Alcator C-Mod Weekly Highlights Jan 24, 2003 Physics ------- The new core Thomson Scattering (TS) polychromators became operational during the last run campaign and give reliable profiles of the electron temperature and density with ~10% accuracy. Both core temperature and density profiles match up well to the edge TS data. The TS temperature is systematically 10-15% higher in the core region than that derived from the ECE diagnostics. The absolute calibration of the new core TS density was made using ECE cutoff data. Integrals of TS profiles mapped along TCI chords are systematically 10-15% lower than nl data; however, the agreement is better for the outer TCI chords. This result is consistent with the TCI inversion profiles, which are close to the TS density profiles at large radii but are too high in the core; possibly because the interferometer sees extra nl from the scrape-off layer. The effective charge derived from the VB and TS data is ~1 in most L-mode discharges and ~1.1-1.4 during H-modes. Impurities are observed to accumulate in the center of some ITB discharges resulting in a Zeff of up to 2.5 in the core. Operations ---------- The first of eight aluminum frames for the new field control coils was completed this week. Cable has arrived for winding the first coil, and the coil winding equipment has been set up in the power room and tested. We expect to have the first coil completed next week. Production of the remaining coil forms has begun. Work is nearly complete on the power supply we will use for the initial control coil experiments. High power tests of the supply into a dummy load is expected next week. Data and Hybrid control system interfaces and software upgrades to support the new coils are also underway. A drawing of the new coils may be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/MACHINE/PF/correction_coils_side.jpg We continued invessel work this week. Reassembly of the cryostat and preparations for re-installation of the vertical flanges also proceeded. Lower Hybrid MIE Project ------------------------ At MIT work was delayed on the high power klystron tests using the HVPS as we work with the vendor to update the crowbar fault detection boards. Components are being fabricated that will support the circulators and dummy loads. Procurement plans for the output waveguide are being finalized. Work continued on the phase and amplitude control system, data acquisition components, and serial fiber optic links. Good progress continued to be made at PPPL on the LHCD launcher. All heaters and thermocouples have been installed on the shroud and forward waveguide. The shroud and waveguide assembly were subsequently welded, and will be leak checked shortly. Cleaning of brazing residue off the ceramic surfaces is progressing, with plans to finish by 2/1. Acid etching may not be required for final cleanup. Microwave transformers, slide bushings and radial motion rails have been delivered to PPPL. The radial motion mechanism is assembled and being tested. The signal patch panel design is completed, and wiring has begun. ICRF Systems ------------ Simulations of the J-Port antenna feedline and straps continues in an effort to model proposed changes needed to increase the breakdown voltages at critical locations. We also continued simulations of the voltage and current probes to be added to the D- and E-Port antennas. The simulations indicate that spurious rf pickup on the current probes could be reduced a factor of 10 by adding multiple slots in the current probe aperture. We continue to develop improved fault detection and control electronics for the transmitters. Travel and Visits ----------------- Stewart Zweben, PPPL, was at MIT this week to discuss plans for the Gas Puff Imaging diagnostic and for a possible mini-proposal on H-mode control. Martin Greenwald traveled to PPPL for the NSTX PAC meeting. Presentations focused on their 5 year proposal.