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H-mode power threshold in JFT-2M during 2000-2004 with ferritic wall and boron coating

8 th Meeting of the ITPA Confinement Database & Modeling Topical Group on 2004.4.20 at Kyto university. H-mode power threshold in JFT-2M during 2000-2004 with ferritic wall and boron coating. K. Tsuzuki JAERI. Contents. Modification of JFT-2M Installation of ferritic steel

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H-mode power threshold in JFT-2M during 2000-2004 with ferritic wall and boron coating

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  1. 8th Meeting of the ITPA Confinement Database & Modeling Topical Group on 2004.4.20 at Kyto university H-mode power threshold in JFT-2M during 2000-2004 with ferritic wall and boron coating K. Tsuzuki JAERI

  2. Contents • Modification of JFT-2M • Installation of ferritic steel • Boron coating • High recycling steady H-mode • Threshold power for L-H transition • Effect of ferromagnetism and boron • BT dependence • Summary

  3. Modification of JFT-2M(1)Installation of ferritic steel Reduced activation ferritic steel is a leading candidate for structure material of DEMO reactor but ferromagnetic and easily oxidized. Compatibility with high performance plasma is a critical issue. Ferritic steel wall Compatibility has been investigated in JFT-2M by installing ferritic wall inside vacuum vessel Graphite tiles

  4. Possible Magnetic effect of the ferritic wall (3) Error field Miss-alignment and/or inhomogeneous installation (4) Wall stabilization • Ripple reduction Ripple amplitude at plasma periphery 2.2% -->0.4% for optimum case (2) Complex field Higher harmonics is produced

  5. Modification of JFT-2M(2)boron coating Boron coating with B(CH3)3 was first applied on JFT-2M in 2000. Oxygen impurity : reduced Hydrogen recycling : strong pumping and fueling according to wall condition

  6. High Recycling Steady (HRS) H-mode New H-mode was found after boronization Enhancement of Da Steady H-mode edge ne/nGW > 0.4

  7. Threshold power with/without ferritic wall • Pth was compared for standard configuration BT = 1.3 T, Ip = 200 kA, q95 = 3.0 Ferritic steel : No effect Boron coating : Improvement

  8. BT dependence of Pth • BT dependence of Pth was not well investigated in JFT-2M • Effect of the ferritic steel change • Permeability : 2 (2T) ~ 4 (0.8T) • Ripple : 1.5% (0.85T) ~ 0.5% (1.3 T) JFT-2M

  9. Other parameters • BT was scanned from 0.85T to 1.9T • Ip is almost constant at 200 kA • q95 varied from 2 to 4.2 • Low recycling conditions; not HRS but ELMy H-mode

  10. BT dependence of Pth Pth obeys scaling law by 15 % for 0.85T < BT < 1.9T J. Snipes, ITER H-mode Threshold Database Working Group, 7th H-mode Workshop, Oxford, 1999 2.84M-1*Bt0.82*n200.58*R*a0.81

  11. Summary • Threshold power (Pth) for L-H transition has been investigated in JFT-2M after installation of ferritic steel and boron coating. • Pth is not changed by the installation of ferritic wall • Boron coating reduced Pth by ~250W • Toroidal field was scanned for wider range than previous data sets. • Ripple amplitude is also scanned from 0.4 % to 1.5 % • Permeability is also scanned from 2 to 4 • Pth obeys conventional scaling law (B0.82) by 15 %

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