TFE Th Loarer – SEWG – 12 September Euratom Th Loarer V Philipps 2, J Bucalossi 1, D Brennan 3, J Brzozowski 4, N Balshaw 3, R Clarke 3, G Esser 2, M Freisinger 2, S Grünhagen 5, J Hobirk 6, S Knipe 3, A Kreter 2, Ph Morgan 3, R Stagg 3, L Worth 3 and JET EFDA contributors* Fuel retention in L and H-mode experiments in JET 1 - Association EURATOM-CEA, DSM-DRFC, CEA Cadarache, St Paul lez Durance, France. 2 - IPP, Forschungszentrum Juelich, D Juelich, Germany 3 - Euratom-UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA, UK. 4 - EURATOM/VR Association - Fusion Plasma Physics, EES, KTH, Stockholm, Sweden 5 - FZ Karlsruhe, Postfach 3640, D Karlsruhe, Germany 6 - Max-Planck IPP-EURATOM Association, Garching, Germany *See Appendix of M.L.Watkins et al., Fusion Energy Conference 2006 (Proc. 21st Int. Conf. Chengdu) IAEA, (2006) Outline Introduction Evaluation of fuel retention at JET Short and long term retention; associated particle fluxes Recycling flux and ELMs Recovery between discharges Summary

TFE Th Loarer – SEWG – 12 September Euratom Introduction - Evaluation of hydrogenic retention in present tokamaks is of high priority to establish a database for ITER (400 sec ~ 7min…10-20 sec today). - A retention of 10% of the T injected would lead to the limit of 350g (working guideline for initial operation) in only 35 pulses. - Fuel retention experiments in JET studied in a series of repetitive and identical discharges to minimise the contribution from previous experiments (history), achieve a high accuracy (~1.2%) - Reference database under C-wall conditions completed before Be/W Evaluation of Long term fuel retention with different materials

TFE Th Loarer – SEWG – 12 September Euratom physics: material erosion, migration & fuel retention QMB measurements Spectroscopy Gas balance measurements Deposition probes 13 C migration Post mortem tile analysis D,T Mechanisms for fuel retention Two basic mechanisms for Long term fuel retention Deep Implantation, Diffusion/Migration, Trapping C, Be C, Be, D,T In JET (and other carbon wall devices ) Codeposition dominates retention (also expected for Be wall conditions, JET ILW, ITER) Codeposition Short term retention (Adsorption: dynamic retention) Recovered by outgasing in between discharges

TFE Th Loarer – SEWG – 12 September Euratom Calibrated Particle Source (Gas, NBI…) Divertor cryo-pumps Retention (wall) Long & Short Term Procedure on JET Regeneration of the cryopump before and after the session (1.2%) Repeat the same discharge (~10) w/o conditioning between pulses Plasma Injection = Pumped + Short Term Ret + Long Term Ret Total Recovered from Cryo regeneration: Pumped + outgassing in between pulses ~800s (Short Term Ret)

TFE Th Loarer – SEWG – 12 September Euratom Gas Balance From cryo-pump regeneration (~1%) and calibrated gas injection Evaluation of the pumped flux - During the plasma - Between pulses t (s) Plasma During plasma inj > pump Retention>0 Short & Long term Between pulses inj =0 pump = Outgasing Retention<0 Short term retention only (dynamic retention) Evaluation of Short and Long term retention Injection = Long Term Ret + Short Term Ret + Pumped flux

TFE Th Loarer – SEWG – 12 September Euratom Type III ELMs # I p /B T =2.0MA/2.4T, 6.0MW ICRH only 13 repetitive pulses Also in L mode and Type I ELMy H-mode Reproducible plasma conditions in all shots Type III ELMs s P TOT ~ 6.0MW Density Fueling Ds -1 D (in & out) Div Pressure Vessel pressure

TFE Th Loarer – SEWG – 12 September Euratom L-mode Total Injected: D (4.511g) Total Recovered (Pumped flux and outgassing in between pulses): D (3.946g) Long Term Retention: D (0.472g) Heating Phase (81 s) Injection Long Term Ret ~1.8x10 22 Ds x10 21 Ds -1 ~10% L-mode, Type I & III ELMy H-mode Evaluation of Short and Long term retention during the pulse Heating Phase Injection Long Term Ret Type III 221s ~0.6x10 22 Ds x10 21 Ds -1 ~20% Type I 32 s ~1.7x10 22 Ds x10 21 Ds -1 ~17%

TFE Th Loarer – SEWG – 12 September Euratom Particle fluxes: L mode Drop of retention not only due to decrease of inj I p =2.0MA, B T =2.4T 1.2MW ICRH sec, Ret~6.5x10 21 Ds -1 LongRet=1.74x10 21 Ds -1 (25%) ShortRet=4.8x10 21 Ds -1 sec, Ret~4.65x10 21 Ds -1 LongRet=1.74x10 21 Ds -1 (35%) ShortRet=2.91x10 21 Ds -1 (65%) Injection Pumped flux Retention Long term Ret

