Axisymmetric MHD Simulation of ITB Crush and Following Disruption Dynamics of Tokamak Plasmas with High Bootstrap Current

N. Takei1), Y. Nakamura*, Y. Kawano*, H. Tsutsui1), T. Ozeki*, K. Tobita*,
M. Sugihara*, S. Tsuji-Iio1), R. Shimada1) and S. C. Jardin**

1) Tokyo Institute of Technology, Tokyo, Japan
*Japan Atomic Energy Research Institute, Ibaraki, Japan
**Princeton Plasma Physics Laboratory, Princeton, New Jersey, USA

In JT-60U, a fast current quench of the major disruption, which places a key design limit on a vacuum vessel and plasma facing components, was observed in a Reversed Shear (RS) mode of high performance discharges with strong ITB (Internal Transport Barrier) [1]. Hence, it is particularly important to clarify the mechanism governing such a fast current quench and to understand not well-known disruption characteristics of RS plasmas with a high bootstrap current fraction generated by ITB in an advanced tokamak scenario [2].
A simple ITB model was installed in the Tokamak Simulation Code (TSC) [3], and a strong RS plasma in JT-60U was reproduced well on the TSC [4]. Then, an ITB crush was introduced by modeling an abrupt disappearance of the core region with the improved energy transport. The consequent current quench followed, and the disruption dynamics such as the time-evolutions of the inductive and non-inductive current profiles and the relevant electric field profile was computationally investigated in detail. It was first clarified that the ITB crush leads to a substantial change of the current profile, which provides a remarkable quench property of the plasma current, like the fast rate observed. Such details of new understanding of the current quench behavior of RS plasmas with ITB-generated, high bootstrap current will be presented.

References

[1] Y. Kawano. M. Sugihara, T. Ozeki and M. Shimada, 30th EPS Conference on Controlled Fusion and Plasma Physics, P-2.129, St Petersburg, Russia, July 7-11, 2003.
[2] N. Takei, Y. Nakamura et. al., 30th EPS Conference on Controlled Fusion and Plasma Physics, P-2.127, St Petersburg, Russia, July 7-11, 2003.
[3] S.C. Jardin, N. Pomphery and J. Delucia, J. Comput. Phys. 66 (1986) 481.
[4] Y. Nakamura, H. Tsutsui, N. Takei, et. al., 30th EPS Conference on Controlled Fusion and Plasma Physics, P-2.128, St Petersburg, Russia, July 7-11, 2003.


1) Present address: Plasma Analysis Division, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Naka-machi, Ibaraki-ken 311-0193, Japan
e-mail: takein@fusion.naka.jaeri.go.jp