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Heat Load Measurements on the JET First Wall During Disruptions

Heat Load Measurements on the JET First Wall During Disruptions. G.Arnoux 1 , B.Bazylev 2 , S.Devaux 3 , T.Eich 3 , W.Fundamenski 1 , T.Hender 1 , S.Jachmich 4 , A.Huber 5 , M.Lehnen 5 , A.Loarte 6 , U.Kruezi 4 , V.Riccardo 1 , G.Sergienko 4 , H.Thomsen 7 and JET-EFDA Contributors.

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Heat Load Measurements on the JET First Wall During Disruptions

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  1. Heat Load Measurements on the JET First Wall During Disruptions G.Arnoux1, B.Bazylev2, S.Devaux3, T.Eich3, W.Fundamenski1, T.Hender1, S.Jachmich4, A.Huber5, M.Lehnen5, A.Loarte6, U.Kruezi4, V.Riccardo1, G.Sergienko4, H.Thomsen7 and JET-EFDA Contributors 1 EURATOM/CCFE Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB 2Forschungzentrum karlsruhe GmbH, PO Box 3640, D-76021 Karlsruhe, Germany 3Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, D-85748 Garching, Germany 4Institüt für Energieforschung – Plasmaphysik, Forschungzentrum Jülich, trilateral Euregio Cluster, EURATOM-Assoziation, D-5225 Jülich, Germany 5Association EURATOM – Belgian State, Laboratory for Plasma Physics Koninklijke Militaire School – Ecole Royale Militaire Renaissancelaan 30 Avenue de la Renaissance B-1000, Brussels, Belgium 6ITER organisation, Fusion Science and Technology Department, Cadarache, 13108 St Paul Lez Durance, France 7Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, EURATOM-Assoziation, D-17491 Greifswald, Germany

  2. Introduction Ip Wdia Prad Soft X-Ray Runaway plateau Thermal quench Current quench • Transient heat loads during disruptions are of great concern for plasma facing component integrity • Heat load sources during disruption are • Plasma thermal energy (thermal quench) • Radiation during thermal and current quench • Runaway electrons during current quench

  3. Introduction • What we know • A significant part of the energy during the thermal quench goes onto the first wall, not onto the divertor [J. Paley et al. J. Nucl. Mater. 2005, P. Andrew et al. JNM 2007] • Heat load on the JET upper dump plate were characterised for different type of disruptions [G. Arnoux et al. NF 2009] • During massive injection of argon, RE impacts were observed on the JET upper dump plate [M. Lehnen et al., J. Nucl. Mater. 2009] • What we can learn from JET fast IR measurements • Heat loads onto the first wall during the thermal and current quench • What time scales? • Distribution onto PFCs: poloidal limiters, upper dump plate,… • RE impacts on the JET upper dump plate • Heat load pattern (distribution) • How much energy (magnetic and kinetic) transfered to the first wall during the RE loss?

  4. Fast IR measurements CFC W • Fast time resolution: • DtIR≃1ms on first wall (Reduced IR view) • DtIR≃86ms on divertor outer target • Region of interest (pulse to pulse) • Outer limiter • Inner limiter • Upper dump plate • Data reduction • Poloidal profiles: T(x,y,t) → T(s,t) • Maximum temperature: T(x,y,t) → T(t) • Heat load profiles with THEODOR • T(s,t) → q(s,t) • On limiters: plasma wall interaction only, no radiation considered (mask) • On divertor, tile 5 only is considered

  5. Heat loads due to plasma wall interaction during the thermal and current quench

  6. TQ an CQ during low q disruptions tIR,in=4.9ms tIR,out=1.2ms tIR,div=0.9ms

  7. Plasma wall interaction after TQ Inner limiter +4ms +6ms +8ms +10ms +12ms JPN77658

  8. Plasma wall interaction after TQ Outer limiter +1ms +3ms +5ms +7ms +8ms +10ms JPN77660

  9. Energy balance During thermal quench (TQ): Wth,TQ = Wrad + Wdiv + Wwall During current quench (CQ): Wmag = Wrad + Wdiv +Wwall with: Wwall = Wlim,in+ Wlim,out+ Wdum Plasma wall interaction only 0.5MJ < Wth,TQ < 2.3MJ Wmag≃ 9.1MJ Toroidal symmetry is assumed!

  10. Heat load due to runaway electrons

  11. RE impact on upper dump plate IRE=502kA ; Bt/Ip = 3.0/2.0 T1 T1 T5 T5 T2 T2 T3 T3 T4 T4 JPN76541, t=4.11ms JPN76541, t=18.58ms

  12. RE impact on upper dump plate T1 T5 T2 T3 T4 RE interaction with dump plate dominated by geometry of PFCs JPN76541 JPN76532 JPN76533 JPN76534 JPN76535 JPN76536 IRE=173 kA IRE=502 kA IRE=425 kA IRE=285 kA IRE=360 kA IRE=502 kA T1

  13. Temp. increase due to RE impact DTdum,av T1 T5 T2 T3 Imeas Ifit T4 JPN76541, t=18.6ms tRE≈2ms

  14. RE energy load on upper dump plate Modelling [B. Bazylev, P1-98]: Energy load at the CFC surface: 0.5 < QRE < 3 MJ/m2 Current flowing into the CFC tile = IRE 60% of IRE get out of the tile => ~10% of magnetic energy dissipated into CFC tile

  15. Conclusion • Heat loads onto the JET first wall have been measured during disruptions using enhanced, fast IR thermography • During TQ of low q disruptions, significant heat loads are measured on the poloidal limiters on a comparable time scale as that of the divertor • During CQ of low q disruptions, about 10% of the magnetic energy is transferred to the first wall via plasma wall interaction. • The RE interaction with the JET upper dump plate leads to very localised patterns, dominated by the wall geometry • Runaway electrons energy deposited on first wall scales with the square of RE current. • Modelling shows that about 10% of the magnetic energy is dissipated into the CFC tiles.

  16. MGI and “natural” disruptions • 50% of Wdia,TQ is radiated prior to TQ • Power toouter divertor target just after TQ higher for “natural” disruption… • …in this example • What is Wdiv,5/Wdia,TQ for 35 pulses?

  17. Energy load on outer divertor tile • Possible mitigation effect during TQ for Wdia,TQ < 1.5MJ • No clear difference with gas species in heated plasmas (Wdia,TQ > 1.5MJ) • What about heat load onto the first wall?

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