Alcator C-Mod Weekly Highlights September 14, 2001 Work continued on the machine inspection this week. Progress was also made on the new inner divertor, and lower hybrid and ICRF systems. Physics ------- Analysis of the turbulence observed in the plasma edge with the PPPL Gas Puff Imaging diagnostic is continuing. Three types of modeling efforts are being pursued. A direct image analysis of the 2-D experimental data attempts to extract spatial correlation lengths, k-spectra, fluctuation levels, "blob" structure and motion, and other pertinent information. Darren Stotler is working on modeling of the relationship between light emission images and the underlying density and temperature fluctuations using the DEGAS 2 code. Klaus Hallatscheck (IPP) and Barrett Rogers (Dartmouth) are performing theoretical modeling of the C-Mod edge turbulence from first-principles models, e.g. Drift-Ballooning Mode and Non-Local Edge Turbulence codes. J. Snipes presented ideas at our weekly physics meeting for where a second set of Active MHD antennas could be placed toroidally in relation to the first set, which will be mounted in the GH sector. Conflicts with antennas, glow discharge electrodes, and other diagnostics limit the location of the new set of antennas to a toroidal region about 72 degrees away from the GH MHD set. Operations ---------- Resistance measurements of the TF sliding joints were carried out this week as part of the machine inspection. The resistance of all the lower-outer joints were measured and detailed potential drop maps were made of selected joints. These measurements together with careful analysis will continue for several days next week. The equipment needed to remove the spring plates holding the joint fingers together has been assembled and tested. We expect to begin pulling selected TF arms and legs off the machine early next week. Lower Hybrid MIE Project ------------------------ Work on the C-Mod Lower Hybrid launcher is progressing well at PPPL. With the determination of the position of the H-taper and of the diagnostic probes, the last details of the 3 dB splitter and front extension are complete. The design of the full scale three-channel test fixture is complete and fabrication drawings are being created. It will be used to test the vacuum integrity under the specified conditions and for all the high power tests of the non-standard waveguide components, probes and cross talk. One set of TPS boards including the front panels have been completed and wired to the PLC I/O control rack. Power-up test of the boards have begun and bidirectional I/O between the TPS and the PLC have been verified. Holes have been bored through the power room wall for the HVPS interface. Installation of the HVPS interface box is progressing. Fabrication of the HVPS dummy load continues in our shop. Development of fiber optic links for the LH project also continues. Analysis of the I/Q detectors that will be used to measure the relative phase of the klystrons continued this week and indicated only a 5 degree variation in phase over a factor of 20 range in signal level. We continued work on the lower hybrid low power microwave rack layout. Contractors continued the site modifications required for the LH project. Coring of the northeast cell wall for the HVPS power and control cables is nearing completion. Rails to secure the HVPS supply are being installed on the new concrete pad in the hi-yard. Specifications for the water system sensors and controls are being reviewed by C-Mod engineers as the 8" and 6" supply line fabrication continues in the power room. ICRF Systems ------------ We continued developing more detailed models of the D, E, and J-Port antennas. Work also continued gathering information for a transmitter, transmission, and coupler systems model. Inner Divertor -------------- We are in the process of fitting-up the entire complement of inner divertor components invessel. A picture of this process can be found at http://www.psfc.mit.edu/cmod/operations/EngImages/Inspection_2001-2002/Disassembly_Assembly/part2/P0002068.JPG The fitup will allow us to determine if any processing of the plates is required to ensure the proper contact with the inner wall needed to meet strength and thermal conduction requirements. Also, any conflicts with inner wall diagnostics will be addressed. After the fitup is complete work will begin on installation of the new studs. Techniques needed to efficiently install and test the new studs are being finalized. Trips and Visits ---------------- Dave Terry and Willy Burke met this week via teleconference with Nevell Greenough, Elmer Fredd, Chris Brunkhorst, and other PPPL engineers, to discuss demodulator and phase detector designs. We hope to pool our knowledge on these systems and develop a new design capable of handling measurement and control tasks much more effectively than the current designs we both use. Dave Terry traveled to Opal-RT in Canada for a demonstration of their RT-Lab software. He discussed three of our possible applications with them, including the Lower Hybrid, Fast Ferrite Tuner, and Hybrid Computer systems.