Alcator C-Mod Weekly Highlights November 10, 1997 Alcator C-Mod continued plasma operation last week with two days of RF conditioning runs. In addition to conditioning the antennas, many diagnostic systems came back on line, and some new data during H-mode operation was obtained. In particular, new data on pedestal formation and EDA modes, some of which will be shown at the upcoming APS meeting, was taken. However, on thursday morning a fault occurred in our newly rewound rotor during the alternator startup procedure. MD&A, the company who performed the rewind, is back on site to make the repair under warranty. This repair will unfortunately delay the resumption of physics plasma operation by a few weeks. One of the diagnostics that began operation last week was the upgraded AM reflectometer. With work done in collaboration with PPPL, this system now has frequency stabilized Gunn oscillators, a new high resolution phase detector for fluctuation analysis, and a lower modulation frequency of 132 MHz. The change in modulation frequency will allow the determination of density profiles to be much more automated, since we will no longer have to keep track of multiple fringe jumps. Installation of the high voltage, low capacitance transmission line conduit between the power supplies and the DNB test lab is complete. The insulators have been installed and installation of the support spine for the HV cables has begun. The components for the system to condition the oil in the accelerator supply were collected so that assembly can begin. Preliminary tests of the crowbar protection for the Mod/Reg tube were completed and an appropriate configuration for tests up to the required 60 kV was devised. Additional dummy loads to be used in power supply commissioning and some fiber optic test equipment were located at UT-FRC and packed for shipment to MIT. The RF was tested and conditioned into D(H), 5.4 T plasma discharges during two experimental runs last week. The conditioning was quite successful with 4 discharges obtaining over 2 MW of injected power, and one discharge with over 3 MW. The H/H+D, determined by the U. of Maryland spectroscopy group (Welsh and Weaver), was about 2% before the RF and climbed to about 4% while RF was on. The RF was approaching the conditioning goal of reliably obtaining 2.5 MW of power from both transmitters. Dr. Gerd Schilling from PPPL visited last week to discuss various upgrades which can be made in the upcoming break. Tuned arc detectors and fast digitizing scopes to monitor the arcs are a top priority. The tuned arc detectors will improve the reliability of transmitter startup and retries when both transmitters are running. Dave Johnson from PPPL also visited last week to work on the x-point Thomson scattering hardware and software. He also discussed possible contributions to the DNB engineering effort from PPPL staff. Pablo Acedo is visiting for the next few week from Carlos III University working on the tangential interferometer. Horatio Lamela also from Carlos III was here on the weekend working out plans for our continued collaboration on interferometry.