Alcator C-Mod Weekly Highlights August 2, 2010 FY2010 weeks of research operations Base Target: 13 weeks Base Completed: 11.0 weeks ARRA Target: 5 weeks ARRA Completed: 5.0 weeks Plasma Shots: 2041 Operations ----------- Plasma operations continued at Alcator C-Mod last week. Four run days were scheduled and 3.5 days were completed. A total of 99 plasma discharges were produced with a startup reliability of 93%. Runs on Tuesday, Wednesday, and Friday supported Diagnostic development and calibration, and LH and ICRF conditioning; the experiment on Thursday contributed to research in Lower Hybrid Physics. Plasma operations are planned to continue this week. Quarterly Review ----------------- A C-Mod DoE quarterly review (FY2010 Q3) was held by video-conference on Monday, July 26. Attending from OFES were Mark Foster, Mark Koepke and Steve Eckstrand. PPPL was represented by Randy Wilson, and U. Texas by Bill Rowan. Presentation viewgraphs from the review are linked at: http://www.psfc.mit.edu/research/alcator/pubs/Q_Reviews/Q_Rev_07_26_2010.pdf Program Planning ---------------- The C-Mod Experimental Program Committee met on Monday to review short-term planning. Three new Miniproposals were reviewed and approved. A C-Mod/NSTX Pedestal Workshop (Sept. 7--8, PPPL) is being organized between MIT and PPPL. The purpose of this meeting will be to gather testable ideas from interested experimentalists, theorists and modelers for research that can advance the predictive capability for the H-mode pedestal, in the FY11 experimental campaigns at C-Mod and NSTX. The test of H-mode pedestal models is the subject of the OFES FY2011 Joint Research Target. Interested parties may contact Jerry Hughes (jwhughes@psfc.mit.edu) or Rajesh Maingi (rmaingi@pppl.gov) for more information. Operations Details ------------------ Part of Tuesday's run was devoted to MP#296 "Confirmation of Thomson scattering density calibration using electron cyclotron emission cutoffs". Ohmic discharges at 3.9 T, with the density ramping in time, were used to calibrate the Thomson Scattering density profile diagnostic by observing cut-off of the ECE emission on the GPC and GPC2 grating polychromators. The resulting calibration is now in use, and has been applied to all core and edge TS data taken during the current experimental campaign. The remainder of Tuesday's run and the entire run on Friday were devoted to conditioning of the ICRF antennas (MP#355b). Each of the D- and E-port dipole antennas is now operating reliably at the 1.5MW power level. The four-strap J-port antenna has achieved 2.5MW, but with reliable fault-free operation at this power not yet established. Thursday's run supported MP#612, "Expanded exploration of LHCD Density Limit". The purpose of this experiment is to extend the results obtained at C-Mod in 2008 regarding the density limit for efficient current drive over an expanded parameter range of density, field, and plasma current. This work is being carried out in association with an ITPA Joint Experiment on the LHCD density limit, with similar experiments performed on JET, Tore Supra, and FTU. Density and phase scans were carried out in 700kA, 5.4T discharges, with results that are similar to similar scans in 2008; detailed analysis of these data are in progress. Difficulties with computer and power systems resulted in delays and early termination of the run. Additional runtime will be scheduled for the completion of this experiment. ICRF Systems ------------ The strap design for the new four strap antenna has been finalized. Completion of the detailed design of the Faraday screen attachment and the connection between the strip line and antenna strap is in progress. The flange cover and bellows tube assembly designs have been finished and await a final check before manufacturing. Lower Hybrid System -------------------- Replacement of a circulator, which had been limiting the power available from one of the klystrons, was successfully completed. The LH-SOL reflectometer external waveguide run is nearing completion. Final measurements are required before the last six sections can be installed. Flanges need to be brazed on these pieces once the lengths are determined. DNB Systems ------------ The DNB resumed operation using the liquid helium cryopump last week. Cryopumping is required in order to avoid perturbing the low-density plasmas that are desired by the experiments involving lower hybrid studies. The DNB ran well on all three run days on which it was requested. Travel and Visitors ------------------- Rajesh Maingi (ORNL) visited MIT Friday and worked with Jerry Hughes to discuss C-Mod and NSTX plans for the FY11 Joint Research Target on pedestal physics, and to prepare for the upcoming C-Mod/NSTX Pedestal Workshop. Analysis and possible publications related to previously completed joint experiments between the two devices were also discussed. Last week (July 26-29) Jim Terry visited the ITER site to participate as an "external expert" on the Conceptual Design Review (CDR) panel for the ITER Upper Port Visible/IR Wide Angle Viewing systems. This US-credited diagnostic system is to be installed in six of the ITER upper ports in order to have ~300 degree imaging coverage of the lower outside divertor. It is important for the following operational categories: Machine Protection, Basic Control, Advanced Control, and Physics Measurements. The CDR is the first of several sequential steps needed for procurement, i.e. the CDR, signing the Procurement Arrangement with the responsible Domestic Agency, the Preliminary Design Review, and the Final Design Review. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly