Alcator C-Mod Weekly Highlights August 8, 2011 FY2011 weeks of research operations Target: 15 weeks Completed: 14.5 weeks Plasma Shots: 1706 New PSFC Associate Director --------------------------- Miklos Porkolab has announced the appointment of Dr. Martin Greenwald as a new Associate Director of the PSFC. Martin will join the Director's office and complement the activities of Dr. Richard Temkin, Associate Director, and Dr. Peter Catto, Assistant Director. Martin will replace Prof. Jeffery Freidberg who retired July 1, 2011. Martin will continue to play an active role in the C-Mod program, where he heads the core transport group and chairs the Experimental Program Committee. He will also continue his responsibilities as head of the PSFC Computer Systems team. Fusion Power Associates 2011 Distinguished Career Award ------------------------------------------------------- Ron Parker has been selected by Fusion Power Associates Board of Directors to receive FPA's 2011 Distinguished Career Award. The Award will be presented at Fusion Power Associates annual meeting and symposium, December 14-15 in Washington, DC. In selecting Ron Parker, the FPA Board recognizes his decades of career contributions to fusion research and development, including his many scientific and technical contributions to fusion development, the leadership he provided to the evolution of the Alcator program at MIT, his leadership of the MIT Plasma Science and Fusion Center and his contributions to the evolution of the ITER project. Physics ------- The LHEAF code has been used to investigate the degradation of Lower Hybrid current drive efficiency which is experimentally observed for increasing plasma densities. In order to assess the validity of ray-tracing calculations, and to explore the effect of a realistic 2D SOL model which includes the effects of flux expansion and parallel heat transport, the full-wave FEM code LHEAF has been used. LHEAF simulations predict that SOL collisional absorption is less than what was previously estimated by ray-tracing/Fokker-Planck modeling. Nonetheless, the experimental drop in core hard X-Ray emissivity is well reproduced. This may be explained by the effect of an n|| spreading due to full-wave effects (localizing damping in the plasma periphery). LHEAF also predicts Bremsstrahlung profiles that are strongly peaked near the plasma edge, a feature which is not observed in the experiment. This apparent inconsistency can be resolved by postulating radial diffusion of the fast electrons near the edge. Evidence for the existence of fast electrons near the edge and in the SOL will be sought in the upcoming campaign. Operations ---------- New, more reliable, driver boards for the piezoelectric gas valves are now in-house. Plans are being made for testing the new boards and installing ten of them in the gas control rack. A new ratiomatic vacuum gauge controller board has also been developed. A program that interfaces with the controller board and allows the pressure data and status information to be displayed have been successfully tested. This board will also provide the fast analog pressure information to the data system that is used to monitor C-Mod pre-ionization startup conditions. ICRF Systems ------------ Most parts for the ARRA funded rotated antenna have been successfully copper plated. The remaining parts to be plated are one back plate (the second of two), one current strap (the fourth of four), and two cover plates. The previously plated back plate has been baked and will be available for installation on the test stand this week. All vacuum feedthroughs have been welded and are awaiting leakchecks. The center conductor bellows have been machined and are being prepared for electron beam welding. Lower Hybrid System ------------------- We continued work on the Transmitter Protection System (TPS) upgrade and 4th cart last week. Five of the RF pin switch/2 W amplifier assemblies have been completed. The remaining eleven 2 W amplifiers will be transferred from the existing carts to the new assemblies as installation proceeds. The remote AC power control boards for the TPS cPCI chassis arrived and are being populated. Modified circuit boards for the circulator arc detector boxes are in-house. A simplified model was developed for estimating the maximum klystron coolant temperature in real time based on the beam power, RF output power, and coolant flow. The model parameters were transferred to the vendor for the TPS control boards in a detailed memo. A collector over-temperature system fault will result if the maximum modeled coolant temperature exceeds the pressure-dependent coolant boiling point during a pulse. Pat MacGibbon observed successful testing of the new filament power supply system at the vendor's site in California. Diagnostics ----------- All major procurements have been completed for the MSE Intershot Calibration System and the new Thermal Isolation System. Efforts over the next few weeks will focus on assembly, testing, calibration, and installation. All in-vessel parts for Correlation Electron Cyclotron Emission (CECE) diagnostic are in-house, and we have begun clean-up and assembly. Preparations are being made for installation of the CECE vacuum flange at A-Hor. All in-vessel parts for the Fast Ion Loss Detector are in-house, and a trial assembly of the components has begun. The QCM ("shoelace") antenna has been installed in-vessel and plans are being made for its alignment. Remote Participation, Travel, and Visitors ------------------------------------------ Anne White attended the APS-DPP 2011 sorter's meeting at the American Center for Physics in College Park, MD, August 4-5. Jerry Hughes traveled to General Atomics, San Diego, CA, to collaborate with Rich Groebner and the rest of the DIII-D pedestal physics group. While there he led an experiment on DIII-D to match dimensionless plasma parameters characteristic of C-Mod ELMy H-mode, thereby obtaining edge profiles and fluctuation data for comparison between the two devices, and for tests of various pedestal models. An initial analysis indicates that this experiment was very successful, and should make a key contribution to the FY11 FES Joint Research Target in pedestal physics. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly