progress and scientific results in the tcv tokamak

Centre de Recherches en Physique des PlasmasEPFL, Association Euratom-Fédération Suisse, Lausanne,

Switzerland

S. Coda, 23rd IAEA Fusion Energy Conference, OV/5-2, Daejeon, 13 October 2010

Progress and scientific resultsin the TCV tokamak

for the TCV team*S. Coda

*including collaborating institutions:IPP, Czech Republic ENEA-CNR Padova,

ItalyEHU, Spain

CEA, France ENEA-CNR Milan, Italy

CCFE Culham, UK

IPP Garching, Germany

ITER-JCT U. Warwick, UK

IPP Greifswald, Germany

NIFS, Japan LLNL, US

F-Z Jülich, Germany IST, Portugal PSFC MIT, USKFKI, Hungary RRC Kurchatov, RF General Atomics,

USIPR, India Keldysh Institute,

RFCompX, US

ENEA Frascati, Italy CIEMAT, Spain

S. Coda, 23rd IAEA Fusion Energy Conference, OV/5-2, Daejeon, 13 October 2010

S. Coda, 23rd IAEA Fusion Energy Conference, OV/5-2, Daejeon, 13 October 2010Progress and scientific results in TCV

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• TCV parameters and capabilities• Scientific mission and guidelines• Technical progress• Scientific highlights

Torque-free generation and transport of rotation

Particle and energy transport, turbulence Advanced real-time control Alternative confinement topologies

• Summary and outlook

Outline


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TCV

R = 0.88 m, a = 0.25 m

Ip < 1 MA, BT < 1.54 T

k < 2.8, -0.6 < d < 0.9

4.5 MW ECRH power, 7 steerable launchers

×4

×2


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• Experiments in preparation for ITER• Alternative configurations,

tokamak concept improvement

Scientific guidelines of the TCV program


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ITER preparation + alternative pathsMultiple steerable EC launchers, r/t control

NTM stabilization


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ITER preparation + alternative pathsFlexible shaping


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Highlights of technical progress

• Improved charge exchange spectroscopy resolution(from 2 to 1 cm) + sensitivity (5-10×): Ti, vf, vq , nC

• New digital real-time network to control coils and EC systems potential to use massively multichannel diagnostics


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Outline


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Symmetry breaking toroidal momentum transport by turbulenceNew theory validated by TCV experiments

• Static, up-down symmetric plasma: fundamental symmetry upon reversal of v// and poloidal angle net turbulence-driven momentum flux is zero

• Symmetry breaking net momentum flux: from vf, vf, or up-down asymmetry(Y. Camenen et al, PRL 2009)


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Same Bf, Ip

inward

outward

Turbulent momentum transport

Y. Camenen et al, PRL 105, 135003 (2010)

• Radial turbulent momentum flux changes signas expected from up-down flip

• vf varies most at edge where asymmetry is greatest

Bdrif

t

Bq

• Direction of radial fluxshould reverse withBf sign, Ip sign, up-down flip

• All reversals have been confirmed by experiment


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• observed systematically in TCV L-modes (no torque)

• at low to moderate current (qedge >3),vf is counter-current in core

• central rotation is limited by sawtooth crashes imparting a co-current spin

• vf changes sign at high current and density

Spontaneous plasma rotation

A. Fasoli, IAEA 2008 overview

New experiments performed to quantify and document effect of sawteeth

(i.e., 1/1 internal kink) and other MHD modes study effect of ECRH on rotation

A. Bortolon et al, PRL 2006B.P. Duval et al, PPCF 2007B.P. Duval et al, PoP 2008


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• Reproducible co-current spin-up inside the inversion radius

• Rapid relaxation (in <15% of sawtooth period)• Enhanced CXRS time resolution by coherent

averaging over multiple sawteeth

Plasma spin-up at sawtooth crash

B.P. Duval et al, EXC/P4-01 (this afternoon)

Inv. radius


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Slightly hollow inside the mixing radius......to the point of changing sign at high enough current

Average effect of sawteeth on rotationSelf-similar gradients outside the mixing radius


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Influencing rotation with ECRHthrough sawteeth

• EC power inside mixing radius hollows out vf profile

• Similar to Ip increase: consistent with effectof current profile peaking on sawteeth

O. Sauter et al,EXS/P2-17


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Outline


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Stronger flattening by sawteeth for impuritiesStronger peaking for impurities than for electronsSawteeth affect particle transportsimilarly to momentum transport