TFE Th Loarer – SEWG – 12 September Euratom During the pulse: H mode Type III I p =2.0MA, B T =2.4T ~5MW ICRH only ITER_like sec, Ret=53% Ret~6.3x10 21 Ds -1 LongRet=1.3x10 21 Ds -1 (33%) ShortRet=2.0x10 21 Ds -1 sec, Ret=43% Ret~2.35x10 21 Ds -1 LongRet=1.3x10 21 Ds -1 (55%) ShortRet=1.05x10 21 Ds -1 (45%) Injection Pumped flux Retention Long term Ret Lower gas rate (1/3) but codeposition becomes dominant

TFE Th Loarer – SEWG – 12 September Euratom Particle fluxes: H mode Type I From L mode to Type I ELM H-mode Increase of long term retention - with the recycling flux - with ELMs Energy I p =2.0MA, B T =2.4T 13MW NBI+ICRH ELM sec, Ret~5.2x10 21 Ds -1 LongRet=2.8x10 21 Ds -1 (54%) ShortRet=2.4x10 21 Ds -1 sec, Ret~2.9x10 21 Ds -1 LongRet=2.8x10 21 Ds -1 (97%) ShortRet=0.1x10 21 Ds -1 (3%) Injection Pumped flux Retention Long Term Ret

TFE Th Loarer – SEWG – 12 September Euratom Strong increase of the recycling flux in Type I ELMy H-mode Same behavior observed with CIII Recycling flux: D signals D Inner leg D Outer leg D Horizontal view Type I Type III L mode - L mode and Type III Similar recycling (D ) In, Out and Horizontal. - No significant variation on the Outer leg region (small ELMs~150kJ). -Strong increase of recycling flux (D ) when moving to Type I ELMy H- mode - Same behavior on the Horizontal view as on the inner leg. Type I Type III L mode CIII Horizontal view CIII Inner leg CIII Outer leg Higher recycling and ELM Enhanced carbon erosion and transport leading to stronger carbon deposition and fuel codeposition

TFE Th Loarer – SEWG – 12 September Euratom Integrated Hα and CIII horizontal light (L-mode, Type III and Type I ELMs) The slope for Type I ELMy H-mode show enhanced recycling and total carbon source. Integrated particle fluxes H α CIII Type I ELMs Type III ELMs L mode

TFE Th Loarer – SEWG – 12 September Euratom Recovery in between pulses Small fraction recovered > plasma content ~ 0.5x10 22 D (70m 3, ~ m -3 ) Except for disruptions, this amount is ~constant and independent of I p, B T, n e, P in, inj, Wdia (plasma scenario) Independent of inventory accumulated during the pulse and previous pulses Within a factor of ~2 the recovery is constant in the range 1-3x10 22 D No major contribution on the overall retention Short term retention

TFE Th Loarer – SEWG – 12 September Euratom Summary - Repetitive pulses on JET for fuel retention analysis (accuracy ~1.2%) Evaluation of both short and long term retention Confirm the strong concerns about fuel retention in C tokamak ITER with mixed material (C, Be, W) Burning Phase Injection Long Term Ret 400s ~ 5x10 22 Ts -1 ? - In all the cases, the recovery in between pulses corresponds to a weak contribution in the overall fuel retention (short term retention) Heating Phase Injection Long Term Ret L mode 81s ~1.8x10 22 Ds x10 21 Ds -1 ~10% Type III 221s ~0.6x10 22 Ds x10 21 Ds -1 ~20% Type I 32 s ~1.7x10 22 Ds x10 21 Ds -1 ~17% - Increase of long term retention - with the recycling flux - with ELMs Energy

TFE Th Loarer – SEWG – 12 September Euratom Slides in reserve

TFE Th Loarer – SEWG – 12 September Euratom ELM induced C deposition QMB1 (inner): Deposition per ELM vs. ELM energy - Increased deposition due to thermal decomposition of co-deposited layers - Enhanced carbon erosion (Recycling and ELM energy) and transport leading to stronger carbon deposition and fuel codeposition Fit formula: y = * x * exp(x/165) "Area" term "Thermal" term B field configuration A.Kreter, H.G.Esser

TFE Th Loarer – SEWG – 12 September Euratom Injection (integral:1.8 x D-atoms) Divertor pumping Wall pumping Long term retention (codeposition) 2 x D/s Dynamic wall retention (decrease in 10 sec by about 50%) 3.9 x x Integrated wall pumping 3 x Measured long term outgassing (800s) 2.85 x Example: particle balance in during steady state phase Long and short term retention V Philipps

TFE Th Loarer – SEWG – 12 September Euratom 1. Campaign averaged retention about 5 times smaller due to effects of long term outgassing, thermal release from subsequent plasma operation, GDC, disruptions (reasonable) Codeposition D C C, D Local C-erosion and redeposition does not contribute much to retention (similar D content of eroded and deposited layers) Needed: long range transport from net erosion to deposition areas main chamber to divertor outer strike zone to PFR, inner divertor,.. freshly deposited C-layers are D-rich (analysis after about 2h) Further reduction by long term outgassing (reduction by about a factor of 2 between 2h and 24h ) and subsequent plasma operation Discussion