Alcator C-Mod Weekly Highlights January 17, 2003 We continued work on the Lower Hybrid, ICRF, and DNB systems this week. Invessel work also continued, while work on the TF tap, TC, and heater leads was completed. Physics ------- Martin Greenwald presented initial results from the analysis of a new database table. The new table has been loaded with 34 physics variables for every EFIT time from every C-Mod shot. This table now contains over 600,000 records and should be a useful tool for analysis of long term performance trends. Some trends are easily visible - for example a drop in Wmhd from efit can be seen for ohmic plasmas beginning in about CY 2000. A drop in electron temperature at constant density can also be seen, though this has quite a different time history. Further analysis, particularly including comparisons with other kinetic data, will be needed to understand these effects. A dimensional identity experiment was carried out on JET and Alcator C-Mod on October - November of 2002. The goal of the experiment is to create plasmas with identical local edge dimensionless parameters (collisionality, beta, normalized gyroradius) on tokamaks of different size, and study the characteristics of the plasmas obtained - global confinement parameters, local H-mode pedestal characteristics and edge fluctuations. Similar experiments were done on C-Mod and DIII-D in 2001. The results from the JET/C-Mod run indicate (similar to DIII-D/C-Mod results) that pedestal profiles are similar in dimensionally identical plasmas, suggesting that plasma transport plays a dominant role in formation of the H-mode transport barrier. However, in the JET/C-Mod experiments JET and C-Mod plasmas have different confinement characteristics and different edge fluctuation properties at similar pedestal parameters. More experimental studies are necessary to understand the observed differences between JET and DIII-D results. The next stage of this experiment is scheduled on JET for 21 March 2003. Operations ---------- Invessel installation of the new lower halo Rogowski was completed this week. Ultrasonic testing of the moly tiles has begun with the upper vessel tile survey completed. Four out of the approximately 600 upper tiles were found to be delaminating and will be replaced. We have completed work on the TF tap and TC lead upgrades and are proceeding with re-assembly of the cryostat. Lower Hybrid MIE Project ------------------------ High-power WR187 directional couplers are being installed. This installation will complete the waveguide assembly for Cart #1. Re-measuring of the klystron positions in the cart is complete, and fabrication drawings for the circulator mounting bracket and water load supports have now been generated. Work continues on low power microwave control instrumentation and software. ICRF Systems ------------ We continue to simulate placement of new current and voltage probes for the D- and E-Port antennas. We are finding that small changes in the location of these probes can result in large changes in response. This effect is under investigation. Samples of a ferrite material that might be used for our fast ferrite tuners have been tested. Initial results indicate that the ferrite can be used in the design of a 40 to 80 MHz high power phase tuner. Progress was made on the ICRF instrumentation upgrade. Diagnostic Neutral Beam ----------------------- A rebuild of the nitrogen cryo frosting valves was completed early this week. The valves were re-installed, and the DNB was conditioned and is now operating at very good performance levels. Travel and Visits ----------------- Amanda Hubbard and Miklos Porkolab attended the FESAC meeting at GA in San Diego this week. Amanda, who is on the FESAC Development Path Panel, attended the meeting from Jan 13-16. Miklos attended the subpanel meeting on the 35 year fusion program (Fasttrack) on Jan 13 and 14 and presented the talk : "High Field Approach to Demo". Ron Parker attended the NRC meeting, also in San Diego this week. Martha Redi, PPPL, visited MIT from Jan 13 to 15. Discussion centered on ITB formation and specific assumptions of impurity levels being used in the gyrokinetic calculations, with MIT experimental physicists, Catherine Fiore, John Rice, Paul Bonoli, Jim Terry and Bruce Lipschultz. Gerd Schilling, PPPL, was at MIT Jan 16 and 17 for discussions on LHCD launcher progress. He also participated in a design review of the new boron nitride tiles for the J-Port ICRF antenna, a design review of the planned modification of the D- and E-Port ICRF antenna feedthroughs, and discussions on the final design of the boron nitride tiles for the LHCD launcher. A further meeting of the C-Mod RF group generated suggestions for presentations at the RF conference in May.