Alcator C-Mod Weekly Highlights April 13, 2001 Work continued this week on the J-Port antenna modifications, LH MIE Project, and several diagnostic systems. Installation of the J-Port antenna will begin early next week. ICRF Systems ------------ All stripline components for the J-Port antenna upgrade are back in-house following copper plating. Final machining operations have been completed and the components have been fitup on the antenna test stand. A picture of the fitup can be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/RF/ICRF/P0001488.JPG Note that the surfaces conducting rf currents have been copper plated while the rest of the surfaces have been left bare inconel. This design detail reduces disruption forces by a factor of two. The components are now undergoing a vacuum bake after which installation invessel will begin early next week. The windows, pressure monitoring tube, electric break, bellows, and gauge have all been successfully leakchecked on the J-Port flange. The fibers have been installed in the windows, back illuminated, and aligned to view the striplines. Components for supporting the gauge, magnetic shielding, and pressure tube have been machined and are undergoing fitup. The PMT amplifiers needed for the fiber views have been modified for the faster response time needed for fault detection and are ready to be re-installed in the cell. The rf vacuum feedthroughs are being installed and leakchecked. Sixteen of approximately twenty phase demodulator modules have been upgraded, checked for proper operation, and re-installed. The primary focus for work on the rf instrumentation has now shifted to maintenance of interconnecting wiring and cabling. Diagnostics ----------- The CXRS F-Top periscope has been reinstalled. Transmission measurements were completed and show that the transmission increases from more than 70% at 2500 A to more than 80% at 7500 A. Measurements following removal at the beginning of the current vacuum break indicated no transmission at the lower wavelenghts due to plasma-induced coating. The coating was removed by polishing. The machining of the core and edge shutters for the invessel CXRS optics is complete. Both systems have been re-installed invessel and tested for proper operation. The only remaining task is spot welding the control cable runs into position. Adding shutters to these systems was a strong recommendation of the DNB review committee. The high-resolution edge CXRS system has also been re-installed. A new window and grounding grid have been added to this systems to protect its mirror from glow discharge cleaning and boronization. The modified waveguides for the heterodyne ECE system were brazed, cleaned and baked, and the optics were re-installed at F-port. The modifications to the in-vessel quasioptical focussing system are now complete. The transition waveguides were modified to improve the imaging of the ECE system and increase the maximum k that can be observed by the system. Work continued on the design of the driver electronics for the MHD antenna. Lower Hybrid MIE Project ------------------------ At PPPL, two three-window prototype couplers have been successfully brazed and passed leakchecks. A process for repairing leaking window seals was also developed and tested successfully. Windows with larger corner radii, which would have reduced stress levels compared to the current windows, are also being prepared. These tests are very encouraging, and indicate we can expect good results as we go to the 24 waveguide coupler modules needed for the lower hybrid launcher. MIT and PPPL are discussing plans for high power component testing to be done when the high voltage power supply and klystron installations are complete in approximately seven to eight months. The list includes 3db couplers, water loads, DC breaks, phaseshifters, and tapers. Limiter shape and field ripple data have been given by MIT to PPPL to be used in designing the coupler plasma facing surface. The prototype digital serial fiber optic link is now running at its design speed of 50 Ksamples/s. The prototype will be linked to the I/Q vector modulator as a primary test of the link. Work on the LH phase and amplitude control system continues. Digital i/o definitions and descriptions have been completed. The walk-through for prospective contractors for the LH site modifications was held this week. Work proceeds on the klystron cart modifications and wiring. A new safety interlock key/lock was test fitted. This lock is manufactured by the same company used by our high voltage power supply vendor, and will use their key interlock system. This system will provide seamless compatability with the safety key interlock system in the power supply container used to provide access to high-voltage areas associated with the Lower Hybrid transmitter. The electrical design of the transmitter control electronics is nearly complete. Work this week concentrated on the interconnection wiring; specifically, the EMI/RFI interface. Inner Divertor -------------- Components continue to arrive and be checked. The vendors for the backing- and C-plates continue to make progress. Pictures of tile fitups on one of the plates can be found at http://www.psfc.mit.edu/cmod/operations/EngImages/MACHINE/Divertor/Apr12_09.jpg The fish scale design of the tiles can be seen as well as the ribs machined into the plate to restrain tile motion. Power Systems ------------- All work on the commutation capacitor banks has been completed, including calibration of the Rogowski coils. Travel and Visits ----------------- Les Gereg and Joe Frangipani from PPPL visited this week to help with the fitup of antenna components and the installation of the rf feedthroughs. Pat Diamond visited Thursday and Friday and gave two informal talks and the PSFC seminar. He talked with several C-Mod physicists. Martin Greenwald travelled to Lausanne Switzerland to participate in the international database meeting held April 2-5. He took the opportunity to meet with Jo Lister, Basil Duval, Richard Pitts and Yves Martin to discuss plans for joint experiments with the TCV group. Last Friday, 4/6, Amanda Hubbard gave the Plasma Physics Colloquium at Columbia University, NYC, entitled "Edge transport barrier and fluctuations in Alcator C-Mod". John Rice was at the Univ. of Wisconsin on Monday, Apr. 9, and gave a seminar on the latest C-Mod results. Rejean Boivin was at GA this week and gave a talk on neutrals. Paul Bonoli participated in the NTCC PAC meeting.