Alcator C-Mod Quarterly Progress Report – FY11 Q3

The main activity at Alcator C-Mod during the third quarter of FY11 was preparation of the new field aligned ICRF antenna.

Publications

A paper on the I-Mode (Dennis Whyte, et al., "I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod", Nucl. Fusion 50, 105005 (2010)) has been designated by the journal as a highlight paper for 2010, and was one of the 20 most frequently downloaded articles of 2010

http://iopscience.iop.org/0029-5515/page/Highlights%20of%202010

Y. Lin et al 2011 Nucl. Fusion 51 063002 doi: 10.1088/0029-5515/51/6/063002

ICRF mode conversion flow drive on Alcator C-Mod

Y. Lin, J.E. Rice, S.J. Wukitch, M.L. Reinke, M.J. Greenwald, A.E. Hubbard, E.S. Marmar, Y. Podpaly, M. Porkolab, N. Tsujii and the Alcator C-Mod team

V.A. Izzo et al 2011 Nucl. Fusion 51 063032 doi: 10.1088/0029-5515/51/6/063032

Runaway electron confinement modelling for rapid shutdown scenarios in DIII-D, Alcator C-Mod and ITER

V.A. Izzo¹, E.M. Hollmann¹, A.N. James¹, J.H. Yu¹, D.A. Humphreys², L.L. Lao², P.B. Parks², P.E. Sieck², J.C. Wesley², R.S. Granetz³, G.M. Olynyk³ and D.G. Whyte³

R. Maingi et al 2011 Nucl. Fusion 51 063036 doi: 10.1088/0029-5515/51/6/063036

Comparison of small ELM characteristics and regimes in Alcator C-Mod, MAST and NSTX

R. Maingi¹, A.E. Hubbard², H. Meyer³, J.W. Hughes², A. Kirk³, R. Maqueda⁴, J.L. Terry² and the Alcator C-Mod, MAST and NSTX teams

Scaling of the power exhaust channel in Alcator C-Mod

B. LaBombard, J. L. Terry, J. W. Hughes, D. Brunner, J. Payne, M. L. Reinke, I. Cziegler, R. Granetz, M. Greenwald, I. H. Hutchinson, J. Irby, Y. Lin, B. Lipschultz, Y. Ma, E. S. Marmar, et al.

Phys. Plasmas 18, 056104 (2011); doi:10.1063/1.3566059

High confinement/high radiated power H-mode experiments in Alcator C-Mod and consequences for International Thermonuclear Experimental Reactor (ITER) Q_DT = 10 operation

A. Loarte, J. W. Hughes, M. L. Reinke, J. L. Terry, B. LaBombard, D. Brunner, M. Greenwald, B. Lipschultz, Y. Ma, S. Wukitch, and S. Wolfe

Phys. Plasmas 18, 056105 (2011); doi:10.1063/1.3567547

Edge energy transport barrier and turbulence in the I-mode regime on Alcator C-Mod

A. E. Hubbard, D. G. Whyte, R. M. Churchill, I. Cziegler, A. Dominguez, T. Golfinopoulos, J. W. Hughes, J. E. Rice, I. Bespamyatnov, M. J. Greenwald, N. Howard, B. Lipschultz, E. S. Marmar, M. L. Reinke, W. L. Rowan, et al.

Phys. Plasmas 18, 056115 (2011); doi:10.1063/1.3582135

Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod

A. Schmidt, P. T. Bonoli, O. Meneghini, R. R. Parker, M. Porkolab, S. Shiraiwa, G. Wallace, J. C. Wright, R. W. Harvey, and J. R. Wilson

Phys. Plasmas 18, 056122 (2011); doi:10.1063/1.3593112

Phys. Rev. Lett. 106, 215001 (2011) [4 pages]

Edge Temperature Gradient as Intrinsic Rotation Drive in Alcator C-Mod Tokamak Plasmas

Download: PDF (626 kB)

J. E. Rice¹, J. W. Hughes¹, P. H. Diamond^2,3, Y. Kosuga³, Y. A. Podpaly¹, M. L. Reinke¹, M. J. Greenwald¹, Ö. D. Gürcan⁴, T. S. Hahm⁵, A. E. Hubbard¹, E. S. Marmar¹, C. J. McDevitt³, and D. G. Whyte¹

Physics

A new rotated ICRF antenna has been designed to minimize impurity production by imposing symmetry along the total magnetic field line.  The antenna is aligned to a 10° field pitch where the typical discharge range is 7-13° in C-Mod.  Using 3-D toroidal electromagnetic finite element models, the integrated E-parallel fields are expected to be 3-10 times lower than with our present antennas.  Four antenna phases were analyzed for the field-aligned antenna: [0,π,0,π], [0,0,π,π], [0,π,π,0], [0,0,0,0]. In each case, the field-aligned antenna had reduced integrated E-parallel relative to the existing non-aligned antenna geometry. However, the most significant integrated E-parallel reduction occurs for monopole [0,0,0,0] phasing. Compared to our standard antennas (0° pitch), the power density (MW/m²) for the rotated antenna is ~50% higher for a given injected power due to a decrease in available surface area.  Due to geometric limitations, two locations have the RF electric field aligned with the total magnetic field and have the potential to limit the antenna voltage handling.

We have done a fit test of the components prior to sending the required elements out to be copper plated and a picture of the antenna without the Faraday screen is shown below.  Copper plating the stainless steel and inconel 625 is one of the remaining higher risk processes.  The risk is strictly to the schedule and not that plating is problematic.  We have successfully plated 7 of the 34 pieces and we had previously successfully verified the plating and re-plating process on test pieces including a test current strap.  The welding of the bellows tube assembly has substantial risk and is underway.  All the Faraday rod elements have been manufactured and half of the Faraday screen has been assembled.  The other half awaits the return of the parts post plating.  We have received all the required boron carbide washers, “resistive washers” and have all the hardware to assemble the Faraday rods.   Diagnostic probe assemblies have been designed but are yet to be manufactured.  Stud welding is the next in-vessel process and we are presently verifying the fixture and process on a test setup.  We are also utilizing the 3-D model in COMSOL to determine the expected electrical characteristics to allow us to design the transmission line network before the antenna is assembled.

Meetings

Over 20 C-Mod researchers participated in the Joint US-EU Transport Task Force meeting held April 6-9 in San Diego. Presentations concerning C-Mod research included one plenary session talk, nine orals, and eight posters. C-Mod presentations are being made available at

http://www.psfc.mit.edu/research/alcator/pubs/TTF/TTF_2011_abstracts.htm

The 2011 International Sherwood Fusion Theory Conference was held May 2-4 in Austin, TX. In attendance from MIT were Peter Catto, Bruno Coppi, Antoine Cerfon, Darin Ernst, Jeff Freidberg, Matt Landreman, Bo Li, P. Rebusco, Jesus Ramos, Linda Sugiyama, Anne White, and T. Zhou. Dr. Matt Landreman gave an invited talk on “Neoclassical flow, Current, and Electric Field in a Quasi-Isodynamic Stellerator”. Experimental investigation of the I-mode, disruption mitigation, edge pedestal studies, and core turbulent transport are active areas of the Alcator C-Mod research program and theoretical work on these areas was the focus of many presentations at the Sherwood conference. Posters directly related to C-Mod experiments included those by B. Coppi and T. Zhou on the I-mode regarding the connection between the Heavy Particle Mode and the observed Weakly Coherent Mode, X. R. Fu (UT Austin) on turbulent impurity transport in C-Mod and A. E. White on the gyrokinetic simulation-based design of the new Correlation ECE system on C-Mod. Many Sherwood presentations focused on theory and models of intrinsic rotation in tokamaks, including those by Felix Parra and Michael Barnes (Oxford, UK), whose work on gyrokinetic theory and simulation of momentum transport was highlighted in the Review Talk “The History and Present Status of Gyrokinetic Theory” given by John Krommes (PPPL). All abstracts, the program and the invited talks from the conference will be available online at the 2011 Sherwood Conference website

http://ptolemy.ph.utexas.edu/

Numerous C-Mod personnel participated in the 19th Topical Conference on Radio-Frequency Power in Plasma, held in Newport, RI June 1-3. Included in the program were invited oral presentations from two MIT graduate students, Orso Meneghini ("Effects of SOL on Lower Hybrid Wave Coupling and Current Drive Performance on Alcator C-Mod") and Naoto Tsujii ("ICRF Mode Conversion Studies with Phase Contrast Imaging and Comparisons with Full-Wave Simulations") along with many poster contributions from C-Mod team members. Presentations and posters can be found at

http://www.psfc.mit.edu/research/alcator/pubs/RF/rf2011index.html

Quarterly Review

The C-Mod DoE Quarterly review (FY2011, Q2) was held on Thursday, May

5. The review was carried out by videoconference with participants from MIT, FES (Germantown and San Diego), PPPL and U. Texas. Presentation viewgraphs from the review are linked at

http://www.psfc.mit.edu/research/alcator/pubs/Q_Reviews/Q-rev_May_2011/q-rev_may_2011.pdf

Mid-Term Review

C-Mod made its presentations to the DoE FES Midterm Review, which is a peer panel review of the three major fusion facilities (C-Mod, DIII-D and NSTX) at about the halfway point of the current 5 year grant period. Earl Marmar, Bruce Lipschultz and Martin Greenwald traveled to DoE Germantown for the review, and other members of the C-Mod team participated by video-conference from MIT, PPPL and U. Texas.

DoE Early Career Research Program

The DOE Office of Science announced last week its selections for five-year awards under the Office's Early Career Research Program. One of these awards went to Professor Anne White, in the MIT Department of Nuclear Science and Engineering. Her application is titled "Electron Temperature Fluctuation Measurements and Transport Model Validation at Alcator C‐Mod". The 65 awardees, encompassing all research areas supported by the Office of Science, were selected from a pool of about 1,150 university- and national laboratory-based applicants. Selection was based on peer review by outside scientific experts. More details on the program can be found at

http://www.science.energy.gov/news/in-the-news/2011/05-06-11/

Matt Reinke, who is currently completing his PhD in the MIT Nuclear Science and Engineering Department, has been awarded a two year DOE-ORISE Postdoctoral Fellowship to continue working on Alcator C-Mod. The proposed research is aimed at improving our understanding of impurity seeded (Ne,N2) plasmas by measuring the 2D (radial/poloidal) power loss layer in the pedestal region due to radiation and charge exchange. One important question to answer is how the non-trace level impurities (~1-2%) impact the pedestal regulation mechanisms in enhanced confinement discharges, including H-mode and I-mode.

Domestic Travel

John Rice attended the ITPA-TC group meeting at GA April 4-5 where he gave updates on Joint Experiments TC-9 and TC-19.

Catherine Fiore, Nathan Howard, Arturo Dominguez, John Rice, Yuri Podpaly, Mike Churchill, John Walk, Yunxing Ma, Ken Liao and Chi Gao attended the TTF meeting in San Diego April 5-9.

Joshua Stillerman served as a member of the NIF Controls and Information

Systems data system review panel at LLNL on April 13 and 14.

Anne White attended the Sherwood Meeting in Austin, TX May 2-4.

A. Bader, S.G. Baek, P. Bonoli, I. Faust, M. Garret, J.P. Lee, Y. Lin, O. Meneghini, R. Ochoukov, R. Parker, A. Ram, S. Shiraiwa, N. Tsujii, G. Wallace, J.C. Wright, Randy Wilson (PPPL), K.T. Liao, UT, and R. Wilson, PPPL, attended the 19th Topical Conference on Radio-frequency Power in Plasmas that was held in Newport, RI from June 1-3, 2011.

Earl Marmar, Bruce Lipschultz and Martin Greenwald traveled to DoE Germantown for the review June 6.

Willy Burke traveled to PPPL June 17 to serve as an outside reviewer of the preliminary design of the NSTX Digital Coil Protection System.

International Travel

Amanda Hubbard and Paul Bonoli attended the 6th Meeting of the ITPA Topical Group on Integrated Operation Scenarios (IOS) that was held at JET, Culham, UK, 11th to 14th, April 2011. Amanda gave an overview talk on recent research on Alcator C-Mod in support of ITER Scenarios and also gave a talk on recent progress and 2011 plans for the Joint Experimental Activity IOS-5.3: "Assessment of lower hybrid current drive at high density for extrapolation to ITER advanced scenarios". Paul gave a talk in which he reported on the status of the Joint Modeling Activity on Steady State Exploration (IOS-JA7).

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.

Amanda Hubbard attended the Chalmers workshop on nonlinear phenomena in fusion plasmas (CNR), held in Varenna, Italy. She gave an invited talk entitled "Transitions to H-mode and I-mode Edge Transport Barriers on Alcator C-Mod".

Martin Greenwald, Tom Fredian, Atma Kanojia and Josh Stillerman attended the IAEA 8th technical meeting on control, data acquisition, and remote participation for fusion research. Martin presented a talk on 'A Metadata Catalog for Organization and Systemization of Fusion Simulation Data'. Tom chaired an MDSplus user's group workshop. Atma presented a poster 'Active Control System Upgrade Design for Lower Hybrid Current Drive System on ALCATOR C-MOD'. Josh was the chairman of the international program committee and program chairman for the meeting. He also presented a poster 'Iscope: a new visualization tool for MDSPlus' on behalf of Syun'ichi Shiraiwa. Dave Hill, LLNL, made a presentation on behalf of the three major US Magnetic Fusion Facilities, 'Overview of U.S. Magnetic Fusion Tokamak Experiments in Support of ITER'.