Plasma and Fusion Research
Volume 1, 046 (2006)
Regular Articles
- Japan Atomic Energy Agency
Abstract
A drop in divertor plasma density was observed during the transition to the ELM free H-mode phase as well as the drop in Dα emission intensity in JT-60U. The time scale for the drop in divertor plasma density ranged from a few ms to several tens of ms. 2-D fluid divertor code simulations indicated that the time scale for the divertor plasma density drop was ranged from several tens of ms to a hundred ms, when thermal and particle diffusivities were instantly reduced in the main plasma edge with a constant recycling coefficient. When it was assumed that the recycling coefficient decreased with a decrease in heat flux and increased with a decrease in particle flux, the time scale was reduced to a few ms in the simulations accompanied by a reduction of edge thermal diffusivity. These results indicate that the sharp drop of the divertor plasma density concomitant with the sharp drop of the Dα emission intensity on a time scale of a few ms can be ascribed to the change of plasma-wall interaction depending on the heat flux to the divertor plates.
Keywords
H-mode transition, divertor plasma density, Dα emission, divertor simulation, recycling coefficient, JT-60U
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References
- [1] F. Wagner et al., Phys. Rev. Lett. 49, 1408 (1982).
- [2] M. Greenwald et al., Nucl. Fusion 37, 793 (1997).
- [3] K. Shinohara et al., J. Plasma Fusion Res. 74, 607 (1998).
- [4] K. Kamiya et al., Nucl. Fusion 43, 1214 (2003).
- [5] M. Kikuchi et al., Proc. 20th EPS Conf. (Lisboa, 1993) Vol.17C, Part I (European Physical Society, 1993) p.179.
- [6] K.H. Burrell et al., Plasma Phys. Control. Fusion 44, A253 (2002).
- [7] H. Takenaga et al., Rev. Sci. Instrum. 69, 3181 (1998).
- [8] D.G. Nilson et al., Fusion Eng. Des. 34-35, 609 (1997).
- [9] A. Kukushkin et al., J. Nucl. Mater. 290, 887 (2001).
- [10] T.D. Rognlien et al., Contrib. Plasma Phys. 34, 362 (1994).
- [11] K. Shimizu et al., J. Nucl. Mater. 313-316, 1277 (2003).
- [12] G.D. Porter et al., J. Nucl. Mater. 313-316, 1085 (2003).
- [13] M.E. Fenstermacher et al., Nucl. Fusion 45, 1493 (2005).
- [14] H. Takenaga et al., Nucl. Fusion 41, 1777 (2001).
- [15] J.W. Davis and A.A. Haasz, J. Nucl. Mater. 241-243, 37 (1997).
- [16] H. Takenaga et al., JAERI-Reviw 2003-029, 62 (2003).
- [17] A.V. Chankin et al., J. Nucl. Mater. 313-316, 828 (2003).
- [18] H. Takenaga et al., Nucl. Fusion 46, S39 (2006).
- [19] G.D. Porter et al., J. Nucl. Mater. 313-316, 1085 (2003).
- [20] J. Biersack, W. Eckstein, Appl. Phys. A 34, 73 (1984).
- [21] D.A. Alman and D.N. Ruzic, Phys. Scr. T111, 145 (2004).
- [22] H. Takenaga and the JT-60 team, Phys. Plasmas 8, 2217 (2001).
This paper may be cited as follows:
Hidenobu TAKENAGA, Naoyuki OYAMA and Nobuyuki ASAKURA, Plasma Fusion Res. 1, 046 (2006).