PEP ITPA Working Group on RMP ELM Control: 2 nd Inter-Meeting Conference Call

1. PEP ITPA Working Group on RMP ELM Control: 2nd Inter-Meeting Conference Call M.E. Fenstermacher (chair) M. Becoulet, P. Cahyna, C.S. Chang, T.E. Evans, A. Kirk, Y. Liang, A. Loarte, R. Maingi, O. Schmitz, W. Suttrop, (members) Conference Call by H.323 Remote ParticipationSeptember 2, 2009

2. Purpose, Deliverables and Agenda for this Meeting • Purpose • PEP ITPA Work Plan on RMP ELM Control: review of actions, objectives, timescales, and proposals for modifications where necessary. • Deliverables • Progress against the work plan in RMP ELM Control Area • Start on formulation of answers to some of the questions, or plan how to address others • Sufficient information for presentation of the status, covering: • Questions that have now been answered • Strategy to address those questions that cannot yet be answered • New questions that the group should address.

3. H. Wilson Requested Information at the PEP ITPA Meeting in Cadarache - Similar Request Appropriate for October at PPPL • At our next ITPA Pedestal Group meeting in Cadarache, 20-22 April, one of the items for review and discussion will be the work plan that was submitted to the CC in December. This work plan, was approved. It is very adventurous, but needs to be. • At each meeting I would like us to spend some time reviewing the actions, objectives and timescales, and make modifications where necessary…. Now would be a good time to take stock of the progress against the work plan in each of these areas, and perhaps start to formulate answers to some of the questions, or to plan how to address others. • In Cadarache, could the working group leaders (or their delegated representative) present the status, covering (for discussion): • (a) questions that have now been answered; • (b) a strategy to address those questions that cannot yet be answered, and • (c) new questions that the group should address.

4. H. Wilson Requested Information at the PEP ITPA Meeting in Cadarache - Similar Request Appropriate for October at PPPL • (Are you) each happy with the approach we are taking to address the ITER urgent issues (see workplan attached) • (Are you) able to come to the next formal ITPA pedestal meeting with • a proposal to meet the workplan objectives, revised if necessary, for discussion and agreement. I suggest that your roles at the formal ITPA meetings will include (You may choose to delegate parts of this to your working group members): • (a) summarizing the status of the answers to the key questions and objectives in the workplan (you probably already have some answers to key questions); • (b) suggesting revisions to the workplan to be approved by the ITPA pedestal members; • (c) chairing a discussion of the approach to address your area; • (d) assigning actions of work to be performed between formal ITPA meetings, and • (e) providing a BRIEF written summary (1-page max) of progress following each formal ITPA meeting, for the meeting minutes.

5. H. Wilson Requested Information at the PEP ITPA Meeting in Cadarache - Similar Request Appropriate for October at PPPL • We would like to propose that you organize one teleconference meeting half-way between each of the formal ITPA meetings • In order to monitor progress on the ITER tasks and actions set at the formal meetings • Perhaps we can use the ITER video-conferencing system as the hub for all of these meetings (Alberto to confirm). • It would be good if you are each able to organize one teleconference meeting of your groups before the next formal ITPA meeting so that you can receive the necessary input for your summary presentation there (though I appreciate that time is short).

6. PEP ITPA Work Plan in RMP ELM Control Based on 4 Assumptions • The complete suppression of ELMs on DIII-D by RMPs, while not eg. on JET, is because the DIII-D coils are off-midplane, as presently designed for ITER • Only MAST and DIII-D are presently in a position to test ITER-relevant coils. • AUG will also be in this position from mid-2010 • Both MAST neutral beam are assumed to be operational early in 2009 to provide reliable ELMing H-modes • Appropriate machine time, experimental and theoretical manpower are made available • The criteria (to be validated) based on a minimum stochastic layer region (width) and alignment of the perturbation with q(r), are the main requirements for ELM suppression • If this proves not to be the case, other model development (including plasma response) and tests will be required. • The target date for input to ITER IO on RMP coil design is Sept 2010, but results will be communicated as they are produced in advance of this date.

7. PEP ITPA Work Plan in RMP ELM Control Now Contains 8 Elements • Reproduce RMP ELM suppression on at least one tokamak other than DIII-D • Identify the criteria for ELM suppression from experimental data and theoretical models • Quantify the impact of ELM suppression by RMPs on the pedestal pressure and core confinement and develop/validate theoretical models • Quantify the power loading on the wall and divertor with RMP-suppressed ELMs; make recommendations on any requirement for rotating RMPs • Explore the capability to suppress or mitigate ELMs during the current ramp phase (ie. close to the L-H transition threshold, and with time varying q95) • Demonstrate ELM control with ITER-like pellet fuelling • Investigate potential for ELM Pacing by RMP coils • Model the performance of the ITER ELM control coil set, and propose changes to the design as appropriate; likely to require further developments in modeling the plasma response (challenging)

8. RMP ELM Control WorkPlan • Revised July 2, 2009 • Hatched areas indicate an extension compared to the original plan • ITPA Coordinating Committee chair R. Stambaugh suggested that ELM Pacing with RMPs be added

9. Progress Toward Work Plan Goals Was Reported to the ITPA Coordinating Committee in July • Progress is being made in understanding parameters that appear to influence ELM suppression. • These include q95 resonance, collisionality, density pump-out, beta, and island overlap width. • DIII-D initially suggested that island overlap width was a good ordering parameter for maximum ELM size and that ELM suppression was correlated with achieving a minimum island overlap width. Recent results from MAST now demonstrate that while this may be a necessary condition, it is not sufficient. • Major tasks: 1) quantify the importance of each of the important parameters, and 2) understand that importance in terms of a physically-motivated theoretical model. • Although both MAST neutral beams are now operational, providing reliable ELMing H-modes, complete ELM suppression has not yet been observed in MAST, so it will be necessary to adjust tasks and timescales. • Plans are progressing for the installation of a very flexible coil set on AUG for operation in 2010 (the full capability is expected to be available from 2011).

10. Agenda (times are PDT, UK add 8, EU add 9 hours) • 8:30 Fenstermacher Agenda, Purpose, Deliverables, Work Plan Summary • 8:40 M. Becoulet Summary of Theory progress toward work plan • 8:48 O. Schmitz Summary of TEXTOR progress toward work plan • 8:56 P. Cahyna Summary of COMPASS progress toward work plan • 9:04 A. Kirk Summary of MAST progress toward work plan • 9:12 Y. Liang Summary of JET progress toward work plan • 9:20 R. Maingi Summary of NSTX progress toward work plan • 9:28 T. Evans Summary of DIII-D progress toward work plan • 9:36 W. Suttrop Summary of AUG progress toward work plan • 9:44 All Discussion of questions answered, strategy for remaining questions, new questions • 10:00 Adjourn