1. Pedestal Structure & Control TSG A. Diallo, R. Maingi, D. Smith NSTX-U Pedestal NSTX-U Pre-forum 2 January 29, 2015 NSTX-U Supported by Culham Sci Ctr York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Inst for Nucl Res, Kiev Ioffe Inst TRINITI Chonbuk Natl U NFRI KAIST POSTECH Seoul Natl U ASIPP CIEMAT FOM Inst DIFFER ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep Coll of Wm & Mary Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Lehigh U Nova Photonics Old Dominion ORNL PPPL Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Tennessee U Tulsa U Washington U Wisconsin X Science LLC

2. 2 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 Brief Outline of TSG PED plans Near term priorities Mid to late run priorities Needed action items for the ROF 2

3. 3 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 NSTX-U PED research topics for FY 15 (I) Early in the run (first 2months of operations) H-mode access and power threshold (L-H transition physics with T&T) Explore H-mode access, variation with Rtan Measure L-H threshold dependencies (power, Rtan, etc...) Characterize the H-Mode pedestal structure at increased BT, Ip, and NBI heating power, -- R15-1-- and shaping (triangularity, DN vs LSN vs USN) may require dedicated time beyond R15-1 Map out the stability diagram for three Ip and 2 shaping parameters Determine the pedestal scaling with beta_pol Pedestal structure and evolution after L-H transition and between ELMs Turbulence characterization to understand the pedestal dynamics Generate database for testing EPED on ST and for gyrokinetic codes 3 To be performed in boronized and lithiated wall

4. 4 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 NSTX-U PED research topics for FY 15 (II) Early in the run (first 2months of operations) Identifying common characteristics in the phenomenology of different ELM types (DivSol & MP) RMP impact on the pedestal stability Effect of (Boron)-Granule-Injection for increasing the ELM frequency Snowflake impact on the pedestal stability (if control is available during the boronized wall phase) –Need to finish edge stability analysis of previous NSTX snowflake experiments that showed ELM destabilization to guide new experiments Exploit the transition from Boronized PFCs to lithium coatings Compare intrinsic and triggered ELMy-H mode in Boron vs Li –Document transition from ELMy-ELM-free transition and then scan in Li ELM-free Document the pedestal structure impact during the transition Boron to Li 4 To be performed in boronized and lithiated wall

5. 5 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 NSTX-U PED research topics for FY 15 Mid-late run Refine pedestal characterization with high triangularity discharges Investigate/characterize ELM-free regimes such EPH mode, I-mode, etc... Pedestal destabilization physics using LGI in ELM-free regimes Develop optimum discharges for simulation-experiment comparison in pedestal region –Discuss with theory team for adequate discharges for simulations –Optimize cross-diagnostics (BES, GPI, reflectometry, and probes) in the edge region Transition from lithiated to boronized walls (with MP) –Impact on pedestal structure/evolution and ELM characteristics (hysterisis study) 5

6. 6 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 Action items from the PED-TSG brainstorming meeting Investigate the impact of 2nd NBI on a fully developed pedestal –need calculations or theoretical arguments to predict effect of NBI tangency radius variation on fully developed pedestal Explore inner-wall limited H-modes space –L-H threshold physics motivated by experiment/theory discrepancies with ITPA scaling: aspect ratio scaling, limited/diverted H-mode access, and edge collisionality. Investigate the impurity effects on pedestal stability –Extend XGC1 JET calcs to NSTX-U to help guide the experiments 6

7. 7 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 Below, I think we should start with three Ip (low=0.7MA, medium=1.0MA, high=1.5 MA) at relatively low and medium triangularity. For each Ip, a two-point scan of BT (0.5 & 1) would be sufficient. As far as the PNBI, we should focus on the 1 st beam to get as much CHERS data. Once the 2 nd beam is introduced, we will not have useful CHERS data. a.L-H threshold scalings b.Pedestal width and height, i.Density, temperature pedestal evolution time scales between ELMs ii.Pedestal evolution from the L-H transition until the first ELM iii.Determine the pedestal width scaling beta_pol. iv.Map out the stability diagram for three Ip c.Characterization of pedestal turbulence using BES, reflectometry and GPI. i.Wavenumber range and spatial localization ii.Magnetic signatures d.ELM characterizations i.Frequency, types e.Generate a database for these pedestal parameters i.Inter-ELM period, density and temperature pedestal width and height 7

8. Pedestal Structure & Control TSG Open Discussion A. Diallo, R. Maingi, D. Smith NSTX-U Pre-forum January 26, 2015 NSTX-U Supported by Culham Sci Ctr York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Inst for Nucl Res, Kiev Ioffe Inst TRINITI Chonbuk Natl U NFRI KAIST POSTECH Seoul Natl U ASIPP CIEMAT FOM Inst DIFFER ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep Coll of Wm & Mary Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Lehigh U Nova Photonics Old Dominion ORNL PPPL Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Tennessee U Tulsa U Washington U Wisconsin X Science LLC

9. 9 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 NSTX-U capabilities for first 2 run-months campaign 9 Facility capabilities –RWM coils; boronization (and later lithium); standard core fuelling; SGI Diagnostics –42-Channel MPTS (with pedestal enhancement),CHERS with Beam 1, filterscopes, tangential ME-SXR, BES, Up & Down SXR, Reflectometer, tangential bolometer, magnetics for EFIT reconstruction, LADA in bolometer mode, MSE. Useful machine parameters –Ip = 0.5 - 1.4 MA, Bt = 0.5 - 0.65 T, PNBI = 4 - 12 MW, Low to mid triangularity, LSN, DN Analysis tools –Python tools refurbishment (Osborne & Canal will be visiting PPPL in Feb.)

10. 10 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 Brainstorm on NSTX-U PED research topics for FY 15 Early in the run –Characterize the H-Mode pedestal structure at increased BT, Ip, and NBI heating power, and triangularity, DN vs LSN Generate database for testing EPED on ST and for gyrokinetic codes Pedestal structure and evolution after L-H transition and between ELMs –H-mode access and power threshold (L-H transition physics with T&T) –Exploit the transition from Boronized PFCs to lithium coatings to investigate the impact on the pedestal structure –Identifying common characteristics in the phenomenology of different ELM Types –Physics of the underlying instabilities Intrinsic ELMs vs LGI-triggered ELMs vs RMP –Transport of ELM heat and particle flux in the SOL, and incident at the divertor and wall (cross-cutting with DiVSol & MP) 10

11. 11 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 Impact of the edge velocity shear on the pedestal stability HHFW effects on the edge turbulence Mechanism of ELMs triggering via LGI Use 2nd NBI to broaden current profile and assess impact on ELM stability 11

12. 12 NSTX-U NSTX-U – Pedestal Structure NSTX-U Pre-forum 2 NSTX-U capabilities for first year campaign 12 Facility capabilities –RWM coils; boronization (and later lithium); standard core fuelling; SGI Diagnostics –42-Channel MPTS,CHERS with Beam 1, filterscopes, tangential ME-SXR, BES, Up & Down SXR, Reflectometer, tangential bolometer, magnetics for EFIT reconstruction, LADA in bolometer mode, MSE. Useful machine parameters –Ip = 0.5 - 1.5 MA, Bt = 0.5 - 0.75 T, PNBI = 4 - 12 MW, 0.3<δ<0.8 Analysis tools –Python tools refurbishment (Osborne & Canal will be visiting PPPL in Feb.)