Alcator C-Mod Weekly Highlights May 11, 2001 The 120C bake of the vessel has been completed and ECDC wall conditioning has begun. Work continues on rf, DNB, divertor, and Lower Hybrid systems. Engineering and diagnostic systems are being checked out and readied for machine operation early next week. Physics ------- At the physics meeting Bruce Lipschultz updated the C-Mod group on the ongoing collaborative work between C-Mod and DIII-D on SOL transport. Similar measurements have been made on both experiments for a range of densities. It is found, at least for the L-mode discharges studied, that the scrapeoff layers of both experiments exhibit two e-folding lengths - a short one in the 'near' SOL (near to the separatrix) and a longer e-folding length in the region farther from the separatrix (far SOL). These measurements have allowed the same analysis technique to be applied to the SOL data from each machine. The results of this analysis show similarities in ionization profiles and an inferred cross-field particle diffusion coefficient, D_eff. D_eff is low near the separatrix, rising by a factor of 10 or more in the far SOL. The main differences between the two experiments in this analysis were in the magnitude of D_eff. The discharges on the two experiments are similar in a dimensionless sense. Using the dimensionless scaling of density (1/a^2) the SOL profiles of density from both experiments can be overlayed, again showing the near and far SOL e-folding length similarities. The profiles overlayed well with the far SOL e-folding length becoming longer (flatter) at higher density . The primary difference was in the near SOL where the DIII-D density e-folding length was longer (in r/a) than that for C-Mod. Operations ---------- The 120C bake was ended with very good results on Monday, 5/7. A helium leakcheck found no leaks. ECDC wall conditioning in deuterium was started in the afternoon and will continue almost continuously until operation begins. A problem with a new data acquisition computer was fixed on Thursday and shot cycle tests were begun. Proper operation of the engineering CAMAC data acquisition equipment was confirmed and new hi-yard and alternator signals were checked. The gas fueling system was used to puff gas into the vessel and confirm operation and measure response times of the diagnostic pressure gauges, including the new J-Port gauge. The rf and magnetics data acquisition modules were tested, among many others. The Hybrid computer, which is used for real-time plasma control, is operational. ICRF Systems ------------ We continue to methodically work through and check all fault and interrupt signals for all transmitters and antennas. Protection electronics trip levels are being checked. Calibration of the phase detectors continues. Lower Hybrid MIE Project ------------------------ Assembly instructions and wiring information for the transmitter equipment rack HV control panel were released this week. The layout for the current transformers has also been completed. The layout of the PC boards for both the transmitter equipment rack and the coupler protection system is proceeding. We continued discussions with our HV power supply vendor to finalize the key-interlock system. We have begun planning the waveguide runs from the klystron carts to the launcher. A list of design requirements is being developed to guide this process. Cable, water, and air runs will be integrated into this design. DNB --- The DNB duct pressure monitors were completed this week. The ion gauge was repaired and reinstalled with a gate valve so that any future failures will not require venting of the beam for repair. Two H-alpha monitors were installed and software developed to compare their signals. The baratron gauge was tested and integrated into the data acquisition system. Continuation of the beam conditioning, which was delayed last week by the failure of a pressure gauge, was further delayed this week by a system-wide CAMAC problem. Conditioning of the beam was resumed on Friday. Inner Divertor -------------- Vendors continued fabrication of the C and backing plates. In house work focused on the new probe array to be installed in the divertor, and completion of the inner divertor mockup. All tiles are now inhouse. The tiles and tile support plates are being baked. Power Systems ------------- The alternator was brought up to 500 RPM on Friday and all major support systems were checked for proper operation. A full speed test will be carried out next Monday. Travel and Visits ----------------- Miklos Porkolab, Steve Wukitch, Paul Bonoli, and Eric Nelson-Melby attended the 14th Topical RF Conference in Oxnard, Ca this week. Steve Wukitch gave an invited talk on "Results from ICRF Experiments on Alcator C-Mod." Eric Nelson-Melby also gave an invited talk on "Phase Contrast Imaging of Ion Bernstein and Fast Waves in Alcator C-Mod." Paul Bonoli presented a poster on the "Analysis of ICRF-heated Transport Barrier Experiments in Alcator C-Mod." Yongkyoon In visited KSTAR (Korea Superconducting Tokamak Advanced Research) project in late April. He was told that the project is on schedule for completion in 2004.