Alcator C-Mod Weekly Highlights July, 17, 2006 FY2006 weeks of research operations: JOULE target: 14 weeks Completed: 15.0 weeks Operations ---------- Last week was a scheduled maintenance week at Alcator C-Mod. No plasma operation was planned. The principal activities carried out during the maintenance period, in addition to from routine preventive maintenance, were calibration of the Lower Hybrid Drive and Monitor legs at increased power levels, and repair of the driver stage on FMIT #1 (D-port ICRF antenna). Research operations are scheduled to resume this week. Run Summaries -------------- Last week, Amanda Hubbard participated remotely in two part-day experiments on MAST, as part of PEP-16 "MAST/NSTX/C-MOD small ELM regime comparison". These runs followed up on prior experiments on C-Mod and NSTX. Several discharges with small ELMs were produced and excellent camera images were obtained. However, limitations of run time and beam power prevented the planned extension to the C-Mod shape. The experiments will be continued later in the MAST campaign when the second NBI system is available. ICRF System ------------ The driver cavity on the FMIT#1 Transmitter was found to have sustained damage during operation, and was replaced by a spare. Some damaged finger stock was also replaced. The driver tube was found to be undamaged. Following completion of these repairs, the driver stage was re-tuned to its nominal frequency of 80.5 MHz, and the transmitter has been returned to service. Lower Hybrid System -------------------- Conditioning of klystrons to higher voltage (45kV) was completed. Klystrons #2-12 have now been calibrated (both Drive and Monitor legs) in preparation for high power experiments this week. The circulator on klystron #1 exhibited arcing, and has been replaced with an older component. We anticipate completing calibration of the klystron #1 legs prior to operation, but if necessary we can operate with this tube bypassed, with no significant impact on the proposed experiments. Long-pulse Diagnostic Neutral Beam System ------------------------------------------ The DNB anode flange water leak repair continued this week. Both the in-service (anode2) flange and the spare (anode1) flange have had their water cooled copper center inserts removed in preparation for furnace brazing of new inserts. The machine shop has completed machining new copper inserts for both flanges. Travel and Visitors ------------------- Sergei Krasheninnikov (USCD) visited with Jim Terry, Bruce Lipschultz and Brian Labombard on Tuesday and Wednesday. Topics of discussion included the physics of a wall-fueling instability that may trigger MARFE instabilities in the plasma edge and the physics of ELMs and blobs. The possibilities for diagnosing the onset of a wall-fueled MARFE event in C-Mod with a combination of IR sensors and D-alpha views were also discussed. John Rice was at CRPP of the EPFL in Lausanne, Switzerland July 10-11 to serve on the thesis committee of Andrea Scarabosio and to discuss future collaborations between C-Mod and TCV. It was agreed to utilize a fast SSEP change on TCV to create a perturbation to the rotation velocity and monitor the momentum transport in experiments this fall. Joe Snipes was at JET last week from 10 - 14 July where he intended to participate in experiments exciting stable TAEs in JET with the new JET TAE antennas. However, JET operations were suspended due to vacuum system problems and are not expected to resume during Joe's visit. LHCD current profile control experiments, in which Joe was also invited to participate, have also been postponed. Joe was able to work with his MIT postdoc, Alex Klein, to get the TAE antennas commissioned and ready for operation when JET experiments resume. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly