Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak
Abstract
A 28 GHz system with a high-power gyrotron tube has been used for the QUEST spherical tokamak to form an over-dense plasma for electron Bernstein wave (EBW) heating and current drive with an 8.2 GHz-wave. Non-inductive high-density plasma ramp-up experiments with dual-frequency (dual-f) electron cyclotron (EC) (8.2 GHz and 28 GHz) waves were conducted. A spontaneous density jump (SDJ) to an over-dense state was first observed as a bifurcation phenomenon in the dual-f wave experiment. The over-dense plasma on the 8.2 GHz wave was non-inductively ramped up to 25 kA, and was maintained for 0.4 s under stable plasma equilibrium after two such jumps in one shot. Heating to mildly energetic electrons and bulk electrons was observed even in the over-dense region. The electrostatic EBW heating effect on the mildly energetic electrons in the over-dense region is assessed following a dispersion analysis of the 8.2 GHz wave. The bulk electron heating effect observed is explained as heat exchange from mildly energetic electrons heated by the electrostatic EBW. Remarkably, a high hard-x-ray-radiation temperature of ~500 keV was also observed in tangential viewing for current-carrying electrons in the over-dense core region. Synergetic heating from the overlap of different 28 GHz EC harmonicmore »
- Authors:
-
[1];
[1];
[1];
[4];
[5];
[8];
[9];
[3]
more »
- Kyushu Univ., Fukuoka (Japan)
- Kyushu Univ., Fukuoka (Japan); Inst. for Plasma Research, Gandinagar (India)
- Univ. of Tsukuba (Japan)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Univ. of Tokyo (Japan)
- Chinese Academy of Sciences (CAS), Hefei (China)
- Kyushu Univ., Fukuoka (Japan); National Inst. for Fusion Science, Toki (Japan)
- Kyoto Univ. (Japan)
- National Inst. for Fusion Science, Toki (Japan)
- National Inst. for Quantum and Radiological Science and Technology Naka (Japan)
- Publication Date:
- Research Org.:
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- USDOE
- OSTI Identifier:
- 1651128
- Grant/Contract Number:
- AC02-09CH11466
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 60; Journal Issue: 1; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Citation Formats
Idei, H., Onchi, T., Mishra, K., Zushi, H., Kariya, T., Imai, T., Watanabe, O., Ikezoe, R., Hanada, K., Ono, M., Ejiri, A., Qian, J., Nakamura, K., Fujisawa, A., Nagashima, Y., Hasegawa, M., Matsuoka, K., Fukuyama, A., Kubo, S., Yoshikawa, M., Sakamoto, M., Kawasaki, S., Higashijima, A., Ide, S., Takase, Y., and Murakami, S. Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak. United States: N. p., 2019.
Web. doi:10.1088/1741-4326/ab4c12.
Idei, H., Onchi, T., Mishra, K., Zushi, H., Kariya, T., Imai, T., Watanabe, O., Ikezoe, R., Hanada, K., Ono, M., Ejiri, A., Qian, J., Nakamura, K., Fujisawa, A., Nagashima, Y., Hasegawa, M., Matsuoka, K., Fukuyama, A., Kubo, S., Yoshikawa, M., Sakamoto, M., Kawasaki, S., Higashijima, A., Ide, S., Takase, Y., & Murakami, S. Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak. United States. https://doi.org/10.1088/1741-4326/ab4c12
Idei, H., Onchi, T., Mishra, K., Zushi, H., Kariya, T., Imai, T., Watanabe, O., Ikezoe, R., Hanada, K., Ono, M., Ejiri, A., Qian, J., Nakamura, K., Fujisawa, A., Nagashima, Y., Hasegawa, M., Matsuoka, K., Fukuyama, A., Kubo, S., Yoshikawa, M., Sakamoto, M., Kawasaki, S., Higashijima, A., Ide, S., Takase, Y., and Murakami, S. Thu .
"Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak". United States. https://doi.org/10.1088/1741-4326/ab4c12. https://www.osti.gov/servlets/purl/1651128.
@article{osti_1651128,
title = {Electron heating of over-dense plasma with dual-frequency electron cyclotron waves in fully non-inductive plasma ramp-up on the QUEST spherical tokamak},
author = {Idei, H. and Onchi, T. and Mishra, K. and Zushi, H. and Kariya, T. and Imai, T. and Watanabe, O. and Ikezoe, R. and Hanada, K. and Ono, M. and Ejiri, A. and Qian, J. and Nakamura, K. and Fujisawa, A. and Nagashima, Y. and Hasegawa, M. and Matsuoka, K. and Fukuyama, A. and Kubo, S. and Yoshikawa, M. and Sakamoto, M. and Kawasaki, S. and Higashijima, A. and Ide, S. and Takase, Y. and Murakami, S.},
abstractNote = {A 28 GHz system with a high-power gyrotron tube has been used for the QUEST spherical tokamak to form an over-dense plasma for electron Bernstein wave (EBW) heating and current drive with an 8.2 GHz-wave. Non-inductive high-density plasma ramp-up experiments with dual-frequency (dual-f) electron cyclotron (EC) (8.2 GHz and 28 GHz) waves were conducted. A spontaneous density jump (SDJ) to an over-dense state was first observed as a bifurcation phenomenon in the dual-f wave experiment. The over-dense plasma on the 8.2 GHz wave was non-inductively ramped up to 25 kA, and was maintained for 0.4 s under stable plasma equilibrium after two such jumps in one shot. Heating to mildly energetic electrons and bulk electrons was observed even in the over-dense region. The electrostatic EBW heating effect on the mildly energetic electrons in the over-dense region is assessed following a dispersion analysis of the 8.2 GHz wave. The bulk electron heating effect observed is explained as heat exchange from mildly energetic electrons heated by the electrostatic EBW. Remarkably, a high hard-x-ray-radiation temperature of ~500 keV was also observed in tangential viewing for current-carrying electrons in the over-dense core region. Synergetic heating from the overlap of different 28 GHz EC harmonic resonances as well as higher harmonic heating is discussed for maintaining the highly energetic electrons in the over-dense core region. In addition, the SDJ process and mechanism are considered based on the discussion of the electron heating effects with the 8.2 GHz wave.},
doi = {10.1088/1741-4326/ab4c12},
journal = {Nuclear Fusion},
number = 1,
volume = 60,
place = {United States},
year = {Thu Dec 05 00:00:00 EST 2019},
month = {Thu Dec 05 00:00:00 EST 2019}
}
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