Article
Automation & Control Systems
Danilo I. Brandao, Rhonei P. dos Santos, Waner Wodson A. G. Silva, Thiago R. Oliveira, Pedro Francisco Donoso-Garcia
Summary: This article proposes a centralized energy management approach for coordinated control of a hybrid ac/dc microgrid, aiming to improve efficiency and ensure uniform operation of energy storage units in different modes.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2021)
Review
Oceanography
Curtis Deutsch, Hartmut Frenzel, James C. McWilliams, Lionel Renault, Faycal Kessouri, Evan Howard, Jun-Hong Liang, Daniele Bianchi, Simon Yang
Summary: The study utilized a model to analyze the mean state and variability of marine biogeochemical and ecosystem processes in the California Current System from 1995 to 2010. The model simulations captured well the seasonal and interannual variations in biogeochemical properties and rates.
PROGRESS IN OCEANOGRAPHY
(2021)
Article
Astronomy & Astrophysics
Neeraj Jain, Jorg Buechner, Horia Comisel, Uwe Motschmann
Summary: The unsolved issue of collisionless dissipation of macroscopic energy into heat in space and astrophysical plasmas is discussed, revealing the formation of kinetic scale current sheets in turbulent plasmas. The instabilities in these current sheets are shown to provide collisionless dissipation and influence turbulence, with spatial gradients and non-Maxwellian velocity distributions providing free energy sources. Simulation results support the formation of ion-scale current sheets primarily by electron shear flows, with significant variations in electron and ion flow vorticities within these sheets.
ASTROPHYSICAL JOURNAL
(2021)
Article
Physics, Fluids & Plasmas
S. Kobayashi, K. Nagasaki, K. Hada, T. Stange, H. Okada, T. Minami, S. Kado, S. Ohshima, K. Tokuhara, Y. Nakamura, A. Ishizawa, Y. Suzuki, M. Osakabe, T. Murase, S. Konoshima, T. Mizuuchi
Summary: The study investigates the role of pre-ionization using non-resonant 2.45 GHz microwave heating in plasma start-up of neutral beam injection for heliotron configurations. Experimental results show that rapid electron heating towards burn-through of low-Z impurities occurs when the seed plasma density produced by non-resonant heating is sufficient for plasma start-up. Proper timing of gas fuelling is critical for plasma expansion as beam fuelling is not significant.
Article
Physics, Multidisciplinary
Bornesson Kharkongor, S. S. Pohlong, Mangal C. Mahato
Summary: This study focuses on the net transport of particles in a potential-free system with a friction coefficient in the form of a traveling wave and driven by a zero-mean sinusoidal force. The direction and magnitude of the particle current heavily depend on the ratio of the frequencies of the friction coefficient and the periodic drive. Additionally, the impact of the amplitudes of the two periodic functions on the net current is also examined.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2021)
Article
Physics, Fluids & Plasmas
Anton V. Sudnikov, Ivan A. Ivanov, Anna A. Inzhevatkina, Mikhail V. Larichkin, Konstantin A. Lomov, Vladimir V. Postupaev, Mikhail S. Tolkachev, Viktor O. Ustyuzhanin
Summary: The paper presents experimental results from the SMOLA device, which is the first facility with a helical mirror section of the magnetic system. The experiments demonstrated the effectiveness of the helical mirror in suppressing axial plasma flow and pinching plasma density to the axis, providing good agreement with theoretical predictions.
JOURNAL OF PLASMA PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
J. Varela, K. Nagasaki, S. Kobayashi, K. Nagaoka, P. Adulsiriswad, A. Cappa, S. Yamamoto, K. Y. Watanabe, D. A. Spong, L. Garcia, Y. Ghai, J. Ortiz
Summary: The effect of electron cyclotron heating (ECH) on the stability of Alfven eigenmodes (AEs) and energetic particle modes (EPMs) triggered by energetic ions in Heliotron J plasma was analyzed in this study. The analysis used the FAR3d code to simulate a reduced MHD model for the thermal plasma coupled with a gyrofluid model for the energetic particle species. The simulations reproduced the observed stability trends of AE/EPM as electron temperature (T-e) increased, modifying various parameters.
Article
Materials Science, Multidisciplinary
Dapeng Yao, Shuichi Murakami
Summary: This paper theoretically demonstrates that a current is induced by chiral phonons representing the microscopic local rotation of atoms in a helical crystal. The time average of the current along the helical axis is finite in the metallic phase but vanishes in the insulating phase. On the other hand, the current in the hexagonal plane changes with time, but its time average vanishes due to the threefold rotation space-time symmetry of the system.
Article
Physics, Multidisciplinary
Debjani Das Gupta, Santanu K. Maiti
Summary: We report the phenomenon of spin current rectification in an antiferromagnetic helix under a transverse electric field within a tight-binding framework based on Green's function formalism. The aperiodic site energies induced by the electric field break the symmetry among up and down spin sub-Hamiltonians, leading to different spin specific junction currents in two bias polarities and resulting in spin current rectification. This behavior is not observed in the absence of either helicity or electric field. Our findings suggest a new route for achieving spin current rectification in helical magnetic systems with vanishing net magnetization.
Article
Chemistry, Physical
Kaichen Yu, Jinbiao Chen, Xintai Xie, Kaiji Lin, Jie Li, Zhicong Shi
Summary: Using a silver coated two-dimensional copper net and an artificial LiF-rich solid electrolyte interphase, the issues of lacking active sites and uneven lithium deposition in anode-free lithium metal batteries can be addressed. This approach provides higher cycling stability and coulombic efficiency at high current densities.
SURFACES AND INTERFACES
(2022)
Article
Engineering, Electrical & Electronic
Fengxiang Wang, Yao Wei, Hector Young, Dongliang Ke, Haotian Xie, Jose Rodriguez
Summary: In this article, a continuous-control-set model-free predictive fundamental current control (MF-PFCC) strategy is proposed for the permanent magnet synchronous motor driving system. This strategy reduces the influence of unnecessary current harmonics caused by the control strategy itself and improves the accuracy of the data-driven model.
IEEE TRANSACTIONS ON POWER ELECTRONICS
(2023)
Article
Instruments & Instrumentation
P. Zhang, S. Ohshima, H. Zhao, C. Deng, S. Kobayashi, S. Kado, T. Minami, R. Matoike, A. Miyashita, A. Iwata, Y. Kondo, D. Qiu, C. Wang, M. Luo, S. Konoshima, S. Inagaki, H. Okada, T. Mizuuchi, K. Nagasaki
Summary: This paper presents a new 320 GHz solid-state source interferometer installed in the Heliotron J helical device for exploring the physics of high-density plasmas. The interferometry system allows for high time resolution measurements in the microsecond range and successfully measured electron density in high-density plasma experiments. The new system can be used for routine diagnostics.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2022)
Article
Environmental Sciences
Zhishun Guo, Lin Wu, Yabo Huang, Zhengwei Guo, Jianhui Zhao, Ning Li
Summary: This paper reviews the literature on water body extraction in SAR images over the past 30 years and proposes some suggestions for the SAR image waterbody extraction community. It summarizes the main ideas and characteristics of traditional water body extraction methods, especially traditional Machine Learning (ML) methods. It also summarizes the application and optimization of Deep Learning (DL) methods in water-body segmentation for SAR images at the pixel and image levels, with a focus on popular networks such as U-Net and novel networks such as the Cascaded Fully-Convolutional Network (CFCN) and River-Net. The paper concludes with an in-depth discussion of the limitations and challenges of DL for water-body segmentation and provides future trends.
Article
Instruments & Instrumentation
M. Kobayashi, S. Ohdachi, Y. Xu, W. Li, A. Shimizu, J. Cheng
Summary: A gas puff imaging system has been developed for measuring edge fluctuations in a large helical device. The system can simultaneously measure the spatial distribution of line ratios of He I, and obtain clear images.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2022)
Article
Physics, Fluids & Plasmas
G. Ruediger, M. Schultz, R. Hollerbach
Summary: The combination of azimuthal magnetic fields and super-rotation in Taylor-Couette flows of conducting fluids can be unstable against non-axisymmetric perturbations. The addition of a weak axial field component allows for axisymmetric perturbation patterns depending on the magnetic Prandtl number and boundary conditions. The typical growth time of the instability and the characteristic time scale of the axial migration of the axisymmetric mode are long compared with the rotation period, but short compared with the magnetic diffusion time.
JOURNAL OF PLASMA PHYSICS
(2021)
Article
Physics, Fluids & Plasmas
Masaki Osakabe, Hiromi Takahashi, Hiroshi Yamada, Kenji Tanaka, Tatsuya Kobayashi, Katsumi Ida, Satoshi Ohdachi, Jacobo Varela, Kunihiro Ogawa, Masahiro Kobayashi, Katsuyoshi Tsumori, Katsunori Ikeda, Suguru Masuzaki, Masahiro Tanaka, Motoki Nakata, Sadayoshi Murakami, Shigeru Inagaki, Kiyofumi Mukai, Mizuki Sakamoto, Kazunobu Nagasaki, Yasuhiro Suzuki, Mitsutaka Isobe, Tomohiro Morisaki, The Lhd Experiment Group
Summary: In recent deuterium experiments on the large helical device (LHD), we have explored techniques to increase the electron and ion temperatures in plasmas. We observed important phenomena such as the isotope effect in the formation of internal transport barrier and the simultaneous formation of edge transport barrier and divertor detachment. Additionally, the contributions of negative-ion based neutral beam injector research and tritium mass balance study to fusion reactor development are discussed.
Article
Physics, Fluids & Plasmas
M. Kobayashi, R. Seki, Y. Hayashi, T. Oishi, K. Tanaka, Y. Takemura, K. Ida, T. Kinoshita, K. Mukai, S. Morita, S. Masuzaki
Summary: This study examines the compatibility between good core plasma performance and divertor heat load mitigation by analyzing the interaction between cold edge plasma and core plasma transport, specifically the edge transport barrier (ETB), in LHD. It is found that the application of resonant magnetic perturbation (RMP) widens the edge stochastic layer and enhances impurity radiation, leading to stable detachment operation. However, as the detachment deepens, the resistive pressure gradient-driven MHD mode is excited, which degrades the ETB. Despite this, the core transport decreases to maintain the global plasma stored energy. Furthermore, a comparison between deuterium and hydrogen plasmas shows that deuterium plasmas exhibit better global confinement.
Article
Physics, Fluids & Plasmas
K. Ida, R. M. McDermott, C. Holland, M. J. Choi, L. M. Yu, T. Kobayashi, J. M. Kwon, Y. Kosuga
Summary: This conference report summarizes the contributions and discussions at the joint meeting of the 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop. The meeting focused on various aspects of transport and physics, including the isotope effect, turbulence spreading and coupling, interplay between magnetohydrodynamic topology/instability and turbulent transport, interaction between energetic particle driven instability and transport, and model reduction and experiments for validation.
Article
Physics, Multidisciplinary
G. Motojima, S. Masuzaki, T. Morisaki, K. Y. Watanabe, M. Kobayashi, K. Ida, R. Sakamoto, M. Yoshinuma, R. Seki, H. Nuga, T. Tsujimura, C. Suzuki, M. Emoto, Y. Tsuchibushi, T. Murase, Y. Takeiri
Summary: The study shows that divertor pumping can effectively control stable plasma density and electron temperature by changing the magnetic axis position, especially in high plasma electron density and inner magnetic axis configuration.
Article
Physics, Fluids & Plasmas
R. Lunsford, S. Masuzaki, F. Nespoli, N. Ashikawa, E. P. Gilson, D. A. Gates, K. Ida, G. Kawamura, T. Morisaki, A. Nagy, T. Oishi, M. Shoji, C. Suzuki, M. Yoshinuma
Summary: Controlled particulate injections have shown positive effects on plasma wall conditions, with experiments demonstrating improvement across a range of parameters. Successful injections are confirmed by both spectroscopic measurements and real-time camera signals, paving the way for further development of real-time boronization techniques.
Article
Physics, Multidisciplinary
M. Kobayashi, K. Tanaka, K. Ida, Y. Hayashi, Y. Takemura, T. Kinoshita
Summary: Turbulence spreading induced by magnetic fluctuation is observed at the boundary region of the large helical device. Density fluctuation excited at the sharp boundary cannot propagate into the boundary due to the blocking effect of pressure gradient. However, when magnetic fluctuation appears at the boundary, density fluctuation starts to penetrate the edge layer and the pressure gradient decreases. This increase in density fluctuation leads to the reduction of divertor heat load.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
T. I. Tsujimura, T. Kobayashi, K. Tanaka, K. Ida, K. Nagaoka, M. Yoshinuma, I. Yamada, H. Funaba, R. Seki, S. Satake, T. Kinoshita, T. Tokuzawa, N. Kenmochi, H. Igami, K. Mukai, M. Goto, Y. Kawamoto
Summary: A plasma with a quasi-steady-state hollow electron-temperature profile can be generated using off-axis electron cyclotron heating. The formation of this profile can be explained by adding the outward heat convection term to the diffusion term in the energy conservation equation. The non-locality of the non-diffusive contribution in electron thermal transport was directly observed.
PHYSICS OF PLASMAS
(2022)
Article
Multidisciplinary Sciences
H. Funaba, R. Yasuhara, H. Uehara, I. Yamada, R. Sakamoto, M. Osakabe, D. J. Den Hartog
Summary: Thomson scattering measurements using a high-repetition-rate laser have been conducted in the Large Helical Device. As an example, measurements at a 20 kHz repetition rate were performed in hydrogen pellet-injected plasmas. Signal processing methods were developed to evaluate electron temperature profiles at nearly 70 spatial points with time intervals of 50 μs. Electron density profiles were derived after Raman scattering calibration, and rapid changes in electron temperature and density profiles within 1 ms were observed.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Multidisciplinary
A. Matsuyama, R. Sakamoto, R. Yasuhara, H. Funaba, H. Uehara, I. Yamada, T. Kawate, M. Goto
Summary: Experimental observations show that adding a small fraction of neon to hydrogenic pellets enhances core density assimilation and reduces outward transport for low magnetic-field side injection.
PHYSICAL REVIEW LETTERS
(2022)
Article
Thermodynamics
S. Imagawa, K. Takahata
Summary: In this study, the residual magnetic field of the Large Helical Device was investigated. The source of the field was found to be the magnetization of the coils in the superconducting magnet system. The distribution of the residual field was measured at different vertical positions and the reduction in field from high current coils was calculated to be around 35%.
Article
Physics, Fluids & Plasmas
F. Nespoli, K. Tanaka, S. Masuzaki, N. Ashikawa, M. Shoji, E. P. Gilson, R. Lunsford, T. Oishi, K. Ida, M. Yoshinuma, Y. Takemura, T. Kinoshita, G. Motojima, M. Osakabe, N. Kenmochi, G. Kawamura, C. Suzuki, A. Nagy, A. Bortolon, N. A. Pablant, A. Mollen, N. Tamura, D. A. Gates, T. Morisaki
Summary: An improvement in the confinement regime of the Large Helical Device has been observed, characterized by reduced turbulent fluctuations, upon the injection of boron powder into the plasma. This article presents the experimental observations of increased plasma temperature and decreased turbulent fluctuations across the plasma cross section, using a larger database. Powder penetration modeling and analysis of neoclassical electric field and fluxes support the interpretation of the experimental results. The article also reports evidence of the temperature improvement depending on powder injection rates, density, and heating power, while the plasma turbulence response varies depending on the initial conditions.
Article
Physics, Fluids & Plasmas
T. Kobayashi, M. Yoshinuma, W. Hu, K. Ida
Summary: This paper proposes a tomography approach to reconstruct a phase-space structure. It is challenging to obtain a sufficiently high signal intensity in a single detector bin for the phase-space resolved diagnostic system that requires signal decomposition in real-space, velocity-space, and time. To overcome this difficulty, three different sets of data with different integration directions are used simultaneously to attempt a reconstruction of the original structure in the phase-space by tomography. The proposed method is demonstrated using a synthetic dataset in a real diagnostic setup and shown to successfully reconstruct the time evolution of a phase-space perturbation induced by Landau damping.
PHYSICS OF PLASMAS
(2023)
Article
Engineering, Electrical & Electronic
Naoki Hirano, Yuta Onodera, Toshiyuki Mito, Yuta Motoki, Akifumi Kawagoe
Summary: Magnetic refrigeration technology is a highly efficient process for hydrogen liquefaction temperature. By applying magnetic field change to a magnetocaloric material, a magnetocaloric effect is obtained. Superconducting coils that can generate strong magnetic fields with low power consumption are essential. We are researching a static magnetic refrigeration system that alters the energizing current to the coil to generate magnetic field changes. The AC loss of the superconducting coil is a key factor in this system.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
Article
Engineering, Electrical & Electronic
Yuta Onodera, Naoki Hirano, Tomosumi Baba, Toshiyuki Mito, Ryozo Kawanami
Summary: Research and development of large-current capacity high temperature superconducting (HTS) conductors for magnet applications in nuclear fusion experimental devices is underway in the world. A candidate conductor, the FAIR conductor, has been developed with REBCO tapes and pure aluminum sheets alternately stacked in an aluminum jacket and covered by friction stir welding (FSW). Current transport tests have been conducted to optimize the manufacturing process, and the properties of the conductors in low temperature under high magnetic fields have also been investigated. Coil shape tests in high magnetic fields are planned as the next step.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
Article
Engineering, Electrical & Electronic
H. Oya, Y. Shirai, R. Kawasaki, F. Matsumoto, Y. Maeda, G. Matsumoto, M. Shiotsu, S. Imagawa, A. Iwamoto, S. Hamaguchi, M. Tsuda, Y. Nagasaki, T. Yagai, H. Kobayashi, M. Ohya
Summary: Development of low-capacity high-temperature superconducting (HTS) coils cooled by gas helium or refrigerant in the temperature range of 15-40 K is ongoing. Liquid hydrogen, with a saturation temperature of 20.7 K, is a potential candidate for refrigerant cooling of large-capacity HTS coils. However, the handling difficulties of liquid hydrogen have limited the studies in this area.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2023)
