g. arnoux (1/19) sewg on transient heat loads ljubljana, 02/10/2009 heat load measurements on jet...
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G. Arnoux (1/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load measurements Heat load measurements on JET first wall during on JET first wall during
disruptionsdisruptions
G. Arnoux, M. Lehnen, A. Loarte, V. Riccardo and JET-EFDA Contributors
G. Arnoux (2/19) SEWG on transient heat loads Ljubljana, 02/10/2009
IntroductionIntroduction
• What we know– 90-50% of the energy during thermal quench goes onto the first wall,
not on the divertor– Transport plays a key role in the heat load deposition (time scale
and distribution) on the first wall– Runaway electron (RE) production and loss is a critical issue for the
design/safety if ITER first wall
• What we can learn from JET measurements– Recent fast IR measurements of heat loads on the first wall and
divertor during thermal quench• What time scales?• What spatial distribution?
– IR measurements of RE impact on first wall• What fraction of RE energy converted into kinetic energy, i.e.
impacts onto the wall?
G. Arnoux (3/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Fast IR on main chamber PFCs (KL7)Fast IR on main chamber PFCs (KL7)
• Fast time resolution: tIR≃1ms• Reduced IR view (coloured areas)• Region of interest (shot to shot)
– Divertor– Outer limiter– Inner limiter– Upper dump plate
• Data reduction– T(x,y,t) → T(s,t)
• Heat load computation (THEODOR)– T(s,t) → q(s,t)
G. Arnoux (4/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Fast IR on divertor targets (KL9)Fast IR on divertor targets (KL9)
CFC
W
TIR = 86s
G. Arnoux (5/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load during thermal Heat load during thermal quench: the case of a quench: the case of a
low q disruption low q disruption
G. Arnoux (6/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load on inner limiterHeat load on inner limiter
s
+8.7ms+4.7ms+2.7ms
G. Arnoux (7/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load on inner limiterHeat load on inner limiter
Bottom Top
G. Arnoux (8/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load on outer limiterHeat load on outer limiter
s
+4.94ms+3.05ms+2.10ms
G. Arnoux (9/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load on outer limiterHeat load on outer limiter
Bottom Top
Divertor
G. Arnoux (10/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Wide view onto divertorWide view onto divertor
JPN77663
No obvious broadening out of tile 5
G. Arnoux (11/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Time scales and plasma movementTime scales and plasma movement
R=-15cm
z=+6cm
Radial position
Inner limiter
Outer limiter
DivertorIR,div=0.9ms
IR,outer=1.2ms
IR,div=4.7ms
15cm inward
G. Arnoux (12/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Summary part ISummary part I
During thermal quench: Eth = Erad + Ediv + Ewall
with Ewall = Einner+Eouter+Eupper
Pulse Eth Erad Ediv* Einner Eouter
** Etot,meas
77658 2.14MJ 31% 7%-14% ? 40-58%
77660 2-13%
On divertor: 4 ≤ t ≤ 10ms
On outer limiter: 4 ≤ t ≤ 60ms
Timescale almost an order of magnitude larger for outer wall heating
G. Arnoux (13/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Summary Part ISummary Part I
• Measurements show– Of the 60% of the thermal energy measured “during” thermal
quench, half is radiated– From the conducted energy measured onto the PFCs, half goes onto
the divertor and half on the outer limiter– The time scale of the heat load on the outer limiter, combined with
plasma movement suggest a strong enhancement of perpendicular transport (MHD)
– The time scale of the heat load on the inner wall seems to be dominated by the plasma movement
– Energy on the inner limiters still to be determined, but data are there…
G. Arnoux (14/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Heat load from RE Heat load from RE generated by massive gas generated by massive gas
injection (DMV experiments)injection (DMV experiments)
G. Arnoux (15/19) SEWG on transient heat loads Ljubljana, 02/10/2009
RE impact on upper dump plateRE impact on upper dump plate
tIR=1.1ms#76533
#76534
Bt=3.0T
Bt=1.8T
G. Arnoux (16/19) SEWG on transient heat loads Ljubljana, 02/10/2009
RE impact on upper dump plateRE impact on upper dump platen0
RE=14x1012 ; Bt/Ip = 3.0/2.0
#76541T1T2
T3
T4
#76541, f9018
G. Arnoux (17/19) SEWG on transient heat loads Ljubljana, 02/10/2009
RE current estimateRE current estimate
Ifit=I0exp{t/}
Imeas
IRE=Imeas-Ifit
T
G. Arnoux (18/19) SEWG on transient heat loads Ljubljana, 02/10/2009
RE energy on upper dump plateRE energy on upper dump plate
G. Arnoux (19/19) SEWG on transient heat loads Ljubljana, 02/10/2009
Conclsion/summaryConclsion/summary
• Recent IR measurement on PFCs showed– Runaway electrons energy deposited on first wall
scales with the square of RE current– Transport plays a key role on heating the outer wall
during the thermal quench and remains not understood– The time scale of conducted heat load on the outer wall
is an order of magnitude larger than that on the divertor• These measurements suggest
– Can we model the heat load observed on first wall during the thermal quench?
– Can we model RE impact on dumplate in order to match measurement?