Alcator C-Mod Weekly Highlights Feb. 11, 2008 FY2008 weeks of research operations: Target: 15 weeks Completed: 4.2 weeks Operations ---------- Last week was a maintenance week at Alcator C-Mod, with no plasma operations scheduled. Research operations will resume this week. PAC Meeting ----------- The 2008 meeting of the C-Mod Program Advisory Committee was held at MIT last week, Feb 6-8. The focus of this year's meeting was the proposal for the next five year research plan on C-Mod, covering the period November 2008 through October 2013. Presentations on the plan from the C-Mod team were made on Feb 6 and 7; links to pdf versions of the viewgraphs can be found at http://www.psfc.mit.edu/research/alcator/pubs/Cmod_PAC_2008.html. The PAC members are: Chuck Kessel, PPPL (Chair), Brian Lloyd, UKAEA, Alberto Loarte, ITER Organization, Craig Petty, General Atomics, George Sips, IPP Garching, Paul Terry, U. Wisconsin, Madison, Jim Van Dam, U. Texas, Austin, and Rostom Dagazian, DoE-OFES (ex-officio). The panel provided the C-Mod team with an initial debriefing on Friday morning, which included recommendations concerning the plan and associated proposal. They will provide a written report in the near future. Quarterly Review ---------------- A quarterly review (FY08 Q1) was held at MIT on Thursday, February 7. In attendance were Rostom Dagazian, Earl Marmar, Miklos Porkolab and Jim Irby. Current operational status and near term plans for C-Mod were discussed. Data Acquisition and Control Systems ------------------------------------ The computer which interfaces to all of the CAMAC data acquisition hardware was replaced with a new diskless rackmount system. ICRF Systems ------------- Using vacuum conditioning, we investigated the Fast Ferrite Tuner (FFT) computer issue and the system voltage limit. Prior to these tests, improvements were made to the shielding in the rf racks and the optical links between components. We were then unable to reproduce the intermittent computer problem. We were also unable to reproduce the arcing we had previously observed during operations. The system was conditioned to 35 kV on the antenna side of the matching network without an FFT optical fault indication. We will further test the system during plasma operation this week. Lower Hybrid System -------------------- Last week's maintenance period was used to make changes to transmission line components (jungle gym) that are intended to reduce faulting in sections of waveguide in close proximity to the phase shifters. Parker seals in three sections of waveguide have been replaced with copper gaskets with generally better rf performance. High power tests into plasma this week will determine if additional changes to the jungle gym are required. One possibility is to use fixed delay phase shifters, which are being fabricated to replace the tunable ones. These faults currently limit coupled power to the plasma to approximately 900 kW. High power acceptance tests of the first of five new circulators have begun. The circulators are tested into matched loads, and into shorts with various waveguide shims to move high voltage points throughout the circulator structure. Four of these circulators will be used in the 4th klystron cart that will increase lower hybrid source power from 3 to 4 MW. Diagnostic Neutral Beam System ------------------------------ Faults in two low voltage power supply systems early last week have stopped operation of the DNB until we can determine the cause of the faults and repairs can be made. We are, in consultation with the vendor, procuring new components, testing supply modules, and repairing damaged cable runs. Diagnostics ----------- The five repaired detector units have been integrated back into the MSE diagnostic. Travel and Visitors -------------------- George Sips, from ASDEX-Upgrade, completed his visit to participate in joint ITPA experiments on current ramp-up at low internal inductance, of interest for control of ITER plasmas during the current rise phase. Randy Wilson (PPPL) was at MIT last week to attend the PAC meeting and to work with the LH group on IAEA submission data analysis and modeling and experimental planning. Stewart Zweben (PPPL) helped set up the two GPI cameras on C-Mod in preparation for the run next week. This will allow simultaneous measurements of the edge turbulence in the midplane and near X-point regions for the first time. Also he worked on the analysis of GEM simulation runs by Bruce Scott of IPP Garching for the B field scan of inner-wall limited plasmas. Dan Floriani and Al Sullender from CPI met with Pat MacGibbon and Dave Terry regarding new klystrons and improvements to be made to some of our current tubes. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly