heat load measurements on the jet first wall during disruptions

G. Arnoux (1/15) 19th PSI conference San Diego, USA, 24-28 May 2010

Heat Load Measurements on the Heat Load Measurements on the JET First Wall During DisruptionsJET 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 3DB2Forschungzentrum karlsruhe GmbH, PO Box 3640, D-76021 Karlsruhe, Germany3Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, D-85748 Garching, Germany4Institüt für Energieforschung – Plasmaphysik, Forschungzentrum Jülich, trilateral Euregio Cluster, EURATOM-Assoziation, D-5225 Jülich, Germany5Association EURATOM – Belgian State, Laboratory for Plasma Physics Koninklijke Militaire School – Ecole Royale Militaire Renaissancelaan 30 Avenue de la Renaissance B-1000, Brussels, Belgium6ITER organisation, Fusion Science and Technology Department, Cadarache, 13108 St Paul Lez Durance, France7Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, EURATOM-Assoziation, D-17491 Greifswald, Germany


Ip

Wdia Prad

Soft X-Ray

IntroductionIntroduction

• 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

Thermal quench

Current quench

Runaway plateau


IntroductionIntroduction

• 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?


Fast IR measurementsFast IR measurements

• Fast time resolution: – tIR≃1ms on first wall (Reduced IR

view) – tIR≃86s 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

CFCW


Heat loads due to plasma Heat loads due to plasma wall interaction during the wall interaction during the

thermal and current quenchthermal and current quench


TQ an CQ during low q disruptionsTQ an CQ during low q disruptions

IR,out=1.2ms

IR,div=0.9ms

IR,in=4.9ms


Plasma wall interaction after TQPlasma wall interaction after TQ

+4ms +6ms +8ms +10ms +12ms

JPN77658

Inner limiter


Plasma wall interaction after TQPlasma wall interaction after TQ

+1ms +3ms +5ms +7ms +8ms

JPN77660

+10ms

Outer limiter


Energy balanceEnergy balance

Wrad Wdiv,5 Wlim Wdum Wtot t [ms]

TQ 56% 7% 4% 1% 75% 2.3±0.4

CQ 46% 3%* 9%** 3%* 61% 15*-100**

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!


Heat load due to Heat load due to runaway electronsrunaway electrons


RE impact on upper dump plateRE impact on upper dump plateIRE=502kA ; Bt/Ip = 3.0/2.0

T1T2

T3

T4

JPN76541, t=18.58ms

T5

JPN76541, t=4.11ms

T1T2

T3

T4

T5


RE impact on upper dump plateRE impact on upper dump plate

JPN76533 JPN76534 JPN76541

RE interaction with dump plate dominated by geometry of PFCs

JPN76535 JPN76536JPN76532

T1

T1

T2

T3

T4

T5

IRE=173 kA IRE=502 kA IRE=425 kA IRE=285 kA IRE=360 kA IRE=502 kA


Temp. increase due to RE impactTemp. increase due to RE impact

RE≈2ms

Tdum,av

T1T2

T3

T4

JPN76541, t=18.6ms

T5

IfitImeas


RE energy load on upper dump plateRE 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


ConclusionConclusion

• 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.


MGI and “natural” disruptionsMGI and “natural” disruptions

• 50% of Wdia,TQ is radiated prior to TQ

• Power to outer divertor target just after TQ higher for “natural” disruption…

• …in this example

• What is Wdiv,5/Wdia,TQ for 35 pulses?


Energy load on outer divertor tile 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?

heat load measurements on the jet first wall during disruptions

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