Letters

Full Text / References

High-Speed Floating Potential Measurement with Phase-Flat Response up to 1 MHz for Sub-Ion Scale Turbulence in PANTA

Yuichi KAWACHI¹⁾, Takashi NISHIZAWA^2,3), Yoshihiko NAGASHIMA^2,3), Makoto SASAKI⁴⁾, Kenichiro TERASAKA⁵⁾, Yusuke KOSUGA^2,3), Shigeru INAGAKI⁶⁾, Takuma YAMADA⁷⁾, Naohiro KASUYA^2,3), Chanho MOON^2,3), Akihide FUJISAWA^2,3)

1)

Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan

2)

Research Institute for Applied Mechanics, Kyushu University, Fukuoka 816-8580, Japan

3)

Research Center for Plasma Turbulence, Kyushu University, Fukuoka 816-8580, Japan

4)

College of Industrial Technology, Nihon University, Narashino 275-8575, Japan

5)

Department of Computer and Information Sciences, Sojo University, Kumamoto 860-0082, Japan

6)

Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan

7)

Faculty of Arts and Science, Kyushu University, Motooka, Fukuoka 819-0395, Japan

(Received 9 December 2025 / Accepted 25 January 2026 / Published 14 April 2026)

Abstract

A high-speed floating potential measurement system has been developed for investigating turbulence at frequencies above the ion cyclotron frequency in the PANTA linear plasma device. The system is designed to have a phase-flat response up to 1 MHz, enabling accurate measurement of the phase relationship between floating potential and density fluctuations extending into the high-frequency regime. Initial results show that the attenuation of gain in the high-frequency range is significantly reduced compared to conventional measurements. A cross-phase analysis between the estimated electric field and density fluctuations shows a clear difference.

Copyright (c) 2026 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

sub-ion scale turbulence, floating potential measurement, turbulent transport

DOI: 10.1585/pfr.21.1302021

Full Text

PDF format (1.9Mbytes)

References

• [1] R.O. Dendy et al., Phys. Rev. Lett. 130, 105102 (2023).
• [2] M. Raeth and K. Hallatschek, Phys. Rev. Lett. 133, 195101 (2024).
• [3] V.V. Mikhailenko et al., Phys. Rev. Lett. 31, 032307 (2024).
• [4] Y. Kawachi et al., Sci. Rep. 12, 19799 (2022).
• [5] Y. Kawachi et al., Plasma Phys. Control. Fusion 65, 115001 (2023).
• [6] Y. Kawachi et al., Phys. Plasmas 31, 044502 (2024).
• [7] J.A. Schmidt, Rev. Sci. Instrum. 39, 1297 (1968).
• [8] F.F. Chen, In Proceedings of the IEEE-ICOPS Meeting, (Jeju, Korea, 5 June 2003).
• [9] Y. Nagashima et al., Rev. Sci. Instrum. 96, 093509 (2025).
• [10] T. Yamada et al., Nat. Phys. 4, 721 (2008).
• [11] S. Inagaki et al., Sci. Rep. 6, 22189 (2016).
• [12] T. Nishizawa et al., Rev. Sci. Instrum. 89, 10J118 (2018).
• [13] Y. Tanaka et al., Plasma Fusion Res. 2, S1090 (2007).
• [14] K. Terasaka et al., Rev. Sci. Instrum. 85, 113503 (2014).
• [15] A. Rich, Analog Devices Application Note AN-347, (1983).
• [16] E. Spinelli and F. Reverter, IEEE Trans. Instrum. Meas. 59, 458 (2010).