@inproceedings{oai:repo.qst.go.jp:00054867,
 author = {Tsujii, Naoto and Takase, Yuichi and Ejiri, Akira and 新屋, 貴浩 and Yajima, Satoru and Yamazaki, Hibiki and Togashi, Hiro and P., Moeller Charles and Roidl, Benedikt and Takahashi, Wataru and Toida, Kazuya and Yoshida, Yusuke and 新屋 貴浩},
 book = {22 Topical Conference on Radio-Frequency Power in Plasmas},
 issue = {157},
 month = {Oct},
 note = {Removal of the central solenoid is essential to realize an economical spherical tokamak fusion reactor, but non-inductive plasma start-up is a challenge. On the TST-2 spherical tokamak, non-inductive plasma start-up using lower-hybrid (LH) waves has been investigated. Using the capacitively-coupled combline (CCC) antenna installed at the outboard midplane, fully non-inductive plasma current ramp-up up to a quarter of that of the typical Ohmic discharges has been achieved. Although it was desirable to keep the density low during the plasma current ramp-up to avoid the LH density limit, it was recognized that there was a maximum current density that could be carried by a given electron density. Since the density needed to increase as the plasma current was ramped-up, the achievable plasma current was limited by the maximum operational toroidal field of TST-2. The top-launch CCC antenna was installed to access higher density with up-shift of the parallel index of refraction. Numerical analysis of LH current drive with the outboard-launch and top-launch antennas was performed and the results were qualitatively consistent with the experimental observations.},
 title = {Fully non-inductive plasma start-up with lower-hybrid waves using the outboard-launch and top-launch antennas on the TST-2 spherical tokamak},
 year = {2017}
}