Alcator C-Mod Weekly Highlights October 15th, 2007 FY2008 weeks of research operations: Target: TBD Completed: 0 weeks Physics ------- A new cluster, consisting of 256 processor cores in 64 nodes, each with two AMD Opteron 2214 (2.2 GHz) dual-core processors, with 1 GB memory per processor core, a head node, a spare node, 2.5 TB RAID storage, and gigabit and Infinipath networks, has been installed at the PSFC. Full-wave lower hybrid field simulations with TORIC that took 5000 cpu-hours on our old cluster can now be done in 1176 cpu-hours, or 4.25 times faster, using the same number of processors. In addition, the new cluster has more than five times the number of processors as the old cluster. The new cluster makes it possible to do nonlinear gyrokinetic turbulence simulations in-house. A well resolved, two species GS2 nonlinear simulation of electrostatic TEM turbulence completes in less than 8 hours on the new cluster. A radial profile of the maximum linear growth rate, for a C-Mod case, can be computed in about 10 minutes. The acquisition and installation were led by Ted Baker, with design requirements and testing by Darin Ernst, John Wright, and Paul Bonoli. This project is supported in roughly equal amounts by SciDAC, the PSFC, and C-Mod. Operations ---------- Inspection of magnet bus work continued. Some TF bus components will be re-plated. Inspection and maintenance of alternator breakers, contactors, and seal oil system components continued. Design work has resumed on a helium recovery system for the DNB and Upper Chamber Cryopump. This system will send the exhaust helium gas via an underground pipeline to the cryogenics lab on main campus for purification and liquification. In-vessel Work -------------- We expect to have the lens mounts needed to complete work on the MSE in-vessel collection optics by early this week. Testing of other MSE optics and electronics continued last week. Work continued last week on the rebuild of the polarimeter shutter. New smaller protection tiles are being installed to reduce eddy current forces and "bumpers" are being machined into the body of the shutter to protect the new tiles against impact from neighboring tiles. Preparations have been made for re-installation of in-vessel components removed for the flux loop work. Lower Hybrid System ------------------- All twelve jungle gym assemblies have been inspected, cleaned, and reassembled. They are ready for installation as soon as inspection and cleaning of the transformers and rear waveguide are complete. Two more klystrons have been shipped to the vendor for evaluation and possible rebuild. Discussions with the vendor concerning the #117 klystron continue, as we decide on a course of action and schedule for bringing this tube back into operation. Simulation of the new lower hybrid coupler design using a cold plasma model is underway. All sixteen waveguides have been included in the latest model which will provide a realistic simulation of the actual coupler. ICRF Systems ------------ New demodulators are being installed and calibrated for the #1 and #2 transmitters, and trip levels are being set. These demodulators have much better phase and amplitude measurement characteristics and a larger dynamic range compared to the old design. We continued to refurbish phase-shifter and tuner components. Resonant loop components for the J-Port antenna are being inspected and reworked. Design of the new 4-strap antenna and the reflectometry diagnostic needed to measure the density profile at the antenna continue. Travel and Visits ----------------- Joe Snipes attended the 10th IAEA Technical Meeting on Energetic Particles in Kloster Seeon, Germany from 8 - 10 October and then the remainder of the 10th ITPA MHD group meeting at IPP-Garching from 10 - 12 October. Bob Granetz also attended the ITPA MHD meeting from 10-12 October. Dennis Mansfield, PPPL, visited last Friday and gave the PSFC seminar on "The NSTX Lithium Conditioning Experiments: Results and Future Plans". He had extensive discussions with Jim Irby on the C-Mod polarimeter system. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly