EX/7-2: Impurity Seeding on JET to Achieve Power Plant like - - PowerPoint PPT Presentation

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EX/7-2: Impurity Seeding on JET to Achieve Power Plant like Divertor Conditions M. Wischmeier Max-Planck-Institut fr Plasmaphysik, Garching, Germany 25 th IAEA Conference, St Petersburg, 2014 M. Wischmeier 1 /27 25 th IAEA

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  • M. Wischmeier 1/27

25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

EX/7-2: Impurity Seeding on JET to Achieve Power Plant like Divertor Conditions

  • M. Wischmeier

Max-Planck-Institut für Plasmaphysik, Garching, Germany 25th IAEA Conference, St Petersburg, 2014

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  • M. Wischmeier 2/27

25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Acknowledgements

Co-authors

  • C.G.Lowry1, A.Huber2, M.L.Reinke3, C. Guillemaut4, L. Aho-Mantila5, S.

Brezinsek2, P. Drewelow5, C.F. Maggi6, K. McCormick6, A.Meigs4, G.Sergienko2, M.F.F.Nave7, G.Sips1, M.Stamp4, and JET contributors*

  • JET-EFDA, Culham Science Centre, Abingdon, OX14 3DB, UK
  • 1European Commision, B-1049 Brussels, Belgium

2Institute of Energy and Climate Research, Forschungszentrum Jülich, Trilateral Euregio Cluster,

D-52425 Jülich, Germany

3University of York, Heslington, York, YO10 5DD, UK 4CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK 5VTT Technical Research Centre of Finland, FI-02044 VTT, Finland 6Max- Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany 7Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, P-

1049-001 Lisboa, Portugal

  • *See the Appendix of F. Romanelli et al., Proc. 25th IAEA FEC 2014, St Petersburg,

Russian Federation

This work was supported by EURATOM and carried out within the framework of the European Fusion Development

  • Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement number 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Boundaries for power exhaust

Ø Limit on acceptable erosion: v With impurity seeding and higher charged states enhancing erosion: Te < 2 - 5 eV Ø Expected power handling limit of actively cooled DEMO divertor component < 10MW/m2: v limit on particle flux to limit power deposition by surface recombination (15.8 eV per ion – electron pair) Ø Power handling limit combined with erosion limit è completely detached divertor

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Radiation in DEMO divertor similar to ITER

  • separatrix

Similar volume and size of divertor è similar absolute amount of radiation in SOL and divertor (ITER ~ 60% – 70% of PSOL=120MW è 70MW) ITER to DEMO:

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Radiation: minimize in core Core

separatrix

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Radiation: minimize in core & optimize edge

  • Core

separatrix

Divertor power dissipation in DEMO similar to ITER è Edge + core > 70% radiation Edge radiation

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

DEMO requires > 90 – 95% radiation

  • Core

separatrix

è Total radiation required sums to > 90% - 95% of Pheat è Maximize radiation in EDGE and SOL à main guidance Edge radiation SOL and divertor

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Vertical target geometry

BT=2.7T IP=2.5MA δ=0.22 (low triangularity) q95=3.3 Pheat= PIN-dW/dt (14-28MW) Pheat/R ~ 5 – 9 Psep/R ~ 3 - 6

R=3m

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Maximum frad independent of Pheat

Ø ~70% frad at maximum P/R ~ 9 Ø Highest frad with only N2 seeding Ø Performance of N2 + Ne seeding evolves qualitatively very similar to pure Ne seeding Ø ASDEX Upgrade reaches frad>85% but higher cW (W from MCW)

Total heating power [MW], R=3m Total radiated power fraction frad 75%

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Maximum frad increases with seeding

  • Pheat: 18 – 20 MW

frad Nitrogen seeding rate [el s-1] Ø Close to maximum: frad low efficiency of seeding on frad

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Higher Pheat è è higher seeding for frad

Total heating power [MW], R=3m Total radiated power fraction frad 0.5E23 el s-1 1.8E23 el s-1 1.0E23 el s-1

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

N2 seeding into H-Mode plasma: stable radiation of 75%

Ø N2 à leads to ELM mitigated H-mode with frad of ~75% Ø ELM mitigated phase with magnetic activity similar to M-Mode

(E. Solano et al., EPS 2013)

Ø cW in core at detection limit (<10-5)

10 12 14 16 18 s

  • A. Huber et al. EPS 2014,
  • M. Wischmeier PSI 2014

(Core density)

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Total radiation Edge density Core density frad

Poloidal radiation at highest frad

  • Ne seeding

Radiative instabilities with transient frad of up to 90%

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Poloidal radiation at highest frad

