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Dear Burning Plasma Aficionados:

This newsletter provides a short update on U.S. Burning Plasma Organization activities. Comments on articles in the newsletter may be sent to the editor (R. Nazikian rnazikian at pppl.gov) or assistant editor (Rita Wilkinson ritaw at mail.utexas.edu).

Thank you for your interest in Burning Plasma research in the U.S.!

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Director's Corner by J. Van Dam

STAC-6 Meeting
The Science and Technology Advisory Committee of the ITER Council held its sixth meeting in Cadarache, France, May 25-27. The ITER Organization presented to the STAC a revised version of the ITER Research Plan. The STAC reviewed the list of STAC Actions and recommended closing out several of them as completed. A significant portion of the STAC meeting was spent reviewing the recent activity of the ITER Organization in analyzing an alternate design for the vacuum vessel. In parallel, several important improvements have been made in the baseline design for the vacuum vessel. Dr. Yuanxi Wan (China) served as the acting chair for this STAC meeting, which was held in the new conference center building at the Chateau de Cadarache, just across the road from the new ITER site.

 

STAC-6 participants from the seven ITER international Members. (Photograph courtesy of ITER Organization)

 

 

U.S. participants at the STAC-6 Meeting: Stan Milora, Jim Van Dam, Tony Taylor, Rob Goldston, and Erol Oktay. (Photograph courtesy of Erol Oktay)

 

During the STAC meeting, on the morning of Tuesday, May 26, the ITER Organization held a special ceremony to dedicate the platform for the ITER site. The platform consists of a huge leveled ground site (about 100 acres), with a pit for the tokamak basement. STAC and MAC members joined ITER staff members at this celebration. Congratulatory speeches were given by Francois Gauché, the head of Agence ITER France, which is in charge of site preparation and leveling, by Dr. Didier Gambier, head of the European Domestic Agency ("Fusion for Energy"), and by ITER Director-General Kaname Ikeda. The ITER Newsline has an article about this event, with a number of photographs (see http://www.iter.org/newsline/Pages/83/526.aspx ), including some taken with a remote camera from an overhead balloon.

 

ITER Director-General Ikeda speaking at the platform dedication. (Photograph courtesy of Tony Taylor.)

 

 

Part of the platform area. (Photograph courtesy of Tony Taylor.)

 

Election for USBPO Council
The Council is the advisory body for the USBPO. It provides oversight of USBPO activities, sets the policies and procedures of the USBPO, and is responsible for long-term strategic planning of burning plasma research. The Council members serve three-year terms. The nominating committee put together an excellent slate of candidates: Larry Baylor (Oak Ridge National Lab.) Michael Bell (Princeton Plasma Physics Lab.) Troy Carter (Univ. California, Los Angeles) Cary Forest (Univ. Wisconsin) Stephen Knowlton (Auburn Univ.) Wayne Meier (Lawrence Livermore National Lab.) Phil Snyder (General Atomics) USBPO members should have received a "Call to Vote" email on June 4 from Jim DeKock with instructions about the election. Each email contains a unique web link. Please click on the link to the election web site (hosted by the University of Wisconsin) and vote for two of the candidates. The election will be open until Friday, June 26.

Upcoming ITPA meetings
Each of the ITPA topical groups typically holds two meetings per year. The schedule for the fall meetings this year is given in the table below, compiled by Michiya Shimada (ITER Organization).

ITPA Meetings through Fall 2009

Topical Group	Date	Place
ITPA Coordinating Committee	15-16 July 2009	Cadarache, France
Energetic Particles	24-25 September	Kiev, Ukraine
Transport and Confinement	5-7 October	PPPL, USA
Pedestal and Edge Physics	5-7 October	PPPL, USA
MHD	6-9 October	Abingdon, UK
Diagnostics	12-16 October	Pohang, Korea
Integrated Operation Scenarios	20-23 October	ENEA Franscati, Italy
SOL and Divertor	14-18 December	San Diego, USA

Compiled by M. Shimada on 8 June 2009 (michiya.shimada@iter.org)

Note that the Transport & Confinement topical group and the Pedestal & Edge Physics topical group will hold a joint meeting. It will be at Princeton Plasma Physics Laboratory, October 5 (Monday) through October 7 (Wednesday). The web site for this meeting is accessible at http://itpa09.pppl.gov. The web site has general information and a registration page, plus information for non-U.S. citizens who need to apply for visas for entry into the U.S. (If you need a visa, please start the process for obtaining one as soon as possible.) The agenda and the presentations will be posted on this web site. This joint meeting will follow the H-Mode/ITB Workshop, September 30-October 2, which will also be held at PPPL.

