1. G. Arnoux (1/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load measurements on JET first wall during disruptions G. Arnoux, M. Lehnen, A. Loarte, V. Riccardo and JET-EFDA Contributors

2. G. Arnoux (2/19) SEWG on transient heat loads Ljubljana, 02/10/2009Introduction 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?

3. G. Arnoux (3/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Fast IR on main chamber PFCs (KL7) Fast time resolution: t IR 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)

4. G. Arnoux (4/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Fast IR on divertor targets (KL9) CFC W T IR = 86 s

5. G. Arnoux (5/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load during thermal quench: the case of a low q disruption

6. G. Arnoux (6/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load on inner limiter s +8.7ms+4.7ms+2.7ms

7. G. Arnoux (7/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load on inner limiter BottomTop

8. G. Arnoux (8/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load on outer limiter s +4.94ms+3.05ms+2.10ms

9. G. Arnoux (9/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load on outer limiter BottomTop Divertor

10. G. Arnoux (10/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Wide view onto divertor JPN77663 No obvious broadening out of tile 5

11. G. Arnoux (11/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Time scales and plasma movement R=- 15cm z=+6cm Radial position Inner limiter Outer limiter Divertor IR,div =0.9ms IR,outer =1.2ms IR,div =4.7ms 15cm inward

12. G. Arnoux (12/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Summary part I During thermal quench: E th = E rad + E div + E wall with E wall = E inner +E outer +E upper PulseE th E rad E div * E inner E outer ** E tot,meas 776582.14MJ31%7%-14%?40-58% 776602-13% On divertor: 4 t 10ms On outer limiter: 4 t 60ms Timescale almost an order of magnitude larger for outer wall heating

13. G. Arnoux (13/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Summary 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…

14. G. Arnoux (14/19) SEWG on transient heat loads Ljubljana, 02/10/2009 Heat load from RE generated by massive gas injection (DMV experiments)

15. G. Arnoux (15/19) SEWG on transient heat loads Ljubljana, 02/10/2009 RE impact on upper dump plate t IR =1.1ms #76533 #76534 B t =3.0T B t =1.8T

16. G. Arnoux (16/19) SEWG on transient heat loads Ljubljana, 02/10/2009 RE impact on upper dump plate n 0 RE =14x10 12 ; B t /I p = 3.0/2.0 #76541 T1 T2 T3 T4 #76541, f9018

17. G. Arnoux (17/19) SEWG on transient heat loads Ljubljana, 02/10/2009 RE current estimate I fit =I 0 exp{t/ } I meas I RE =I meas -I fit T

18. G. Arnoux (18/19) SEWG on transient heat loads Ljubljana, 02/10/2009 RE energy on upper dump plate

19. G. Arnoux (19/19) SEWG on transient heat loads Ljubljana, 02/10/2009Conclsion/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?