I Attended the DIII-D PAC Meeting

S. M. Kaye

Supported byOffice ofScience

Culham Sci CtrU St. Andrews

York UChubu UFukui U

Hiroshima UHyogo UKyoto U

Kyushu UKyushu Tokai U

NIFSNiigata UU Tokyo

JAERIHebrew UIoffe Inst

RRC Kurchatov InstTRINITI

KBSIKAIST

ENEA, FrascatiCEA, Cadarache

IPP, JülichIPP, Garching

ASCR, Czech RepU Quebec

College W&MColorado Sch MinesColumbia UComp-XGeneral AtomicsINELJohns Hopkins ULANLLLNLLodestarMITNova PhotonicsNew York UOld Dominion UORNLPPPLPSIPrinceton USNLThink Tank, Inc.UC DavisUC IrvineUCLAUCSDU ColoradoU MarylandU RochesterU WashingtonU Wisconsin

DIII-D PAC Lasted 1 Day (2 Half-Days)

• First morning – presentations by international members of PAC– Guenther: AUG– Miura: JT60U and NCT– Janeschitz: Technology for DEMO– Shimada: High-priority physics issues for ITER

• Next two half days – DIII-D presentations– Overview: Taylor– Diagnostics: Boivin– 9 topical talks (contained results, goals, plans)

Guenther - AUG

• NTMS– Coupled low-n mode NTMs less severe than single mode– Seen on AUG, JET, DIII-D; good for ITER– Modulated ECCD stabilizes better than NMECCD

• Fast ion CD – co vs ctr– No q-profile mod seen at high power (>4 MW)– Fast ion diffusion (D=0.5 m2/s) explains– Source not clear (scales with thermal transport, no MHD/AE)

• Turbulent transport– R/LTe scales as TEM linear growth rate– Correlation reflectometry shows change in Lc from L to H

• Tungsten – heading towards full W; only lower divertor remains– Impurity problems in core only if density peaks (neo pinch)

• Plans– Upgrade ECH to 10 s– Internal coils planned for ELM/RWM control

Miura – JT60U & NCT

• Ops started in Nov – preliminary results• Ferritic steel tiles to reduce ripple

– See significant increase in heating, confinement (30-50% depending on beam)

– Beta exceeds no wall limit (n>3.7)

– No serious impurity effects in core; metals observed only close to outer wall

– Wall saturation observed in ELMy H-mode

• National Centralized Tokamak– JAERI/EU collaboration – approved (procurement starts next year)

– ITER development device• Half-size, current, similar q, 41 MW NB+EC (no ICRH)

– Passive stabilizers, internal coils for ELM/RWM control

– Operate in ELMy H-mode, hybrid

– Want JT60U to operate another 5 years• Does not look good (JAERI)

Shimada – Major Physics R&D for ITER

• Design issues– Disruption mitigation (gas injection)– First wall loading (ELMs, blobs, TAEs, shine-thru in HH)– Tritium inventory

• Initial estimates a disaster, but recent JET results promising in reducing T buildup

• Large uncertainty

– Low-f noise on magnetics, eddy currents increase load on cryogenics

• Physics Issues– L-H power threshold (40-70 MW)– Effect of ripple on edge pedestal– Steady-state (integrated) control– Accessibility of hybrid mode (140-220 MW required?)– Redistribution of NBCD by EPM

Taylor - Overview

• Starting ops after Long Torus Opening Activity (LTOA)– 12 run weeks in FY06, 20 in FY07– Semi-contiguous (maybe a small vent in between

• Major elements of opening– 3 additional 1 MW (800 kW), 10 s ECH gyrotrons– Rotation of beam line from co to ctr– Lower divertor pumping in high- (ITER) configuration– TF, FW, diagnostics

• Stressed DIII-D world leader in providing ITER support (design and physics basis) – listed all areas

• Described open planning process– RC (goals, ITPA, milestones) → Thrusts (exptl planning) → RC (run time

allocation)• 586 total proposals, 484 unique, 46.5 in FY06, 135.5 in 06/07, 348.5 backlog• “DIII-D is an integrated science program aimed at an energy goal”

– Fundamental science understanding and ITER support• Some PAC members indicated DIII-D is promising too much with too little run

time– All ITPA areas covered in run plan

Boivin - Diagnostics

• 24 additional MSE channels (8 core, 16 edge)– Look at ctr beam; improve radial, signal resolution

• New j(r) measurement based on amp of Stark spectrum– ITER prototype; proof-of-principle

• Upgraded turbulence diagnostics (FIR scattering, BES, PCI, correlation reflectometry)

• ECE upgrade to 400 MHz – Allows measurement of radial profile of TAE

• Edge imaging, probes• Others

– Massive gas puffing system– Fast pellet dropper– Lower divertor tiles contoured for better diagnostic access– Li pellet injector to be reinstalled during run “as time permits”

Allen – Edge and Boundary

• FY06/07 benefits from new AT divertor (scale to ITER), divertor measurements (filterscopes, probes, microbalance)

• Address ITER design and physics issues– Heat load on first walls (ELMs/disruptions)– C erosion/deposition/control, Tritium buildup– Private region PFC– SOL transport– Lifetime of PFC mirrors and optical systems– Study dust

• FY06/07– Tritium inventory and C transport 2/4 days– Mirror and tile gaps– Heat flux control and fueling (puff and pump ITER hybrid and AT plasmas)

1/4– Poloidal dependence of transport and ELMs 0/2– AT divertor (commission in AT shape, compare pumping with predictions,

dome shape for ITER) 2/4• Stress experiment/theory collaborations • CB: too few run days for what needs to be done (true for all groups)

Burrell – Confinement and Transport

• Main goals – DIII-D playing major role in – Developing predictive understanding of transport– Investigating fundamental transport issues– Performing ITER/ITPA relevant experiments

• Take advantage of new capabilities– Balanced beam injection– Improved fluctuation diagnostics– Upgraded computer cluster for GYRO calculations

• Stress exp’t/theory collaboration– Group meetings, seminars include theorists, modelers, experimentalists– Gave example of ITB triggering in NCS L-mode (Austin, APS05 Invited)

• Dynamics of Te gradient relative to integer q-evolution

• Primary focus areas (06/07) – 7 run days in FY06, 15 in 06/07– Angular momentum transport (rotation control)– scaling at low rotation speeds– Transport barrier physics and control (exploit ExB control)– Electron thermal transport (high-k)– Turbulence characterization (zonal flows)

• ITG vs TEM (particle pinch direction)• Do zonal flows trigger L-H transition

Burrell – cont’d

• RP – KB being too US-centric• CB – DIII-D claim of developing a predictive

understanding should derive from the broader U.S. program goals and capabilities– Do not go it alone– KB admitted he really does not know, in practice, the best

way to develop a fully-integrated predictive capability (resource-management)

Strait – Stability and Disruption Physics

• Physics goals closely aligned with ITER needs– Active control of instabilities

• Disruption mitigation with gas feed• RWM, ELM, NTM control

– MHD stability physics• NTM threshold and seeding• Fast ion interactions with AEs• Sawtooth instability – understand and control severity• Plasma response to error fields

• New capabilities– High throughput gas jet– Counter beam– Upgraded ECH, CD (NTM, q-profile control)– High bandwidth amplifiers for I-coils (RWM, NTM)

• FY06– Plasma control (re-optimize EF; feedback control of rotation)– Stability physics (disruption mitigation, fast ion transport, low rotation NTM)

Strait – cont’d

• FY07– Giant sawtooth physics, control (localized ECCD)– RSAE– Plasma response to EF at low rotation– Disruption physics (size scaling with JET)

• CB- what are priorities, what is logic behind priorities?– RWM, ELM, disruptions most important, fast ion physics

secondary

Prater – Heating & CD

• New tools– Counter beam– ECH improvement– FW being refurbished

• 1 run day in FY06– Validate NB physics and CD models using ctr beam

• FY07– FW absorption– Core and pedestal bootstrap– Far off-axis ECCD– Alpha-channeling CD using NB and TAEs– Startup assist with 2nd harmonic ECH

Luce – AT Scenario Development

• Goal is steady-state ops development: high fusion gain for ITER• Elevated q-scenarios – active scenario control (4 days in FY06)

– qmin>1.5: extend to 2R

– qmin>2: extend to E

• Integration– Radiative divertor

– Te=Ti at low rotation – effect on energy transport

• High li– Extend qmin>1 to >5E

• Profile control (2 days in FY06)– Target q-control

– Density control

• No plan for FY07

• PAC questioned ability to get qmin>2 goal without FWCD (no significant power in FY06)

Petty – Hybrid Scenarios

• Forget about steady-state AT and H-mode; focus on hybrid modes as the baseline

• Features– Pulsed (not steady-state)– Hot-ion mode in DIII-D (although some high density reduced Ti/Te

while maintaining mode characteristics/performance)– n/nGW ~0.4 (0.85 in ITER)– Large region of low shear with q0>=1 (theory indicates due to ctr-cd

from electron Landau damping of kinetic Alfven wave)• GJ questioned whether extrapolation to ITER is valid given the

above• Goals

– Improve fundamental understanding– Validate reactor like conditions– Extrapolation issues

• FY06 (4 days)– Hybrid in LSN, high Ip/BT

– Low rotation plasmas– Dependence of Ti/Te on collisionality – swap 3 MW NB for ECH

Petty – cont’d

• FY07 (5 days)– High Ip/BT cont’d

– Increase beta-limit (high-li, ECCD stabilization of 2/1)

– scaling– Divertor and ELM solutions

Leonard – Pedestal Width Physics

• Characterize and understand using improved diagnostics (kinetic and turbulence)– Gyroradius scaling– Effect of pellet fueling with pumping

• Pedestal simulation key ingredient• FY06 (1 day)

– DIII-D/JET similarity

• FY07 (6 days)– Continue similarity– Pellet fueling– Pedestal time-dependent profiles

Garofalo – RWM Control

• Attempted to justify for ITER by calculating theoretical critical rotation frequency– However, theory is factor of 2 too pessimistic (JET, DIII-D)– Critical rotation velocity for ITER may be factor 2 smaller– Weakens justification somewhat, but still large uncertainty

• Key upgrade is ctr beam– Separate heating and rotation: can provide effective rotation control without

having to apply either resonant (n=1) or non-resonant (n=3) magnetic perturbations

• FY06 (5 days)– Develop and characterize low rotation target– Demonstrate f/b stabilization at near zero toroidal rotation– Assess internal vs external coils

• FY07– Continue ’06– Develop low rotation AT target– Optimize RWM f/b in high beta AT target

LaHaye – NTM

• ITER thrust• FY06 (4 days)

– Slowly rotating islands (PCS rotation control using ctr beam)– ECCD of 3/2, 2/1: broad vs narrow, CW vs modulated– Real-time ECCD mirror steering, island location

• FY07 (2.5 days)– ECCD in ITER shape– Simultaneous 3/2, 2/1 stabilization

Fenstermacher – ELM Control for ITER

• ELM suppression by RMPs (3 days in FY06, 4 in ’07)– Divertor pumping gives low collisionality at high (ITER)

• ELM-free QH mode (3 days in FY06, 3 in ’07)– Divertor pumping, co vs ctr beam

• Pellet pacing of ELMs (0 days in FY06, 1.5 in ’07)– Pellet hardware upgrade (50-100 Hz) to induce small ELMs

instead of Type I

• Small ELM regimes (0 days in FY06, 1.5 in ’07)– Rotational shear, collisionality variation, pellet dropper)