Alcator C-Mod Weekly Highlights April 9, 2012 FY2012 weeks of research operations Target: 17 Completed: 5.6 Plasma Shots: 753 Research -------- Nathan Howard successfully defended his PhD thesis last week on "Experimental and Gyrokinetic Studies of Impurity Transport in the Core of Alcator C-Mod Plasmas". Using a unique set of diagnostics and modeling tools, a comprehensive study of impurity transport was performed on Alcator C-Mod L-mode discharges. A new, multi-pulse laser blow-off system was designed and constructed to introduce trace amounts of non-recycling, non-intrinsic, impurities into the plasma edge. This system was coupled with an x-ray crystal spectrometer, a single chord x-ray/ultraviolet spectrometer, and measurement of the laser blow-off neutral source at the plasma edge to provide full, time-evolving, radial profiles of a single impurity charge state. An iterative chi^2 minimization scheme was created to infer the experimental impurity transport coefficients and their uncertainty by minimizing the difference in the measured and STRAHL simulated emission. These measurements and data analysis methodology allowed for determination of impurity transport coefficient profiles with realistic errors from 0.0< r/a< 0.6. The gyrokinetic code, GYRO, was use to analyze the same discharges. Operations ---------- Alcator C-Mod is presently up-to-air for planned maintenance and upgrades. Refurbishment of the ARRA-funded Field Aligned ICRF Antenna has been completed. Installation of the Polarimeter shutter has also been completed and proper operation of the shutter verified. ICRF Systems ------------ Re-assembly of the external coaxial transmission line network for the ARRA-funded field aligned J-Port antenna was completed last week. The decoupling loop was measured and found to have at least 40 dB decoupling at 78 MHz. The system is being purged with nitrogen gas to ensure that it is ready for operation. As-built assembly drawings are being made so that adjustments for current drive phase and 50 MHz operation can be easily made. In preparation for the installation of a new set of FFTs on the D-Port antenna, cable wiring documents have been prepared that will allow a third party assembler to manufacture the within-rack and between-rack cables. Our initial examination of the equipment ratings indicates that we can use the existing 480/208 transformer to power the D-Port FFT. New water fittings have been installed onto FFT#1 as re-assembly of this unit continues. We have finished replacing bushings and ceramic washers on the H-Port SOL reflectometer horns - these horns map to the field aligned J-Port antenna. Lower Hybrid Systems -------------------- The lower hybrid launcher position calibration was successfully completed last week. Remote Participation, Travel, and Visitors ------------------------------------------ Miklos Porkolab attended the bi-Annual Hungarian Fusion Program Review and Workshop in Tata, Hungary (near Budapest) on April 2 to 4. He gave a 40 minute invited talk on "Gyrokinetic Transport Analysis of the Linear Ohmic Confinement regime in Alcator C-mod". Miklos was also asked to head up the international review panel which advises the Hungarian Academy of Sciences about progress and future direction of this particular EU sponsored program. The Head of the program is Sandor Zoletnik, well known from collaborations with MIT C-Mod, U Wisconsin, K-Star, East, Asdex-U and JET. The group consist approximately of 60 researchers, including professional physicists, research engineers, and graduate and undergraduate students. John Rice and Jerry Hughes attended the ITPA Transport/Confinement and Pedestal Topical Group meetings in Hefei, China, April 2 to 4. They gave several physics talks and led discussion on progress in several joint experiments, including both the topics of L-H transition and I-mode. While there, they had discussions with members of the EAST and JET teams about potential collaboration opportunities with MIT. The 2012 International Sherwood Fusion Theory Conference was held in Atlanta, GA from March 31st to April 3rd. The plenary Sherwood talk was given by Dennis Whyte on "The future of boundary plasma and material science". Other presenters from MIT-PSFC included Paul Bonoli, Matt Landreman, Bo Li, Felix Parra-Diaz, Abhay Ram, Jesus Ramos, Antoine Cerfon, and Anne White. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly