPA MHD meeting and the US/Japan MHD workshop in Toki, Japan. The former concentrated mostly on disruption mitigation issues, which are particularly relevant for C-Mod, now that the US has been assigned responsibility for the disruption mitigation system on ITER. The latter meeting focused on 3D effects on MHD in tokamaks, RFP's, and stellerators (conference venue was at the LHD site). The work on impurity-generated n=1 snakes in C-Mod provided a timely example of helical core equilibria embedded in an axisymmetric configuration, which was one of the principal topics at this workshop. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly