Alcator C-Mod Quarterly
Progress Report – Oct-Dec. 2004
The primary activities at Alcator C-Mod during the first quarter of FY05 was installation of the LH launcher.
The Fiscal Year 2004 Level 1 DoE JOULE Target SC6-1b, Compare energy confinement, H-Mode thresholds, and divertor particle dynamics in Alcator C-Mod discharges, was completed on schedule.
The first quarterly milestone for our FY05 level 1 target was completed ahead of schedule on December 21, "Install molybdenum protection tiles on all RF antennas and remove boron-nitride tiles from active MHD antennas". The milestone completion report can be found at
http://www.psfc.mit.edu/cmod/sciprogram/FY05_level1_targets/q1_complete.pdf
Science
Results
Core Confinement and Transport
MHD
Joe Snipes has been working with Nikolai Gorelenkov of PPPL to learn how to use the Nova-K code to model Alfven eigenmode stability in C-Mod ICRF heated discharges. The stability part of the code is a fully kinetic treatment with a distribution in pitch angle, a Maxwellian velocity distribution, and a radial distribution of the fast ion beta profile from TRANSP calculations. The experiments showed that for central or outboard resonances out to R_res/R_axis =1.1, Alfven cascades and TAEs were unstable, whereas for inboard resonance heating at R_res/R_axis = 0.9 no Alfven cascades were observed and only a weak downward sweeping frequency mode was observed. To attempt to model this effect, the Alfven eigenmode stability was calculated for the central resonance case leaving everything fixed but varying the ICRF resonance position in the distribution function of the fast ions from R_res/R_axis = 0.8 to 1.14. A slightly reversed shear q profile was chosen with q_0 = 2.8 and q_min = 2.7 at r/a = 0.4. Two n=2 modes were found and their growth rates were the largest when the resonance was just to the outboard side. The growth rate fell off rapidly on the inboard side becoming stable for the lower frequency mode at 311 kHz by R_res/R_axis = 0.9 as in the experiment. The other mode at 385 kHz was also nearly stable by that resonance position. The mode frequency in the experiment was 360 kHz, just in between these two unstable modes, suggesting that a slight modification to the assumed q profile would be required to fit the frequency precisely. There was qualitative agreement between the experiment and the calculations in that the inboard resonance was stable or nearly stable to the calculated eigenmodes.
The PCI diagnostic has been recently upgraded. The number of channels has been increased from 12 to 32, and the sampling rate from 1 to 10 MHz. This expansion of diagnostic capability has been used to study broadband turbulence, in addition to the analysis of the QC-mode associated with EDA H-mode.
Delivery of the new long pulse DNB is scheduled for Feb. 2005 with installation to be complete in March.
Eight new linux workstations have been installed in the control room and all of the C-Mod workstations (43) have been upgraded to RedHat Enterprise 3.0 WS edition. This upgrade should provide a supported and more stable operating system. The systems are now subscribed to an automatic updating services which should apply bug fixes and security patches in a timely fashion.
A picture of the couplers and the six Langmuir probes for measuring edge density can be found at http://www.psfc.mit.edu/cmod/operations/EngImages/RF/lower_hybrid/IMG_0708.JPG
The lower hybrid limiters were also installed in-vessel and can be seen at http://www.psfc.mit.edu/cmod/operations/EngImages/RF/lower_hybrid/DCP_0170.JPG
C-Mod quarterly review video conference was held 11/10. Earl Marmar discussed FY04 Program Execution Agreement (PEA) tasks and the FY05 operations schedule. Jim Irby discussed engineering systems status and plans, and Ron Parker discussed the status of the lower hybrid launcher and installation plans. The presentations can be found at
http://www.psfc.mit.edu/cmod/sciprogram/Q_rev11_04/01_doe_quarterly.pdf
Attending from MIT were Bob Granetz, Jim Irby, Earl Marmar, Ron Parker, and Miklos Porkolab. From OFES were Rostom Dagazian, T.V. George, and Ken Hill. From PPPL was Gerd Schilling, and from UT-FRC were Ron Bravenec, Perry Phillips, and Bill Rowan.
The C-Mod Ideas Forum, which began Dec 2, was completed on Monday, Dec 6. A total of 113 ideas were submitted representing twelve institutions, and the Forum was extended to three days so that they could all be presented. Participation in the Forum was also conducted by video and audio links from all around the country. Follow-up meetings in each of the task groups will be held to evaluate proposals and define priorities for experiments to be undertaken during the next campaign. See the Ideas Forum web page
http://www.psfc.mit.edu/cmod/sciprogram/ideas2005/index.htm
l
for more information.
Alcator C-Mod papers and posters presented at the IAEA conference can be found at
http://www.psfc.mit.edu/cmod/sciprogram/iaea/index.html
Presentations from the APS meeting can be found at http://www.psfc.mit.edu/cmod/sciprogram/APS/aps2004/index.html including six invited oral presentations, 9 contributed orals, and 21 poster presentations.
Joe Snipes visited with Nikolai Gorelenkov at PPPL 10/4 to 10/6 to learn to use the Nova-K code.
Earl Marmar and Amanda Hubbard were in Denver, Colorado on Oct.14-15 at the FESAC Priorities Panel Meeting.
Monty Grimes, Dexter Beals, and Bob Childs visited SLAC and our klystron rebuilding vendor the week of Oct.18 to discuss klystron rebuild procedures and changes to the klystron cathodes that could extend filament lifetimes.
Charley Schwartz visited a vendor in Albuquerque, NM to discuss high dielectric constant materials, and their application techniques for the J-Port DC breaks. These materials may also find application in the transmitters for the screen by-pass and the coupling capacitors. The vendor will coat two DC break inner conductors for tests here at MIT.
Josh Stillerman traveled to the ESnet Collaboration Workshop at Berkeley Lab the week of Nov.1 and gave a presentation on our current use of remote collaboration services.
Bruce Lipschultz represented the C-Mod group at two meetings last week. At the first meeting entitled 'Plasma-Facing Component Technology Meeting' held from December 6-8, 2004 in Livermore, California, Lipschultz gave a presentation describing the C-Mod program in general and the first-wall interaction experience in detail.
Dexter Beals and Bob Granetz spent the week of Oct. 4 in Novosibirsk, Russia at the Budker Institute of Nuclear Physics participating in the successful operation, testing, and characterization of new long pulse DNB. They also discussed the installation schedule. Darin Ernst, Martin Greenwald, Ian Hutchinson, Earl Marmar, Miklos Porkolab, John Rice, Jim Terry, and John Wright attended the IAEA Fusion Energy Conference the week of Nov.1 in Vilamoura, Portugal. Amanda Hubbard attended the Pedestal ITPA group meeting in Lisbon, Portugal where she gave three presentations on C-Mod results and modeling. Bruce Lipschultz and John Rice attended the Divertor and Transport ITPA meetings. Joe Snipes spent 6 - 8 December at the European Fusion Physics Workshop where he presented a talk entitled "Energetic Particle Physics Studies on Alcator C-Mod". He then went to CRPP (Lausanne) to work with Ambrogio Fasoli through our collaboration with JET on the new TAE antennas for JET. These are being built at the CRPP and should be ready for testing. Bruce Lipschultz went from California to a meeting of the IEA/ITPA coordinating committee, held outside of Oxford UK. He represented the C-Mod group as well as the ITPA SOL/divertor committee, of which he is co-chair. This meeting, held on Dec 8-10, was held to review proposals by the ITPA committees and collaborators to do joint experiments across tokamaks. The heads of machines were there to understand the proposals and indicate whether they were willing to support such experiments in 2005. C-Mod was part of 21 proposals for joint work. Most proposals were enthusiastically endorsed thus enhancing the possibility that such experiments will be run. In between the two meetings, on Wednesday, the 8th, Bruce Lipschultz visited the JET site for discussions with Guy Matthews on the collaborative work both in the area of SOl transport and on the development of W-brush tiles.
The short term schedule may be found at:
http://www.psfc.mit.edu/cmod/operations/schedule.txt