Alcator C-Mod Weekly Highlights Nov 21, 2011 FY2011 weeks of research operations Target: tbd Completed: 0 weeks Plasma Shots: 0 Operations ----------- Preparations for resumption of C-Mod plasma operations continued last week. A 120C vessel bake was successfully completed on Wednesday. Following leak checking, the vacuum vessel was briefly back-filled on Thursday to 1 atmosphere of argon in order to replace the pre-ionization "sparker" assembly. Cooling of the magnets and structure to liquid nitrogen temperature was then carried out in preparation for power testing. The MIT alternator, which provides prime power for most of the C-Mod magnet power supplies, was successfully brought up to full speed following replacement of a faulty relay in the motor drive control system. On Friday, we carried out a full test of all major C-Mod operations systems. The access control system was brought back on-line for operation. The coil systems were successfully hi-potted at operating temperature, and the fault protection systems were checked out and verified. All magnet power systems were tested under load, and made ready for operation. An issue with operation of the reverse bridge of the EF4 supply was identified and successfully resolved. A latched fault in the EF1 commutation switch control, which appeared after successful operation, will be addressed during maintenance this week. The gas fueling system, including new circuitry for the piezoelectric valve drivers, was tested in conjunction with the digital plasma control system (DPCS). Four out of five valve systems tested performed nominally. One fiber optic transmitter from DPCS was found to require adjustment in order to function correctly with the new receivers in all operating modes. This adjustment, as well as a modification to the receiver over-range setting, will be carried out during this week's maintenance day. The testing on Friday concluded with a fully integrated test of all subsystems using a normal plasma shot setup, which resulted in a successful breakdown but no sustained plasma current. Post-shot analysis indicated a satisfactory field null, but the discharge was apparently too dirty to support a normal current rise. This result was not unexpected, since no discharge cleaning had been carried out since pump-down. Electron cyclotron discharge cleaning (ECDC) in deuterium was begun over the weekend. Plasma operations are planned to begin this week. ICRF System ----------- Progress continued in preparation for testing of the new, ARRA-funded, Fast Ferrite Tuner (FFT) systems, to be carried out at the vendor's site. Measurements were made of the vacuum RF characteristics of the newly-installed ARRA-funded rotated antenna with the coax transmission lines connected. The results are being reviewed and analyzed. Lower Hybrid System -------------------- Testing of the new Transmitter Protection System (TPS) circuitry continues. Indicated modifications to the boards are being performed by the vendor, along with upgrades to the firmware. Data acquisition issues were successfully resolved. Communication between the lower hybrid equipment racks and the klystron cart interface boxes was tested using a PLC I/O test program created for this task. Panel Interlocks, high voltage relays, air flow switches, soft starters, body current test, pin switch assemblies, arc detectors, waveguide pressure switches, waveguide antenna/load switches, etc. were tested for all three carts. Diagnostic Neutral Beam System ------------------------------ The Diagnostic Neutral Beam is being brought back into operation. The DNB operated routinely in conjunction with the C-Mod cycle during power testing on Friday, including firing into the tokamak on several shots. The beam voltage and current reached 50kV and over 7 Amps, as conditioning proceeded. Diagnostics ----------- The Two-Color Interferometer (TCI), including the density feedback circuitry, was operational during power testing and the first plasma attempt on Friday. The electrical service to the TCI rack has been modified to accommodate installation of a new cPCI crate, which will be used primarily for density fluctuation measurements using differential interferometry during the 2012 campaign. The shutters protecting the polarimeter retro-reflectors on the inner wall were found not to fully close when cycled under vacuum. The shutters were successfully closed during the brief argon backfill on Thursday and will be left closed until completion of the first round of ECDC. The cause of the mechanical interference preventing full closure after pumpdown is being investigated. Travel and Visitors ------------------- Most of the C-Mod scientists and graduate students participated in the 2011 APS-DPP Meeting in Salt Lake City, Utah this week. A total of 67 presentations dealing with C-Mod research were presented. Copies of posters and viewgraph's are being posted to http://www.psfc.mit.edu/research/alcator/pubs/APS/index.html A group of science teachers participating in the Institute for Science Instruction and Study (ISIS) program from Southern Connecticut State University toured the Alcator C-Mod facility on Friday morning. Jim Irby led the tour and presented an overview of the C-Mod research program and goals. The goal of the ISIS program is to expose science teachers with advanced degrees to cutting-edge reasearch going on in the New England region. -- Stephen M. Wolfe M.I.T. Plasma Science and Fusion Center Room NW17-101 175 Albany Street Cambridge, MA 02139 telephone: (617) 253-5510 fax: (617) 253-0627 e-mail: wolfe@psfc.mit.edu _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly