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Kenmochi N, Ida K, Tokuzawa T, Mizuno Y, Yasuhara R, Funaba H, Uehara H, Den Hartog DJ, Yoshinuma M, Takemura Y, Igami H, Yanai R. Fast nondiffusive response of heat and turbulence pulse propagation. Sci Rep 2024; 14:13006. [PMID: 38844607 PMCID: PMC11156975 DOI: 10.1038/s41598-024-63788-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 06/03/2024] [Indexed: 06/09/2024] Open
Abstract
The experimental findings from the Large Helical Device have demonstrated a fast, nondiffusive behavior during the propagation of heat pulses, with an observed increase in speed with reduction in their temporal width. Concurrent propagation of the temperature gradient and turbulence, in a timeframe spanning from a few milliseconds to tens of milliseconds, aligned with the avalanche model. These results indicate that the more spatiotemporally localized the heat and turbulence pulses are, the greater the deviation of the plasma from its equilibrium state, coupled with faster propagation velocity. This insight is pivotal for future fusion reactors, which necessitate the maintenance of a steady-state, non-equilibrium condition.
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Affiliation(s)
- Naoki Kenmochi
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan.
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan.
| | - Katsumi Ida
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - Tokihiko Tokuzawa
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - Yoshinori Mizuno
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - Ryo Yasuhara
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - Hisamichi Funaba
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - Hiyori Uehara
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - Daniel J Den Hartog
- Wisconsin Plasma Physics Laboratory, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Mikirou Yoshinuma
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - Yuki Takemura
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - Hiroe Igami
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - Ryoma Yanai
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
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Spatiotemporal dynamics of high-wavenumber turbulence in a basic laboratory plasma. Sci Rep 2022; 12:19799. [PMID: 36509803 PMCID: PMC9744746 DOI: 10.1038/s41598-022-23559-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 11/02/2022] [Indexed: 12/14/2022] Open
Abstract
High-spatial resolution observation of high-wavenumber broadband turbulence is achieved by controlling the magnetic field to be relatively low and measuring with a azimuthally arranged multi-channel Langmuir array in a basic laboratory plasma. The observed turbulence consists of narrowband low-frequency fluctuations and broadband high-frequency turbulent fluctuations. The low-frequency fluctuations have a frequency of about 0.7 times the ion cyclotron frequency and a spatial scale of 1/10 of the ion inertial scale. In comparison, high-frequency fluctuations have a higher frequency than the ion cyclotron frequency and spatial scales of 1/10-1/40 of the ion inertial scale. Two-dimensional correlation analysis evaluates the spatial and temporal correlation lengths and reveals that the high-wavenumber broadband fluctuations have turbulent characteristics. The measurements give us further understanding of small scale turbulence in space and fusion plasmas.
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Hall-Chen VH, Damba J, Parra FI, Pratt QT, Michael CA, Peng S, Rhodes TL, Crocker NA, Hillesheim JC, Hong R, Ni S, Peebles WA, Png CE, Ruiz Ruiz J. Validating and optimizing mismatch tolerance of Doppler backscattering measurements with the beam model (invited). THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:103536. [PMID: 36319398 DOI: 10.1063/5.0101805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 09/07/2022] [Indexed: 06/16/2023]
Abstract
We use the beam model of Doppler backscattering (DBS), which was previously derived from beam tracing and the reciprocity theorem, to shed light on mismatch attenuation. This attenuation of the backscattered signal occurs when the wavevector of the probe beam's electric field is not in the plane perpendicular to the magnetic field. Correcting for this effect is important for determining the amplitude of the actual density fluctuations. Previous preliminary comparisons between the model and Mega-Ampere Spherical Tokamak (MAST) plasmas were promising. In this work, we quantitatively account for this effect on DIII-D, a conventional tokamak. We compare the predicted and measured mismatch attenuation in various DIII-D, MAST, and MAST-U plasmas, showing that the beam model is applicable in a wide variety of situations. Finally, we performed a preliminary parameter sweep and found that the mismatch tolerance can be improved by optimizing the probe beam's width and curvature at launch. This is potentially a design consideration for new DBS systems.
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Affiliation(s)
- V H Hall-Chen
- Institute of High Performance Computing, Singapore 138632, Singapore
| | - J Damba
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - F I Parra
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - Q T Pratt
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - C A Michael
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - S Peng
- UKAEA/CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
| | - T L Rhodes
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - N A Crocker
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - J C Hillesheim
- UKAEA/CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
| | - R Hong
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - S Ni
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - W A Peebles
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - C E Png
- Institute of High Performance Computing, Singapore 138632, Singapore
| | - J Ruiz Ruiz
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
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Kenmochi N, Ida K, Tokuzawa T, Yasuhara R, Funaba H, Uehara H, Den Hartog DJ, Yamada I, Yoshinuma M, Takemura Y, Igami H. Preceding propagation of turbulence pulses at avalanche events in a magnetically confined plasma. Sci Rep 2022; 12:6979. [PMID: 35577787 PMCID: PMC9110360 DOI: 10.1038/s41598-022-10499-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/11/2022] [Indexed: 11/09/2022] Open
Abstract
The preceding propagation of turbulence pulses has been observed for the first time in heat avalanche events during the collapse of the electron internal transport barrier (e-ITB) in the Large Helical Device. The turbulence and heat pulses are generated near the foot of the e-ITB and propagate to the peripheral region within a much shorter time than the diffusion timescale. The propagation speed of the turbulence pulse is approximately 10 km/s, which is faster than that of the heat pulse propagating at a speed of 1.5 km/s. The heat pulse propagates at approximately the same speed as that in the theoretical prediction, whereas the turbulence pulse propagates one order of magnitude faster than that in the prediction, thereby providing important insights into the physics of non-local transport.
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Affiliation(s)
- N Kenmochi
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan.
| | - K Ida
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - T Tokuzawa
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - R Yasuhara
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - H Funaba
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - H Uehara
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - D J Den Hartog
- Wisconsin Plasma Physics Laboratory, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - I Yamada
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
| | - M Yoshinuma
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - Y Takemura
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
- The Graduate University for Advanced Studies, SOKENDAI, Toki, Gifu, 509-5292, Japan
| | - H Igami
- National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan
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