ITER oral session at APS
Similar to last year, the USBPO will again organize a special session of contributed talks about research work related to ITER at the APS Division of Plasma Physics Annual Meeting (November 2-6, Atlanta). For details, please contact USBPO Deputy Director Chuck Greenfield (greenfield@fusion.gat.com).

New OFES Associate Director
Dr. Edmund Synakowski, a member of the USBPO Council, was selected by the U.S. Department of Energy to become the new Associate Director for the Office of Fusion Energy Sciences. He also had served for the past year and a half as a member of the international working group that has been writing the ITER Research Plan document. Ed was introduced in his new role during the Research Needs Workshop on Magnetic Confinement (June 8-12), where he was warmly applauded by the 175 ReNeW participants. We wish him the very best with his important responsibilities!

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Announcments

Submit BPO-related announcements for next month’s eNews to Raffi Nazikian at rnazikian at pppl.gov.

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Reports

Minutes of the Second Transport and Confinement ITPA Meeting, Naka, Japan 3/31 - 4/2/09
Written by Stan Kaye (Princeton Plasma Physics Laboratory, US)

The second meeting of the Transport and Confinement (T&C) ITPA group was held jointly with the Integrated Operating Scenarios (IOS) group in Naka, Japan, March 31-April 2, 2009. The joint session with the IOS group was held on Tuesday, March 31, and it focused on Transport Model Benchmarking activities. After this day, both groups met separately. The meeting was attended by approximately 60 physicists, divided roughly equally between the two ITPA groups.

Joint Session with IOS - L to H and Transport Model Benchmarking (S. Kaye, D. Mikkelsen)

This session dealt with the ITER Organization high-priority topic on ITER ramp-up (and ramp-down). A key component of this development is the assumption concerning the transport model to be used for this scenario development. The task of the T&C group is to assess the various transport models by benchmarking them against data from existing devices during these same phases. This is a relatively high-level benchmarking exercise, and it is not as detailed as the validation of gyrokinetic calculations, which involves assessing details of the calculated and measured turbulence as well as transport levels. The T&C plan was to obtain ITER-Demo discharge data from JET, DIII-D, C-Mod, and ASDEX-Upgrade (AUG) in order to perform this analysis. Models would be tested by using several codes to examine a single model, and then examining several models with the same code. This would be done by multiple modelers with the idea that this approach would allow for less "singular" assessments. To date, data was received from the first three devices, and some benchmarking was performed.

In summary, there were many attempts to benchmark various transport models during the transient phases, but with varied agreement. These models at present do not form the basis for confident predictions of ITER ramp-up/ramp-down phases, although they may serve the useful purpose of identifying larger sources of uncertainty. One feature that crystallized was the need to focus on agreement in the outer region (r/a > 0.5) rather than the very center of the plasma, since the T_e in this outer region has a large influence on current diffusion and the resulting l_i. It was suggested that near-term ITER ramp-up/down scenario development be devoted to determining if the heating range is sufficient to compensate for the transport uncertainties. This could be done by specifying the profile shape of T_e from ITER-similarity discharges in existing devices and adjusting the absolute magnitude of the profile with the range of heating that is planned for ITER. This will allow an assessment of whether these profile shapes lead to acceptable or undesirable current profiles (i.e., l_i).

Effect of Rotation on Performance (H. Takenaga)

Studies of the effect of rotation on confinement based on joint experiments (TC-6) were reported from JT-60U, TCV, DIII-D, AUG, and C-Mod. In weak shear plasmas in JT-60U, the highest confinement was achieved with co-rotation. The rotation direction seemed to be important rather than the ExB shear in plasmas with ion ITBs. Rotational shear was important, however, for plasmas exhibiting reversed magnetic shear. Decreased ExB shear reduced the confinement in DIII-D and C-Mod and enhanced the transport in NSTX, where high confinement or reduced transport was observed with large co-rotation and rotation shear. In DIII-D, the electron and ion thermal diffusivity, as well as the momentum diffusivity, decreased with increasing rotation. In C-Mod, the increase in confinement with increased rotation was linked to an increase in the pedestal pressure gradient and depth of the E_r well there. In NSTX, rotation and rotation shear in the outer region of the plasma were controlled by application of n=3 magnetic perturbations. With no applied fields, the ion thermal diffusivity was nearly neoclassical. The ion thermal diffusivity increased both absolutely and relatively to the neoclassical level as the rotation and rotation shear decreased in response to the braking due to the applied fields. In AUG, additional electron heating by ECH in low-density NBI heated plasmas led to a significant reduction of confinement and toroidal rotation, while additional RF ion heating did not reduce confinement as much, but had similar effect on the toroidal rotation. This result indicated that T_e/T_i seemed to be more important than the ExB shear, although both played a role. The measured normalized ion temperature gradient was consistent with that for the ITG threshold when both T_e/T_i and E_rxB shear are taken into account. In TCV, high confinement could be obtained with large reversed shear in plasmas that had low rotation. The discussion should be continued to close out this joint experiment after next meeting, especially with higher rotation TCV operation in 2009.

Momentum Transport (J. Rice)

Wednesday, April 1 was devoted to TC-6 and momentum confinement. For the Momentum Confinement Session, a total of 12 talks were presented. Most of the talks fell under the categories of momentum pinches and residual stress.

1. Momentum Pinches

Two similar theories were described, by T.S. Hahm and C. Angioni, of the momentum pinch, which can be broken down into two components, the turbulent equipartition pinch, V_TEP, and the thermo-electric pinch, V_TH. While V_TH has a complicated dependence on mode characteristics, V_TEP has a relatively simple form, related to the momentum diffusivity as V_TEP R/c_f = -4, with some corrections due to the density and ion temperature gradients. There is also a connection between particle and momentum pinches in these theories. From beam modulation experiments on JT-60U and JET, reported by M. Yoshida and T. Tala, and from modeling of C-Mod H-mode rotation by J. Rice, experimental values of V R/c_f can reach -16, which indicates other mechanisms besides the turbulent equipartition pinch are at work. Results from C-Mod demonstrate many examples where the density and velocity profiles are not correlated. A database of momentum transport coefficients from all devices is in the process of being formed.

2.Residual Stress

A detailed theoretical description of the residual stress, the part of the momentum flux from Reynolds stress that is not proportional to the velocity or velocity gradient, was presented by P. Diamond. This comprehensive model offers explanations for several observations: a Prandtl number greater than unity seen on JT-60U, the scaling of H-mode intrinsic rotation proportional to the edge pressure gradient, rotation reversals observed in TCV and C-Mod plasmas, and the offset torque required to balance intrinsic rotation in DIII-D, as presented by W. Solomon. Torque sweeping was also proposed as a more definitive method for isolating the residual stress. K. Ida elaborated on the residual stress, showing examples of non-diffusive E_r driven momentum flux in LHD, as well as offset rotation with balanced beam injection. Some sort of symmetry breaking is required to facilitate a non-zero residual stress, and one example from up-down flux surface asymmetries was given by C. Angioni.

There were other related presentations, showing very favorable comparisons of observed rotation velocity profiles in JET with fluid simulations of J. Weiland, including poloidal rotation. F. Nave presented the results of L-mode intrinsic rotation profiles from JET, in Ohmic, ion cyclotron RF heated (ICRF), and Lower Hybrid plasmas, including the effects of toroidal field ripple. J. Rice gave an update of TC-9 and TC-14, and T. Tala presented an update of TC-15.

Electron Transport (F. Ryter)

The aim of the session on electron transport was to review the recent results on this topic and define possible fields for future Joint Experiments and/or Activities. Nine contributions were presented (7 experimental, 2 theoretical) and the session concluded with a general discussion.

In the discussion, a consensus emerged on the fact that the majority of the plasmas with dominant electron heating (T_e > T_i) are dominated by the Trapped Electron Mode (TEM) instability. However, further assessment is desirable, in particular concerning the comparison of turbulence measurements and theory, as well as the TEM-driven heat flux yielded by non-linear gyro-kinetic calculations. For the latter, results from AUG are expected for the next meeting.

For the cases with T_e ≤ T_i, where all type of instabilities might contribute, it has been agreed to focus on the following priorities:

1. Assessment of the Ion Temperature Gradient (ITG)-driven electron heat flux (off-diagonal terms).
2. Role of Electron Temperature Gradient (ETG)-driven heat transport with further turbulence measurements at high κ, where available. A comparison between NSTX and MAST should be organized for the next T&C meeting.
3. Discussion of the possible role of Alfvén eigenmodes in electron transport, as suggested by NSTX results.
4. The role of micro-tearing modes, extensively investigated in MAST, to be discussed at the next meeting.

Concluding Session

The concluding session consisted of several additional discussions. The first had to do with forging stronger links between the T&C ITPA group and the US and EU Transport Task Forces. This discussion was particularly timely due to the in-person and remote participation of C. Hidalgo (Chair of the EU TTF) and P. Diamond (Chair of the US TTF), respectively.

