Acknowledgments: L. Horton, D. Borba, G. Sips and JET Task Force - PowerPoint PPT Presentation

Acknowledgments: L. Horton, D. Borba, G. Sips and JET Task Force Leaders F. Romanelli 1 FEC 2014 Saint Petersburg 13-18 October 2014

DT integrated experiment Plasma scenarios ITER-like Plasma scenario in ITER wall compatibility configuration experiment [J. Paméla, Fusion Eng. Des. 82 (2007) 590] F. Romanelli 2 FEC 2014 Saint Petersburg 13-18 October 2014

DT integrated The JET programme in support of ITER is experiment now completing the characterization of the ITER-like wall and progressing towards the DT experiment. Plasma scenarios ITER-like Plasma scenario in ITER wall compatibility configuration experiment [J. Paméla, Fusion Eng. Des. 82 (2007) 590] F. Romanelli 3 FEC 2014 Saint Petersburg 13-18 October 2014

Beryllium ¡ JET ITER-like Wall Saddle ¡coil ¡ W-­‑coated ¡CFC ¡ protec:on ¡ Inconel+8 µ m ¡Be ¡ Bulk ¡W ¡ Upper ¡ Restraint ¡Ring ¡ Mushrooms ¡ Dump ¡ Protec:ons ¡ Plate ¡ Inner ¡Wall ¡ Cladding ¡ Poloidal ¡ Normal ¡NBI ¡Inner ¡ Limiters ¡ Wall ¡GL’s ¡ Inner ¡ Re-­‑ionisa:on ¡ Wall ¡ Protec:ons ¡ Guard ¡ Limiters ¡ Normal ¡NBI ¡IW ¡ Magne:c ¡ Cladding ¡ covers ¡ LH ¡+ ¡ICRH ¡ Protec:on ¡ B&C ¡ Saddle ¡Coil ¡ :les ¡ Protec:ons ¡ Divertor ¡ Bulk ¡W ¡ 4 ¡ F. Romanelli 4 FEC 2014 Saint Petersburg 13-18 October 2014

P max P NBI (MW) Total power Max possible NBI Octant 4 Max possible NBI Octant 8 P ref 30 NB project Max possible targets FEC 2010 FEC 2012 FEC 2014 New hardware of 20 Neutral Beam enhancement performing according to design. 10 Maximum power approaching target value NBI ¡water ¡ ILW ¡shutdown ¡ 2012 ¡shutdown ¡ ERFA ¡ leak ¡ 0 2009 2010 2011 2013 2012 2014 CFC Be/W F. Romanelli 5 FEC 2014 Saint Petersburg 13-18 October 2014

JET-­‑CFC ¡(2009) ¡ JET-­‑ILW ¡  ¡2014 ¡ After 3 years of operation with the ITER- I p ¡ 4.5MA ¡ 4.0MA ¡ like wall: P NBI ¡ 23.2MW ¡ 28MW ¡ • System capabilities at P ICRH ¡ 8.7 ¡MW ¡(+ ¡ILA) ¡ 6 ¡MW ¡ a similar level NBI ¡input ¡ 185MJ ¡ 230MJ ¡ compared to the Pulse ¡rate* ¡ 18 ¡/day ¡ 17.5 ¡/day ¡ carbon wall. *: Successful physics pulses • Higher NBI power and input energy Main limitation: Surface temperature (Be and W), to avoid melt damage.  Substantial increase in real-time protection systems (as required in ITER):  Infra Red protection of PFC’s  Closed-loop use of Massive Gas Injection for disruption mitigation  Disruption avoidance and plasma termination scenarios F. Romanelli 6 FEC 2014 Saint Petersburg 13-18 October 2014

JET-­‑CFC ¡(2009) ¡ JET-­‑ILW ¡  ¡2014 ¡ After 3 years of operation with the ITER- I p ¡ 4.5MA ¡ 4.0MA ¡ like wall: P NBI ¡ 23.2MW ¡ 28MW ¡ • System capabilities at P ICRH ¡ 8.7 ¡MW ¡(+ ¡ILA) ¡ 6 ¡MW ¡ a similar level NBI ¡input ¡ 185MJ ¡ 230MJ ¡ JET experience with Be+W shows the need compared to the Pulse ¡rate* ¡ 18 ¡/day ¡ 17.5 ¡/day ¡ of a careful preparation (as now integrated carbon wall. *: Successful physics pulses in the ITER research plan with the choice • Higher NBI power and input energy of the W divertor from the beginning) to achieve continuous improvement in the Main limitation: Surface temperature (Be and W), to avoid melt damage. plasma performance.  Substantial increase in real-time protection systems (as required in ITER):  Infra Red protection of PFC’s  Closed-loop use of Massive Gas Injection for disruption mitigation  Disruption avoidance and plasma termination scenarios F. Romanelli 7 FEC 2014 Saint Petersburg 13-18 October 2014

Outline • JET programme in support of ITER • Operation of JET with the ITER-like wall (ILW) • Tungsten Melt Experiment • Material Migration & Retention • Disruptions and Runaway Electrons • H-mode physics in an all-metal environment • H-mode optimization with the ILW • Stationary N-seeded discharges • Progress to maximum fusion performance • Conclusions and perspectives F. Romanelli 8 FEC 2014 Saint Petersburg 13-18 October 2014

Outline • JET programme in support of ITER • Operation of JET with the ITER-like wall (ILW) • Tungsten Melt Experiment • Material Migration & Retention • Disruptions and Runaway Electrons • H-mode physics in an all-metal environment • H-mode optimization with the ILW • Stationary N-seeded discharges • Progress to maximum fusion performance • Conclusions and perspectives F. Romanelli 9 FEC 2014 Saint Petersburg 13-18 October 2014

2013 programme focussed on the support to an ITER decision on the day-one W divertor • One lamella on stack A intentionally misaligned • IR measurements on the top surface. A B C D • Modelling of lamella temperature evolution by conduction through [G. Matthews EX/4-1 Wednesday, supporting structure J. Coenen, PSI 2014] • Note: the temperature on the vertical surface B is not resolved. New stack to be installed in the next shutdown. F. Romanelli 10 FEC 2014 Saint Petersburg 13-18 October 2014

Shallow W-melting does not impact JET operation • Strategy: 1s heating to raise bulk lamella temperature to facilitate shallow melting by ~300 kJ ELMS q || = 0.5 – 1.0 GW/m 2 • Results consistent with melting followed by resolidification. • Small W events associated with the occasional expulsion of droplets but no impact on JET operation ! F. Romanelli 11 FEC 2014 Saint Petersburg 13-18 October 2014

84686 – Before melting q || q || Special lamella 5.5mm Special lamella 5.5mm Special lamella 5.5mm Special lamella 5.5mm Low High Field Field Side Side F. Romanelli 12 FEC 2014 Saint Petersburg 13-18 October 2014

After 84724 Special lamella Low High Field Field Side Side F. Romanelli 13 FEC 2014 Saint Petersburg 13-18 October 2014

After 84778 Special lamella Low High Field Field Side Side F. Romanelli 14 FEC 2014 Saint Petersburg 13-18 October 2014

After 84779 Special lamella Low High Field Field Side Side F. Romanelli 15 FEC 2014 Saint Petersburg 13-18 October 2014

After 84781 Special lamella Low High Field Field Side Side F. Romanelli 16 FEC 2014 Saint Petersburg 13-18 October 2014

After 84782 Special lamella Low High Field Field Side Side F. Romanelli 17 FEC 2014 Saint Petersburg 13-18 October 2014

After 84783 J x B B ⊗ J thermionic 5.5mm Low High Field Field Side Side Erosion: 150-300 µ m per pulse, 5-10 µ m per ELM (frequency 30Hz) Total volume moved: ~6mm 3 F. Romanelli 18 FEC 2014 Saint Petersburg 13-18 October 2014

After 84783 J x B B ⊗ J thermionic 5.5mm Molten material on the lamella observed to HFS coalesce and grow, which increases the risk for longer pulse duration above the melt Erosion: 150-300 µ m per pulse, 5-10 µ m per ELM (frequency 30Hz) threshold. Total volume moved: ~6mm 3 F. Romanelli 19 FEC 2014 Saint Petersburg 13-18 October 2014

Side heat load lower than expected Matching the experimental measurements requires mitigation factors instead of pure geometrical assumptions q n = q perp * f n ; f n = 1 q s = q || * f s ; f s = 0.4 Vapour shielding included Larmor radius smoothing not sufficient F. Romanelli 20 FEC 2014 Saint Petersburg 13-18 October 2014

Side heat load lower than expected Matching the experimental measurements requires mitigation factors instead of pure geometrical assumptions Potentially positive implications for ITER, which may be less sensitive than previously feared to q n = q perp * f n ; f n = 1 exposed edges created by chipping of mono- block edges or components outside tolerance q s = q || * f s ; f s = 0.4 Vapour shielding included Larmor radius smoothing not sufficient F. Romanelli 21 FEC 2014 Saint Petersburg 13-18 October 2014

Modelling of Melt layer • The melt layer motion is modelled correctly by MEMOS by including the JxB mitigation factors and the JxB force. [Bazylev TH/P3-40] 1 mm after seven pulses F. Romanelli 22 FEC 2014 Saint Petersburg 13-18 October 2014

Outline • JET programme in support of ITER • Operation of JET with the ITER-like wall (ILW) • Tungsten Melt Experiment • Material Migration & Retention • Disruptions and Runaway Electrons • H-mode physics in an all-metal environment • H-mode optimization with the ILW • Stationary N-seeded discharges • Progress to maximum fusion performance • Conclusions and perspectives F. Romanelli 23 FEC 2014 Saint Petersburg 13-18 October 2014

Material Migration �������� • Sputtering at inner wall and limiter at low impact energies (<10 eV) • At low energy, Be sputtering yield (JET-ILW) is lower than total C sputtering yield (JET-C) !"#$ !"#$ • Spectroscopy and ex situ analysis revealed a factor 4-5 smaller primary source %&' %&' • Absence of chemical erosion by low energy particles in case of ILW! • Majority of Be transported in !"# $"# SOL towards inner divertor [S. Brezinsek, EX/P5-26] F. Romanelli 24 FEC 2014 Saint Petersburg 13-18 October 2014