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Radiation process of carbon ions in JT-60U detached divertor plasmas

O-26(15+3min.) 29May2008 PSI-18@Toledo Spain. Radiation process of carbon ions in JT-60U detached divertor plasmas. J apan A tomic E nergy A gency T. Nakano , H. Kubo, N. Asakura, K. Shimizu, H. Kawashima, S. Higashijima. Introduction.

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Radiation process of carbon ions in JT-60U detached divertor plasmas

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  1. O-26(15+3min.) 29May2008 PSI-18@Toledo Spain Radiation process of carbon ions in JT-60U detached divertor plasmas Japan Atomic Energy Agency T. Nakano,H. Kubo, N. Asakura, K. Shimizu, H. Kawashima, S. Higashijima

  2. Introduction • Heat & particle control is essential in future fusion devices • Remote radiative cooling by impurities ( 85% in Demo SS) • Changes of plasma parameters and spatial distribution • Radiation is not proportional to an impurity flux necessarily • Radiation control requires understanding of physics • Physics to be understood: elementary processes and transport • Radiator ( C3+, C2+,,,,(Carbon devices)) • Recombination/Ionization • Source (from divertor plates, • & main plasma) C3+ emissivity Cq+ (q>3) Cq+ Cp+ Cp+ (p<3) C C

  3. What is known & new Radiation (%) Ioniz. flux (1018 /m2s) Recomb. flux (1018 /m2s) C 2+ C4+ C4+ 220 2 C 3+ >~60% C3+ C3+ (2%) C 2+ C 2+ Nakano T. et al 2007 NF 47 1458 Kubo H. et al 1995 PPCF 37 1133 Fenstermacher M.E. et al 1997 PoP 4 1761

  4. Outline • Experiment • Waveforms of density-scan discharge • C2+ intensity distribution • Analysis model • Collisional-radiative model for C2+ • Results • Determination of Te and ne • Flux balance ( Recombination vs. Ionization ) • Radiation power of C2+ • Discussion • Transport of C3+ • Summary

  5. Radiation zone moves towards the X-point • Viewing chords • Visible spectrometer • Bolometer C2+ emission also peaks around the X-point

  6. C2+ intensity peaks around the X-point 1 60 92 61

  7. C2+: population decreases rapidly

  8. Collisional-Radiative model C2+ energy level D0 energy level C 3+ Solution of Rate Equation under Steady-State (~ 10-8s ) nC2+(p) = R0nenCV(Recombining ) + R0'nDnCV(CX-Recomb. ) + R1nenCIV(Ionizing ) D+ n=… H-like n=7 n=6 n=5 D0 C2+ (Be-like) Charge eXchange recomb. n=4 (De) Excitation Recombination l-, Sing- & triplet resolved Ionization Spontaneous transition n=1 n=3 -13.6eV 2s -49.7eV

  9. C2+: Ionization components dominates Population No recombining component.

  10. C3+ :n < 4 : Ionizing component (Term Energy < ~50eV) n > 5 : Recombining component Total Population ( Excitation energy from the ground state (2s) (eV) Nakano T. et al 2007 NF 47 1458

  11. C2+: Ionizing components dominates Population No recombining component.

  12. Flux balance : C2+ ioniz. >> C3+ recomb. 220 2 160 Flux (1018 /m2s) C4+ Ionization C2+ (3s3S-3p3P) C3+ 0 Transport loss of C3+ is suggested C2+

  13. Radiation power : C2+ contributes 30% (J/ph) C4+ C4+ 220 2 Radiation C2+ (3s3S-3p3P) 0.8MW/m2 (60%) C3+ C3+ 0 160 160 0.4MW/m2 (30%) C2+ C2+ C3+ & C2+ contribute 90% of total radiation

  14. Source of C3+:main plasma and divertor comparable Recomb. flux (1018 /m2s) Ioniz. flux (1018 /m2s) C4+ C4+ from main plasma Suggesting C4+ source from main plasma. 220 2 C3+ C3+ Cq+ (q>3) Cq+ 0 Suggesting C2+ source from divertor • 160 C2+ Cp+ C2+ Cp+ (p<3) C from divertor C

  15. Summary • In a detached plasma with an X-point MARFE of JT-60U, • Absolute C2+ line intensity was measured with a VUV and a visible spectrometer. • The C2+ line intensity ratios ( population ratios ) were analyzed with a collisional-radiative model. • C2+ population was dominated by an ionizing plasma component ( excitation from the ground state ). • No recombination of C3+ was observed. • With the results of C3+ , • C3+ & C2+ radiate 60% and 30%, respectively, • of total radiation power • C3+ is produced by C2+ ionization and C4+ recombination • C3+ is NOT lost by C3+ ionization and C3+ recombination • Significant transport loss of C3+ from the X-point • C3+ originates the main plasma and the divertor, comparably

  16. Thank your for your attention. This work was partly supported by Grant-in-Aid for Scientific Research for Priority Area #19055005

  17. 2D wide-spectral-band spectrometer 60ch • Spectrometer • Grating : 300 g/mm • F : 2 • f : 0.2 m • CCD • Back-illuminated • Pixel size : 20 x 20 m • Format : 1340 x1300 32ch • Specifications • Instrumental width (FWHM): • ~ 0.74 nm (2.3 pixels) • Spectral band: • ~ 430 nm ( 350 - 780 nm) • Spatial resolution (92ch): • ~ 1 cm

  18. Vacuum Ultra Violet spectrometer • Grating: • Holographic ( 300g / mm ) • Incident angle : 85o • Dispersion : 2 nm / mm • Resolution : • Slit: • 10m x 5mm • Detector : • MCP 50 m x 1024ch • Similar viewing chord to the visible spectrometer • Absolute calibration of sensitivity by a branching ratio method • Comparison of visible and VUV spectrum

  19. 8本の C III スペクトル線を同時解析 VUV スペクトル 可視スペクトル

  20. C IV スペクトル（VUV） C IV ( 2 - 3, 4 ) が観測された

  21. C IV スペクトル（VUV） C IV ( 2 - 5 ) は弱く、解析は困難

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