Alcator C-Mod Quarterly Progress Report – FY10 Q4
The main activity at Alcator C-Mod during the fourth quarter of FY10 was operation of the machine. There was a total of 25.2 research days and 6.3 research weeks. The grand total for FY2010 was 21.0 research weeks.
Publications
Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak
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Phys. Plasmas 17, 082508 (2010)
Papers authored by two C-Mod physicists have been selected to the short list for the 2010 Nuclear Fusion Journal award. "Plasma-surface interaction, scrape-off layer and divertor physics: Implications for ITER", by B Lipschultz et al. and "Inter-machine comparison of intrinsic toroidal rotation in tokamaks" by J E Rice et al. were among the 11 short-listed papers selected. Nominations are based on citation record and recommendation by the Board of Editors.
Physics
We are not able to predict accurately the width of the Scrape-Off-Layer heat-flux. First-principles’ physics-based transport models are unable to match reliably multiple present-day experiments, and existing empirical scaling laws for heat-flux widths are ambiguous and uncertain. Yet this information is crucial for ITER and beyond, since it will dictate the difficulty of a “divertor solution” that satisfies the power outflow and materials constraints. The US DoE’s 2010 Joint Research Target was directed at this crucial problem by "Conduct[ing] experiments on major fusion facilities to improve understanding of the heat transport in the tokamak scrape- off layer (SOL) plasma..."
The final report on this milestone was submitted to the Office of Fusion Energy in early October. The research consisted of coordinated experiments carried out on Alcator C-Mod, DIII-D, and NSTX, as well analyses of the observations by groups from the simulation and modeling communities. A number of important results were obtained, and all high level goals of the milestone were met. The 207-page report can be found at
http://www.science.energy.gov/ofes/ProgramTargets/FY2010_JRT_Q4report_final.pdf
On
C-Mod the major results included documentation of dependencies of the heat-flux
width on plasma current (width in the near-SOL ~ Ip-1)
and on plasma stored-energy (integral width ~ Wp-0.3). A
typical heat-flux “footprint” on the outer divertor target is shown in Fig. 1.
Additionally no dependence on toroidal field, power entering the SOL, or total
field-line connection length was found for the heat-flux width. The Ip
dependence (and Bt independence) of the width are shown in Fig. 2. Critical
pressure gradient physics is strong candidate to explain Ip scalings
and the insensitivity of width to SOL connection length. The width
dependence on stored energy implies connection of the width with confinement
and/or pedestal transport. On C-Mod this research motivated the build-up of a
diagnostic infrastructure that will continue to yield valuable results well
beyond the time period of the milestone.
A number of C-Mod presentations at the APD-DPP meeting (November 8-12) are related to this research, including two invited talks (B. LaBombard, A. Loarte) and three contributed talks/posters. The inter-laboratory working group assembled for this JRT effort is continuing to meet and analyze the results from the three devices.
Meetings
Ian Hutchinson and Anne White traveled to Cambridge, U.K., July 19-23 to attend a Workshop on Kinetic-Scale Turbulence in Laboratory and Space Plasmas at the Isaac Newton Institute of Mathematical Sciences. This Workshop was the first week of a month long meeting on Gyrokinetics in Laboratory and Astrophysical Plasmas. Ian presented an invited talk entitled "Spontaneous tokamak rotation: observations turbulent momentum transport has to explain" and Anne presented an invited talk on "Measurements of electron temperature fluctuations on DIII-D". The program focused on gyrokinetics for fusion plasmas as well as applications to space and astrophysical plasmas. More information can be found at
http://www.newton.ac.uk/programmes/GYP/gypw01p.html
A C-Mod DoE quarterly review (FY2010 Q3) was held by video-conference on Monday, July 26. Attending from OFES were Mark Foster, Mark Koepke and Steve Eckstrand. PPPL was represented by Randy Wilson, and U. Texas by Bill Rowan. Presentation viewgraphs from the review are linked at:
http://www.psfc.mit.edu/research/alcator/pubs/Q_Reviews/Q_Rev_07_26_2010.pdf
Yuri Podpaly attended the ASOS (Atomic Spectra and Oscillator Strength) 2010 meeting in Berkeley, CA from August 3rd through August 7th and presented an invited talk titled "Tungsten Measurements on Alcator C-Mod and EBIT for Future Fusion Reactors." All conference presentations will be available at
http://sprg.ssl.berkeley.edu/labastro/ASOS10/
A C-Mod/NSTX Pedestal Workshop was held on September 7--8 at PPPL. The purpose of this 1.5-day workshop, which was co-chaired by Jerry Hughes (MIT/C-Mod) and Rajesh Maingi (ORNL/NSTX) was to gather and discuss ideas for FY11 research on both C-Mod and NSTX that could advance the predictive capability for the H-mode pedestal, i.e. the goal of the FES FY11 Joint Research Target. Twenty-four talks were presented by experimentalists, theorists and modelers from several institutions, including GA, LANL, LLNL, MIT, NYU, ORNL, PPPL and U. Wisconsin. The ideas discussed at this workshop will provide input for the planning of the FY11 run campaigns on both devices. Talks will be archived at the meeting website:
http://www.psfc.mit.edu/research/alcator/pubs/Cmod_NSTX_Wkshp_2010/
Domestic Travel
Paul Bonoli attended the annual Scientific Discovery Through Advanced Computing Conference ("SCIDAC 2010"), held in Chattanooga, TN from July 11-15, 2010.
Steve Wukitch participated in a Fusion Simulation Project-Wave Particle Interaction conference call the week of July 19. He also participatd in the sorters' meeting for the APS Division of Plasma Physics Meeting at APS Headquarters in Greenbelt, MD.
Dennis Whyte and Joe Minervini attended an OFES meeting in Washington, DC the week of July 19 discussing Fusion Nuclear Science Pathways.
Martin Greenwald traveled to Washington D.C. to attend a "NERSC requirements workshop" for FES. He also attended a focus group, convened by undersecretary Koonin, to comment on the DOE 2010 strategic plan currently under development.
Yuri Podpaly attended the ASOS (Atomic Spectra and Oscillator Strength) 2010 meeting in Berkeley, CA from August 3rd through August 7th.
Aaron Bader traveled to Oak Ridge National Labs the week of Aug.9 to work with Fred Jaeger and Lee Berry on running simulations to model Compact Neutral Particle Analyzer (CNPA) fast ion data.
On Monday 8/9/2010, Arturo Dominguez traveled to PPPL to discuss plans to use the FWR2D code to analyze data from the correlation reflectometry system.
Jerry Hughes and Michael Churchill traveled to Princeton, NJ to participate in the C-Mod/NSTX Pedestal Workshop on Sept.7-8.
John Wright, Haruhiko Kohno, Jungpyo Lee, and Paul Bonoli attended the annual workshop of the SciDAC Center for Simulation of Wave-Plasma Interactions that was held at Princeton Plasma Physics Laboratory on September 14-16.
Martin Greenwald was at PPPL the week of Sept.20 to make presentations to the FSP
(Fusion Simulation Project) PAC. Earl Marmar was also there as a member of the PAC.
Amanda Hubbard, Bill Rowan, UTexas, and Perry Phillips, UTexas, attended the U.S. ITER Diagnostic Conceptual Design Workshop at PPPL the week of Sept.20.
Pat MacGibbon traveled to Palo Alto, CA, the week of Sept.27 to witness the acceptance tests of two new klystrons.
International Travel
Ian Hutchinson and Anne White traveled to Cambridge, U.K., July 19-23 to attend a Workshop on Kinetic-Scale Turbulence in Laboratory and Space Plasmas at the Isaac Newton Institute of Mathematical Sciences.
July 26-29 Jim Terry visited the ITER site to participate as an "external expert" on the Conceptual Design Review (CDR) panel for the ITER Upper Port Visible/IR Wide Angle Viewing systems. This US-credited diagnostic system is to be installed in six of the ITER upper ports in order to have ~300 degree imaging coverage of the lower outside divertor.
Yijun Lin taught courses on "ICRF theory and experimental applications on tokamaks" at the 4th Chinese Summer School on Plasma Physics in Shanghai, China.
John Rice attended the EU/US TTF meeting in Cordoba Spain Sept. 6-10 and gave a talk on C-Mod rotation results in I-mode.