EU Plasma-Wall Interactions Task Force

Transcription

1 Recent results on material migration and fuel retention in JET V. Philipps and JET TFE co-workers* Overview on present results on erosion, deposition and fuel retention in last JET campaign ( ,C5-C15) Recent results from QMB on local material transport Conclusions * P. Coad, A. Widdeshoven (UKAEA), J. Likonen (Tekes), M. Rubel (VR), M. Mayer (IPP), H.G. Esser, A. Kreter (FZJ)

2 Large effort to analyse erosion, material migration and fuel retention MK SRP campaign Divertor plasma sec(23 h) Louver clips Deposition monitor QMB Louver clips Deposition monitor 3 μm W stripe on poloidal row of divertor tiles Analysis by NRA, Sims, metallography on cross sections, T-off gas measurements

3 Long term samples in main chamber graphite plug probes on inner wall coated with 50 nm W layer or 280 nm Ni layer (exposed all times) M. Mayer et al, IPP Samples with thin layers of Be, C, Ni and W on different substrates behind flaps in octants 3 and 5, opened only during plasma discharges (4 samples behind and one outside)

4 No deposition EU Plasma-Wall Interactions Task Force Integral deposition in μm Deposit 3µm W W CFC erosion W JG c 100μm 50 μm 280μm 200μm No W layer Only 50% of time in C 14-C15 3µm W

5 73g Estimate : integrated deposition Total deposition inner and outer : 950 g ( C/sec) 63g 55g 35g 38 g 5g Total deposition inner: 543 g 35g louver 578 g total No clear erosion or deposition Outer 380g erosion 300g Louver: 35 g (from QMB) Not analysed yet Total deposition outer : 380 g

6 200 g on plasma viewing sides, majority ( 750g) on shadowed areas of base tiles 4 and 6 some part leaves towards louvers (estimate from QMB 35 g, needs additional input from deposition monitors) basic operating temperature : 80C (morning) - 140C(evening), but tile 1,3 much hotter during plasma operation Total C deposition : Only inner divertor: C/sec C/sec

7 Estimate: deuterium retention in layers D/C fraction tile 1,3: 0.2 D/C fraction tile 4 (and 6) g D D/ sec (of divertorplasma) [ Total D inlet : 1800g Relative fuel retention : 3.8 % ] No size scaling, ITER behaves like JET (50/50 D:T) mix 1x10 23 T/shot = 0.25gT/shot 1400 shot until limit Surface area(m 2 ) Power (MW) Particle flux (divertor) JET (avarage) ~ ITER 1000 (X 4 ) 350 (X 70) (x 400 ) A carbon ITER has large T inventory problems

8 D-Fluence RBS: Amount of W [10 18 Atoms/cm 2 ] x x x RBS PIXE 5 6 Outer vertical tile: net erosion 7 8 Before After Manipulator x [mm] Initial PIXE: Amount of W [a.u.] Dtile7 RBS analysis of W stripe before and after operation Erosion Remaining W Tile Distance (Z direction) cm erosion, large areas of complete W Non uniform W-erosion, W large areas of complete W-erosion M. Mayer, PSI 17

9 Main wall probes W layer erosion All main wall probes ( in between poloidal limiters) show erosion, 60 nm of W, all Ni layers (280 nm) totally eroded (W erosion behind and before flap about the same ) Erosion by charge exchange, modelling underway Main wall erosion dominated

10 Comparison of integrated material deposition 12 Only inner B Carbon Deposition ( / sec) Outer + inner AUG C dominated Recent results in AUG show a significant decrease under full W first wall conditions!! (M. Mayer et al) 0 JETMKIIA JETSRP JETMKGB DIII-D TEXTOR Similar material deposition rates in different carbon dominated devices

11 frequency [Hz] ISP at horizontal tile integral erosion 1 3 #64980 #64976 LBSRP QMB4 4 6 Recent QMB data from MK LBSRP campaign #65281 #65282 LBSRP QMB JET pulse # Integral deposition when inner strike point at vertical tile 3 Integral erosion when inner strike point at horizontal tile 4 PFR areas can turn form deposition to erosion dominated areas ISP at vertical tile integral deposition ISP at horizontal tile integral erosion 1 3 #65409 # LBSRP QMB4 ISP at vertical tile integral deposition A. Kreter, H. Esser #65667 #65668 ISP at horizontal tile integral erosion LBSRP QMB

12 7000 QMB1 (inner) and QMB5 (outer) data overview frequency [Hz] integral behaviour QMB1 (inner) QMB5 (outer) JET pulse # Integral deposition on inner and outer QMB louver outer louver deposition dominated but about a factor of 2.5 less compared with inner divertor

13 Material transport ways EU Plasma-Wall Interactions Task Force Under same strike point and plasma conditions, very reproducible deposition With plasma on tile 4, about 5 times more deposition in shots with larger Elms ( type I) than in L mode Dedicated Shot series have been performed on step wise C- transport, history effect First C deposition on vertical tiles In L mode or with small Elms small transport to tile 4 (also confirmed by 13 C deposition, L mode from top) Large transport to tile 4 with larger Elms (type I Elms) Large C transport to louver ( QMB) with plasma lying on tile 4 Transport much more effective with larger Elms then without In L mode or small Elms plasmas, majority of deposit would remain on tile 1,3

14 In agreement with all other observations, large net material deposition in inner divertor. In last campaign, 25% on plasma viewing sides, 75% on shadowed areas on base tiles, smaller amount leaves to louvers. Outer base tile also net deposition area also outer louver region but about 2.5 smaller deposition than on inner louver Total C deposition in divertor ( inner+outer ) from post mortem: C/sec, D retention estimation: D/sec Outer vertical strike point tile (7) erosion dominated Main chamber net erosion area Local divertor C transport ways determined by strike point and tile geometry. Local transport largely promoted by larger Elms PFR can change from deposition to erosion zone

15 Reserve slides

16 QMB currently in JET EU Plasma-Wall Interactions Task Force QMB # Features Position Shutter Working period QMB1 replacement system inner divertor, module 13 QMB2 heated inner divertor, module 02 yes QMB4 compact under LBSRP, module 02 no QMB5 heated outer divertor, module 02 yes monitoring Be QMB6 apron outer divertor, module 02 no evaporations yes now (68200) cabling problems during installation , then overheated (electronic failure in fast stop ) now (68200) 1 8 QMB 1,2,3 3 LBSRP 7 QMB 5 QMB 6 QMB 4 4 6

17 Deposit Deposit Deposit CFC bulk tile3 tile1 CFC bulk W stripe W stripe CFC bulk tile4 New data from recent JET campaign: inner divertor is always a deposition dominated region (P. Coad, J. Likonen, M. Roedig) V.Philipps, Seminar IPP, 30_03_06

18 CONCENTRATION RATIO: BERYLLIUM - TO - CARBON Be / C Inner M. Rubel et al Outer MKIIA DIVERTOR TILE (POLOIDAL DIRECTION) Present conditions Plasma facing sides: stable Be-C C mix (~Be( 2 C?) D content : Shadowed areas: more pure C layers D content: We need for more information on chemical state of deposits & influence of oxygen V.Philipps, Seminar IPP, 30_03_06

19 10C 1Be Present conditions Further C- transport by carbon chemistry (?) ~ Be 2 C (?) C layer C 1C(?) 10 Be New conditions (?)?? Further transport of Be (new PISCES data (?)) Be 2 W?? W C V.Philipps, Seminar IPP, 30_03_06

20 1. Understanding of in vessel T retention Example (1) After the JET DT1 T-experiment, 3.5 g of T (94%) was found in flakes, 0.1 g T (3%) was trapped by the 480 CFC divertor tiles (based on 100 analysis points) and 0.1 gt (3%) estimated to be trapped by the rest of the wall (N. Bekris, FZK ) From the T retained in the 480 CFC tiles, a significant fraction (20-50% typically) was found in depths larger then 1mm For fine grain graphite, the bulk retention fraction is much lower (about 1%) V. Philipps, IEA Greifswald 2006

21 Fuel retention in JET MkIIGB Divertor time: sec (16 hours) D injection: 766g Inner ion flux: 1.3x10 27 C deposition: 400g Rate: 3.4x10 20 Cs -1 Inner Divertor: D/C~0.2 Retention of 3% (25g) (MKII GB) D/C J Likonen, P Coad et al., (NRA: D/C ratio, SIMS: layer thicknesses) Only plasma facing surfaces at divertor included (not tile gaps, inner limiters...) -D retention in the divertor: 3% (Mk-IIGB), 2.4% (MKII-SRP).

22 AUG: 2002/2003: Deposition of D and C 8 6A 6B 5 4 9C M Mayer et al., PSI 2004 Deposition [10 19 at./cm 2 ] B + C D measured D assumed 2002/2003 campaign: Mainly carbon machine (45% W) Retention governed by trapping on inner tile surface (70% inner divertor tiles, 20% in remote ares (below roof baffle,...) Total retention ~4% of input (10-20% from gas balance) 2004/2005 campaign: Full W machine except the divertor (Carbon) No significant difference in retention between 2002/2003 and 2004/2005

23 layer D, at.% Be, at.% 12 C, at.% O, at.% Cr, at.% Poster Likonen