Alcator C-Mod Weekly Highlights May 31, 2011 FY2011 weeks of research operations Target: 15 weeks Completed: 14.5 weeks Plasma Shots: 1706 Physics ------- "Edge temperature gradient as intrinsic rotation drive in Alcator C-Mod tokamak plasmas", J.E. Rice et. al., has been published online in the 27 May 2011 issue of Physical Review Letters (Vol.106, No.21): URL: http://link.aps.org/doi/10.1103/PhysRevLett.106.215001 DOI: 10.1103/PhysRevLett.106.215001 This paper discusses the intrinsic rotation of I-mode plasmas from the C-Mod tokamak, which is found to be similar to that seen in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge Grad(T), but completely different edge Grad(n), it may be concluded that the drive of the intrinsic rotation is the edge Grad(T) rather than Grad(P). Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated. Operations ---------- With help from PPPL, we used our Faro Coordinate Measurement Machine (CMM) to make precise measurements of in-vessel component locations. The location of the installed studs for the new QCM antenna were some of the first locations measured. Measurements were also made that will be needed for the new rotated ICRF antenna installation as well as the new outer divertor. We continued routine maintenance of C-Mod power systems. ICRF Systems ------------ Work on the rf breakdown experiment continued last week. All 4 current straps for the new ARRA funded ICRF antenna are in-house and being prepared for plating. A Fast Ferrite Tuner (FFT) test coil has been fabricated and will be used to test new servo amplifiers. The three chillers needed for the ARRA funded FFT system upgrade have been shipped. Lower Hybrid System ------------------- Work continued on the design and testing of a high power waveguide FFT based on garnet ferrite material. Design of system protection and interlocks required for the voltage-controlled attenuator and phase shifter is in progress. Diagnostics ----------- A procurement order has been placed for a new MSE shutter that will provide 4 positions for in-vessel angular calibration. Design has been completed for a fiber assembly to carry light from outside the C-Mod vacuum vessel to the in-vessel calibration system, and RFQs have been issued for fabrication. A ceiling module containing a flush probe array was installed in-vessel, and a brightness calibration of the CXRS system was completed. Travel and Visitors ------------------- Steve Raftopoulos, PPPL, visited last week and worked with Rui Vieira and Sam Pierson setting up and operating the CMM arm in-vessel. Jim Terry And Luis Delgado-Aparico attended the ITPA Diagnostics Topical Group meeting in Noordwijk, the Netherlands, held May 23-May 26. Jim reported on ITER-relevant diagnostics work in the US, including the latest results from the C-Mod polarimetry diagnostic. Jim also presented a report, for which Ken Young (PPPL) was the lead author, on R&D needed for diagnostics on a next-step device. Luis reported on the on-going work at C-Mod to test methods of high resolution x-ray crystal spectrometer calibration. X-ray spectroscopy is planned as a key plasma rotation diagnostic for ITER, and a precise wavelength calibration technique is needed to ensure that the ITER measurement requirements will be met. Bruce Lipschultz traveled to Helsinki Finland to chair the ITPA SOL/divertor meeting held May 16-19. A number of topics were covered including molecular dynamics modeling of surfaces, efforts to remove fuel from Be and W, material migration, and tungsten melting. He then traveled to Forschunzentrum Juelich to visit the Textor group (May 20 and May 23). He gave a talk on the C-Mod plasma boundary program and visited with several scientists to discuss work on tungsten/molybdenum melt dynamics, disruption heat loads and in-situ measurements of H and impurities in and on surfaces. Bill Dorland visited the Alcator group to discuss gyrokinetic modeling using the gs2 code. He gave an informal seminar on 'entropy cascades' to the turbulence simulation users group. We anticipate active collaboration in this area especially with his former student (Michael Barnes) who will be joining the PSFC theory group at the end of the summer. Doug McCune, PPPL, visited the Alcator group to discuss various issues related to the use of TRANSP on C-Mod including data preparation for TRANSP runs, physics enhancements, and workflow tools for supporting the use of TRANSP output in gyrokinetic simulations. _______________________________________________ Cmod_weekly mailing list Cmod_weekly@lists.psfc.mit.edu http://lists.psfc.mit.edu/mailman/listinfo/cmod_weekly