  • Ne seeding

Radiative instabilities with transient frad of 90%

Ar seeding

Maximum frad ~60%

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Poloidal radiation at highest frad

  • Ne seeding

Radiative instabilities with transient frad of 90%

Ar seeding

Maximum frad ~60%

N2 seeding

Maximum frad ~75% Concentrated around X-point

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Radiation concentrated at X-point independent of seeding species

  • Ne seeding

Ar seeding N2 seeding Ø Peaking of radiation density (W/m3) varies with seeding species as well as poloidal extent Ø No radiating belt formed

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Definition of radiation distribution

  • A. Huber et al. EPS 2014
  • M. Wischmeier et al. PSI 2014

Ø According to reconstruction at highest frad this accounts for largest part of edge & SOL radiation

Above X-point ~ inside LCFS excluding X- point èdue to poloidal distribution ~ core radiation

Divertor and X-point

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Limit of radiation above X-point for N2

  • Above X-point / total radiation

Total radiated power fraction

Ø Lowest fraction of above X-point radiation for seeding that includes N2 Ø Fraction of experimental radiation above X-point not directly comparable to requirements for DEMO

75%

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Above frad of 70% close to L-H threshold

  • 75%

(Pheat-PMC) / PL-H (Martin scaling J. Phys. 08) Total radiated power fraction

Ø Ar seeding even for low seeding rates close to L-H threshold Ø N2 seeding approaches threshold for highest frad Ø At low ratios radiative instabilities in case of Ne

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Impact of seeding on confinement scaling

  • H98(y,2)

βN In highly seeded discharges H98(y,2) is function of βN

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Impact of N2 seeding on confinement scaling

  • H98(y,2)

Total radiated power fraction

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Impact of N2 seeding on confinement scaling

H98(y,2) Total radiated power fraction

Low Pheat ~ 14 MW

High fueling and seeding levels N2 rate: 5 – 18 1022 el s-1 D2 rate: 2 – 6.5 1022el s-1

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Core & pedestal profiles at high frad

  • !
  • A. Huber et al. EPS 2014

Ø With N2 seeding mainly pedestal ne depletes Ø Profiles recover and surpasses unseeded values in core Ø No reliable information on changes in SOL profiles yet

Pheat ~ 20MW

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

JET: Complete detachment with N2

  • −0.05

0.05 0.1 0.15 0.2 0.25 0.3 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Distance along target [m] Ion current density

#84884 D only #85425 N seeding

Ion saturation current Temperature [eV]

Distance along outer target [m] Time averaged outer target LP profiles for 12s -14s for #84884 and #85425

Ø Highest N2 seeding evolves to complete detachment on outer and inner target Ø Complete detachment coincides with strong radiation at X-point

D only N seeded

−0.05 0.05 0.1 0.15 0.2 0.25 0.3 2 4 6 8 10 12 14

Distance along target [m] Temperature [eV]

#84884 D only #85425 N seeding

D only N seeded

[MA/m2]

Te outer target

  • M. Wischmeier et al. PSI 2014

Similar to ASDEX Upgrade (A. Kallenbach et al. EX/7-1, F. Reimold et al., subm. to Nucl. Fusion)

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Operational stability of radiation

  • Loss of NBI power and no backup
  • Ch. 3
  • Ch. 5
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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Numerical modeling

  • COREDIV: 1D core modeling and 2D slab geometry for

SOL (G. Telesca et al. PSI2014) Ø For highest N2 seeding, radiation in divertor does not increase further due to low divertor Te Ø Highest frad with X-point not accounted for due to 1D core (strong poloidal gradients in Te and radiation)

  • EDGE2D-EIRENE simulations demonstrate detachment

achievable with N2 seeding (TH/P5-34 A.E. Jarvinen et al.)

  • Dedicated numerical modeling with full geometry pending
  • SOLPS5.0 (w. EIRENE) simulations including activated

drift terms for similar ASDEX Upgrade cases: complete detachment induced by loss of upstream pressure due to strong X-point radiation (EX/P3-16 P M. Wischmeier et al. , F. Reimold et al. PSI 2014)

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25th IAEA Conference, St Petersburg, EX/7-2 17th of October 2014

Conclusions

Ø Stable discharges with radiation peaked around X-point for N2, Ne, Ar and N2+Ne Ø Maximum radiation independent of heating power v Maximum radiation achieved 75% - DEMO requires > 90% v Physics reason not yet understood – link to maximum stable radiation in edge region? v ELM mitigation for marginal H-mode Ø Stable completely detached outer and inner divertor achieved Ø Pedestal profile degradation recovered by steeper core profiles Ø Future: Combine seeding of higher Z at higher Pheat with N2