Electrons Carbon ions

Similar edge gradients

Y. Martin et al, EXC/P8-13 (Friday afternoon)


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The effect of shape on turbulence• Triangularity strongly influences transport:

confinement of EC-heated d=-0.4 plasmas is up to twice as good as for d=+0.4 (for similar profiles)

• Gyrokinetic simulations explain this through the effect of toroidal precessional drift of trapped electrons on TEM turbulence

A. Fasoli, IAEA 2008 overview

Y. Camenen et al, NF 2007A. Marinoni et al, PPCF 2009


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The effect of shape on turbulence• Measurements of temperature fluctuations by

a tunable 2-channel correlation ECE system reveal a broadband spectrum in the expected 20-150 kHz range


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Longer correlation length at d>0larger random-walk step, consistent with more

transport

B. Labit et al, EXC/P8-08 (Friday afternoon)


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Outline


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Real-time control in TCV• All algorithms developed in powerful and

intuitive Simulink environment• Real-time nodes generate C code

automatically from Simulink


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Profile control with ECRH

J.I. Paley et al, PPCF 51, 124041 (2009)F. Felici, Ph.D. thesis (2011)

• Based on soft X-ray profile• Simple system with 2 actuators: on-

and off-axis ECRH powers to control amplitude and width

• Model parametrized through System Identification from random binary modulation of the EC power


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Profile peak amplitude

Profile control with ECRH

J.I. Paley et al, PPCF 51, 124041 (2009)F. Felici, Ph.D. thesis (2011)


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Outline


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The “snowflake” divertor• 2nd order null point (Bq=0, Bq=0)• Six separatrix branches, four divertor legs• Increased flux expansion and connection

lengthmay alleviate divertor heat loads

• Snowflake (SF) is a point along a continuumfrom SF+ to SF-


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The snowflake divertor in TCVSF+ SF SF-

F. Piras et al, PPCF 51 055009 (2009)


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SFcompared to

single-null:• similar L-H threshold

SFcompared to

single-null:• similar L-H threshold• 2-3× slower ELMs

Snowflake H-modeSF compared to single-null:• 2-3× slower (type-I) ELMs• only 20-30% more energy loss per ELM

F. Piras et al, PRL 105, 155003 (2010)B. Labit et al, EXC/P8-08

Promising scaling for average power loss

B. Labit et al, EXC/P8-08 (Friday afternoon)


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• Studies aligned with ITER requirements: spontaneous generation and transport of

momentum particle and energy transport effect of shape on turbulence real-time profile and MHD control

• Concept improvement and theory testing: new mechanism for turbulent momentum

transport snowflake divertor in L- and H-mode

Summary


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• Up to 3 MW NBI heating• Up to 3 MW additional X3 ECRH heating• Refurbished LFS first wall for increased power

handling• In-vessel ergodization and error-field coils

for ELM control

Outlook: major upgradesTCV research is built on unique flexibilityin ECRH and plasma shaping further empower these unique characteristics

diversify and expand operational domain


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• TCV EXS/P2-17: O. Sauter et al, “Effects of ECH/ECCD on tearing modes in

TCV and link to rotation profile”, Tue pm EXC/P4-01: B.P. Duval et al, “Momentum transport in TCV across

sawteeth events”, Wed pm EXC/P8-08: B. Labit et al, “Transport and turbulence with innovative

plasma shapes in the TCV tokamak”, Fri pm EXC/P8-13: Y. Martin et al, “Impurity transport in TCV: neoclassical and

turbulent contributions”, Fri pm• Fusion technology

FTP/P1-16: N. Baluc et al, “From materials development to their test in IFMIF: an overview”, Tue am

• JET THS/9-1: J.P. Graves et al, “Sawtooth control relying on toroidally

propagating ICRF waves”, Sat am EXW/P7-27: D.S. Testa et al, “Recent JET experiments on Alfvén

eigenmodes with intermediate toroidal mode numbers: measurements and modelling, Fri am

• Basic plasma physics EXC/P8-09: A. Fasoli et al, “Turbulence and transport in simple

magnetized toroidal plasmas”, Fri pm

CRPP contributions

progress and scientific results in the tcv tokamak

Documents

iaea fusion energy conference

scientific results

energy transport

duval et

camenen et

labit et

bortolon et

toroidal momentum transport