IF2011 Pedestal/JRT Summary. J.W. Hughes 21 Jan 2011

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1 IF2011 Pedestal/JRT Summary J.W. Hughes 21 Jan 2011

2 Predictive capability for the H-mode pedestal is the subject of the FY11 JRT Statement of FY11 FES Joint Research Target: (1) Improve the understanding of the physics mechanisms responsible for the structure of the pedestal and compare with the predictive models described in the companion theory milestone. Perform experiments to test theoretical physics models in the pedestal region on multiple devices over a broad range of plasma parameters (e.g., collisionality, beta, and aspect ratio). Detailed measurements of the height and width of the pedestal will be performed augmented by measurements of the radial electric field. The evolution of these parameters during the discharge will be studied. Initial measurements of the turbulence in the pedestal region will also be performed to improve understanding of the relationship between edge turbulent transport and pedestal structure. (2) A focused analytic theory and computational effort, including large-scale simulations, will be used to identify and quantify relevant physics mechanisms controlling the structure of the pedestal. The performance of future burning plasmas is strongly correlated with the pressure at the top of the edge transport barrier (or pedestal height). Predicting the pedestal height has proved challenging due to a wide and overlapping range of relevant spatiotemporal scales, geometrical complexity, and a variety of potentially important physics mechanisms. Predictive models will be developed and key features of each model will be tested against observations, to clarify the relative importance of various physics mechanisms, and to make progress in developing a validated physics model for the pedestal height. The Pedestal topic comprises ideas which could support this research effort J.W. Hughes, 2011 C-Mod Ideas Forum, Jan 10 12,

3 Key capabilities to be leveraged in FY11/12 RED=available now campaigns BLUE=work needs to be done Profile measurements Edge Thomson scattering (existing + upgrades) DNB and gas-puff assisted CXRS (HFS/LFS) X-mode reflectometry (low n, B T ) Langmuir probes: RF sheath mitigation Fluctuation measurements Fast GPI with D and He X-point GPI O-mode and X-mode reflectometry PCI masking Magnetic probe Langmuir probes: RF sheath mitigation and T e fluctuations Active MHD QCM antenna Codes ELITE, GYRO, TGLF, BOUT/UEDGE, XGC0/XGC1, M3D J.W. Hughes, 2011 C-Mod Ideas Forum, Jan 10 12,

4 New ideas categorized by theme Testing pedestal models 103. Hughes, ELMy H-mode in unfavorable grad-b drift plasmas 111. Beurskens, Pedestal width and height scaling in a multi-device experiment 112. Chang, Analysis of pedestal physics with XGC 113. Hughes, Edge electric field and fluctuations for pedestal modeling 411. Churchill, Measurement of boron poloidal pedestal asymmetries 412. Churchill, Validation of flux surface constants in the NC velocity equation 606. Sugiyama, Extended MHD plasma edge instabilities Pedestal fluctuations 102. Hughes, EDA H-mode access in unfavorable grad-b drift plasmas 105. Terry, Poloidal V phase of the QCM and WCM in the plasma frame 106. White, Characterization of edge turbulence preceding ELMs 107. Cziegler, Study of the parameter dependence of the QCM nonlinearity 108. Golfinopoulos, Active stimulation of the QCM by external antenna 207. Cziegler, I-mode T e and n e fluctuations using D 2 and He GPI 407. White, T e -tilde component of QCM and WCM via ECE and GPI Integration with edge/divertor studies 101. Elder, Analysis of pedestal fueling using OEDGE 104. Terry, H-mode pedestal parameters and near-sol heatflux footprint 109. Loarte, Physics mechanisms for plasma fueling in H-mode plasmas H-mode formation and pedestal evolution 110. Churchill, Time resolved CXRS measurements of the pedestal formation 403. Ma, Power threshold and L-H transition with low Bt at high densities 404. Ma, H-mode access and evolution with ICRF+LH at low densities RED=submitted under Pedestal/JRT BLUE=submitted under other topics, e.g. Transport or H-mode Baseline J.W. Hughes, 2011 C-Mod Ideas Forum, Jan 10 12,

5 FY11 experimental campaign priorities (including old and new ideas) The following runs (~3 4 days) would be considered very high priority for completing the C-Mod contribution to the FY11 JRT: MP578: EPED tests in ELMy H-mode: Keep a day in reserve to fill in any holes in the existing data set. Up to 1 day at normal B T, 80MHz D(H) heating Piggybacking: IF11-106, IF (Edge electron thermal transport inferred from ELM transients) MP636: Study of ELMy H-mode: Toroidal field scan. 1 day in normal BT direction, ~3.5T, 50MHz D(H) heating IF11-113: Obtain more complete data sets (flows, E r, fluctuations) with a current scan for JRT modeling 1 day at normal BT, 80MHz D(H) heating Piggybacking: IF11-104, IF11-105, IF11-411, IF11-412, MP600 (Fast RF Power Modulation on the QCM) IF11-103: EPED tests in ELMy H-mode in reversed field to attempt to lower collisionality 1 day in reversed BT direction, 80MHz D(H) heating Piggyback: IF11-102, IF The following runs (~3 days) would be considered high priority for completing the C-Mod contribution to the FY11 JRT: MP614: Extend operational space of LH in EDA plasmas; lower collisionality and maintain steady H-mode 1 run day with normal BT direction, 80MHz D(H) heating, LH IF11-110, IF11-403: Time-resolved studies of pedestal formation, with fast CXRS and X-mode reflectometry 1 days with normal BT direction, ~3.5T, 50MHz D(H) heating. May get data from MP636 IF09-605: Modification of ELMy H-mode with lower hybrid 1 day with normal BT direction, 80MHz D(H) heating, LH The following runs could contribute significantly to the FY11 JRT, but are expected to be ranked in other topical areas: IF11-202: Explore the radial correlation lengths of edge turbulence, radial structure of the QCM [Edge] IF11-207, IF Separation of Te fluctuations from ne fluctuations in WCM and QCM [Edge, Transport] Numerous IF-xxx and MPs: Assess I-mode with a proper divertor and optimized diagnostics, coordinated investigation of the WCM [Transport] The following new experimental ideas will likely be deferred until FY12: IF11-101, 109: Edge plasma fueling IF Beurskens, Pedestal width and height scaling in a multi-device experiment IF Golfinopoulos, Active stimulation of the QCM by external antenna IF09-208: Ion isotope and I P scaling of transport J.W. Hughes, 2011 C-Mod Ideas Forum, Jan 10 12,

6 Follow-up meetings will explore plans for FY12 campaign Prior unfulfilled ideas and MPs will be considered alongside new ideas Will prioritize according to standard criteria, and strategize for efficient use of run time Develop list of facilities, diagnostic improvements that may be desired during planned maintenance period Thanks to all who contributed ideas! J.W. Hughes, 2011 C-Mod Ideas Forum, Jan 10 12,