Alcator C-Mod Weekly Highlights April 27, 2009 FY2009 weeks of research operations: Target: TBD Completed: 0 weeks Physics ------- A full wave simulation of the lower-hybrid (LH) wave based on the finite element method (FEM) has been developed by Orso Meneghini and Syun'ichi Shiraiwa. For the LH wave, the most important terms of the dielectric tensor are the cold plasma contribution and the electron Landau damping (ELD) term which depends on the parallel component of the wave vector. In the real space domain, this results in an integro-differential Helmholtz equation, which has been solved iteratively. The simulation results for LH waves in a circular tokamak plasma with major radius of 0.64 m, minor radius of 0.17 m, central density of 5E19/m^3, and central electron temperatures of 2, 3, 5, 10 keV were presented. Comparisons of the wave trajectories with the results from a ray-tracing code showed very good agreement. The advantages of the new approach include a significant reduction in computational requirements and opening up the possibility for a seamless treatment of the core, the Scrape Off Layer (SOL) and the launcher regions. Operations ---------- Preparations continue to be made for re-assembly of the alternator. All equipment and protective mats needed during the ring sample machining effort have been removed from the stator. A careful inspection of the stator is underway. The vendor chosen to re-assemble the alternator will arrive on-site early this week. A teleconference was held with the vendor last Friday to discuss the scope of work and schedule details. The cryostat cover has been raised into position below the machine, and the upper half of the cryostat has been installed. All instrumentation cabling has been fed through the cryostat and boots and seals around the cabling are being installed. The cryostat top cover is being prepared for installation. Work has begun sealing the horizontal port boots to the cryostat. We continued the modifications to the horizontal port flange to incorporate the new reflectometer windows and horns. Lower Hybrid System ------------------- The former lower hybrid launcher is being removed from the cell in preparation for the new launcher. Cabling, detector diodes, and other instrumentation components have been removed and stored. We continued work on the control system upgrade and the rf probe instrumentation. ICRF Systems ------------ Calibration of transmitter current levels and trip settings continued last week. High voltage has been applied to the FMIT#3 driver stage and the crowbar successfully tested. The water flow interlock for the driver stage dummy load has also been successfully tested. A simulation of the 5" vacuum feedthroughs needed for the new 4-strap antenna has been completed indicating we can expect these components to behave properly at the 2 MW level for 5 s long pulses. Travel and Visits ----------------- On April 17, Steve Knowlton, Auburn University, visited MIT to give a PSFC Seminar on "Current-Driven Stellarator Plasmas". On April 24, Jon Menard, PPPL, Program Director of NSTX, visited MIT to give a PSFC Seminar on "Progress and plans for the National Spherical Torus Experiment". PSFC scientists enjoyed useful individual discussions with both speakers. Mark Smith, PPPL, visited the PSFC this week for a test fit of the gold-plated thermal shield for the Motional Stark Effect diagnostic. Jerry Hughes attended the ITPA Pedestal Topical Group meeting in Cadarache, April 20--22. Representatives from most international fusion devices discussed both joint experimental work among machines and detailed plans for addressing high-priority ITER research needs in the H-mode pedestal area. Jim Terry attended the IPTA Topical Group meeting for Diagnostics, held in St. Petersburg, Russia. He presented a talk on the latest developments from the US relevant to ITER diagnostics. He also chaired one of the sessions. Robert Granetz also attended an ITPA Topical Group meeting last week, but on MHD issues, at the KSTAR facility in Daejeon, South Korea. He presented a summary of ITPA work done on several tokamaks on disruption runaways. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly