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INADA Yuki
| Mathematics, Electronics and Informatics Division | Associate Professor |
| Department of Electrical Engineering,Electronics, and Applied Physics |
Performance information
■ Paper- Direct Combinational Measurements of the Electron Density and Electric Field in Secondary Streamer Discharge under Atmospheric-Pressure Air
Yuki Inada; Tatsutoshi Shioda; Ryosuke Nakamura; Akiko Kumada; Mitsuaki Maeyama; Ryo Ono
Physical Review Letters, Volume：135, Number：24, Dec. 2025, [Reviewed], [Lead, Corresponding]
The electron density and electric field govern physical and chemical reactions in a secondary streamer discharge under atmospheric-pressure air. We present direct combinational measurements of these essential quantities and demonstrate their consistency by solving the continuity equation for electrons. The measurements enabled validity examination of previous computational studies and clarified contradictions; the prominence was a near-cathode phenomenon measured during primary-to-secondary transition, which caused unpredicted ionization inside the positive secondary discharge. The thorough comparison revealed that a fundamental governing mechanism to be established for the secondary discharge is current continuity.
American Physical Society (APS), Scientific journal
DOI：https://doi.org/10.1103/5sv6-28qp
DOI ID：10.1103/5sv6-28qp, ISSN：0031-9007, eISSN：1079-7114 - Turbulent self-quenching mechanism of high-temperature-gradient arc plasma in a converging–diverging cylinder: a numerical study
Masaya Shigeta; Yuki Inada; Yasunori Tanaka
International Journal of Heat and Mass Transfer, Volume：250, First page：127291, Last page：127291, Nov. 2025, [Reviewed]
Elsevier BV, Scientific journal
DOI：https://doi.org/10.1016/j.ijheatmasstransfer.2025.127291
DOI ID：10.1016/j.ijheatmasstransfer.2025.127291, ISSN：0017-9310 - Two-dimensional spectroscopic measurement of hot air gas and residual arc for applicability examination of thermal and dielectric reignition theory in air switchgear installing splitter plate
Yunosuke Hiraide; Akio Saitsu; Naoya Yamaguchi; Yuki Inada
Journal of Physics D: Applied Physics, Volume：58, Number：34, First page：345206, Last page：345206, Aug. 2025, [Reviewed], [Last, Corresponding]
Abstract
This study experimentally investigated the influences of a hot gas and residual arc on current interruption failure in a modeled air switchgear installing splitter plates, using a four-wavelength spectroscopic imaging sensor for the judgement of thermal or dielectric reignition. Experimental results showed that the interruption failure was observed both inside and outside the arc-extinguishing box. The hot gas outside the box caused thermal reignition due to retention effects caused by combustion reactions, while the residual arcs inside the box caused not only thermal reignition but also dielectric reignition. These experimental results demonstrated that spatiotemporal dynamics of hot gas and residual arcs significantly influences the reignition phenomena in the air switchgears, which can not be directly explained by traditional reignition mechanisms.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.1088/1361-6463/adf755
DOI ID：10.1088/1361-6463/adf755, ISSN：0022-3727, eISSN：1361-6463 - Experimental comparison of arc resistance and current limiting rate in low-current phase between SiO2-sand and pure water in DC electric fuse
Taihei Kobayashi; Naoto Kodama; Sota Nonoyama; Yasunobu Yokomizu; Yuki Inada
Japanese Journal of Applied Physics, Volume：64, Number：7, First page：076002, Last page：076002, Jul. 2025, [Reviewed], [Last, Corresponding]
Abstract
This paper presents a direct-current (DC) arc quenching experiment using SiO2-sand, a conventional DC arc quenching medium, under a 1.3 kA/100 V condition. Based on the experiment, we experimentally clarified that the drawback of the SiO2-sand was its low-performance in the current limiting rate |di/dt| at a low-current phase. Therefore, through theoretical calculation of gas properties, we selected pure water (H2O) as a novel arc quenching medium that can overcome the drawback of the SiO2-sand. Then, we conducted a DC arc quenching experiment using H2O under the 1.3 kA/100 V condition. As an experimental result, the H2O utilization successfully increased |di/dt| at the low-current phase. For instance, |di/dt| under the H2O condition was 1000 A ms−1, which was higher than 200 A ms−1 under the SiO2-sand condition. This high |di/dt| under the H2O condition arises from high arc resistance at the low-current phase. The present result is beneficial for improving the DC interruption performance of electric fuses.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.35848/1347-4065/ade83b
DOI ID：10.35848/1347-4065/ade83b, ISSN：0021-4922, eISSN：1347-4065 - Improving the Practicality of Innovative DC Circuit Breakers Using Linear Motors
Reon Sasaki; Wataru Ohnishi; Naoto Kodama; Yusuke Nakano; Shungo Zen; Yasushi Yamano; Yuki Inada
IEEJ Transactions on Industry Applications, Volume：145, Number：7, First page：506, Last page：513, Jul. 2025, [Reviewed], [Last, Corresponding]
Institute of Electrical Engineers of Japan (IEE Japan), Scientific journal
DOI：https://doi.org/10.1541/ieejias.145.506
DOI ID：10.1541/ieejias.145.506, ISSN：0913-6339, eISSN：1348-8163 - Two-dimensional electron density imaging of nanosecond-pulsed arc plasma in supercritical CO2
Tomohiro Furusato; Mitsuru Sasaki; Yuki Inada
Journal of Physics D: Applied Physics, Volume：58, Number：25, First page：255203, Last page：255203, Jun. 2025, [Reviewed], [Last]
Abstract
Until now, the plasma parameters of supercritical (SC) fluids have remained largely unknown. In this study, two-dimensional electron density distributions were observed using Shack–Hartmann sensors for nanosecond-pulsed arc plasma in SC-CO2 (7.38 MPa) and high-pressure CO2 (1.59 MPa) generated in a 1 mm needle-to-plane electrode. The maximum electron density in SC-CO2 reached 1026 m−3, which was several times higher than that under the high-pressure CO2 (1.59 MPa), and was several-order higher than that of a typical arc discharge under vacuum (1019−22 m−3) and the atmospheric-pressure gas phase (1022−24 m−3). We investigated difference of the electron density decay characteristics between the SC and high-pressure CO2. The electron density for the SC CO2 has a longer decaying time constant than the high-pressure CO2, because the arc discharge under the SC CO2 maintains the arc temperature due to radiative re-absorption and one-order-smaller diffusion coefficient of the SC medium in contact with the plasma than that of the high-pressure phase. The results provide a database for numerical simulations of the pulsed-arc discharge in SC CO2 in the future.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.1088/1361-6463/ade1e7
DOI ID：10.1088/1361-6463/ade1e7, ISSN：0022-3727, eISSN：1361-6463 - Concept Proof of Voltage Suppression across
IGBT Application for Fuse‐Current‐Limiting HybridDCCBs
Yuki Okegawa; Hu Long; Yubin He; Shungo Zen; Nozomi Takeuchi; Wataru Ohnishi; Yusuke Nakano; Naoto Kodama; Yuki Inada
IEEJ Transactions on Electrical and Electronic Engineering, Volume：20, Number：12, First page：1973, Last page：1981, May 2025, [Reviewed], [Last, Corresponding]
Abstract
DC power systems require reliable and cost‐effective DC circuit breakers (DCCBs). In a previous study, we introduced a hybrid DCCB featuring a current‐limiting fuse, insulated gate bipolar transistor (IGBT), and a varistor connected in parallel. However, this DCCB could not seamlessly mitigate IGBT voltage stress caused by factors such as the arc voltage induced by the fuse during current limitation, the transient recovery voltage during current interruption, and the source voltage. Traditionally, multiple IGBT connections in series have been utilized to address the risk of IGBT breakdown caused by overvoltage. However, this method may lead to voltage imbalances among the serially connected IGBTs, causing them to break. In this study, we present a novel commutation‐path design for DCCBs that incorporates a vacuum contactor (VC) connected in series with the IGBT, alongside a capacitor connected in parallel with the IGBT path. The inclusion of the VC reduces the voltage across the IGBT; the inclusion of the parallel capacitor also reduces it at the moment of current interruption. This new commutation path design enables the voltage across the IGBT to be suppressed below original design requirements throughout the entire interruption process. © 2025 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.
Wiley, Scientific journal
DOI：https://doi.org/10.1002/tee.70073
DOI ID：10.1002/tee.70073, ISSN：1931-4973, eISSN：1931-4981 - Optical design of spectral filtering system in sequentially timed all-optical mapping photography for enhancing temporal resolution
Keitaro Shimada; Kohei Azuma; Yuki Inada; Keiichi Nakagawa
Review of Scientific Instruments, Volume：96, Number：5, May 2025, [Reviewed]
Ultrafast imaging is crucial for understanding phenomena in the femtosecond to nanosecond time domains. Among ultrafast imaging techniques, sequentially timed all-optical mapping photography utilizing spectral filtering enables single-shot acquisition of ultrafast images with high spatial resolution and high quality. However, conventional designs based on Fourier optics struggle to achieve high temporal resolution while maintaining high pixel resolution, because the spatial-spectral dependence in this configuration makes laser wavelengths within each frame broad, resulting in longer exposure times. Here we propose an optical design that minimizes the bandwidth of laser wavelengths within each frame to achieve high temporal resolution by collimating the beam incident on the diffractive optical element. Numerical analysis showed that increasing the magnification of the imaging system before the diffractive optical element sufficiently narrows the bandwidth within each frame compared to the conventional designs. We experimentally demonstrated the effectiveness of the proposed configuration, achieving a bandwidth of 0.9 nm and a wavelength interval of 2.1 nm. These spectral properties enabled imaging with a 1.4 ps frame interval and an exposure time of 0.8 ps, which is 40% of the exposure time in the conventional Fourier configuration with similar setup parameters. Furthermore, the proposed configuration maintained a high pixel resolution of 480 pixels × 480 pixels for each of the five frames and was successfully applied to visualize laser ablation of glass. This article presents a highly spatiotemporally resolved imaging method for the detailed analysis of ultrafast phenomena such as laser ablation, shockwaves, and electric discharges.
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/5.0240730
DOI ID：10.1063/5.0240730, ISSN：0034-6748, eISSN：1089-7623 - Massive, long-time generation of OH(X) in ball lightning discharge
Y. Shibuya; M. Maeyama; Y. Inada
Physics of Plasmas, Volume：32, Number：4, First page：042110, Apr. 2025, [Reviewed], [Last, Corresponding]
Three-dimensional dynamics of an OH(X) density and gas temperature in a ball lightning discharge were measured by broadband UV absorption spectroscopy. The maximum radius of the OH(X) density distribution was 40 mm, and the absolute number density remained approximately 1022 m−3 even at 35 ms after the energy input to the discharge was completed. The density profiles of OH(X) revealed that the density in the outer region of the discharge was higher than that in the central region during the energy supply to the discharge. Conversely, the central temperature was higher than the outside. The ball lightning discharge was found to be capable of producing 3×1014 molecules of OH(X) per 1 W, which is about 1000 times more efficient than corona and dielectric-barrier discharges in the atmospheric pressure air. The ability of the ball lightning discharge to supply large amounts of OH radicals for long time periods presented the possibility of its wide application as a plasma source for the decomposition and control of pollutants in the atmospheric pressure air.
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/5.0251196
DOI ID：10.1063/5.0251196, ISSN：1070-664X, eISSN：1089-7674 - Single-shot ultrafast multiview imaging based on temporal wavelength division for capturing volumetric dynamics in femtosecond to nanosecond timescales
Keitaro Shimada; Yuki Inada; Keiichi Nakagawa
Real-time Measurements, Rogue Phenomena, and Single-Shot Applications X, First page：12, Last page：12, Mar. 2025, [Reviewed]
SPIE, International conference proceedings
DOI：https://doi.org/10.1117/12.3039256
DOI ID：10.1117/12.3039256 - Simultaneous Observation of Micro Current and Small Metallic Particles Preceding Non-Sustained Disrupted Discharge in Vacuum
R. Ito; Y. Yamano; A. Daibo; Y. Himata; N. Asari; Y. Niwa; Y. Sasaki; Y. Inada
IEEE Transactions on Dielectrics and Electrical Insulation, First page：1, Last page：1, 2025, [Reviewed], [Last, Corresponding]
Institute of Electrical and Electronics Engineers (IEEE), Scientific journal
DOI：https://doi.org/10.1109/tdei.2025.3628285
DOI ID：10.1109/tdei.2025.3628285, ISSN：1070-9878, eISSN：1558-4135 - Single-shot ultrafast imaging of plasma dynamics induced by dual-angle ultrashort laser pulses with subpicosecond delay
Keitaro Shimada; Takao Saiki; Yuki Inada; Keiichi Nakagawa
Japanese Journal of Applied Physics, Volume：63, Number：11, First page：110901, Last page：110901, Nov. 2024, [Reviewed]
Abstract
Spatiotemporal manipulation of ultrashort laser pulses is crucial for enhancing laser processing and phonon generation. Optimization of these applications requires ultrafast visualization of the underlying processes. In this study, we induced laser ablation using spatiotemporally manipulated double pulses focused from two angles onto a glass surface with a 0.7 ps interval, and captured the images of its dynamics with 5 sequential frames at a frame interval of 0.8 ps. The observed dynamics suggest that the laser profile reflected on the glass surface is influenced by its topography, which in turn affects the behavior of air breakdown plasmas.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.35848/1347-4065/ad8999
DOI ID：10.35848/1347-4065/ad8999, ISSN：0021-4922, eISSN：1347-4065 - Fault and Load Current Interruption in Low-Voltage System Using Fuse-Semiconductor Current-Limiting Circuit Breaker
Yuki Inada; Shungo Zen; Wataru Ohnishi; Naoto Kodama; Yusuke Nakano; Yasuhiro Takada; Reon Sasaki; Yuta Miyaoka; Kosuke Tsukamoto; Keiya Yamada; Yasushi Yamano
IEEJ Transactions on Industry Applications, Volume：144, Number：6, First page：502, Last page：508, Jun. 2024, [Reviewed], [Lead, Corresponding]
Institute of Electrical Engineers of Japan (IEE Japan), Scientific journal
DOI：https://doi.org/10.1541/ieejias.144.502
DOI ID：10.1541/ieejias.144.502, ISSN：0913-6339, eISSN：1348-8163 - Optimized Sequence Control of a Fuse-Semiconductor Hybrid Circuit Breaker through Real-Time Fuse State Estimation.
Songah Shin; Reon Sasaki; Yusuke Nakano; Naoto Kodama; Shungo Zen; Yasushi Yamano; Yuki Inada; Wataru Ohnishi
IECON, First page：1, Last page：6, 2024
International conference proceedings
DOI：https://doi.org/10.1109/IECON55916.2024.10905360
DOI ID：10.1109/IECON55916.2024.10905360, DBLP ID：conf/iecon/ShinSNKZYIO24 - Single-shot optical imaging with spectrum circuit bridging timescales in high-speed photography
Takao Saiki; Keitaro Shimada; Ayumu Ishijima; Hang Song; Xinyi Qi; Yuki Okamoto; Ayako Mizushima; Yoshio Mita; Takuya Hosobata; Masahiro Takeda; Shinya Morita; Kosuke Kushibiki; Shinobu Ozaki; Kentaro Motohara; Yutaka Yamagata; Akira Tsukamoto; Fumihiko Kannari; Ichiro Sakuma; Yuki Inada; Keiichi Nakagawa
Science Advances, Volume：9, Number：51, Dec. 2023, [Reviewed]
Single-shot optical imaging based on ultrashort lasers has revealed nonrepetitive processes in subnanosecond timescales beyond the recording range of conventional high-speed cameras. However, nanosecond photography without sacrificing short exposure time and image quality is still missing because of the gap in recordable timescales between ultrafast optical imaging and high-speed electronic cameras. Here, we demonstrate nanosecond photography and ultrawide time-range high-speed photography using a spectrum circuit that produces interval-tunable pulse trains while keeping short pulse durations. We capture a shock wave propagating through a biological cell with a 1.5-ns frame interval and 44-ps exposure time while suppressing image blur. Furthermore, we observe femtosecond laser processing over multiple timescales (25-ps, 2.0-ns, and 1-ms frame intervals), showing that the plasma generated at the picosecond timescale affects subsequent shock wave formation at the nanosecond timescale. Our technique contributes to accumulating data of various fast processes for analysis and to analyzing multi-timescale phenomena as a series of physical processes.
American Association for the Advancement of Science (AAAS), English, Scientific journal
DOI：https://doi.org/10.1126/sciadv.adj8608
DOI ID：10.1126/sciadv.adj8608, eISSN：2375-2548 - Spectrum shuttle for producing spatially shapable GHz burst pulses
Keitaro Shimada; Ayumu Ishijima; Takao Saiki; Ichiro Sakuma; Yuki Inada; Keiichi Nakagawa
Advanced Photonics Nexus, Volume：3, Number：01, Dec. 2023, [Reviewed]
SPIE-Intl Soc Optical Eng, English, Scientific journal
DOI：https://doi.org/10.1117/1.apn.3.1.016002
DOI ID：10.1117/1.apn.3.1.016002, ISSN：2791-1519 - Internal State of Fuse Arc Differentiating Interruption Success and Failure in Fuse‐Semiconductor
DC Circuit Breaker
Yuta Miyaoka; Mitsuaki Maeyama; Yasushi Yamano; Yuki Inada
IEEJ Transactions on Electrical and Electronic Engineering, Volume：19, Number：1, First page：41, Last page：50, Oct. 2023
For the realization of sustainable society installing renewable energy sources, we have proposed a compact, low‐cost, versatile DC circuit breaker that combines a fuse and a power semiconductor. However, even under the same interruption conditions, there are cases where the interruption success and failure are observed probabilistically; the reason for this is still unknown. In the interruption failure, thermal reignition of an arc discharge occurs inside the fuse under transient recovery voltage. In this study, the spatiotemporal dynamics of the fuse arc was diagnosed for both interruption success and failure by a voltage–current waveform recording, high‐speed arc‐emission videography and borescope‐integrated optical emission spectroscopy, in order to identify the difference between the interruption success and failure. The waveform recording and videography demonstrated that at the arc initiation inside the fuse, the radial arc length for the interruption failure was longer than the interruption success. In the current interruption phase, the radial arc length was still longer, axial arc length was shorter, and arc column resistance was lower for the interruption failure. Further, the optical emission spectroscopy showed that localized regions with higher temperature and electrical conductivity existed for the failure in the current interruption phase. From these results, the dominant factors differentiating interruption success and failure were identified as the arc shape and electrical conductivity of the arc. To improve the interruption performance of the fuse and our DC circuit breaker, it is effective to increase the axial arc length, suppress the radial arc length, and reduce the electrical conductivity of the arc. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.
Wiley, Scientific journal
DOI：https://doi.org/10.1002/tee.23928
DOI ID：10.1002/tee.23928, ISSN：1931-4973, eISSN：1931-4981 - Spatiotemporal evolution of electrical conductivity in current-limiting-fuse arc
Yuki Inada; Yusuke Fukai; Naoki Takayasu; Yusuke Nakano; Shungo Zen; Wataru Ohnishi; Yasushi Yamano; Mitsuaki Maeyama; Naoto Kodama
Journal of Physics D: Applied Physics, Volume：56, Number：50, First page：505205, Last page：505205, Oct. 2023
Abstract
To improve the interruption capacity of a current-limiting fuse, a detailed diagnosis of the spatial electrical conductivity distribution inside the fuse arc under the current limiting phase around current zero is required, because this distribution determines the distribution of transient recovery voltage inside the fuse. However, well-established methodologies applicable to fuse arcs are lacking, so the spatial distribution remains unknown. This study presents a borescope-integrated spectroscopic system that simultaneously obtains single-shot recordings of the axial distributions of the electron density and arc temperature in the fuse arc just before extinction. Combining the electron densities and arc temperatures, we can identify the fuse arc composition and hence calculate the axial electrical conductivity distribution under the first Chapman–Enskog approximation. The electrical conductivity provided by this systematic methodology includes no large uncertainties, thus demonstrating its superiority against previous estimation methods of the electrical conductivity.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.1088/1361-6463/acf9b2
DOI ID：10.1088/1361-6463/acf9b2, ISSN：0022-3727, eISSN：1361-6463 - Single-shot ultrafast dual-view imaging of shock waves in parallel laser processing
Takao Saiki; Keitaro Shimada; Ichiro Sakuma; Yuki Inada; Keiichi Nakagawa
Applied Physics Express, Volume：16, Number：9, First page：092004, Last page：092004, Sep. 2023, [Reviewed]
Abstract
Single-shot ultrafast optical imaging has revealed various non-repetitive processes, but it has conventionally provided only single-view measurements. Here, we demonstrate a single-shot ultrafast dual-view imaging technique by monitoring shock waves in laser processing of glass using single or parallelized excitation pulses. We visualize the spatiotemporal evolution of shock waves in air at 0.5 Gfps with five frames in both top and side views, indicating the velocity anisotropy and interaction of shock waves. Our technique can contribute to a comprehensive understanding not only of shock wave dynamics but also of other spatially complex ultrafast phenomena including laser-induced plasma and electrical discharge.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.35848/1882-0786/acfa62
DOI ID：10.35848/1882-0786/acfa62, ISSN：1882-0778, eISSN：1882-0786 - Two-dimensional electron density measurement of pulsed positive secondary streamer discharge in atmospheric-pressure air
Yuki Inada; Atsushi Komuro; Ryo Ono; Akiko Kumada; Kunihiko Hidaka; Mitsuaki Maeyama
JOURNAL OF PHYSICS D-APPLIED PHYSICS, Volume：52, Number：18, May 2019, [Reviewed]
English, Scientific journal
DOI：https://doi.org/10.1088/1361-6463/ab0725
DOI ID：10.1088/1361-6463/ab0725, ISSN：0022-3727, eISSN：1361-6463, Web of Science ID：WOS:000460136800002
- Verification of Fuse-Semiconductor Commutation Based on Online Estimation of Fuse Current-Limiting Status
LIU Yecheng; SASAKI Reon; OHNISHI Wataru; KOSEKI Takafumi; ZEN Shungo; YAMANO Yasushi; INADA Yuki
電気学会全国大会講演論文集(CD-ROM), Volume：2024, 2024
J-Global ID：202402278002552527
- レーザーによる大気圧空気中ストリーマ放電の電子密度・電界計測
稲田 優貴
Mar. 2025, [Invited]
Invited oral presentation - 球雷放電によるインジゴカルミン分解処理特性
加世田 倭杜; 前山 光明; 稲田 優貴
Mar. 2025
Oral presentation - 平板電極を用いたMCS放電の開発とその放電特性
浜坂 大輔; 前山 光明; 稲田 優貴
Mar. 2025
Oral presentation - 感度と速度を極めた中赤外画像診断による革新的プラズマの創出
稲田 優貴
Mar. 2025, [Invited]
Invited oral presentation - 超臨界 CO2中パルスアーク放電の電流波形の FFT 解析
田中 泰生; 藤田 真一; 手島 大智; 古里 友宏; 稲田 優貴
Mar. 2025
Oral presentation - Single-shot ultrafast multi-view imaging based on temporal wavelength division for capturing volumetric dynamics in femtosecond to nanosecond timescales
Keitaro Shimada; Yuki Inada; Keiichi Nakagawa
SPIE Photonics West 2025, Jan. 2025
Jan. 2025 - Jan. 2025, Oral presentation - 直流遮断時にヒューズ内で発生するフルグライト空洞と遮断限界の相関
大山 響紀; 山納 康; 稲田 優貴; 松本 章史; 松本 剛明
Jan. 2025
Oral presentation - 超臨界CO₂中の過渡的アーク放電の消失過程及び電圧電流波形の解析
手島 大智; 藤田 真一; 田中 泰生; 稲田 優貴; 古里 友宏
Jan. 2025
Oral presentation - プラズマ内における活性種生成機構の解明に向けた電子密度・電界計測
稲田 優貴
Jan. 2025
Nominated symposium - 超高速ダイナミクス診断技術に基づくプラズマ現象の理解
稲田 優貴
Dec. 2024
Keynote oral presentation - Active Control of Pyro-Fuse in Circuit Breaker with State Estimation of Current-Limiting Fuse
TAICHI NAKANO; Reon Sasaki; Wataru Ohnishi; Yasushi Yamano; Yuki Inada
IECON2024
Nov. 2024 - Nov. 2024, English, Oral presentation - Optimized sequence control of a fuse-semiconductor hybrid circuit breaker through real-time fuse state estimation
SONGAH SHIN; Reon Sasaki; Yusuke Nakano; Shungo Zen; Naoto Kodama; Yasushi Yamano; Yuki Inada; Wataru Ohnishi
IECON2024
Nov. 2024 - Nov. 2024, English, Oral presentation - Electron density and electric field measurement of space-time-controlled single-filament streamer discharge in atmospheric-pressure air
Yuki Inada
GEC2024 The 77th Annual Gaseous Electronics Conference, Oct. 2024, [Invited]
Sep. 2024 - Oct. 2024, English, Invited oral presentation - Computational Study of Turbulence Generation Around Arc Plasma Sustained in a Converging-Diverging Cylinder
Masaya Shigeta; Yuki Inada; Yasunori Tanaka
GEC2024 The 77th Annual Gaseous Electronics Conference
Sep. 2024 - Oct. 2024, English, Oral presentation - E-FISH法を用いた空気ストリーマ放電の電界計測
稲田 優貴
Sep. 2024, [Invited]
Invited oral presentation - 高速ICCDカメラによる超臨界CO2アーク放電プラズマの観測
手島 大智; 藤田 真一; 稲田 優貴; 古里 友宏
Sep. 2024
Oral presentation - 数値シミュレーションによる収縮拡大ノズル内SF6系流れ場のアークプラズマ誘発対流熱輸送の研究
茂田 正哉; 稲田 優貴; 田中 康規
Sep. 2024
Oral presentation - スペックルによる真空アーク消弧前後の電極表⾯粗さ測定
及川 拓真; 稲田 優貴; 前山 光明
Sep. 2024
Oral presentation - MHCD ⽤絶縁体の違いによる MCS 放電特性の⽐較,” 第48回静電気学会全国大会
小島 舞斗; 稲田 優貴; 前山 光明
Sep. 2024
Oral presentation - 真空アークカソードスポットの紫外域発光分光
國森 敬斗; 稲田 優貴; 前山 光明; 大坊 昂; 浅利 直紀; 佐々木 遥; 丹羽 芳充
Sep. 2024
Oral presentation - 平板電極を用いた２次元的並列なMCS放電に関する研究
浜坂 大輔; 前山 光明; 稲田 優貴
Sep. 2024
Oral presentation - モーションコントロール技術の異分野融合と新領域への展開ー電力・鉄道分野への展開
佐々木 怜音; 大西 亘; 兒玉 直人; 中野 裕介; 全 俊豪; 山納 康; 稲田 優貴
Aug. 2024
Oral presentation - Experimental Validation of Optimized Sequence Control for Fuse Current Under Diverse Conditions
SHIN SONGAH; 佐々木 怜音; 大西 亘; 稲田 優貴; 山納 康; 中野 裕介; 兒玉 直人; 全 俊豪
Aug. 2024
Oral presentation - 限流ヒューズを活用した直流遮断器の開発
山田 圭矢; 小林 泰平; 山田 雄大; 山納 康; 稲田 優貴
Aug. 2024
Oral presentation - 限流ヒューズ内で生じる直流アークの遮断に対するポリイミド樹脂と純水の試適用
兒玉 直人; 野々山 颯太; 横水 康伸; 小林 泰平; 山田 圭矢; 山田 雄大; 前山 光明; 山納 康; 稲田 優貴
Aug. 2024
Oral presentation - 純水を消弧材とした限流ヒューズの遮断試験
小林 泰平; 兒玉 直人; 山田 圭矢; 山田 雄大; 野々山 颯太; 前山 光明; 山納 康; 稲田 優貴
Aug. 2024
Oral presentation - Single-shot THz-bursts-in-GHz-burst (BiBurst) imaging of picosecond dynamics in each GHz burst laser ablation
Keitaro Shimada; Denisa Todorache; Rikako Tanaka; Takao Saiki; Yuki Inada; Keiichi Nakagawa
The 23rd International Conference On Ultrafast Phenomena
Jul. 2024, English, Oral presentation - プラズマの電子電解加速から活性種生成・反応に至る一連のプロセス解明
稲田 優貴
Jun. 2024
Public discourse - Numerical and experimental study of spectrum shuttle for generating GHz burst pulses without sacrificing spectral ranges in advanced ultrafast imaging
K. Shimada; A. Ishijima; T. Saiki; I. Sakuma; Y. Inada; K. Nakagawa
the 26th Photonics North Conference
May 2024, English, Oral presentation - Laser diagnostics of single-filament streamer discharge for numerical simulation validation
R. Ono; K. Tomita; Y. Inada; A. Komuro
FLTPD XV Frontiers in Low Temperature Plasma Diagnostics, [Invited]
Apr. 2024, English, Invited oral presentation - 高速イメージングで構築したビッグデータの活用法探索
稲田 優貴
Apr. 2024, [Invited]
Invited oral presentation
■ Research projects
- 高電圧直流遮断用ヒューズを実現する液体・固体複合型アーク消弧媒体の開発
01 Apr. 2024 - 31 Mar. 2027
Grant amount(Total)：18590000, Direct funding：14300000, Indirect funding：4290000
Grant number：24K00866 - 電子の超高速ダイナミクス診断技術を駆使した放電活性種の選択的・大量生成法の創成
01 Apr. 2024 - 31 Mar. 2027
Grant amount(Total)：18590000, Direct funding：14300000, Indirect funding：4290000
Grant number：24K00863 - Creation of electron density diagnostic technique for plasma in supercritical CO2 for innovative CO2 decomposition technology
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 01 Apr. 2023 - 31 Mar. 2026
Nagasaki University
Grant amount(Total)：19500000, Direct funding：15000000, Indirect funding：4500000
Grant number：23K26097 - International collaborative research on highly sensitive fiber optic sensor for early detection of dielectric breakdown signs in power line
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)), 07 Oct. 2021 - 31 Mar. 2024
Tokyo University of Agriculture and Technology
Grant amount(Total)：17680000, Direct funding：13600000, Indirect funding：4080000
Grant number：21KK0067 - 卓越したプラズマ可視化技術に基づく放電活性種の生成機構解明
01 Apr. 2021 - 31 Mar. 2024
Grant amount(Total)：17810000, Direct funding：13700000, Indirect funding：4110000
Grant number：21H01304 - Elucidation of Vacuum Arc Phenomena for Realization of Ultra-High Voltage DC Vacuum Circuit Breakers
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 01 Apr. 2018 - 31 Mar. 2021
Kumada Akiko, The University of Tokyo
Grant amount(Total)：17550000, Direct funding：13500000, Indirect funding：4050000
We developed the system to measure the temperature distribution and particle (electron, metal vapor, and ion) density distribution of vacuum arc plasma with high temporal and spatial resolution, and measured these arc phenomena under the conditions of varying the composition ratio and microstructure of the alloy used for the electrode and the superimposed current waveform injected from an external circuit at the time of arc interruption. Arc phenomena were measured under different conditions. Although the accuracy of the electrode temperature measurement remained to be improved, we succeeded in visualizing the state of metal vapor supply at the current zero point and developed a model that qualitatively explains the vapor supply and diffusion in the arc interruption process.
Grant number：18H01419 - Electron density visualization technique for elucidation of production mechanism of reactive species
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 01 Apr. 2018 - 31 Mar. 2021
Inada Yuki, Saitama University
Grant amount(Total)：17940000, Direct funding：13800000, Indirect funding：4140000
The reactive species generated in atmospheric-pressure nonthermal plasma, e.g. a streamer discharge, has been expected to be utilized in wide range application fields, such as environmental pollution control, plasma-assisted ignition and combustion, plasma medicine, and plasma agriculture. However, the production mechanism of the reactive species is not fully understood. This difficulty is partially caused by the fact that the electron density determination using conventional measurement systems has been extremely difficult due to spatial non-reproducibility of the atmospheric-pressure nonthermal plasma and the low electron density in the plasma. Here, we developed a highly sensitive, single-shot electron density sensor capable of visualizing a two-dimensional electron density distribution over the streamer discharge in an unmeasurable phase.
Grant number：18H01418 - Suppression Method of Disruptive Vacuum Breakdown for Next-Generation DC Transmission and Distribution Power Network
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Challenging Research (Exploratory), 29 Jun. 2018 - 31 Mar. 2020
Inada Yuki, Saitama University
Grant amount(Total)：6240000, Direct funding：4800000, Indirect funding：1440000
We developed a shadowgraph imaging system with a ～100-ns time resolution and ～1-μs framing rate, which enabled the world first capturing of a vacuum breakdown phenomenon induced by a microparticle. In our series of observations, the vacuum breakdown was found to be caused by two types of microparticles: those with diameters of ～100μm and ～10μm. Further, all the particle-induced vacuum breakdowns occurred at the time of particle collision with the negative electrode. In addition, the decrease in the particle size was not observed during the particle flight between the electrodes or at the particle collision with the negative electrode.
Grant number：18K18845 - Development of an atmospheric pressure plasma source capable of generating massive amounts of chemically active species and evaluation of decomposition performance for refractory solutions
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), 01 Apr. 2015 - 31 Mar. 2018
MAEYAMA Mitsuaki; SUZUKI Hitoshi; TAKATORI Yoshimitsu; TOKAJI Kimio; IKEDA Kazumi; SUZUKI Fumiya; IMAMURA Kengo; MORI Yuuya; MIYAMOTO Rei; KANAMORI Yasotoshi, Saitama University
Grant amount(Total)：4420000, Direct funding：3400000, Indirect funding：1020000
By the ball-lightning discharge, first announced in 2002, decomposition performances and its abilities generating chemical active species, such as ozon and OH radicals, depending on the discharge polarities were studied experimentally.
As a result, its performance was evaluated by decomposition of indigo carmine dye and acetic acid,which are widely used for evaluation of water treatment. And it can be estimated about 1/2 of the maximum efficiency obtained by other water treatment, as initial results. We also found a difference between the decomposition characteristics due to the polarity of discharge and its active species. Furthermore, the decomposition process was examined by two-dimensional measurement of luminescence from active species and liquid chromatography analysis.
Grant number：15K05932 - Highly sensitive and temporally resolved electron density measurement of discharge plasma for effective and selective generation of reactive species
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (A), 01 Apr. 2015 - 31 Mar. 2018
INADA Yuki, Saitama University
Grant amount(Total)：23400000, Direct funding：18000000, Indirect funding：5400000
The streamer discharge in open air is one of the important types of atmospheric-pressure non-thermal plasma, and it has been attracting interest in a wide range application fields: environmental pollution control, plasma-assisted ignition and combustion, and plasma medicine. However, the processes by which reactive species are produced in air streamers are not fully understood because the electron density determination using conventional measurement
systems has been extremely difficult.
In order to overcome the difficulty, we developed novel electron density sensors capable of visualizing two-dimensional electron density distributions from single-shot recordings under sensitivity of 10^20m^-3 and temporal resolution of 1ns. These sensors were successfully used for the electron density imaging over the air streamer discharges and production mechanisms of several reactive species were elucidated.
Grant number：15H05515 - Evolutionary study toward practical use of high-performance environmentally-friendly gas insulation system using CF3I gas
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), 01 Apr. 2013 - 31 Mar. 2016
Hidaka Kunihiko, The University of Tokyo
Grant amount(Total)：46800000, Direct funding：36000000, Indirect funding：10800000
CF3I gas is one of the alternatives for SF6. Its insulation performance is superior to SF6 in uniform field and its Global Warming Potential (GWP) is quite low as same as CO2. The electrical properties of CF3I and CF3I/N2, CF3I/CO2 and CF3I/SF6 mixtures are closely examined and the results show that CF3I can be used as SF6-substitute gas in Gas Insulated transmission-Line (GIL). A simple ranking method is proposed where the dielectric properties, saturated gas pressure, and GWP are taken into account in selecting the mixture ratio as pragmatic gas mixture to GIL. With this method, it turns out that CF3I(20%)/CO2(80%) or CF3I(20%)/N2(80%) gas mixtures are the reasonable choices. In addition, the applicability of these CF3I gas mixtures to the existing 275kV-GIL is evaluated through computation of cross sectional size of conductors based not only on insulation designing but also on thermal designing.
Grant number：25249028