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
für Energieforschung – Plasmaphysik, Forschungzentrum Jülich, trilateral Euregio Cluster,
EURATOM-Assoziation, D-5225 Jülich, Germany
4Institüt
EURATOM – Belgian State, Laboratory for Plasma Physics Koninklijke Militaire School
– Ecole Royale Militaire Renaissancelaan 30 Avenue de la Renaissance B-1000, Brussels, Belgium
5Association
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
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
Introduction
• 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
Ip
Wdia
Prad
Soft X-Ray
Runaway
plateau
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
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?
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
Fast IR measurements
• 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
G. Arnoux (‹#›/15)
19th PSI conference
CFC
W
San Diego, USA, 24-28 May 2010
Heat loads due to plasma
wall interaction during the
thermal and current quench
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
TQ an CQ during low q disruptions
tIR,in=4.9ms
tIR,out=1.2ms
tIR,div=0.9ms
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
Plasma wall interaction after TQ
Inner limiter
+4ms
+6ms
+8ms
+10ms
+12ms
JPN77658
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
Plasma wall interaction after TQ
Outer limiter
+1ms
+3ms
+5ms
+7ms
+8ms
+10ms
JPN77660
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
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
Wrad
Wdiv,5
Wlim
Wdum
Wtot
Dt [ms]
TQ
56%
7%
4%
1%
75%
2.3±0.4
CQ
46%
3%*
9%**
3%*
61%
15*-100**
Plasma wall
interaction only
0.5MJ < Wth,TQ < 2.3MJ
Wmag ≃ 9.1MJ
• Toroidal symmetry is assumed!
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
Heat load due to
runaway electrons
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
RE impact on upper dump plate
IRE=502kA ; Bt/Ip = 3.0/2.0
T1
T2
T1
T2
T5
T3
T5
T3
T4
T4
JPN76541, t=4.11ms
JPN76541, t=18.58ms
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
RE impact on upper dump plate
RE interaction with dump plate dominated by geometry of PFCs
T
T5 1
T2
T3
T4
JPN76532
JPN76533
JPN76534
JPN76535
JPN76536
IRE=173 kA
IRE=502 kA
IRE=425 kA
IRE=285 kA
IRE=360 kA
T1
G. Arnoux (‹#›/15)
19th PSI conference
JPN76541
IRE=502 kA
San Diego, USA, 24-28 May 2010
Temp. increase due to RE impact
T1
T2
T5
T3
Ifit
Imeas
T4
DTdum,av
JPN76541, t=18.6ms
G. Arnoux (‹#›/15)
tRE≈2ms
19th PSI conference
San Diego, USA, 24-28 May 2010
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
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
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.
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
MGI 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?
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010
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?
G. Arnoux (‹#›/15)
19th PSI conference
San Diego, USA, 24-28 May 2010