Alcator C-Mod Weekly Highlights December 17, 2012 FY2013 weeks of research operations Target: tbd Completed: 0.53 weeks Plasma Shots: 61 DoE C-Mod Quarterly Review -------------------------- On Thursday, a DoE C-Mod quarterly review, covering FY2012-Q4, was held by video-conference. Attendees from OFES included Mark Foster, Jim Van Dam, John Mandrekas and Curt Bolton. Slides from the presentations can be found at: http://www.psfc.mit.edu/research/alcator/pubs/Q_Reviews/Q-rev_Dec12/Q-rev_012-13-12.pdf Operations ---------- In-vessel calibrations of the Hi-REX system were completed last week. The first set of toroidal and poloidal calibrations for the U. Texas Core CXRS system has been completed. Radiometric calibrations for the "boron", "helium" and "hydrogen" gratings have been finished. Routine maintenance work on the alternator and magnet power supplies continued. Advanced Outer Divertor (AOD) ----------------------------- Development of the spherical bearing test stand continued last week. More drawings were finalized and made ready to issue to vendors. Test fit-ups of the vacuum flanges were completed. An assembly procedure for the test stand has been developed. Design of the connector assembly for the Langmuir probes has been completed, and is ready for review. Work continues on the probe bar assemblies, and the tile designs needed to accommodate the surface temperature and thermocouple assemblies. Heater connector prototypes are being fabricated and testing is expected to begin soon. Vacuum feedthroughs and cabling for the heaters is being specified. ICRF Systems ------------ FMIT#4 was tuned at low power (300 kW) to 53 MHz and the inter-stage matches were found to be good. However, the drive anode current was too high and resulted in an overload condition at 500 kW. After installation of a second current sensor, a series of tests showed that the high driver anode current reading was the result of inaccurate metering. A pulse power source has been set up to test the driver anode current sensor. It was also determined that 50 MHz filters were attenuating the monitoring signals such that the signals were under-reported. The filters will have to be replaced. Inspection of the newly arrived FFTs has continued, and 3 of the 4 have residual liquid and machining marks that require cleanup. A location for the power supply cabinets has been identified in the cell that allows efficient routing of interconnection cabling. Lower Hybrid Systems -------------------- Work on the LH FFT continues. An IQ detector was set up and calibrated for the FFT control system. The "LH Mod Box" (part of the klystron control system upgrade) attenuator/phase shifter combination was used to generate the raster scan for the IQ calibration. The rounded corner ferrite sample was reconditioned and tested at high power for longer pulses. The ferrite was able to withstand 105 kW for 99 ms. A plan was made to continue high power testing of the FFT with sulfur hexafluoride in the waveguide. A safe handling procedure was developed for using SF6 in the LH waveguides. Design work has begun on the mezzanine extension needed to support control cabinets for the 4th cart. Plans are being made for moving the 4th cart and upgrading the LH water cooling system to support the cart. Diagnostic Systems ------------------ Zach Hartwig presented a run summary and first physics results from the accelerator-based in-situ PFC beam diagnostic on Alcator C-Mod at the C-Mod DoE Quarterly Review last week. Several experiments were conducted between early August (installation) and mid-November (pre up-to-air). Experiments included the final three hours of plasma shots during the FY12 campaign, in which inner-wall limited shots were run continuously in an attempt to perturb the PFCs available for measurement. Other experiments included a dedicated boronization of the inner wall PFCs followed by electron cyclotron discharge and glow discharge cleaning. Two physics results were presented: first, relative boron-11 and oxygen-16 isotope concentrations at a single location were shown to decrease during plasma and cleaning operations, consistent with the erosion of a thin film coating the PFC; second, relative boron-11 and oxygen-16 isotope concentrations at 5 poloidal locations over ~21 cm of the inner wall were shown to be significantly different, possibly indicative of complex transport and plasma-wall interaction processes. It was emphasized that only a small fraction of the total FY12 data had been analyzed so far; further analysis is presently underway. Remote Participation, Travel, and Visitors ------------------------------------------ Bruce Lipschultz attended the ITPA Coordinating committee meeting as well as the IEA cooperation agreement meeting in Cadarache, December 10-12, as the C-Mod representative. Presentations were made by all ITPA groups for the Coordinating committee. C-Mod participation in both past and future ITPA collaborations was discussed during many of these presentations. It was clear that C-Mod contributions to ITPA work were very significant, particularly for the size of the C-Mod program. Bruce then spent two days visiting the ASDEX-Upgrade tokamak staff. Most of the discussions were about efforts at AUG and C-Mod to improve impurity seeding capabilities. Research on both tokamaks indicates that it is essentially impossible to detach the divertor plasma at high power without putting a lot of impurities in the core. David Mikkelsen, PPPL, visited MIT to discuss simulations of electron-driven turbulence in Alcator C-Mod. Two classes of simulations have been run that included ETG turbulence (without low-k turbulence), and dominantly TEM drive (without ETG-range turbulence). We continued to work with Chang-Le Liu, EAST tokamak, Hefei Institutes of Physical Science, to develop COMSOL and ANSYS models to be used for analysis of the EAST divertor. More accurate eddy current calculation can now be done. Seung Gyou Baek presented a 30 minute oral talk, "Observations of ion cyclotron parametric decay instability at the high-field side of Alcator C-Mod tokamak" at the US-Japan RF heating physics workshop in Nara, Japan. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly