Alcator C-Mod Weekly Highlights August 7, 2006 FY2006 weeks of research operations: JOULE target: 14 weeks Completed: 16.7 weeks Physics ------- Lower hybrid power was increased during the week of July 24th to 900 kW absorbed. The current drive efficiency was found to increase with current, and at 1 MA, the loop voltage was held at or above 0 for 160 ms (polarity in the direction of re-charging the transformer for about 1 current rearrangement time for these plasma conditions). A similar improvement of LHCD efficiency with plasma current has been seen on Tore Supra which was explained by an increase in the upper bound on the fast electron distribution velocity, due to a downshift in the parallel wavenumber that can occur at lower q. Detailed modeling for the C-Mod case is underway. Operations ---------- Alcator C-Mod has begun an extended up-to-air period. The warm-up of the machine was begun on 7/28 at the end of the last run day. A first up-to-air was performed on 8/2 to neutralize the diborane products on the vessel wall by exposure to water vapor. The machine was then pumped back down and a period of glow discharge cleaning in helium was used to complete the cleanup process. The final up-to-air was performed on 8/7, and a room air purge of the vessel has now begun. The primary tasks during the up-to-air period will be installation of the new upper divertor cryopump and the lower divertor tungsten tile lamellae. A picture of the cryopump prototype being installed in the test chamber may be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/MACHINE/Divertor/DSCN1332.JPG and a draft schedule for the up-to-air and FY07 run period can be found at http://www.psfc.mit.edu/research/alcator/facility/operation_schedule.pdf During this up-to-air we will also install the prototype real-time tuning system on the E-Port ICRF antenna transmission line, rotate the DNB several degrees off radial to reduce trapping of beam ions in the ripple field, inspect and refurbish as needed all ICRF antennas, upgrade the lower hybrid control system, fabricate and install new couplers on the lower hybrid launcher, add new diagnostics, and upgrade old ones. Inspections and preventative maintenance has already begun on the alternator and other power systems. DoE Quarterly Review -------------------- A Quarterly Review of the C-Mod program was held last Wednesday, 8/2, via video conference. At MIT were Earl Marmar, Ron Parker, Valerie Izzo, Jim Terry, Brian Labombard, Martin Greenwald, Amanda Hubbard, Steve Wolfe, Jim Irby, and Steve Scott. Bill Rowan and Perry Phillips were connected from Texas. Representing DoE were Adam Rosenberg (contract monitor), Steve Eckstrand, Gene Nardella, John Mandrekas, Rostom Dagazian, Darlene Markevich, and Francis Thio. The agenda included presentations on Campaign Run Statistics -- Steve Wolfe Lower Hybrid Current Drive -- Ron Parker Disruption Mitigation and Modeling -- Valerie Izzo ELM Studies -- Jim Terry Cryopump Status -- Brian LaBombard Plans for the Up-to-Air -- Jim Irby Viewgraphs of the presentations can be found at http://www.psfc.mit.edu/research/alcator/pubs/Q-Rev_Aug_06.pdf _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly