Status of the 2008 ASC TSG Run plan

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Status of the 2008 ASC TSG Run plan

Presented by D. A. Gates(J. Menard Deputy)

At the NSTX Mid-run asessment

PPPLApril 16, 2008

Supported byOffice ofScience

Culham Sci CtrU St. Andrews

York UChubu UFukui U

Hiroshima UHyogo UKyoto U

Kyushu UKyushu Tokai U

NIFSNiigata UU Tokyo

JAEAIoffe Inst

RRC Kurchatov InstTRINITI

KBSIKAIST

ENEA, FrascatiCEA, Cadarache

IPP, JülichIPP, Garching

ASCR, Czech RepU Quebec

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

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XP-823 “Robustness of improved error field suppression in long-pulse discharges” – Day 1

Determine optimal n=3 EFC gain relative to IPF5 and/or IP

• Re-verify existence of n=3 EF in IP=900kA reference discharge STATUS: re-verified at 700kA with early H-mode. n=3 EF was less apparent w/o early H-mode

• Optimize n=3 EFC for two new plasma currents: 700kA and 1.2MA STATUS: Optimal EFC current at 700kA was similar to level at 900kA

Is EFCC proportional to IP?

– Need to optimize at 1.1-1.2MA to determine proportionality – needs 6-8 shots

Test combined n=3 EFC + n=1 RFA suppression for IP=0.7, 0.9, 1.2MA

• Add n=1 feedback – 2 shots for each IP – use optimal 2007 gain & phase

– STATUS: Worked well at 900kA, worked ok at 700kA but plasma still disrupted suggesting higher gain might be beneficial

– Need data at 1.1-1.2MA – need 3-4 shots

Day 1

GOAL: Extend optimal EFC to wider range of scenarios and IP

STATUS – 1 run day so far for XP-823

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XP-811 Vertical Stability Physics and Performance Limits in Tokamaks with Highly Elongated Plasmas

• XP complete in 1/2 run day

• Measured zmax , the maximum controllable vertical displacement, by turning of the plasma control and then tuning it back after the plasma had drifted vertically

• Interim report written and distributed to the ITER team which was well received

– “Dear David, Many thanks - the report makes very interesting reading and the work behind it is very valuable for us. Best Wishes, David Campbell”

• Detailed analysis ongoing

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XP-823 “Robustness of improved error field suppression in long-pulse discharges” - Day 2

Optimize n=1 RFA suppression controller• Reproduce 2007 900kA reference shots which used externally applied

n=1 error field to trigger rotation collapse and disruption (3 shots)

• Scan RWM control proportional gain until feedback system is unstable (4 shots)

– Add LPF to control coil currents as necessary to avoid very large SPA currents

• With gain at highest stable value, increase LPF from 0 to:– 1ms, 3ms, 10ms, 30ms, 100ms (2 shots for each LPF)

(10 shots)

• For LPF where AC RMS control power is reduced by factor 2-4, increase gain again and determine highest stable value (4 shots)

• Test controller for two new plasma currents: 700kA and 1.2MA (4 shots)

STATUS – Day 2 plan has not yet been run – scheduled for April 28

Completing XP-823 may require additional 1.5 days vs. 1 day asked for

Day 2

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XP-826 "X-point limiter plasmas"

• Investigate plasma configurations where dominant lower X-point is brought very close to, or possibly outside, the outer divertor plate

• Possible alternative way to reduce divertor heat flux• Assess access to H-mode, energy confinement and

heat flux on divertor• The initial experiment is planned to be run before

lithium coating• If successful, perform a second round with lithium on

the lower divertor

Goal: Investigate benefit of this configurationStatus: Scheduled for review

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XP-8** - Impact of 2 LITER system on long-pulse discharges

STATUS – XP has not been run – waiting for dual LITER – requests 1.5 days

• Goal is to determine if usage of 2 LITER system can:– Eliminate He glow, or reduce glow time to 5 mins

• Will likely be done in boundary physics TSG XPs

– Lower the electron density, and achieve density flat-top• Likely requires SGI to replace HFS gas

– Increase the NBICD fraction of long-pulse discharges• Significant shot development will be needed to optimize low ne operation

– Obtain sufficient flat-top duration to “measure” NICD profiles w/ VLOOP analysis

• Methodology– Reduce/eliminate HFS gas by utilizing SGI – 0.5 days

• Find lower bound of HFS pressure, incrementally add SGI

– If/when plasma disrupts in ramp or early flat-top, optimize early shot phase to obtain flat-top sufficient for NBI-CD analysis – 1 days (optimistic!)

• Vary beam timing and power• Vary plasma current ramp-rate and flat-top value• Vary early density/SGI fueling rate

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XP-8** Parametric study of high elongation plasmas

• Use second LITER and experience gained to optimize wall conditions

• Use n=1 feedback and n=3 correction to improve performance (higher )– Previous attempts limited to N < 4

• Perform current and field scan to optimize non-inductive current fraction

Goal: Investigate high elongation low-li scenario first developed in 2007Status: Waiting for LITER

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XP status summary

Lead Author Institution TitleSpecial

Requirements

Run days requested

TSG Ranking

Run days assigned

RelatedITPA Task

Status

J. Menard PPPLRobustness of improved error field suppression in long-pulse discharges

1 1 1 1/2 done

D. Gates PPPLParametric study of high elongation plasmas

LITER 1.5 2 1.5 Waiting

J. Menard PPPLImpact of 2 LITER system on long-pulse discharges

LITER 1.5 3 1.5 Waiting

E. Kolemen Princeton U.Vertical Stability Physics and Performance Limits in Tokamaks with highly elongated tokamaks

1 4 1 MDC-13 Complete

M. G. Bell PPPLDevelopment and Assessment of X-point limiter plasmas

1 5 1 Scheduled

C. E. Kessel PPPLHHFW into Early diverted plasmas and late (end of Ip ramp) Discharges

1.5 6 1 ?

C. E. Kessel PPPL Hybrid Discharges on NSTX 1 7 0 SSO-2.2

D. Humphreys GAUse of Nonaxisymmetric Coils for Vertical Stability Control in NSTX

1 8 0

D. Humphreys GADevelopment and Performance of model based multivariable shape controllers

1 9 0

D. Mueller PPPL Low li startup 0.5 10 0

V. Soukhanovskii LLNLH-mode fuelling optimization with high pressure multi-pulse SGI

0 11 0

E. Schuster LeHigh U. Advanced Model-based Shape controller 0 12 0 No run time

E. Schuster LeHigh U. Model-based rotation profile control 0 13 0 No run time