Alcator C-Mod Weekly Highlights November 6, 2006 FY2007 weeks of research operations: Tentative target: 14 weeks Completed: 0 weeks Physics ------- The C-Mod FY06 4'th quarter review was held on Wednesday, Nov 1, following the C-Mod poster session at the APS meeting. Earl Marmar met with Adam Rosenberg. Facility status and plans were presented and discussed. Viewgraphs may be found at http://www.psfc.mit.edu/research/alcator/pubs/Q_rev_110106/doe_110106_quarterly.pdf The quarterly report has also been posted to the web: http://www.psfc.mit.edu/cmod/sciprogram/..%5Cquarterly/FY2006_Q4_REPORT.PDF ITPA Joint Experiment MDC-6 on low-beta error field induced locked mode thresholds has been successfully completed. The purpose of MDC-6 was to perform an error field non-dimensional identity experiment to unambiguously determine the error field threshold size scaling. One outstanding issue from the 2004 C-Mod, DIII-D and JET identity experiments was the apparent difference in Bt scaling on C-Mod. JET data (and previously published DIII-D data) show that the error field threshold to induce a locked mode scales weakly with toroidal field (at fixed q and plasma density). Data from C-Mod in a JET-like shape showed an error threshold that scaled inversely with Bt between 4.1T and 6.2T. To clarify this issue, experiments on C-Mod were extended to 7.8T. The result is that the 6.2T and 7.8T data are consistent with dimensionally scaled JET data and so are consistent with a weak Bt scaling of the applied error field. The 4.1T data seem to indicate a departure from a power law scaling behavior at lower field. These data were presented at the 2006 APS DPP meeting and a journal paper on the results is planned. There do remain issues of discrepancies in the identity matched error field thresholds between DIII-D and JET/C-Mod (C-Mod agrees reasonably with JET), as well as issues of understanding of the Bt scaling of the error threshold in C-Mod. However, the experimental data specified for the proposed Joint Experiment are complete and unambiguous. Operations ---------- The re-installation of inner wall tile modules was completed last week. Some tiles on these modules had cracks and chipped edges after many years of use. These have been replaced with TZM molybdenum alloy rather than the original pure molybdenum. Removal of old studs that would interfere with the cryopump installation continued in-vessel. Preparations are being made to install the 3/8" studs that will secure the cryopump shim plates. Machining of the new bolometer box has begun. Support component drawings for the Surface Science Station have been submitted to the shop for machining. Components for the new Edge CXRS system have been machined. The new B-Port flange has been machined and is now being checked. Modifications to the F-Port flange have been completed and the flange is ready for welding. All standard tungsten tile modules for the lower outer divertor have been received, and we have begun preparing them for installation. Drawings needed for special edge tiles that require one more machining operation are being checked. Sixteen new PC workstations have been upgraded to run the new PLC control program. All primary engineering systems will be running the new software during the next run campaign and will have much enhanced logging capability, particularly in our ability to log information to MDSPlus. An updated operations schedule has been posted at http://www.psfc.mit.edu/research/alcator/facility/Operations/operation_schedule.pdf with 14 weeks of research operation tentatively planned for FY2007. Lower Hybrid System ------------------- Last Wednesday the lower hybrid high voltage power supply was brought back into full operation. All modules passed an extensive set of tests before being re-installed into the supply. Successful tests of the high voltage transformer were also conducted prior to re-commissioning the supply. Long Pulse Diagnostic Neutral Beam ---------------------------------- Modifications to the stand for the 7 degree toroidal rotation are complete and the DNB is ready to be re-installed. The high voltage transformer for the beam has been refurbished and is also ready for re-installation. Travel and Visits ----------------- Most C-Mod scientists, including students, were participating in the APS Division of Plasma Physics meeting last week. A link to the invited talks, orals, and posters can be found at: http://www.psfc.mit.edu/research/alcator/pubs/APS/APS2006/philadelphia2006index.htm Juergen Alex, an engineer representing the vendor for the LH HVPS, visited last week to participate in the re-commissioning of the supply. While at APS, Amanda Hubbard participated in a meeting of the U.S. Burning Plasma Organization Council. Amanda is the Vise-Chair of the Council. Jerry Hughes attended the ITPA Pedestal Topical Group meeting from 23--25 October in Chengdu, China, a primary goal of which was the evaluation and prioritizing of ITPA-generated ITER issue cards. While there, he presented recent C-Mod results on H-modes and ELMs, and reported on the contribution of C-Mod to an ITPA-sanctioned multi-machine joint experiment (PEP-7) with JET, ASDEX Upgrade and DIII-D. Robert Granetz attended the ITPA MHD meeting, held in China following the IAEA conference. The major topics pertained to the ITER issue cards. After much discussion, the MHD group has decided that two topics will be declared as important ITER issues to be seriously considered for the ITER design review, namely the addition of an active coil system for stabilizing resistive wall modes (possibly incorporated into the ELM suppression coils and/or locked mode coils), and a gas jet system for disruption mitigation. Paul Bonoli attended the ITPA Steady State Operations (SSO) Workshop in Chengdu, China from October 23-26, 2007. He gave two talks at this workshop. The first talk was entitled "Benchmarking of Lower Hybrid Current Drive Codes with Application to ITER-Relevant Regimes" and the second talk was titled "Lower Hybrid Current Drive Experiments on Alcator C-Mod: First Results and Analysis". At the meeting, time was devoted to summary discussions on benchmarking activities for the LHCD and ECCD actuators. Talks were also given on the use of these actuators in real time feedback control situations on TORE SUPRA and JET. Time was also devoted to integrated scenario modeling of the ITER Hybrid and Steady State Operating Modes. In these discussions, it was noted that results from the GLF23 transport model in the time dependent scenario studies imply it would be extremely difficult to achieve Q=5 in the Steady State Scenario 4, without having excessively high pedestal temperatures (> 6-8 keV). As a consequence, it was decided to proceed in the near term with time dependent scenario studies in which the transport (profiles of Chi_e and Chi_i) would be imposed, and then scoping studies of the actuator capabilities performed. Finally, the SSO Group spent a great deal of time discussing ITER Issue Cards for the EC, LH, IC, and NB systems. Steve Wukitch visited The Institute of Plasma Physics, Hefei, China, home of the EAST tokamak, following IAEA for 3 days to discuss progress on PRC-US collaboration and ICRF physics and technology issues with Prof. Li, Prof. Zhao, and Dr. Qin. In particular, he discussed the ICRF screen power supply layout that ASIPP is building for us as part of the PRC-US collaboration. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly