(EX/P5-7) Investigation of Compact Toroid Penetration for Fueling Spherical Tokamak Plasmas on CPD

N. Fukumoto1), K. Hanada2), S. Kawakami2), S. Honma2), M. Nagata1), N. Nishino3), H. Zushi2), K. Sato2), K. Nakamura2), H. Idei2), M. Sakamoto2), M. Hasegawa2), S. Kawasaki2), H. Nakashima2), A. Higashijima2), R. Bhattachayay2), K. Okamoto2), Y. Kikuchi1)
1) University of Hyogo, Himeji, Japan
2) Kyushu University, Kasuga, Japan
3) Hiroshima University, Higashihirosima, Japan

Abstract.  In previous Compact Toroid (CT) injection experiments on several tokamaks, although CT fueling had been successfully demonstrated, the CT fueling process has been not clear yet. We have thus conducted CT injection into simple toroidal or vertical vacuum magnetic fields to investigate quantitatively dynamics of CT plasmoid in the penetration process on a spherical tokamak (ST) device. Understanding the process allows us to address appropriately one of the critical issues for practical application of CT injection on reactor-grade tokamaks. In the experiment, the CT shift amount of about 0.26 m in a vertical magnetic field has been observed by using a fast camera. In addition to toroidal magnetic field, vertical one appears to affect CT trajectory in not conventional tokamak but ST devices operated at rather low toroidal fields. We have also observed the CT kinetic energy loss larger than the energy required for penetration into a toroidal magnetic field. Observation of CT attacks on the target plate with an IR camera has indicated that CT shifts 39 mm at the toroidal field of 261 G and the input energy due to CT impact in vacuum without magnetic fields is estimated to be 44 J, which is less than 10% of the initial CT kinetic energy. These suggest that unexpected adverse effects occur in CT penetration process.

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