Alcator C-Mod Weekly Highlights January 20, 2009 FY2009 weeks of research operations: Target: TBD Completed: 0 weeks Physics ------- It is critical to understand the poloidal length over which the edge exhaust power is distributed in the divertor for ITER and future fusion reactors, since it is predicted that the peak steady-state heat removal requirements could surpass technology limits for actively cooled materials. Empirical laws for divertor heat widths, derived from fitting measured power widths in many devices, have been used by Dennis Whyte to develop a multi-device database that also contains upstream SOL profiles. It was found that, in general, the divertor heat width increased ~R, even if R was not a parameter in the scaling law, due to co-dependences with power and field. The divertor power width also correlates to the upstream power width, although the mapped divertor footprint is much wider than 2/7 of the upstream Te width, and scales more like the upstream plasma pressure width, which is consistent with simplified interpretations of the two-point SOL model. Further analysis is being carried out to verify the inferred power widths on C-Mod, since the empirical laws did not use C-Mod data in their fits. Operations ---------- All the lower TF arms were installed last week. Preparations are being made for installation of the spring-plates that provide the pressure and compliance required for proper operation of the sliding joints. We continued testing vessel heaters and vessel and structure thermocouples. Fabrication of the flexible boots that allow the cryostat to be sealed around the vertical ports is well underway. The vendor performing the UT and eddy current inspection of the rotor completed the 2nd half of the inspection last week. We expect this latest set of data to be available in the next few days. Two independent companies are in the process of analyzing data from the 1st half of the inspection that was done from roughly the mid-rotor out to the collector end. They will continue with the analysis of the 2nd set of data as soon as it is available. Lower Hybrid System ------------------- Fabrication of 2nd launcher components continued last week both in-house and at our vendor. Fabrication of tooling and fixturing for brazing the windows into the forward waveguides also continued. Design efforts have begun on the interface required to incorporate the new probe signals into the CPS (coupler protection system). Work also continued on the TPS (transmitter protection system) Upgrade. ICRF Systems ------------ Work continued on the FPA (final power amplifier) grid regulator. The installation of ferrite beads stopped the oscillation found when replacement MOSFETs were installed in the regulators. Somewhat more stable MOSFETs are also being tested, and in combination with the ferrite beads should provide a robust design. The original, more stable, MOSFETs used in the regulators are no longer available. Travel and Visits ----------------- Alan Binus and Steve Wukitch met with a leading vendor in power system design regarding upgrading an FMIT transmitter as part of a Phase I SBIR. We are specifically interested in eliminating the ignitron based crowbar unit, increasing the FPA anode supply current to 200 A, and improving FPA voltage regulation. Amanda Hubbard participated in the FESAC meeting held in Gaithersburg, Maryland on Jan 13th. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly