1 / 31

Presented by Gerard van Rooij

Tungsten divertor erosion in all metal devices: lessons from the ITER-like wall of JET and the all tungsten ASDEX Upgrade. Presented by Gerard van Rooij Dutch Institute For Fundamental Energy Research, Assoc. EURATOM-FOM, The Netherlands PSI-20, Aachen, May 2012.

kaylee
Download Presentation

Presented by Gerard van Rooij

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Tungsten divertor erosion in all metal devices: lessons from the ITER-like wall of JET and the all tungsten ASDEX Upgrade Presented by Gerard van Rooij Dutch Institute For Fundamental Energy Research, Assoc. EURATOM-FOM, The Netherlands PSI-20, Aachen, May 2012

  2. with thanks to co-authors J.W. Coenen1, L. Aho-Mantila2, S. Brezinsek1, M. Clever1, R. Dux3, M. Groth4, K. Krieger3, S. Marsen3, G.F. Matthews5, A. Meigs5, R. Neu3, S. Potzel3, T. Pütterich3, J. Rapp6, M.F. Stamp5, the ASDEX Upgrade Team3 and JET-EFDA Contributors** JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon, UK 1Institute of Energy and Climate Research, ForschungszentrumJülich, Assoc EURATOM-FZJ, Jülich, Germany* 2VTT, P.O. Box 1000, FI-02044 VTT, Finland 3Max-Planck-Institut fürPlasmaphysik, Association EURATOM-IPP, Germany 4Aalto University, Association EURATOM-Tekes, Espoo, Finland 5Culham Centre for Fusion Energy, EURATOM-CCFE Association, Abingdon, UK 6Oak Ridge National Laboratory, Oak Ridge, USA *Partner in the Trilateral Euregio Cluster **See App. of F. Romanelli et al., Proceedings of the 23rd IAEA Fusion Energy Conf. 2010, Daejeon, Korea

  3. The questions • W impurity in plasma core leads to radiative cooling of plasma  must be controlled • ITER-Like Wall: highest W sputtering in outer divertor • This work: • What is the tungsten source in the outer divertorand by what is it determined: JET (& ASDEX Upgrade) • as a first step towards: • Divertor screening – how much comes out and how much is retained W?

  4. The ingredients • What is the tungsten source in the outer divertor and by what is it determined: • Identity and concentration of impurities (sputtering by hydrogen ions is insignificant) • Energy of impinging particles: • charge state, i.e. Te and transport • sheath acceleration, i.e. Te (and Ti)

  5. Outline • Approach to quantify W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species – compare JET & ASDEX-Upgrade • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering – compare JET & ASDEX-Upgrade • How to control sputtering • Conclusions

  6. Approach to quantify W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering • How to control sputtering • Conclusions

  7. W source from spectroscopy Divertor plasma • Integrating over line of sight: • and also S′ ne, Teincrease W+ * W+ Hn e.g. 400.9 nm S B W* W Imp X Y W target

  8. S/XB from experimental data base • Previously (e.g. ASDEX Upgrade) constant S/XB = 20 was commonly used • This work uses multi-machine fit for S/XB (Te) M. Laengner, this conference

  9. Direct imaging divertor spectrometer system New los (orange) and old (blue) Design covers full outer divertor target plate (360 mm = 20 ROI) MeigsHTPD andthisconference

  10. Example W I measurement in L-mode Three heating steps intensity profile of W I (400.9 nm) versus time spatial resolution ~1.8 cm time resolution ~40 ms sawteeth

  11. Te and G: probes or spectroscopy • Spectroscopy on Balmer epsilon G • (nearby W I 400.9 nm) • Probes  Te, G • In both cases correlation of local flux densities as well profile integrated G’s agree!

  12. Approach to quantifying W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering • How to control sputtering • Conclusions

  13. Investigate Yeffective(Te) • #82195: 1 MW NBI • Ramping divertor fuelling • Increases divertor ne • decreases Te • Increases G • Z-eff (i.e. impurity influx) changes with 10% • Tungsten erosion drops • Similar experiment with steps in density

  14. Be content sufficient for Yeff(Te) • Be fraction on basis of spectroscopy: 0.5% !! • Be fraction on basis of Z-eff: 3% • C fraction on basis of spectroscopy: 0.05% !! • Be charge state not evident, but at least 2+ • coronal equilibrium Be Be+ Be2+ Be3+ Be4+ • Thus beryllium sputtering dominates over carbon and oxygen!

  15. Compared with ASDEX Upgrade 4.0% C4+ 2.0% C4+ 1.0% C4+ 0.5% Be4+ 0.5% Be2+ 0.1% Be4+ ASDEX Upgrade JET, density steps JET, density ramp ASDEX Upgrade data: Dux et al., J Nucl Mat 390–391 (2009) 858

  16. Approach to quantifying W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering • How to control sputtering • Conclusions

  17. Zeff scan & Te oscillations (sawteeth) impurity content varies 3 MW 1 MW 2 MW ne = 1.6·1019 m-3 2.0·1019 m-3 2.8·1019 m-3 Te oscillations dominate Te (eV) Experimental approach: 3 steps in heating power for three densities t (s)

  18. Correlate instantaneous Yeff and Te WI 400.9 (ph/s·cm2·sr) WI 400.8 nm, PMT, raw WI 400.8 nm, PMT, smoothed Te from Langmuir probes 15.0 15.2 15.4 15.6 15.8 16.0

  19. W I measurement

  20. Zeffnotonly parameter forYeff 3 MW ICRH 2 MW ICRH 1 MW ICRH Effect of steps in power in line with Be impurity variation Sputtering yield ~quadruples in each density step ne = 1.6·1019 m-3 3 MW ICRH 2 MW ICRH 1 MW ICRH ne = 2.0·1019 m-3 0.5% Be2+ 3 MW ICRH 2 MW ICRH 1 MW ICRH ne = 2.8·1019 m-3 1 MW NBI ramp Be fraction doubles in each step 1 MW 2 MW 3 MW • Density determines: • impurity content / charge state • CX D-atoms •  D. Harting, this conference ne = 1.6·1019 m-3 2.0·1019 m-3 2.8·1019 m-3

  21. Approach to quantifying W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering • How to control sputtering • Conclusions

  22. Signature of prompt redeposition?  B Divertor plasma W+ Hn e.g. 364 nm S′ rL B ′ ne, Teincrease lion W+ * W+ W0 X′ Hn e.g. 400.9 nm S B W* W Imp X Y W target

  23. Where to expect changes?

  24. Suitable lines in UV

  25. WII / WI changes observed! 1.41019 m-3, 50 eV: 41018 m-3, 50 eV: Factor 2 change indicates >50% redeposition Textorsameresultatsame Te and ne S. Brezinsek et al., Phys. Scr. T145 (2011) 014016.

  26. Approach to quantifying W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering • How to control sputtering • Conclusions

  27. H-mode sputtering dominated by ELM 13 MW NBI, ne =7.5·1019 m-3, 10 Hz ELMs • Striking constancy of He

  28. JET and ASDEX Upgrade H-mode sputtering compared JET: 13 MW NBI, ne =7.5·1019 m-3, 10 Hz ELMs average between ELMs • Factor 6 between inter- and intra-ELM sputtering  • Similar ratio for JET Te=20 eV and AUG Te=6 eV ASDEX: Dux et al., J Nucl Mat 390–391 (2009) 858

  29. Approach to quantifying W erosion • L-Mode divertor tungsten sputtering • Identification of the main sputtering species • Effect of varying the beryllium concentration • Diagnosing prompt redeposition • H-mode divertor tungsten sputtering: inter- versus intra-ELM sputtering • How to control sputtering • Conclusions

  30. ImpurityseedingtodecreaseTdiv Increasing N • Trade off betweenincreasingimpurityconcentrationanddecreasingTdiv • Possible in L-modeand in-between ELMs. • ELMs, however, will burnthrough Increasing N L. Aho-Mantila, this conference

  31. Conclusions • Beryllium main sputtering particle, carbon order of magnitude less • Effective erosion yields of typically 10-4 in L-mode order of magnitude lower compared to intra-ELM sputtering in ASDEX Upgrade • Intra-ELM sputtering dominates, in given example by factor 5 • Total W source between 2·1018 and 3·1019 /s have been observed for the outer divertor • For the first time effect of prompt deposition observed in tungsten divertor spectroscopy • N2 seeding effectively suppresses sputtering

More Related