overview of east h-mode plasma

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Overview of EAST H-mode Plasma

Liang Wang*, J. Li, B.N. Wan, H.Y. Guo, Y. Liang, G.S. Xu, L.Q. Hu for EAST Team & Collaborators

Institute of Plasma Physics, Chinese Academy of Sciences

*Email: [email protected]

2nd A3 Foresight Workshop on Spherical Torus, January 6 - 8, Tsinghua University, 2013 Beijing, China

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Outline

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Introduction

H-mode access & power threshold

ELM characteristics, energy loss and divertor power load

Active control of giant ELMs Long pulse H-mode over 30 s in EAST

Summary and conclusion

ASIPPExperimental Advanced Superconducting Tokamak

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Major radius: R0 = 1.9 m

Minus radius: a = 0.5 m

Plasma duration: t=1000 s

Plasma current: Ip = 1 MA

Toroidal field: BT = 3.5 T

Triangularity: δ = 0.3-0.65

SN/DN divertor configuration

Commenced operation on 26 Sept. 2006 First H mode on 7 Nov. 2010H-mode duration over 30s on 28 May 2012Divertor operation over 400s on 21 June 2012

ASIPPEAST Upgrade Capacity & Near-term Plan

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RMP Coils (n=4)

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Outline

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Introduction





ASIPPLithium wall conditionings

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• Increasing Li Coverage (85% @2012 vs 30% @2010) • Active Li injection to help operate long pulse H-mode• Need one more oven for full surface coating.

Reduce recycling Suppress impuritiesBenefit ICRF &LHCD couplingMitigate ELMs

ASIPPH-mode threshold power

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Threshold power of EAST H modes is aligned with predictions of the international tokamak scaling 2010 campaign

2012, dithering LH transition

Threshold power shows no dependence on heating method

Appears to have a roll-over ne ~ 2.2 1019/m3

Low density limit for H-mode access

B.N. Wan et al., Nucl. Fusion 53, 104006 (2013)

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Unfavorable BB facilitates H-mode access in EAST

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H-mode access in EAST favors the divertor configuration with ion B× B drift away ∇from the X-point, in contrast to other tokamaks.

Thus, LSN with reversed Bt facilitates access to H-modes Type I ELMy H-mode in EAST was only achieved in LSN.

Reversed Bt, 2010 campaign

Normal Bt, 2012

H.Y. Guo et al., Nucl. Fusion 54, 013002 (2014)

BB ↓

BB ↑

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Outline

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Introduction





ASIPPType-I ELMs in EAST

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LSN with LHW+ICRH

Heating power: Pheat~1.5PLH

Good confinement: H98 ~1

Lower density : ne/nG < 0.5

Repetition freq.: fELM < 50 Hz

Peak heat flux: ~10 MWm-2

Contours of js at UI (a), UO (b), LI (c) and LO (d) divertor targets for a typical Type-I ELMy H-mode.

ion sj e

Divertor particle fluxes

L. Wang et al., Nucl. Fusion 53, 073028 (2013)

ASIPPType-I ELM power load, pedestal energy loss

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ELMdiv diaW W

ELMdia diaW W

Pedestal energy loss: ~ 8.5%

Divertor power load: ~ 5%Most of Type I ELM ejected power

is deposited on the outboard divertor

Characteristics of divertor power load and peak heat flux for a Type I ELM.

ELM energy loss and divertor heat load for two groups of coherent type-I ELMs in #41200 & #42556

ASIPPCompound ELMs in EAST

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Characteristic: an initial ELM spike followed by a number of small ELMs.

Achieved in DN (δ=0.46) with LHW+ICRH, Pheat~1.3MW

Good confinement: H98 ~1Density: ne/nG >0.5 ELM frequency: fELM ~50HzThe plasma energy loss & div.

power load: both ~ 4.5% .Peak heat flux : between that of

type-I and type-III ELMs.

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Essential difference between compound ELMs &ELM filaments: different time scale

13Type-III ELM filaments observed by divertor LPs (left) and visible camera w/ BOUT++ (right).

The time scale of a compound ELM: a few msThe interval time betw. adjacent ELM filaments: 150-250μs

X.Q. Xu et al 24th IAEA FEC

ASIPPType-III ELMs in EAST

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The most common ELMs observed in EAST up to now.

Achieved USN, DN, LSN Pheat~PLH: LHW only, ICRF

only, LHW+ICRFfELM=0.2-0.8kHz

ne/nG = 0.2-0.65

Confinement: H98 = 0.5-0.8

No ∆Wdia was observed

∆Wdiv/Wdia : 1-2%.

Peak heat flux: ~2MW/m2.G. S. Xu et al., NF 51, 072001 (2011); L. Wang et al., NF 52, 063024 (2012)

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Three diagnostics (Divertor LPs + IR camera + LFS Reciprocating LPs) independently demonstrated .

L. Wang et al., submitted to Nucl. Fusion, December 2013

Scaling of divertor power footprint width in RF-heated type-III ELMy H-mode

In addition, the systematic experiments of EAST shows the inverse scaling is independent div-configuration (LSN, DN, USN).

ASIPPVery small ELMs in EAST (type-II like)

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Achieved with LHW+ICRH, Pheat~1.7MW, q95 ≥ 4.5

H98= 0.8-0.9, between type-I and type-III ELM regimes

High δ: very small ELMs type-I ELMs when δ was reduced to ~ 0.4.

High density: ne/nG = 0.5 - 0.6

High freq: fELM = 0.8-1.5kHz

Peak heat flux: < 1MWm-2 largely

No ∆Wdia was observed

Broadband MHD mode: 20-50kHzL. Wang et al., Nucl. Fusion 53, 073028 (2013)

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Outline

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Introduction





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Demonstrated for the 1st time Edge magnetic topology change by LHCD

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Helical Radiation Belts (helical current sheets) induced by LHCD

Y. Liang, …, L. Wang et al., PRL 110, 235002 (2013)

ASIPPStrong mitigation of ELMs with LHCD

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ICRF-dominated + 10Hz LHW modulation (LHW-off: 50ms ~ ½τE)

H98=0.8; Wdia|LH: 50 100kJ

LHW off: fELM ~150Hz

LHW on: ELMs disappear or sporadically appear w/ fELM~600Hz

Peak particle flux: ↓ by 2-4

Wdia varied slightly: within ±5%

A quick reduction of Гi,div during inter-ELM can be seen when LHW was switched off.

Y. Liang, …, L. Wang et al., PRL 110, 235002 (2013)

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Collaborated with PPPL

Demonstrated for the 1st time ELM Pacing by Innovative Li-granule Injection

Triggering ELMs (~25 Hz) with 0.7 mm Li granules @ ~45 m/s.ELM trigger efficiency after L-H transition: ~100%.Much lower divertor particle/heat loads than intrinsic type-I ELMs.

D. Mansfield et al., Nucl. Fusion 53, 113023 (2013)

ion sj e

Li

ASIPPELM control by SMBI

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SMBI: Supersonic Molecular Beam Injection, Initially developed by SWIP.CN, successfully applied on HL-2A, KSTAR & EAST

X. L. Zou et al., 24th IAEA FEC, San Diego

ASIPPSHF can be actively controlled with SMBI

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Striated Heat Flux (SHF ) region in the far-SOL can be actively controlled with SMBI.

Characteristic of LHCD heating scheme

SMBI significantly enhancing SHF, while reducing peak heat fluxes near strike point.

Achieving similar results with conventional gas puff or Ar seeding.

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SHF can be actively controlled by regulating edge particle fluxes

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For SHF: qSHF ~ ΓiTped, Tped~ 350 eV qSHF

increases with Γi.

At OST: qOST ~ ΓiTdiv, Tdiv ~ Γi-1,

qOST remains similar.

A unique physics feature of ergodized plasma edge by LHCD.

Allowing control of the ratio of qSHF/qOST, thus divertor power deposition area via control of divertor plasma conditions.

J. Li, …, L. Wang et al., Nature Phys. 9, 817 (2013)L. Wang et al., submitted to PSI - 2014, invited talk

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Achieved long pulse H-mode over 30s w/ small ELMs to minimize transient heat load

Predominantly small ELMs with H98 ~ 0.9, between type-I and type-III ELMy H-modes.

Target heat flux is largely below 2 MW/m2.

Accompanied by QCM, continuously removing heat and particles.

J. Li, … , L. Wang et al., Nature Physics 9, 817 (2013)

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Outline

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Introduction





ASIPP Significant progress has been made on H-mode & ELMs toward

long pulse operations in EAST on both technol. & phys. fronts.Various ELM dynamics and their behaviors have been characterized.

LHCD leads to edge plasma ergodization, mitigating ELM transient heat load and broadening the divertor footprint. LHCD + SMBI allows control of SS target heat flux distribution by regulating divertor conditions. H-mode access in EAST favors the divertor configuration with ion B×B drift away from the X-point, in contrast to other tokamaks.Achieved repeatable, long-pulse H-mode over 30 s successfully.

EAST is being upgraded with ITER-like W mono-block divertor and more than 20 MW CW H&CD, offering an exciting opportunity and great challenge for H-mode studies.

Summary & Conclusion

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Thank you!Welcome to join EAST experiments! We will be

right here waiting for you …

EAST – Test Bed for ITER

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Back up

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ASIPP

Mo first wallWater-cooledCryo-pump

LFS & HFS wall: Graphite Molybdenum

2012: Mo + graphite div.

2010: full graphite

ASIPPType-III ELMs in EAST

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The most common ELMs observed in EAST up to now.

Achieved in DN, LSN, USNLHW only, ICRF only,

LHW+ICRH, Pheat~PLH

Frequency: fELM=0.2-0.8kHzDensity: ne/nG = 0.2-0.65Confinement: H98 =0.5-0.8No ∆Wdia was observedDivertor power load: 1-2%.Peak heat flux: ~2MW/m2.

1.25, , ,

1.19 0.08, ,

RF-heated (ITER relevant)

NBI-heated (except C-Mod,

1.3 1.15 ,

(0.63 0 Eich'13. NF08 )) ,

EAST EASTq IR q div LPs p omp

multi machinesq IR p omp

B

B

ASIPPThe very small ELMs are type-II like

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Operation space of Type II ELMs: high δ, high κ, high ne , and high q95

Confinement of Type II ELMs: H98 being 10% less than Type I ELMs Unique feature of Type II ELMs: w/ broadband MHD mode ( 30±10kHz@ASDEX-Upgrade; 10-40kHz@JET)

Time-frequency spectrum of Mirnov magnetic signal.

ASIPPFlexible boundary control with LHCD

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The long pulse H-mode was achieved with dominant LHCD, with additional ICRH.

LHCD induces drives n=1 helical currents at edge, leading to 3D distortion of magnetic topology, similar to RMP

LHCD appears to be effective at controlling ELMs over a broad range q95, in contrast to fixed RMP coils.

overview of east h-mode plasma

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