Alcator C-Mod Weekly Highlights November 22, 2002 Alcator C-Mod was brought up-to-air this week, and preparations are being made for vessel entry early next week. Work continues on the Lower Hybrid, ICRF, and DNB systems. Operations ---------- After warming up the machine for approximately one week the vessel was brought up-to-air on Thursday morning. Tests for beryllium and diborane were carried out on Thursday afternoon. On Friday the vessel was cleared for manned entry and preparations were begun for entry early next week. Tests of the TF magnet over the week indicate that the high resistance path to ground is located near the G-right leg of the magnet. Preparations are being made for inspection of instrumentation cables inside the cryostat at this location. ICRF ---- The dummy load on loan from General Atomics will be used over the next few weeks in long pulse tests of the ICRF transmitters. Final installation steps for the dummy load are in progress. Simulations of the D and E-Port antennas indicate small changes to the coax feed can produce a very substantial increase in the voltage handing ability of the antennas. We plan to implement these changes during the current up-to-air period. A test fixture to measure the acceleration imparted to the BN antenna tiles has been fabricated and brought into operation. This fixture has been used to simulate the damage seen on the J-Port tiles and will also be used as a final test of the new tile design before installation on the antennas. Lower Hybrid Project -------------------- At PPPL, all of the Lower Hybrid couplers have been profiled to match plasma curvature. The couplers are being cleaned in preparation for plating. The waveguide shroud sub-assembly is being trial fit and will be welded in the coming week. A design review for the high power phase shifter will be held 11/25. All major components are now being fabricated, with the exception of the BN tiles and the support stand. Fabrication of the BN tiles is being held in order to review C-Mod issues with antenna arcing and tile attachment. Support stand drawings have been completed, and we will place an RFQ shortly. At MIT, the first circulator/waveguide support structure has undergone a successful test fit-up on klystron cart #3. Fabrication of supports for carts #1 and #2 can now proceed. The control card for the new HVPS crowbar has been installed and wired into the control cabinet, and support fiber optic cables installed between the HVPS and the HV junction box. Work on the Lower Hybrid phase and amplitude control system proceeded. DNB --- Several DNB systems received attention during the past week. The anode gas valve was inspected and found to require preventive maintenance. Some control software upgrades to simplify firing of the beam during the C-Mod shot cycle, and to correct some erratic operation was also begun. Documentation for the thermocouple system was translated from the Russian to facilitate diagnosis of low signals on a couple of channels. The Russian supplied Java source code has been imported into a Java development environment, and successfully recompiled. This code provides control for the DNB camac crate and other control functions on the beam system. This step moves us toward resolving some of the Java control issues that have been problematic since we received the beam. At UT-FRC, plans were completed for in-vessel work and travel to MIT to implement them. The work includes better securing of the ECE mirror, testing of the invessel shutters, and diagnosing the status of invessel optics. Travel and Visits ----------------- David Mikkelsen spent the week at MIT discussing how to optimize comparisons of experiment with turbulence simulations. One avenue involved a search for low collisionality C-Mod discharges, and several group members provided fruitful leads. The candidate discharges will be studied in more detail with the aim of eventually producing pairs of discharges for comparing with turbulent transport simulations. In C-Mod lower collisionality plasmas are expected to have slightly longer L_T.