Physics of Plasmas最新文献

From L-mode to the L–H transition, experiments on ASDEX upgrade and related gyrokinetic simulations 从 L 模式到 L-H 过渡，ASDEX 升级实验及相关陀螺动力学模拟

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0202867

N. Bonanomi, C. Angioni, G. D. Conway, T. Happel, U. Plank, P. Schneider, G. Staebler

{"title":"From L-mode to the L–H transition, experiments on ASDEX upgrade and related gyrokinetic simulations","authors":"N. Bonanomi, C. Angioni, G. D. Conway, T. Happel, U. Plank, P. Schneider, G. Staebler","doi":"10.1063/5.0202867","DOIUrl":"https://doi.org/10.1063/5.0202867","url":null,"abstract":"This work combines experimental observations from the ASDEX Upgrade tokamak with related gyrokinetic simulations of the turbulence moving from L-mode toward, and beyond, the L–H transition. Dedicated experiments have been performed with slow steps of increasing electron cyclotron heating power. Gyrokinetic simulations of the edge turbulence of these plasmas highlight the key roles of the non-linear electromagnetic effects and the external flow shear (E × B shear), both related to the evolution of the plasma pressure profile with increasing heating power. The increase in the plasma βe destabilizes turbulence at low toroidal mode numbers, that, in turn, is strongly suppressed by the external flow shear. This allows the plasma pressure profiles to evolve without a sharp rise in the turbulent fluxes. When all the experimentally measured plasma parameters are consistently included as inputs of the local gyrokinetic simulations, both the experimental electron and ion heat fluxes are quantitatively reproduced on the whole L-mode phase of the selected discharge. Simulations carried out with edge parameters of an ELM-free H-mode phase still show the importance of the mechanisms discussed earlier while also indicating possible limitations of the local approach.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"8 31","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141696384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Toward machine-learning-assisted PW-class high-repetition-rate experiments with solid targets 实现机器学习辅助的 PW 级固体目标高重复率实验

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0190553

D. Mariscal, B. Djordjević, R. Anirudh, J. Jayaraman-Thiagarajan, E. Grace, R. Simpson, K. Swanson, T. C. Galvin, D. Mittelberger, J. Heebner, R. Muir, E. Folsom, M. P. Hill, S. Feister, E. Ito, K. Valdez-Sereno, J. J. Rocca, J. Park, S. Wang, R. Hollinger, R. Nedbailo, B. Sullivan, G. Zeraouli, A. Shukla, P. Turaga, A. Sarkar, B. Van Essen, S. Liu, B. Spears, P.-T. Bremer, T. Ma

{"title":"Toward machine-learning-assisted PW-class high-repetition-rate experiments with solid targets","authors":"D. Mariscal, B. Djordjević, R. Anirudh, J. Jayaraman-Thiagarajan, E. Grace, R. Simpson, K. Swanson, T. C. Galvin, D. Mittelberger, J. Heebner, R. Muir, E. Folsom, M. P. Hill, S. Feister, E. Ito, K. Valdez-Sereno, J. J. Rocca, J. Park, S. Wang, R. Hollinger, R. Nedbailo, B. Sullivan, G. Zeraouli, A. Shukla, P. Turaga, A. Sarkar, B. Van Essen, S. Liu, B. Spears, P.-T. Bremer, T. Ma","doi":"10.1063/5.0190553","DOIUrl":"https://doi.org/10.1063/5.0190553","url":null,"abstract":"We present progress in utilizing a machine learning (ML) assisted optimization framework to study the trends in a parameter space defined by spectrally shaped, high-intensity, petawatt-class (8 J, 45 fs) laser pulses interacting with solid targets and give the first simulation-based overview of predicted trends. A neural network (NN) incorporating uncertainty quantification is trained to predict the number of hot electrons generated by the laser–target interaction as a function of pulse shaping parameters. The predictions of this NN serve as the basis function for a Bayesian optimization framework to navigate this space. For post-experimental evaluation, we compare two separate neural network (NN) models. One is based solely on data from experiments, and the other is trained only on ensemble particle-in-cell simulations. Reviewing the predicted and observed trends across the experiment-capable laser parameter search space, we find that both ML models predict a maximal increase in hot electron generation at a level of approximately 12%–18%; however, no statistically significant enhancement was observed in experiments. On direct comparison of the NN models, the average discrepancy is 8.5%, with a maximum of 30%. Since shot-to-shot fluctuations in experiments affect the observations, we evaluate the behavior of our optimization framework by performing virtual experiments that vary the number of repeated observations and the noise levels. Here, we discuss the implications of such a framework for future autonomous exploration platforms in high-repetition-rate experiments.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141690659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Foreword to Special Issue: Papers from the 65th Annual Meeting of the APS Division of Plasma Physics, October 30–November 3, 2023 特刊前言：美国物理学会等离子体物理分会第 65 届年会论文，2023 年 10 月 30 日至 11 月 3 日

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0223942

E. Thomas, Michael Mauel

引用次数: 0

Hysteresis between gas breakdown and plasma discharge 气体击穿与等离子放电之间的滞后现象

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0198151

Yusuke Yamashita, K. Hara, S. Sriraman

{"title":"Hysteresis between gas breakdown and plasma discharge","authors":"Yusuke Yamashita, K. Hara, S. Sriraman","doi":"10.1063/5.0198151","DOIUrl":"https://doi.org/10.1063/5.0198151","url":null,"abstract":"In direct-current (DC) discharge, it is well known that hysteresis is observed between the Townsend (gas breakdown) and glow regimes. Forward and backward voltage sweep is performed using a one-dimensional particle-in-cell Monte Carlo collision (PIC-MCC) model considering a ballast resistor. When increasing the applied voltage after reaching the breakdown voltage (Vb), transition from Townsend to glow discharges is observed. When decreasing the applied voltage from the glow regime, the discharge voltage (Vd) between the anode–cathode gap can be smaller than the breakdown voltage, resulting in a hysteresis, which is consistent with experimental observations. Next, the PIC-MCC model is used to investigate the self-sustaining voltage (Vs) in the presence of finite initial plasma densities between the anode and cathode gap. It is observed that the self-sustaining voltage coincides with the discharge voltage obtained from the backward voltage sweep. In addition, the self-sustaining voltage decreases with increased initial plasma density and saturates above a certain initial plasma density, which indicates a change in plasma resistivity. The decrease in self-sustaining voltage is associated with the electron heat loss at the anode for the low pd (rarefied) regime. In the high pd (collisional) regime, the ion energy loss toward the cathode due to the cathode fall and the inelastic collision loss of electrons in the bulk discharge balance out. Finally, it is demonstrated that the self-sustaining voltage collapses to a singular value, despite the presence of a initial plasma, for microgaps when field emission is dominant, which is also consistent with experimental observations.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"30 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141697992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Generation of the vortex terahertz radiation by the interaction of two-color Laguerre–Gaussian laser with plasmas in the presence of a static magnetic field 双色拉盖尔-高斯激光在静磁场存在下与等离子体相互作用产生的涡旋太赫兹辐射

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0207570

De-Sheng Zhang, Xue-Ren Hong, Xiao-Bo Zhang, R. Tang, Bai-Song Xie

引用次数: 0

OPTEMIST: A neutral beam for measuring quasi-omnigenity in Wendelstein 7-X OPTEMIST：用于测量文德尔施泰因 7-X 中准同源性的中性光束

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0218670

S. Lazerson, David Kulla, P. McNeely, N. Rust, Lucas van Ham, D. Hartmann

{"title":"OPTEMIST: A neutral beam for measuring quasi-omnigenity in Wendelstein 7-X","authors":"S. Lazerson, David Kulla, P. McNeely, N. Rust, Lucas van Ham, D. Hartmann","doi":"10.1063/5.0218670","DOIUrl":"https://doi.org/10.1063/5.0218670","url":null,"abstract":"A new neutral beamline (OPTEMIST) uniquely capable of exploring the predicted improvement of fast ion confinement in Wendelstein 7-X (W7-X), which comes with increasing plasma beta, is proposed. As the plasma beta increases in the W7-X device, the high mirror magnetic configuration has drift orbits that begin to close, enhancing the confinement of the deeply trapped particles. The existing neutral beam system is found to produce particle populations that do not adequately probe the deeply trapped orbits. Fast tritons generated by thermal deuterium–deuterium fusion reactions are found to probe the necessary conditions for demonstrating this effect. However, it is found that diagnostically measuring this effect will be difficult. A scoping study of a neutral beamline that directly populates the trapped orbits is performed. It is found that a monoenergetic population of 120 kV injected protons provides the largest confinement enhancement in the fast ion population as the plasma beta is increased. The necessity to raise plasma density to increase plasma beta results in blinding of spectroscopic beam measurements by bremsstrahlung. An array of novel fast ion loss detectors that would adequately assess the confinement of these particles is proposed.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"79 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141702023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Generation of gamma photons and pairs with transverse orbital angular momentum via spatiotemporal optical vortex pulse 通过时空光涡旋脉冲产生具有横向轨道角动量的伽马光子和光对

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0214297

Cui-Wen Zhang, De-Sheng Zhang, Bai-Song Xie

{"title":"Generation of gamma photons and pairs with transverse orbital angular momentum via spatiotemporal optical vortex pulse","authors":"Cui-Wen Zhang, De-Sheng Zhang, Bai-Song Xie","doi":"10.1063/5.0214297","DOIUrl":"https://doi.org/10.1063/5.0214297","url":null,"abstract":"We present the generation of well-collimated gamma photons and pairs with extrinsic transverse orbital angular momentum (TOAM) through the head-on collision of an intense spatiotemporal optical vortex (STOV) pulse carrying intrinsic TOAM and a high-energy electron beam. It is found that the TOAM of STOV pulse remains almost unchanged, and the TOAM is conserved in the center-of-mass frame. Moreover, there exhibits a duality for particles TOAM in the CMF and laboratory frame when the initial location of high-energy electron beam is different. Furthermore, the TOAM of gamma photons in the CMF increases while that of positrons decreases as the topological charge of STOV pulse increases, whereas in the LF, the TOAM of both gamma photons and positrons decreases. The result under the same pulse intensity is better than that under the same pulse energy. The increase in the initial energy of high-energy electrons leads to an enhancement of the TOAM of both gamma photons and positrons in both frames. Gamma photons and electrons/positrons with TOAM as a new degree of freedom may have extensive applications in optical communication, astrophysics, nanomaterials, and other fields.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"6 21","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141696394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Tunable plasmonic tweezers based on nanocavity array structure for multi-site nanoscale particles trapping 基于纳米空腔阵列结构的可调谐等离子镊子，用于多点纳米级粒子捕获

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0193932

Xiaoya Yan, Hongyan Shi, Pengxue Jia, Xiudong Sun

{"title":"Tunable plasmonic tweezers based on nanocavity array structure for multi-site nanoscale particles trapping","authors":"Xiaoya Yan, Hongyan Shi, Pengxue Jia, Xiudong Sun","doi":"10.1063/5.0193932","DOIUrl":"https://doi.org/10.1063/5.0193932","url":null,"abstract":"The ability of plasmonic optical tweezers based on metal nanostructure to stably trap and dynamically manipulate nanoscale objects at low laser power has been widely used in the fields of nanotechnology and life sciences. In particular, their plasmonic nanocavity structure can improve the local field intensity and trap depth by confining electromagnetic fields to subwavelength volumes. In this paper, the R6G dye molecules with 10−6 M were successfully trapped by using the Ag@Polydimethylsiloxane nanocavity array structure, and a R6G micro-ring was formed under the combined action of plasmonic optical force and thermophoresis. Subsequently, the theoretical investigation revealed that the trapping performance can be flexibly adjusted by changing the structural parameters of the conical nanocavity unit, and it can provide a stable potential well for polystyrene particles of RNP = 14 nm when the cavity depth is 140 nm. In addition, it is found that multiple trapping sites can be activated simultaneously in the laser irradiation area by investigating the trapping properties of the hexagonal conical nanocavity array structure. This multi-site stable trapping platform makes it possible to analyze multiple target particles contemporaneously.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"15 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141711165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Gaussian process based surrogate approach for the optimization of cylindrical targets 基于高斯过程的圆柱形目标优化替代方法

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0204411

William Gammel, J. Sauppe, Paul Bradley

{"title":"A Gaussian process based surrogate approach for the optimization of cylindrical targets","authors":"William Gammel, J. Sauppe, Paul Bradley","doi":"10.1063/5.0204411","DOIUrl":"https://doi.org/10.1063/5.0204411","url":null,"abstract":"Simulating direct-drive inertial confinement experiments presents significant computational challenges, both due to the complexity of the codes required for such simulations and the substantial computational expense associated with target design studies. Machine learning models, and in particular, surrogate models, offer a solution by replacing simulation results with a simplified approximation. In this study, we apply surrogate modeling and optimization techniques that are well established in the existing literature to one-dimensional simulation data of a new cylindrical target design containing deuterium–tritium fuel. These models predict yields without the need for expensive simulations. We find that Bayesian optimization with Gaussian process surrogates enhances sampling efficiency in low-dimensional design spaces but becomes less efficient as dimensionality increases. Nonetheless, optimization routines within two-dimensional and five-dimensional design spaces can identify designs that maximize yield, while also aligning with established physical intuition. Optimization routines, which ignore constraints on hydrodynamic instability growth, are shown to lead to unstable designs in 2D, resulting in yield loss. However, routines that utilize 1D simulations and impose constraints on the in-flight aspect ratio converge on novel cylindrical target designs that are stable against hydrodynamic instability growth in 2D and achieve high yield.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"62 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141696569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Numerical analysis of three-dimensional magnetopause-like reconnection properties by Hall MHD simulation for SPERF-AREX 通过霍尔 MHD 仿真对 SPERF-AREX 的三维磁ause-like 再连接特性进行数值分析

Physics of Plasmas Pub Date : 2024-07-01 DOI: 10.1063/5.0213566

Xianglei He, Aaohua Mao, S. Apatenkov, Zhonglin Zhang, Zhibin Wang, Mengmeng Sun, Jitong Zou, Xiaogang Wang

{"title":"Numerical analysis of three-dimensional magnetopause-like reconnection properties by Hall MHD simulation for SPERF-AREX","authors":"Xianglei He, Aaohua Mao, S. Apatenkov, Zhonglin Zhang, Zhibin Wang, Mengmeng Sun, Jitong Zou, Xiaogang Wang","doi":"10.1063/5.0213566","DOIUrl":"https://doi.org/10.1063/5.0213566","url":null,"abstract":"The ground-based device, the Space Plasma Environment Research Facility (SPERF), is established for experimentally simulating magnetosphere plasma processes, with one of its major components, asymmetric reconnection experiment (AREX), for three-dimensional physics relevant to dayside asymmetric magnetopause reconnection. As an outstanding property of fast magnetic reconnection in collisionless plasmas, the Hall effect and its geometric features can be experimentally investigated in SPERF-AREX with various magnetic configurations related to different driven scenarios for simulating interplanetary magnetic field (IMF) conditions. In this work, the Hall effect and its geometric characteristics in such proposed experiments are numerically studied based on a Hall MHD model. The simulation results reveal that in the X-line geometry relevant to southward IMFs, the Hall field features in cross section perpendicular to the X-line are mostly analogous to typical two-dimensional Hall quadrupole structures, clearly an “anti-parallel reconnection” feature. In the separator (A-B null-line) geometry relevant to arbitrary IMF orientations, along the separator between magnetic nulls, the magnetic field configuration near a magnetic null also demonstrates the typical quadrupolar pattern. However, the pattern is distorted away (>10di, here di=c/ωpi is the ion inertial length) from the nulls, in a way similar to that in “component reconnection.” Furthermore, the Hall effect induces a dawn-dusk asymmetry for both the X-line and the separator geometries.","PeriodicalId":510396,"journal":{"name":"Physics of Plasmas","volume":"313 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141692080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0