Alcator C-Mod Weekly Highlights June 1, 2004 We continued work on the Lower Hybrid and ICRF systems last week. Invessel work continued with documentation, disassembly of some major invessel components, and the beginnings of the MSE calibration. Physics ------- The International Conference on Plasma Surface Interactions in Controlled Fusion Devices was held in Portland, Maine from May 24 to 28. This MIT organized conference had over 260 presentations from scientists from all over the world. A complete list of all the abstracts can be found at http://www.psfc.mit.edu/psi16/programme/abstracts/index.html Alcator C-Mod related papers covered, among many other things, Edge/Sol turbulence and turbulent structures, plasma flows and neutral penetration in the SOL, poloidal transport asymmetries, and impurity flows and screening. Alcator C-Mod related abstracts presented at the meeting included: X. Bonnin, http://www.psfc.mit.edu/psi16/programme/abstracts/P2-Bonnin.pdf T. Chung, http://www.psfc.mit.edu/psi16/programme/abstracts/P3-Chung.pdf O. Grulke, http://www.psfc.mit.edu/psi16/programme/abstracts/I-6-Grulke.pdf J. Hughes, http://www.psfc.mit.edu/psi16/programme/abstracts/P1-Hughes.pdf B. Labombard, http://www.psfc.mit.edu/psi16/programme/abstracts/I-5-LaBombard.pdf B. Lipschultz, http://www.psfc.mit.edu/psi16/programme/abstracts/P1-Lipschultz.pdf S. Lisgo, http://www.psfc.mit.edu/psi16/programme/abstracts/I-3-Lisgo.pdf K. Marr, http://www.psfc.mit.edu/psi16/programme/abstracts/P2-Marr.pdf N. Smick, http://www.psfc.mit.edu/psi16/programme/abstracts/P1-Smick.pdf D. Stotler, http://www.psfc.mit.edu/psi16/programme/abstracts/P2-Stotler.pdf J. Terry, http://www.psfc.mit.edu/psi16/programme/abstracts/O-Terry.pdf On Friday of last week a tour of the Alcator C-Mod facility and VTF was given to 80 of the PSI scientists. Martin Greenwald gave an introductory talk on C-Mod, and tours were given of Alcator and the alternator. A reception for the visitors followed the tour and talk. Operations ---------- Entry invessel was restricted early last week pending radiation analysis of dust samples. After analysis and further consultation with the PSFC safety officer, and the MIT Radiation Protection Office, invessel activity proceeded. By Friday we had completed removal of the j-port antenna and the j-port vacuum flange. Modifications to improve the high voltage standoff capability of the antenna will be made during this up-to-air. Work also began on the removal of the bolometer array at k-port. This diagnostic will be reworked during the up-to-air to improve signal-to-noise levels. The photographic survey of the vessel also continued. The calibration of the MSE diagnostic has proceeded far enough so that we can begin removal of the D and E-Port antennas this week. The antennas were in the field-of-view of the MSE optics and were left in place until we could confirm their presence had no effect on the calibrations. ICRF Systems ------------ We are still working to understand the oscillations that limited low frequency (50 MHz) performance of FMIT#3 and #4 during the last campaign. Measurements of the tuning responses of the Driver and FPA are underway to determine if there is a unique set of conditions at 50 MHz that does not occur at 70 or 78 MHz. The new FMIT#1 and #2 digital tuning meters are ready for installation. This installation is expected to be completed this week. Routine inspection of the transmitter cabinets will begin next week with the filament controllers on all transmitters and the crowbar cabinets of FMIT#3 and #4 being the first systems to be inspected. Lower Hybrid Systems -------------------- We continued testing the rwg/fwg assembly last week. After changes were made to the load fixturing, and the rf gasket performance was improved , nine rwg input channels (18 fwg channels) were driven successfully to 100 kW for 0.5 s. One other guide, near the edge of the stack, displayed a low level discharge on the external surface that we are investigating. Simulations for the Lower Hybrid strip line probe package and probes are continuing. One strip line layout (branch line coupler) was released for prototype layout and etching. This design was for one package/connector orientation. The other orientation design still has to be submitted. The machining of waveguide fixtures needed to test the probes will start this week. Drawings are complete. A pressure fitting was added so that we can test the electrical and mechanical effects of adding a gasket at the probe to waveguide interface. Prototypes drawings for both probe housings were sent out for fabrication. Diagnostics and Data System --------------------------- The invessel MSE diagnostic calibration has begun. The calibration jig was installed in the C-Mod vacuum vessel early last week. Some data has been taken using unpolarized light. A calibration of one channel near the optical axis with polarized light was completed successfully. The CXRS detector will be returned next week following repairs. The FRC-ECE radiometer will be upgraded for the next campaign by the addition of a cooling system to maintain constant temperature in the electronics rack. This change will improve the longevity of a calibration. This week, the RFQ's for the new components were distributed. The main C-Mod linux servers were upgraded to Redhat Enterprise Linux. The archive/data acquisition server was reconfigured to include its original internal raid array, a new 3 TB SATA raid array, and the CAMAC highways. The oldest 1.2TB raid array was taken out of service. Travel and Visits ----------------- David Mikkelsen, PPPL, visited the C-Mod group last week to discuss with Nils Basse, Amanda Hubbard, John Rice, Catherine Fiore, and Darin Ernst the use of the 132 GHz reflectometer channel (developed at PPPL) to measure fluctuations in the core of ITB plasmas. The type of ITB discharge needed to ensure reflectometer access to the steep density gradient region was discussed. Possible experiments to study turbulence and zonal flows in lithium pellet discharges was also discussed with Brock Bose and Earl Marmar. Mark May and Merv Lawrence, LLNL, visited C-Mod last week to discus installation of their visible Doppler spectrometer before the start of the next run campaign. Martin Greenwald traveled to San Diego to give a seminar at UCSD on the C-Mod transport program. Myeun Kwon, Korea Basic Science Institute, visited MIT on Monday to discuss collaborations between the PSFC and KBSI.