Plasma and Fusion Research

Volume 5, S2100 (2010)

Regular Articles

Merging Startup Experiments on the UTST Spherical Tokamak

Takuma YAMADA, Ryota IMAZAWA¹⁾, Shuji KAMIO, Ryuma HIHARA, Keita ABE, Morio SAKUMURA, Qinghong CAO, Takuya OOSAKO, Hiroaki KOBAYASHI, Takuma WAKATSUKI²⁾, Byungil AN²⁾, Yoshihiko NAGASHIMA, Hajime SAKAKITA³⁾, Haruhisa KOGUCHI³⁾, Satoru KIYAMA³⁾, Yoichi HIRANO³⁾, Michiaki INOMOTO, Akira EJIRI, Yuichi TAKASE and Yasushi ONO

: Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan
1): Graduate School of Engineering, The University of Tokyo, Bunkyo 113-8656, Japan
2): Graduate School of Science, The University of Tokyo, Bunkyo 113-0033, Japan
3): National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan

(Received 22 December 2009 / Accepted 31 March 2010 / Published 10 December 2010)

Abstract

The University of Tokyo Spherical Tokamak (UTST) was constructed to explore the formation of ultrahigh-beta spherical tokamak (ST) plasmas using double null plasma merging. The main feature of the UTST is that the poloidal field coils are located outside the vacuum vessel to demonstrate startup in a reactor-relevant situation. Initial operations used partially completed power supplies to investigate the appropriate conditions for plasma merging. The plasma current of the merged ST reached 100 kA when the central solenoid coil was used to assist plasma formation. Merging of two ST plasmas through magnetic reconnection was successfully observed using two-dimensional pickup coil arrays, which directly measure the toroidal and axial magnetic fields inside the UTST vacuum vessel. The resistivity of the current sheet was found to be anomalously high during merging.

Keywords

spherical tokamak, merging startup, magnetic reconnection

DOI: 10.1585/pfr.5.S2100

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References

[1] A. Sykes et al., Nucl. Fusion 41, 1423 (2001).
[2] Y. Ono et al., Phys. Plasmas 4, 1953 (1997).
[3] Y. Ono and M. Inomoto, Phys. Plasmas 7, 1863 (2000).
[4] Y. Ono et al., Nucl. Fusion 43, 789 (2003).
[5] R. Imazawa et al., Bull. Am. Phys. Soc. 52, 307 (2007).
[6] R. Imazawa et al., to be submitted to Nucl. Fusion.

This paper may be cited as follows:

Takuma YAMADA, Ryota IMAZAWA, Shuji KAMIO, Ryuma HIHARA, Keita ABE, Morio SAKUMURA, Qinghong CAO, Takuya OOSAKO, Hiroaki KOBAYASHI, Takuma WAKATSUKI, Byungil AN, Yoshihiko NAGASHIMA, Hajime SAKAKITA, Haruhisa KOGUCHI, Satoru KIYAMA, Yoichi HIRANO, Michiaki INOMOTO, Akira EJIRI, Yuichi TAKASE and Yasushi ONO, Plasma Fusion Res. 5, S2100 (2010).