Article
Astronomy & Astrophysics
Joel C. Allred, Graham S. Kerr, A. Gordon Emslie
Summary: During solar flares, thermal conduction plays a key role in energy transport. Recent research has extended the traditional theory, considering nonlocality and turbulent suppression. It is found that reducing the heat flux leads to slower dynamics, weaker line emission, and longer cooling times. By comparing with observations, a suppression factor between 0.3 and 0.5 can better explain the observed Doppler velocities.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Fluids & Plasmas
Zhongyong Chen, Zhifang Lin, Wei Yan, Duwei Huang, Yunong Wei, You LI, Nianheng Cai, Jie Hu, Yonghua Ding, Yunfeng Liang, Zhonghe Jiang
Summary: This paper summarizes the main works on disruption mitigation, including suppression and mitigation of runaway current, on the J-TEXT tokamak. Two strategies for the mitigation of runaway electron beams are applied in experiments. The first strategy completely suppresses the runaway electrons by using supersonic molecular beam injection, resonant magnetic perturbation, and secondary massive gas injection. The second strategy allows the runaway current to form but should be dissipated within tolerance. It has been observed that the runaway current can be significantly dissipated by massive gas injection and ohmic field. Shattered pellet injection has been chosen as the main disruption mitigation method, as it can inject material deeper into the plasma for higher density assimilation compared to massive gas injection. Simulation works also show the strong influence of different phases and sizes of locked islands on the RE seeds in the plasma during thermal quench. The robust runaway suppression and runaway current dissipation provide important insights for the disruption mitigation of future large tokamaks.
PLASMA SCIENCE & TECHNOLOGY
(2022)
Article
Physics, Applied
A. Yu. Starikovskiy, N. L. Aleksandrov, M. N. Shneider
Summary: The simulations and experiments show that positive and negative streamers exhibit drastically different behaviors when decelerating and stopping.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Physics, Fluids & Plasmas
T. Tang, L. Zeng, D. Chen, Y. Sun, H. Zhao, T. Zhou, A. Ti, S. Lin, R. Zhou, X. Zhu, J. Qian, H. Liu, Y. Jie, Y. Liang, X. Gao
Summary: Runaway currents have been detected in the Experimental Advanced Superconducting Tokamak (EAST) during disruptions, with up to 80% of the pre-disruption plasma current being carried by the runaway electron (RE) plateau. This anomalous behavior is attributed to the acceleration of pre-existing wave resonant suprathermal electrons by lower hybrid waves during disruption decay phase.
Article
Chemistry, Inorganic & Nuclear
Miguel Reina, Luis Felipe Hernandez-Ayala, Maria Elena Bravo-Gomez, Virginia Gomez, Lena Ruiz-Azuara
Summary: Three novel second generation Casiopeinas complexes were synthesized, characterized, and evaluated for their antiproliferative activity against HeLa and MCF-7 cancer cell lines. By replacing the usual negatively charged secondary ligand with a neutral bidentate ligand, the compounds showed improved hydrophilicity and antiproliferative activity. The study found that the [Cu(4,7-dimethyl-1,10-phenanthroline)(2AMB)(NO3)]NO3 complex was more effective than cisplatin against both cell lines, with structure-activity relationships influenced by molar volume or redox potential.
INORGANICA CHIMICA ACTA
(2021)
Article
Physics, Multidisciplinary
A. Chilingarian, G. Hovsepyan, M. Zazyan
Summary: This letter introduces a method to gain insight into the charge structure of thunderclouds by simultaneously measuring electron and gamma-ray energy spectra of thunderstorm ground enhancement. We discuss and compare two main scenarios supporting the initiation of relativistic runaway electron avalanches in thunderclouds, including the emergence of a lower positive charged layer (LPCR).
