Alcator C-Mod Weekly Highlights July 19, 2004 FY 2004 weeks of operation planned: 18 weeks, completed: 18.9 weeks. We are currently up-to-air with the primary goal of installing the lower hybrid launcher. In addition, a large number of invessel activities are ongoing in support of ICRF and diagnostic systems. Maintenance and upgrades to diagnostic and power systems are also in progress. Operations ---------- We continued to upgrade the engineering systems PC to PLC software interface. Equipment racks, diagnostics, and the LPI injector are being repositioned in the cell to make room for the lh launcher and other new equipment. Power Systems ------------- The installation of the 120 gate drive boards in TF #3, convertors 5 & 6 has been completed and the boards are ready to be tested. The long pulse DNB 1000 kVA power transformer has been installed in the power room. Preparations are being made to extensively test the transformer before it is powered up. The alternator seal oil system has been leak checked successfully. Preventative maintenance of the 2000 HP main drive motor is in progress. The contractor has started work on the river cooling water backup system. This system will reduce downtime in the event of a primary system failure. Diagnostics ----------- A comprehensive in-vessel calibration of the MSE diagnostic has been completed. The system response to unpolarized, linearly polarized, and circularly polarized light has been measured. Apart from small (< 1 degree) effects caused by phase shifts imposed by the MSE mirrors, the MSE hardware appears to function as originally designed. Including corrections for the phase shifts, the pitch angle measured by MSE is within 0.02 degrees of the actual pitch angle for linearly polarized light as the pitch angle of a linearly-polarized light source is rotated through a full 360 degrees. However, the invessel-calibration data have not been reconciled with beam-into-gas calibration data taken over the past 18 months. We are currently investigating potential causes of this discrepancy, including geometrical effects on the polarization of the emission spectrum; atomic physics of the Stark emission spectrum; Zeeman splitting of the spectrum; Faraday rotation in the MSE optical components; and stress-induced birefringence of the vacuum window. ICRF Systems ------------ 2 MW FPA tubes scheduled for delivery to both MIT and PPPL will be delayed several weeks because of a manufacturing problem at the vendor. This delay should not affect the C-Mod operating schedule. Lower Hybrid Project -------------------- High power testing of the rwg/fwg assembly indicated only one of forty-eight input guides was power limited below our 100 kW/0.5 s test specification. We have tracked this problem down to a displaced section of rf gasket. The fwg and rwg will be separated to allow a careful inspection and gasket replacement. Plated alumina windows sized to fit the PPPL couplers arrived in-house last week. Preparations are being made to braze these couplers as soon as the windows are qualified. New windows sized to fit the MIT couplers are being plated. Results of the latest three-window brazing prototype tests with samples of these new windows indicate the possibility of lower shear strength compared to previous samples, and evaluation is ongoing. A high temperature vacuum oven has been procured and is currently being installed at the PSFC. This facility will be used for rapid braze prototyping, and can also handle the full size production couplers. Microstripline PC boards for the lower hybrid launcher rf probes are now in house and under test. Initial results are consistent with simulations made of the probes. We continued work on the klystron amplitude and phase control system. Calibration procedures are being developed for components needed for this system. The real-time lookup table within the ACS controllers has been successfully implemented to correct and adjust for IQ detector non-linearities, offsets, gains, etc. Travel and Visits ----------------- Miklos Porkolab visited the new Max Planck Institute fur Plasmaphysik Laboratory in Greifswald, Germany,on Monday and Tuesday, July 5,6, after the EPS meeting in London. After visiting the experimental facilities, including Wendelstein 7X, he gave a seminar with the title "PSFC Overview and the Alcator C-Mod Program." He was invited by Profs. T. Klinger and F. Wagner earlier this year. Robert Granetz attended the 7th NCSX PAC meeting last week at PPPL. Unlike earlier PAC meetings, which concentrated on design and engineering issues, this PAC concentrated mostly on the NCSX research plans and diagnostics. Steve Wukitch participated in the US-Japan RF physics workshop held at Tsukuba University in Tsukuba, Japan July 14-16. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly