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

2. 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 ( C 3+, C 2+,,,,(Carbon devices)) Recombination/Ionization Source (from divertor plates, & main plasma) Introduction C 3+ emissivity C q+ C C (q>3) C q+ C p+ (p<3)

3. - 3 - What is known & new C 3+ C 2+ Kubo H. et al 1995 PPCF 37 1133 Fenstermacher M.E. et al 1997 PoP 4 1761 Ioniz. flux (10 18 /m 2 s) Recomb. flux (10 18 /m 2 s) C 3+ Nakano T. et al 2007 NF 47 1458 C 4+

4. Outline Experiment Waveforms of density-scan discharge C 2+ intensity distribution Analysis model Collisional-radiative model for C 2+ Results Determination of T e and n e Flux balance ( Recombination vs. Ionization ) Radiation power of C 2+ Discussion Transport of C 3+ Summary

5. Radiation zone moves towards the X-point Viewing chords Visible spectrometer Bolometer C 2+ emission also peaks around the X-point

6. C 2+ intensity peaks around the X-point 160 61 92

7. C 2+ : population decreases rapidly

8. -49.7eV 2s n=4 n=7 n=3 n=6 n=5 (De) Excitation C 2+ (Be-like) C 3+ n=1 -13.6eV Charge eXchange recomb. Spontaneous transition Recombination Collisional-Radiative model Ionization C 2+ energy level D+D+ D 0 energy level l-, Sing- & triplet resolved n= … H-like D 0 Solution of Rate Equation under Steady-State (~ 10 -8 s ) nC 2+ (p) = R 0 n e n CV (Recombining ) + R 0 ' n D n CV (CX-Recomb. ) + R 1 n e n CIV (Ionizing )

9. C 2+ : Ionization components dominates No recombining component. Population

10. C 3+ :n 5 : Recombining component Population ( Excitation energy from the ground state (2s) (eV) Nakano T. et al 2007 NF 47 1458 Total

11. C 2+ : Ionizing components dominates Population No recombining component.

12. Flux balance : C 2+ ioniz. >> C 3+ recomb. C 4+ C 2+ C 3+ Transport loss of C 3+ is suggested Flux (10 18 /m 2 s) Ionization C 2+ (3s 3 S-3p 3 P)

13. C 4+ C 2+ C 3+ Radiation power : C 2+ contributes 30% C 4+ C 2+ C 3+ 160 C 3+ & C 2+ contribute 90% of total radiation Radiation C 2+ (3s 3 S-3p 3 P) (J/ph)

14. Source of C 3+ :main plasma and divertor comparable C q+ C C (q>3) C q+ C p+ (p<3) Suggesting C 4+ source from main plasma. Suggesting C 2+ source from divertor C 4+ C 2+ C 3+ Recomb. flux (10 18 /m 2 s) C 4+ C 2+ C 3+ Ioniz. flux (10 18 /m 2 s) from divertor from main plasma

15. Summary In a detached plasma with an X-point MARFE of JT-60U, Absolute C 2+ line intensity was measured with a VUV and a visible spectrometer. The C 2+ line intensity ratios ( population ratios ) were analyzed with a collisional-radiative model. C 2+ population was dominated by an ionizing plasma component ( excitation from the ground state ). No recombination of C 3+ was observed. With the results of C 3+, C 3+ & C 2+ radiate 60% and 30%, respectively, of total radiation power C 3+ is produced by C 2+ ionization and C 4+ recombination C 3+ is NOT lost by C 3+ ionization and C 3+ recombination  Significant transport loss of C 3+ from the X-point C 3+ 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. - 17 - Specifications Instrumental width (FWHM): ~ 0.74 nm (2.3 pixels) Spectral band: ~ 430 nm ( 350 - 780 nm) Spatial resolution (92ch): ~ 1 cm Spectrometer Grating: 300 g/mm F : 2 f: 0.2 m CCD Back-illuminated Pixel size: 20 x 20  m Format: 1340 x1300 32ch 60ch 2D wide-spectral-band spectrometer

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

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

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

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