Article
Physics, Fluids & Plasmas
J. W. Q. S. A. Z. X. Decker, G. Papp, S. Coda, B. P. Duval, U. Sheikh, P. Blanchard, D. Choi, C. Galperti, L. Calacci, D. Carnevale, O. Ficker, M. Gobbin, B. Labit, E. Macusova, J. Mlynar, V. Plyusnin, O. Sauter
Summary: The fully conversion from ohmic to runaway electron driven current was achieved in the tokamak a configuration variable (TCV) by injecting a large amount of neon into a low-density limited circular plasma. A stable 200 kA runaway electron beam was maintained for over 1 s after a partial disruption. The control of beam decay rate and vertical position was demonstrated, and the formation of runaway electron beam was observed in elongated plasma configurations.
Article
Physics, Multidisciplinary
Dan Wang, Xuan Wang, Guoqian Liao, Zhe Zhang, Yutong Li
Summary: This article investigates the integration of a terahertz pump into an ultrafast electron diffraction experiment and proposes several solutions to reduce the deflection effect on the electron probe. A terahertz-pump-electron-probe UED experiment with high temporal resolution is successfully achieved.
Article
Physics, Fluids & Plasmas
Yueqiang Liu, K. Aleynikova, C. Paz-Soldan, P. Aleynikov, V Lukash, R. Khayrutdinov
Summary: The mitigation of runaway electrons in the ITER scenario has been numerically investigated using three-dimensional magnetic field perturbations. The results show that the resonant magnetic perturbation is moderately effective in mitigating the RE seeds, but the efficiency is reduced when plasma response is taken into account. Additionally, the study finds that the resistive kink instabilities can also mitigate REs, with the best results achieved when the edge safety factor drops below 3.
Article
Physics, Fluids & Plasmas
S. Olasz, O. Embreus, M. Hoppe, M. Aradi, D. Por, T. Jonsson, D. Yadikin, G. Pokol
Summary: Efforts to model runaway electrons are driven by the risk they pose to fusion devices, with sophisticated kinetic models being able to capture most features of their generation. This paper compares reduced kinetic and kinetic models to determine when the former, based on quasi-stationarity assumptions, can be used. Results show that on time scales shorter than or comparable to the electron-electron collision time at the critical velocity for runaway electron generation, kinetic effects not captured by reduced kinetic models play an important role, suggesting the need for kinetic modeling.
Article
Physics, Multidisciplinary
A. A. Rodionov, A. Agafonov, V. A. Ryabov, K. Shpakov, I. S. Baidin, Ya K. Bolotov, M. A. Medvedev, E. Parkevich, A. G. Mozgovoi, A. Oginov
Summary: The time and energy parameters of X-ray radiation from a nanosecond megavolt atmospheric discharge with a reverse-conical cathode and tip-grid anode configuration have been measured for the first time. The results show that the radiation pulses are clustered in time and coincide with features of the time derivative of the applied voltage. The most intense and hard X-ray radiation is observed when the applied voltage reaches its maximum value.
Article
Physics, Multidisciplinary
K. Zhukovsky
Summary: Theoretical analysis examines the physical reasons for the occurrence of second harmonic generation in undulators in free electron lasers (FELs). The calculation of harmonic powers, especially the second harmonic, using different analytical methods is compared with experimental data from LEUTL and LCLS FELs. The study identifies various contributions to the harmonic powers and explores their influence. Examples from LCLS FEL and SwissFEL demonstrate the possibility of suppressing second harmonic radiation and the amplification and radiation of the second FEL harmonic using harmonic lasing self-seed (HLSS) and separate harmonic buncher and amplifier.
Article
Physics, Multidisciplinary
Lisa-Marie Koll, Laura Maikowski, Lorenz Drescher, Tobias Witting, Marc J. J. Vrakking
Summary: This article reports the crucial role that entanglement plays in pump-probe experiments involving ionization, and demonstrates that the degree of entanglement and vibrational coherence in the ion can be controlled by tailoring the spectral properties of attosecond extreme ultraviolet laser pulses.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
M. De Angeli, P. Tolias, S. Ratynskaia, D. Ripamonti, L. Vignitchouk, F. Causa, G. Daminelli, B. Esposito, E. Fortuna-Zalesna, F. Ghezzi, L. Laguardia, G. Maddaluno, G. Riva, W. Zielinski
Summary: Post-mortem and in situ evidence is presented in favor of high-velocity solid dust generation during the explosion-like interaction of runaway electrons with metallic plasma-facing components in FTU. The freshly-produced solid dust causes secondary de-localized wall damage through high-velocity impacts, leading to the formation of craters. This mechanism, supported by surface analysis, theoretical arguments, and dust dynamics modeling, may be of importance for ITER and DEMO.
Article
Engineering, Civil
Dong Zeng, Lauren Gagnon, Yi Wang
Summary: This study investigates the thermal runaway propagation (TRP) of LIB modules made of 18650 form-factor LIB cells. The experiments showed that the TRP rates across the LCO cell arrays were significantly faster than those across the LFP cell arrays. In addition, heat transfer by ejected material was found to significantly accelerate TRP.
FIRE SAFETY JOURNAL
(2023)
Article
Nuclear Science & Technology
M. W. Lee, J. Kang, N. C. Logan, M. J. Choi, L. Jung, J. Kim, M. G. Choi, M. H. Kim, B. A. Grierson, S. P. Smith, O. Meneghini, M. Romanelli, C. Sung
Summary: An integrated workflow for fast-ion analysis was developed using OMFIT workflow manager to support KSTAR users. The analysis suite offers a graphical user interface-based workflow for easy access and handling of experimental data in various formats. Modules are available for tasks like profile fitting and equilibrium reconstruction. The common workflow manager streamlines the preparation of inputs for fast-ion simulations and allows parallel processing of tasks for efficient analysis of large datasets. Furthermore, the OMFIT platform is flexible and supports non-standard applications.
FUSION SCIENCE AND TECHNOLOGY
(2023)
Article
Physics, Fluids & Plasmas
E. M. Hollmann, L. Baylor, A. Boboc, P. Carvalho, N. W. Eidietis, J. L. Herfindal, S. Jachmich, A. Lvovskiy, C. Paz-Soldan, C. Reux, D. Shiraki, R. Sweeney
Summary: Experimental trends in thermal plasma partial recombination resulting from massive D-2 injection into high-Z (Ar) containing runaway electron (RE) plateaus in DIII-D and JET are studied. The study finds that thermal electron density drops by about 100x when partial recombination occurs, with a minimum at a D-2 density of 10(20)-10(21)m(-3). The results also show that achieving low electron density will be easier with Ar as a background impurity.
Article
Physics, Fluids & Plasmas
T. Q. Jia, J. P. Qian, D. L. Chen, D. Moreau, B. Shen, B. Zhang, X. Z. Gong, J. Huang, J. Y. Zhang, X. D. Yang, R. R. Liang, Y. C. Hu, L. X. Chen, Y. F. He, Y. Tao, Z. H. Wang, L. Zeng, Y. W. Sun
Summary: This paper describes the scaling characteristics of the H-mode confinement database of NBI-LHW and ECRH-LHW plasmas in the EAST tokamak. The scaling models τE,EAST,H,NBI LHW and τE,EAST,H,ECRH LHW are obtained for the thermal energy confinement time. The scaling τE,EAST,H,NBI LHW shows a similar dependency on plasma current and power loss, a lower dependency on plasma density and elongation, but a stronger dependency on toroidal field than the scaling τth,98y2.
Article
Physics, Multidisciplinary
Y. H. Wang, Y. D. Li, G. J. Wu, P. Li, L. Zeng, H. L. Zhao, C. W. Mai, J. S. Geng, F. Chen
Summary: Avoiding plasma instability, particularly disruption instability, is crucial for the stable operation of tokamak. Large-scale instabilities driven by free energy can lead to disruption. This paper examines the evolution of electron-scale turbulence in the pre-precursor phase of TMs included disruption using the CO2 laser coherent scattering system in EAST. The study found significant changes in turbulence characteristics (e.g. intensity, spatial correlation) for more than 30 ms in the pre-precursor phase of disruption. Additionally, the spatial correlation of turbulence significantly increased in two regions before major disruption, while the opposite trend was observed before minor disruption. The warning time for disruption prediction using microscale turbulence is competitive at 30 ms for ITER. The experimental results in EAST provide new evidence for improving disruption prediction methods.
Article
Physics, Fluids & Plasmas
Wonjun Lee, Jaewook Kim, Semin Joung, G. J. Choi, J. Kim, M. Woo, T. Rhee, K. D. Lee, J. G. Bak, J. S. Kang, Y. -c. Ghim
Summary: This study investigates the general characteristics of fishbone modes in KSTAR tokamak. The temporal evolutions of fluctuations in poloidal magnetic fields, electron temperatures, and densities are observed and found to be similar to other tokamaks. A notable feature in KSTAR fishbone modes is the non-monotonic radial coherence structures of electron temperature and density with respect to magnetic fluctuations, with a local minimum at r/a ≈ 0.7 and a maximum at r/a ≈ 0.9. The slow temporal evolution of temperatures is explained by the presence of barely trapped resonating fast ions, transiting the core and edge regions simultaneously without trespassing the mid-plane intermediate region. Published under an exclusive license by AIP Publishing.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
A. O. Nelson, A. Hyatt, W. Wehner, A. Welander, C. Paz-Soldan, T. Osborne, H. Anand, K. E. Thome
Summary: Through experiments on DIII-D, the vertical stability of low beta diverted plasmas with strong negative triangularity (NT) is evaluated, and the effects of coupling with the DIII-D wall on stability are studied. The results show that the growth rates of vertical instability in NT plasmas can be controlled to lower values. The stability calculations in NT plasmas on DIII-D using GSdesign are validated, with errors of no more than 20% between modeled and measured growth rates.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
Wenbin Liu, Kangning Geng, Long Zeng, Weiwen Xiao, Kaixuan Ye, Tao Zhang, Bin Cao, Xiang Zhu, Tian Tang, Haiqing Liu, Ang Ti, Hailin Zhao, Zhe Gao, Yi Tan, Chu Zhou, Ah Di Liu, Muquan Wu, Baolong Hao, Hang Li, Guoqiang Li, Xiang Gao
Summary: A coherent mode (CM) induced by SMBI was observed in Ohmic plasmas of EAST tokamak, which existed in the fluctuation spectra of electron temperature and density but not in the Mirnov fluctuation spectrum. The CM had multiple discrete frequencies between 5 to 20 kHz, occasionally dominated by a single frequency. It was found to be correlated to a high local transport level but did not have a clear influence on global confinement.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
W. Xia, L. Zeng, T. Tang, D. Chen, Y. Duan, X. Zhu, A. Ti, T. Shi, L. Xu, Y. Huang, X. Gao
Summary: The timescale of thermal quench (TQ) during disruptions on the EAST tokamak has been examined using electron cyclotron emission and soft x-ray diagnostic systems since 2015. The database includes major disruptions (MDs) and hot vertical displacement events (VDEs), with different durations and different triggering processes. The study found that the TQ duration decreases as the plasma current increases, and an approximate formula is proposed to estimate the TQ duration in MDs.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
Tao Wang, Xiang Zhu, Long Zeng, Sergio Briguglio, Gregorio Vlad, Fulvio Zonca, Zhiyong Qiu
Summary: Toroidal Alfven eigenmodes (TAEs) associated with runaway electrons are observed in low density EAST Ohmic discharges. Simplified hybrid MHD-kinetic simulations are used to explore the possible destabilization mechanism. It is found that barely circulating energetic electrons can satisfy the resonance condition with the TAE due to vanishing transit frequency near the phase space circulating/trapped separatrix. Additionally, the study suggests that the phase space resonance structure plays an important role in the eventual saturation amplitude, favoring a low toroidal mode number in this scenario.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Instruments & Instrumentation
M. W. Lee, Junghee Kim, M. H. Kim, Soobin Lim, Jayhyun Kim, C. Sung
Summary: We have developed a new scintillator-based optical soft x-ray (OSXR) diagnostic system for KSTAR, using fiber optic faceplates, mm-size lens arrays, and fiber bundles to overcome vacuum-port limitations. The scintillator material selected for the system is P47 (Y2SiO5), with fast rise and decay times suitable for detecting plasma instabilities. The OSXR data obtained during the 2022 KSTAR experimental campaign showed validity and consistency with other diagnostics, capturing magnetohydrodynamic activities and providing valuable information for disruption mitigation studies.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2023)
Article
Physics, Fluids & Plasmas
Q. M. Hu, J. -K. Park, S. M. Yang, S. K. Kim, N. C. Logan, R. Nazikian, J. Kang, C. Paz-Soldan, W. H. Ko, G. Y. Park
Summary: TM1 simulations reveal key characteristics of density pump-out caused by pedestal-foot island formation when applying resonant magnetic perturbation (RMP). Dedicated experiments in KSTAR and DIII-D tokamaks validate these features and show a bifurcation in pump-out, sensitivity to q(95), and scaling proportional to the square root of the RMP coil current. These experimental observations are consistent with TM1 simulations.
Article
Physics, Fluids & Plasmas
I. G. Stewart, R. S. Granetz, C. E. Myers, C. Paz-Soldan, R. Sweeney, C. J. Hansen, D. T. Garnier, D. J. Battaglia, A. J. Creely, M. L. Reinke
Summary: Accurate reconstruction of plasma equilibrium is crucial for the successful operation of the SPARC tokamak. The deployment of the EFIT equilibrium reconstruction code, along with comparisons to other methods, ensured successful reconstruction of various reference discharges. The optimized equilibrium magnetic sensor set and workflow achieved a balance between engineering constraints and reconstruction fidelity.
Article
Physics, Fluids & Plasmas
S. K. Kim, N. C. Logan, M. Becoulet, M. Hoelzl, Q. Hu, G. T. A. Huijsmans, S. J. P. Pamela, Q. Yu, S. M. Yang, C. Paz-soldan, E. Kolemen, J. -K. Park
Summary: Nonlinear 3D MHD simulations and validations reveal that the hybrid particle-MHD transport is a key process for driving the pump-out in the presence of Resonant Magnetic Perturbations (RMPs) in the KSTAR tokamak. Near-resonant responses and the neoclassical ion diffusion across perturbed magnetic surfaces play important roles in the pump-out. The study also investigates the pump-outs in double-null-like plasmas and captures the effect of the double-null shape on the pump-outs. The findings reveal the impact of toroidal geometry and mode coupling on 3D physics and the importance of near-resonant components in suppressing ELMs.
Article
Physics, Multidisciplinary
Chang Liu, Andrey Lvovskiy, Carlos Paz-Soldan, Stephen C. Jardin, Amitava Bhattacharjee
Summary: Alfvenic modes in the current quench stage of the tokamak disruption have been observed, which are associated with high-energy runaway electrons (REs). Kinetic-MHD simulations reveal that high energy trapped REs can resonate with the Alfven mode through their toroidal precession motion. The perturbed magnetic fields from the modes can lead to spatial diffusion of REs, providing a theoretical basis for RE mitigation.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
D. G. Whyte, C. Paz-Soldan, B. Wirth
Summary: The academic community and universities are playing a crucial role in supporting the development of fusion energy industry. Analyzing the distribution of full time faculty engaged in fusion and plasma research, it is evident that universities need significant growth in numbers and wider distribution across disciplines to better support and promote the fusion energy sector.
PHYSICS OF PLASMAS
(2023)