Alcator C-Mod Weekly Highlights March 23, 2009 FY2009 weeks of research operations: Target: TBD Completed: 0 weeks Operations ---------- We continued machine re-assembly last week with the installation of the retaining cylinder and top dome. TF hi-pot, ring, and joint resistance measurements were successfully repeated following tensioning of the draw bars that hold the domes and cylinder together. The magnet bus tunnel has been moved back into position, and the TF bus is being connected to the TF magnet. Preparations are being made for installation of the curved bus components that are supported by the cylinder and provide electrical connections to the other magnets. Testing of alternator rotor samples also continued last week. Fatigue crack growth tests of samples from the collector end of the rotor indicated good properties with very slow growth rates, consistent with those expected of rotor steels. Tensile tests of turbine end samples also indicated good material properties. Compact tension and crack growth samples from the turbine end of the rotor have been machined and documented in preparation for testing this week. Lower Hybrid System ------------------- Fabrication of the 2nd lower hybrid launcher components continued. We also began bringing the klystrons back on line, and updating control system parameters taking into account repositioning of one of the klystrons. Transmission line components are being leak checked to ensure proper operation when they are pressurized (nitrogen or SF6). Electromagnetic simulations of transmission line components to determine how to maximize rf power handling capability continued. ICRF Systems ------------ Development of the rf control system upgrade continued and discussions with one of our vendors solved some micro-controller issues. We continue to prepare FMIT#3 for use with the rf breakdown test stand. Diagnostics ----------- On Friday, March 20 Professors Russel Chipman and Steve McClain of the University of Arizona College of Optical Sciences visited the PSFC for discussions with Steve Scott and others on the MSE optical components. Their measurements of the MSE dielectric-mirror phase shift indicate that it is much larger than the original design specification. It is not known whether the discrepancy is due to fabrication errors or deterioration over time. Their analysis confirms a prior suggestion at the PSFC that the spurious change in pitch angle caused by stress birefringence in the lenses can be reduced not only by reducing the (variable) thermal gradients in the lenses, but also by reducing the (fixed) phase shift in the mirrors. Delivery of new high-performance mirrors with a maximum phase shift of 3 degrees is expected in April. Prof. Chipman and McClain also had some useful suggestions for reducing field curvature at the fiber dissector, and for investigating loss of etendue. Travel and Visits ----------------- Syun'ichi Shiraiwa participated in the US-Korea-Japan rf workshop held in Toki, Japan last week. Greg Hanson, ORNL, visited for discussions on the placement and testing of the SOL reflectometer electronics. Remaining tests and waveguide layout external to the machine were also discussed. David Mikkelsen visited MIT to discuss proposals for the C-Mod Ideas Forum. Topics discussed included documentation of collisionality and q scans in peaked-density H-mode plasmas, documentation of the full evolution of ITER similarity discharges, and measuring the radial correlation length of density fluctuations in peaked-density H-mode plasmas. Pat Diamond, UCSD, visited lasted week and gave a seminar on the physics of off-diagonal momentum flux and the origins of intrinsic rotation. He had discussions with several C-Mod scientists on rotation. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly