H. Takahashi, T. Shimozuma, S. Kubo, I. Yamada, S. Muto, M. Yokoyama, H. Tsuchiya, T. Ido, A. Shimizu, C. Suzuki, K. Ida, S. Matsuoka, S. Satake, K. Narihara, N. Tamura, Y. Yoshimura, H. Igami, H. Kasahara, Y. Tatematsu, T. Mutoh and the LHD experiment group
High Te, low collisional plasma confinement characteristics in LHD
Date of publication:
22 IAEA Fusion Energy Conference, EXC/P8-15
High electron temperature (Te) plasmas of more than 15 keV were achieved due to the upgraded electron cyclotron resonance heating system with newly installed 77 GHz-over 1 MW gyrotrons in the Large Helical Device. The value of Te greatly exceeds ~10 keV, which was obtained in previous experiments. The configuration dependence of high Te plasma performance was investigated under the magnetic field strength of ~2.7 T and the optimum configuration for achieving high Te plasma was observed. These high Te plasmas accompanied an electron internal transport barrier (e-ITB). Clear threshold of density-normalized ECRH power for an e-ITB formation was found. The foot point of an e-ITB moved outward during ECRH injection and the flat Te profile gradually healed with the propagation of the e-ITB foot point. The foot point finally reached to a lower order rational surface of ¦É/2pi = 0.5.