Plasma curent start-up experiment using waves in the lower hybrid frequency range in TST-2

Y. Takase, T. Wakatsuki, A. Ejiri, H. Kakuda, C. P. Moeller, T. Ambo, K. Hanashima, J. Hiratsuka, H. Kasahara, R. Kumazawa, Y. Nagashima, K. Saito, T. Sakamoto, T. Seki, F. Shimpo, R. Shino, M. Sonehara, O. Watanabe, T. Yamaguchi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Noninductive plasma current (I p) start-up experiments using RF power in the lower hybrid frequency range are being conducted on the TST-2 spherical tokamak. The lower hybrid wave (LHW) has demonstrated efficient current drive in conventional tokamaks. However, in spherical tokamak (ST) plasmas with very high dielectric constants (ε∼ω pe 2/Ω| e 2≫1), accessibility of the LHW to the plasma core is severely limited. Our approach is to keep the plasma density low (such that ε∼1) during I p ramp-up. Once I p reaches a level sufficiently high for neutral beam current drive, plasma can be densified and transformed into an advanced tokamak plasma dominated by the self-driven bootstrap current. Initial plasma start-up experiments were performed on TST-2 using a combline antenna which excites a traveling fast wave. After formation of toroidal flux surfaces, RF power and vertical field were ramped up to increase I p. Up to 12 kA of Ip has been obtained by this method. Soft X-ray measurements indicate that the electron temperature increases as I p increases, and hard X-ray spectroscopy indicates that energetic electrons build up as I p is ramped up.

Original languageEnglish
Title of host publicationRadio Frequency Power in Plasmas - Proceedings of the 19th Topical Conference
Pages427-430
Number of pages4
DOIs
Publication statusPublished - 2011
Externally publishedYes
Event19th Topical Conference on Radio Frequency Power in Plasmas - Newport, RI, United States
Duration: Jun 1 2011Jul 3 2011

Publication series

NameAIP Conference Proceedings
Volume1406
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other19th Topical Conference on Radio Frequency Power in Plasmas
CountryUnited States
CityNewport, RI
Period6/1/117/3/11

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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