EX/7-2: Impurity Seeding on JET to Achieve Power Plant like Divertor Conditions � M. Wischmeier � Max-Planck-Institut für Plasmaphysik, Garching, Germany � 25 th IAEA Conference, St Petersburg, 2014 � M. Wischmeier 1 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Acknowledgements � Co-authors � � C.G.Lowry 1 , A.Huber 2 , M.L.Reinke 3 , C. Guillemaut 4 , L. Aho-Mantila 5 , S. Brezinsek 2 , P. Drewelow 5 , C.F. Maggi 6 , K. McCormick 6 , A.Meigs 4 , G.Sergienko 2 , M.F.F.Nave 7 , G.Sips 1 , M.Stamp 4 , and JET contributors* � � JET-EFDA, Culham Science Centre, Abingdon, OX14 3DB, UK � 1 European Commision, B-1049 Brussels, Belgium � 2 Institute of Energy and Climate Research, Forschungszentrum Jülich, Trilateral Euregio Cluster, � D-52425 Jülich, Germany � 3 University of York, Heslington, York, YO10 5DD, UK � 4 CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK � 5 VTT Technical Research Centre of Finland, FI-02044 VTT, Finland � 6 Max- Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany � 7 Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, P- � 1049-001 Lisboa, Portugal � � *See the Appendix of F. Romanelli et al., Proc. 25 th IAEA FEC 2014, St Petersburg, � Russian Federation � This work was supported by EURATOM and carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission. � This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement number 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. � M. Wischmeier 2 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Boundaries for power exhaust � Ø Limit on acceptable erosion: � v With impurity seeding and higher charged states enhancing erosion: T e < 2 - 5 eV � Ø Expected power handling limit of actively cooled DEMO divertor component < 10MW/m 2 : � v limit on particle flux to limit power deposition by surface recombination (15.8 eV per ion – electron pair) � Ø Power handling limit combined with erosion limit è completely detached divertor � M. Wischmeier 3 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Radiation in DEMO divertor similar to ITER � separatrix � ITER to DEMO: � Similar volume and size of divertor è similar absolute amount of radiation in SOL and divertor (ITER ~ 60% – 70% of P SOL =120MW è 70MW) � M. Wischmeier 4 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Radiation: minimize in core separatrix � Core M. Wischmeier 5 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Radiation: minimize in core & optimize edge � separatrix � Core Edge radiation Divertor power dissipation in DEMO similar to ITER � è Edge + core > 70% radiation � M. Wischmeier 6 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
DEMO requires > 90 – 95% radiation � separatrix � Edge radiation Core SOL and divertor è Total radiation required sums to > 90% - 95% of P heat � è Maximize radiation in EDGE and SOL à main guidance � M. Wischmeier 7 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Vertical target geometry B T =2.7T I P =2.5MA δ =0.22 (low triangularity) q 95 =3.3 P heat = P IN -dW/dt (14-28MW) P heat /R ~ 5 – 9 P sep /R ~ 3 - 6 R=3m M. Wischmeier 8 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Maximum f rad independent of P heat Total radiated power fraction f rad Ø ~70% f rad at maximum P/R ~ 9 75% Ø Highest f rad with only N 2 seeding Ø Performance of N2 + Ne seeding evolves qualitatively very similar to pure Ne seeding Ø ASDEX Upgrade reaches f rad >85% but Total heating power [MW], R=3m higher c W (W from MCW) M. Wischmeier 9 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Maximum f rad increases with seeding � P heat : 18 – 20 MW � Ø Close to maximum: f rad low efficiency of f rad � seeding on f rad � Nitrogen seeding rate [el s -1 ] � M. Wischmeier 10 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Higher P heat è è higher seeding for f rad Total radiated power fraction f rad 1.0E23 el s -1 1.8E23 el s -1 0.5E23 el s -1 Total heating power [MW], R=3m M. Wischmeier 11 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
N 2 seeding into H-Mode plasma: stable radiation of 75% Ø N 2 à leads to ELM mitigated H-mode with f rad of ~75% (Core density) Ø ELM mitigated phase with magnetic activity similar to M-Mode (E. Solano et al., EPS 2013) Ø c W in core at detection limit (<10 -5 ) s 10 14 16 18 12 A. Huber et al. EPS 2014, M. Wischmeier PSI 2014 M. Wischmeier 12 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Poloidal radiation at highest f rad � Ne seeding Total radiation Core density Radiative instabilities with transient f rad of up Edge density to 90% � f rad M. Wischmeier 13 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Poloidal radiation at highest f rad � Ne seeding � Ar seeding � Radiative Maximum f rad instabilities with ~60% � transient f rad of 90% � M. Wischmeier 14 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Poloidal radiation at highest f rad � N 2 seeding � Ar seeding � Ne seeding � Maximum f rad Radiative Maximum f rad ~75% � instabilities with ~60% � Concentrated transient f rad of around X-point � 90% � M. Wischmeier 15 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Radiation concentrated at X-point independent of seeding species � N 2 seeding Ar seeding Ne seeding Ø Peaking of radiation density (W/m 3 ) varies with seeding species as well as poloidal extent � Ø No radiating belt formed � M. Wischmeier 16 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Definition of radiation distribution Above X-point Ø According to ~ inside LCFS reconstruction at highest excluding X- f rad this accounts for point è due to largest part of edge & poloidal SOL radiation � distribution ~ core radiation � Divertor and X-point � A. Huber et al. EPS 2014 M. Wischmeier et al. PSI 2014 M. Wischmeier 17 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Limit of radiation above X-point for N 2 � Above X-point / total radiation � 75% Total radiated power fraction � Ø Lowest fraction of above X-point radiation for seeding that includes N 2 � Ø Fraction of experimental radiation above X-point not directly comparable to requirements for DEMO � M. Wischmeier 18 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Above f rad of 70% close to L-H threshold � (P heat -P MC ) / P L-H (Martin scaling J. Phys. 08) 75% Ø Ar seeding even for low seeding rates close to L-H threshold � Ø N 2 seeding approaches threshold for highest f rad � Ø At low ratios radiative instabilities in case of Ne � Total radiated power fraction M. Wischmeier 19 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Impact of seeding on confinement scaling � H98(y,2) β N In highly seeded discharges H98(y,2) is function of β N M. Wischmeier 20 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Impact of N 2 seeding on confinement scaling � H98(y,2) Total radiated power fraction M. Wischmeier 21 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Impact of N 2 seeding on confinement scaling H98(y,2) Low P heat ~ 14 MW High fueling and seeding levels � N2 rate: 5 – 18 10 22 el s -1 � D2 rate: 2 – 6.5 10 22 el s -1 � Total radiated power fraction M. Wischmeier 22 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
Core & pedestal profiles at high f rad � P heat ~ 20MW ! A. Huber et al. EPS 2014 Ø With N2 seeding mainly pedestal n e depletes � Ø Profiles recover and surpasses unseeded values in core � Ø No reliable information on changes in SOL profiles yet � M. Wischmeier 23 /27 25 th IAEA Conference, St Petersburg, EX/7-2 17 th of October 2014
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