Joint Experiment updates were given for TC-1 (C. Petty), TC-2 (Y. Martin), TC-7 and TC-13 (P. Mantica), and TC-8 (P. Gohil). Updates on the H-mode and L-H databases were given by K. Thomsen and Y. Martin (for J. Hughes) respectively.

The next meeting will be held at PPPL, Princeton University, Princeton NJ, USA, October 5-7, 2009, following the H-mode/ITB workshop. Possible topics on which to focus for that meeting were discussed, but no decisions were made. This meeting will be held jointly with the Pedestal Group.

Summary of the Meeting of the ITPA Topical Group on MHD Stability, Daejeon, Korea, April 21-24, 2009
Written by E.J. Strait (General Atomics, US), A. Sen (Institute for Plasma Research, India), and Y. Gribov (ITER Organization, Cadarache, France)

The ITPA Topical Group on MHD Stability held its second meeting at Daejeon, Korea, on April 21-24, 2009, hosted by the National Fusion Research Institute. The key topics discussed at the meeting focused on the High Priority Research areas in MHD stability for ITER: disruptions (control, mitigation and loads), vertical stability, Neoclassical Tearing Modes (NTMs), error field effects, and Resistive Wall Mode (RWM) control. There was also a joint session with the Energetic Particles Topical Group for discussion of runaway electrons and the interaction of fast ions with MHD modes. The next meeting will be held at Culham Science Center, UK, on October 6-9, 2009, in conjunction with an IEA workshop on disruptions.

Disruptions

Disruption-related issues received major attention at this meeting in view of the urgent need to address ITER concerns about the resultant forces and to design effective means of control and mitigation. Several talks presented ITER's needs in this area and the plans for mitigation of disruptions and runaway electrons in ITER. Topics of other talks related to vertical stability and electromagnetic forces included halo current measurements in NSTX, modeling and measurement of vessel forces during Vertical Disruption Events (VDEs) in DIII-D, benchmarking of the DINA code halo current model against JT-60U data, modeling of VDEs for KSTAR, and a model of kink mode-driven vessel currents leading to horizontal forces. Discussions also covered results from massive gas injection experiments in JET and DIII-D and analysis of current quench times in JT-60.

The joint session with the energetic particle group included discussion of runaway electron generation in JET, runaway generation and suppression in TEXTOR, and NIMROD modeling of runaways in C-Mod. Plans for the ITER test blanket module mockup experiment in DIII-D were presented. A summary of interactions of fast ions with sawteeth, RWMs, and other MHD modes was given, and several talks discussed experiments and modeling on TAE modes and other fast ion-driven modes.

Other MHD topics

Talks on resistive wall mode stability discussed feedback control of current-driven RWMs in DIII-D, kinetic stabilization at high beta in NSTX, modeling of RWM stability in ITER with a 3D vessel, and modeling of power requirements for RWM feedback stabilization in ITER. Analysis of DIII-D experiments compared the measured and predicted plasma response of a stable, driven n=1 kink mode over a range of beta values.

Modeling of the planned neoclassical tearing mode stabilization in KSTAR was presented. Experimental results on helical states in RFX-Mod were discussed, as was the implementation of EFIT equilibrium reconstruction in KSTAR.

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Upcoming Burning Plasma Events

Jun 14-18
ANS Annual Meeting
Atlanta, GA USA

Jun 24-26
18th Conference on RF Power in Plasmas
Gent, Belgium

Jun 29-Jul 3
14th International Conference on Emerging Nuclear Energy Systems (ICENES-2009)
Ericeira, Portugal

Jul 15-16
ITPA Coordinating Committee Meeting
Cadarache, France

Sep 6-11
6th International Conference on Inertial Fusion Sciences and Applications (IFSA 2009)
San Francisco, CA USA

Sept 7-12
14th International Conference on Fusion Reactor Materials (ICFRM-14)
Sapporo, Japan

Sept 21-23
ITPA Energetic Physics Topical Group Meeting
Kiev, Ukraine

Sept 21-24
14th International Symposium on Laser-Aided Plasma Diagnostics (LAPD-14)
Castelbrando, Treviso, Italy

Oct 5-7
ITPA Transport & Confinement Topical Group Meeting
PPPL, Princeton, New Jersey, USA

Oct 6-8
ITPA Pedestal & Edge Physics Topical Group Meeting
Princeton, New Jersey, USA

Oct 11-16
9th International Symposium on Fusion Nuclear Technology (ISFNT-9)
Dalian, China

Nov 2-6
51st APS-DPP Meeting
Atlanta, GA USA

Nov 15-19
ANS Winter Meeting
Washington, DC USA

 

Fusion Research-related events can also be seen on the USBPO website at http://burningplasma.org/events.html 

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