Alcator C-Mod Weekly Highlights November 8, 2004 FY 2005 weeks of research operation planned: 14 weeks, completed: 0 weeks. We are currently up-to-air with the primary goal of installing the lower hybrid launcher. In addition, a large number of in-vessel activities are ongoing in support of ICRF and diagnostic systems. Maintenance and upgrades to diagnostic and power systems are also in progress. Physics ------- Martha Redi's summer research student, Jessica Baumgaertel, has been selected to present her work at the annual AAAS meeting in February. Her research paper, "Marginal Stability Studies of Microturbulence Near ITB Onset on Alcator C-Mod", has been selected to be reviewed for publication in Volume 5 of the Department of Energy's Journal of Undergraduate Research. The paper appeared as PPPL Report #3999 and can be found at http://www.pppl.gov/pub_report//2004/PPPL-3999.pdf Steve Scott, PPPL, working with Howard Yuh and Ian Hutchinson, has carried out a quantum mechanical calculation of polarized emission including both the (motional) Stark electric field and a magnetic field. The major difference between these calculations and previous analyses by Isler (1976), Breton (1980) and Souw (1983) is that they include the phase of the electric field rather than just the intensity, which is necessary to correctly compute the polarization angle of elliptically polarized emission. The addition of a magnetic field to the usual Stark electric field creates transitions which emit light polarized parallel to the magnetic field. They find that even in the usual situation prevailing in tokamak MSE/DNB systems where the Stark splitting is much larger than the Zeeman splitting, the expected polarization angle of composite sigma lines (i.e. the actual sigma lines plus the transitions with degenerate energies that are polarized parallel to B) is changed significantly if the upper states are not populated statistically. The corresponding effect on the polarization direction of composite pi lines is negligible. This physics may explain why some MSE systems observe a discrepancy between beam-into-gas and beam-into-plasma measurements. Operations ---------- Preventive maintenance on the back-up lube and seal oil pump starters for flywheel bearings 2 and 3 is nearly complete. The starters were inspected and the enclosures were cleared out with pressurized air and wiped clean. The starters will be tested early this week to assure continued satisfactory operation. Wiring for the new AC Unit in the YAG laser lab has begun. The new system will stabilize the temperature in the lab and reduce drifts in the Thomson scattering system alignment. ICRF System ----------- The new rf bypass capacitors for the J-Port antenna have been successfully installed. Installation later this week of the stainless steel covers needed to protect the capacitors will complete all in-vessel work on the J-Port antenna. Upgrade work has been completed on the #1 and #2 crowbar trigger circuits and they will be installed later this week. Lower Hybrid System ------------------- We continued tests of braze repair processes for the PPPL #3 coupler, and now hope to re-braze the #3 coupler later this week. Final machining on PPPL #1 and #2 couplers has been completed. PPPL #1 has had a successful test fit-up in the fwg (forward waveguide), and is now ready for final installation. Machining of the new lower hybrid limiter box has been completed. Fabrication of the moly tiles for the limiter will begin this week. Design of the launcher probes has been completed and the vendor will begin fabrication of the probes within the next few days. Studs for mounting the limiter in-vessel will be installed this week. The LH Probe Patch panel has been machined and is being assembled and labeled in the electronics shop. Several LH top exit probe boards were modified (.010" milled off of the tops) for a better fit in housings and were then successfully tested. Construction continues on the CPS (coupler protection system). The cables and the optical interface board are being fabricated. Work also continued on the filament V-f and f-V system. One chassis containing the receiver board, filament variacs, and the new digital panel meters has been installed and calibrated in the cart 1 rack. The PLC scale factors have been changed to appropriate values for the new boards, and all filament voltage and current readings display properly on the cart 1 operator interface screen. The old filament control chassis that was used for cart 1 is currently in the electronics shop getting stripped and retrofitted for the new control boards. Re-calibration work continued on the the vector modulators and IQ detectors used in the microwave phase and amplitude control system. Labview and IDL programs are being reviewed and documentation improved. Discussions have begun on the timing system and interlock hardware cabling requirements. Long Pulse DNB -------------- The old control rack is currently being disassembled in preparation for re-installation into the new shorter rack. Several modifications are underway for gauge control mounting and general cleanup of the rack. The installation of the DNB AC power control system continues. The wiring in the LimitAmp is in progress, and the installation and wiring for the cell Hoffman control/status box has been completed. The wiring in the hi-yard of the 5 kV circuit breaker cubicle has also been completed. The power room mezzanine wiring interconnections have been made at the cross-connect blocks, and the control room SBM breaker control switch and status lights should be wired by the end of this week. Our vendor has installed the cable tray and 5 kV cable from the sub-station to the Power Room LimitAmp. Cell control wiring for the 5 kV LimitAmp interface relays to the PLC has begun. Our vendor has identified the GE IOC's needed and will be quoting cost and availability. The Westinghouse ground IOC relay replacements are being evaluated. Diagnostics ----------- We continued procurements and fabrication work for the new polarimeter prototype diagnostic. Power supplies and rf driver components for the Bragg cells are being procured, optical component layouts are being developed, and the vacuum flange and window design has been completed. Travel and Visits ----------------- Josh Stillerman traveled to the ESnet Collaboration Workshop at Berkeley Lab last week and gave a presentation on our current use of remote collaboration services. Darin Ernst, Martin Greenwald, Ian Hutchinson, Earl Marmar, Miklos Porkolab, John Rice, Jim Terry, and John Wright attended the IAEA Fusion Energy Conference last week in Vilamoura, Portugal. Alcator C-Mod papers and posters presented at the conference can be found at http://www.psfc.mit.edu/cmod/sciprogram/iaea/index.html _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly