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Versatile tape-drive target for high-repetition-rate laser-driven proton acceleration

High Power Laser Science and engineering 2023年第4期11卷 59-69页

作者： N.Xu M.J.V.Streeter O.C.Ettlinger H.Ahmed S.Astbury M.Borghesi N.Bourgeois C.B.Curry S.J.D.Dann N.P.Dover T.Dzelzainis V.Istokskaia M.Gauthier L.Giuffrida G.D.Glenn S.H.Glenzer R.J.Gray J.S.Green G.S.Hicks C.Hyland M.King B.Loughran D.Margarone O.McCusker P.McKenna C.Parisuaña P.Parsons C.Spindloe D.R.Symes F.Treffert C.A.J.Palmer Z.Najmudin John Adams Institute for Accelerator Science Blackett LaboratoryImperial College LondonLondonUK School of Maths and Physics Queen’s University BelfastBelfastUK Central Laser Facility STFC Rutherford Appleton LaboratoryDidcotUK SLAC National Accelerator Laboratory Menlo ParkUSA ELI Beamlines Centre Institute of PhysicsCASDolni BrezanyCzech Republic Faculty of Nuclear Sciences and Physical Engineering Czech Technical University in PraguePragueCzech Republic Department of Physics SUPAUniversity of StrathclydeGlasgowUK Department of Mechanical Engineering Stanford UniversityStanfordUSA Department of Applied Physics Stanford UniversityStanfordUSA Department of Electrical and Computer Engineering University of AlbertaEdmontonCanada Institut für Kernphysik Technische Universität DarmstadtDarmstadtGermany

We present the development and characterization of a high-stability,multi-material,multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 *** tape surface position was measured to be stable on the sub-micrometre scale,compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers(>kHz).Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended *** target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team,with the exception of tape replacement,producing the largest data-set of relativistically intense laser–solid foil measurements to *** tape drive provides robust targetry for the generation and study of high-repetitionrate ion beams using next-generation high-power laser systems,also enabling wider applications of laser-driven proton sources.

关键词： high-repetition-rate laser target laser-plasma acceleration proton generation tape-drive target

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Large effective magnetic fields from chiral phonons in rare-earth halides

arXiv

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arXiv 2023年

作者： Luo, Jiaming Lin, Tong Zhang, Junjie Chen, Xiaotong Blackert, Elizabeth R. Xu, Rui Yakobson, Boris I. Zhu, Hanyu Department of Materials Science and Nano Engineering Rice University HoustonTX77005 United States Applied Physics Graduate Program Rice University HoustonTX77005 United States

Time-reversal symmetry (TRS) is pivotal for materials’ optical, magnetic, topological, and transport properties. Chiral phonons, characterized by atoms rotating unidirectionally around their equilibrium positions, generate dynamic lattice structures that break TRS. Here we report that coherent chiral phonons, driven by circularly polarized terahertz light pulses, can polarize the paramagnetic spins in CeF3 like a quasi-static magnetic field on the order of 1 Tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found the transient magnetization is only excited by pulses resonant with phonons, proportional to the angular momentum of the phonons, and growing with magnetic susceptibility at cryogenic temperatures, as expected from the spin-phonon coupling model. The time-dependent effective magnetic field quantitatively agrees with that calculated from phonon dynamics. Our results may open a new route to directly investigate mode-specific spin-phonon interaction in ultrafast magnetism, energy-efficient spintronics, and non-equilibrium phases of matter with broken TRS. Copyright © 2023, The Authors. All rights reserved.

关键词： Phonons

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Correlations between student connectivity and academic performance: A pandemic follow-up

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Physical Review physics Education Research 2023年第1期19卷 010106-010106页

作者： Nathan Crossette Lincoln D. Carr Bethany R. Wilcox Department of Physics University of Colorado Boulder Boulder Colorado 80309 USA Quantum Engineering Program Colorado School of Mines Golden Colorado 80401 USA Department of Physics Colorado School of Mines Golden Colorado 80401 USA Department of Applied Mathematics and Statistics Colorado School of Mines Golden Colorado 80401 USA

Social network analysis (SNA) has been gaining traction as a technique for quantitatively studying student collaboration. We analyze networks, constructed from student self-reports of collaboration on homework assignments, in two courses from the University of Colorado Boulder and one course from the Colorado School of Mines. All three courses occurred during the COVID-19 pandemic, which allows for a comparison between the course at the Colorado School of Mines (in a fully remote format) with results from a previous pre-pandemic study of student collaboration at the Colorado School of Mines (in an in-person format), as well as comparison between the Mines results with the two University of Colorado courses (in a hybrid format). We compute nodal centrality measures and calculate the correlation between student centrality and performance. Results varied widely between each of the courses studied. The course at the Colorado School of Mines had strong correlations between many centrality measures and performance which matched the patterns seen in the pre-pandemic study. The courses at the University of Colorado Boulder showed weaker correlations, and one course showed nearly no correlations at all between students’ connectivity to their classmates and their performance. Taken together, the results from the trio of courses indicate that the context and environment in which the course is situated play a more important role in fostering a correlation between student collaboration and course performance than the format (remote, hybrid, in-person) of the course, a finding which has implications for the broader use of SNA within physics education research. Additionally, we conducted a short study on the effect that missing nodes may have on the correlations calculated from the measured networks, an analysis largely missing from the SNA literature within PER. This investigation showed that missing nodes tend to shift correlations towards zero, providing evidence that the stati

关键词： Learning environment Research methodology Upper undergraduate students

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Emulating complex synapses using interlinked proton conductors

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Physical Review applied 2025年第1期23卷 014027-014027页

作者： Lifu Zhang Ji-An Li Yang Hu Jie Jiang Rongjie Lai Marcus K. Benna Jian Shi Department of Materials Science and Engineering Rensselaer Polytechnic Institute Troy New York 12180 USA Neurosciences Graduate Program University of California San Diego La Jolla California 92093 USA Department of Mathematics Purdue University West Lafayette Indiana 47907 USA Department of Neurobiology School of Biological Sciences University of California at San Diego La Jolla California 92093 USA Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy New York 12180 USA

In terms of energy efficiency and computational speed, neuromorphic electronics based on nonvolatile memory devices are expected to be one of most promising hardware candidates for future artificial intelligence (AI). However, catastrophic forgetting, networks rapidly overwriting previously learned weights when learning new tasks, remains a pivotal obstacle in either digital or analog AI chips for unleashing the true power of brainlike computing. To address catastrophic forgetting in the context of online memory storage, a complex synapse model (the Benna-Fusi model) was proposed recently [M. K. Benna and S. Fusi, Nat. Neurosci. 19, 1697 (2016)], the synaptic weight and internal variables of which evolve following diffusion dynamics. In this work, by designing a proton transistor with a series of charge-diffusion-controlled storage components, we have experimentally realized the Benna-Fusi artificial complex synapse. Memory consolidation from coupled storage components is revealed by both numerical simulations and experimental observations. Different memory timescales for the complex synapse are engineered by the diffusion length of charge carriers and the capacity and number of coupled storage components. The advantages of the demonstrated complex synapse for both memory capacity and memory consolidation are revealed by neural network simulations of face-familiarity detection. Our experimental realization of the complex synapse suggests a promising approach to enhance memory capacity and to enable continual learning.

关键词： Nonvolatile storage

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Increased light-emission efficiency in disordered InGaN through the correlated reduction of recombination rates

arXiv

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arXiv 2023年

作者： Pant, Nick Kioupakis, Emmanouil Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Materials Science & Engineering University of Michigan Ann ArborMI48109 United States

Experiments have shown that the light-emission efficiency of indium gallium nitride (InGaN) light-emitting diodes improves with increasing indium concentration. It is widely thought that compositional fluctuations due to indium incorporation suppress diffusion of carriers to non-radiative centers, thus leading to defect-insensitive emission. However, recent experiments have challenged this hypothesis by revealing unexpectedly long diffusion lengths at room temperature. Here, we demonstrate an alternative mechanism involving the correlated reduction in radiative and nonradiative recombination rates that explains the increase in light-emission efficiency of InGaN with increasing indium concentration, without invoking the suppression of carrier diffusion. Our analysis challenges the notion that carrier localization gives rise to defect tolerance in InGaN. Copyright © 2023, The Authors. All rights reserved.

关键词： III-V semiconductors

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GBEC: Geometry-Based Hand-Eye Calibration

arXiv

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arXiv 2024年

作者： Liu, Yihao Zhang, Jiaming She, Zhangcong Kheradmand, Amir Armand, Mehran The Department of Computer Science Johns Hopkins University BaltimoreMD21218 United States The Department of Mechanical Engineering Johns Hopkins University BaltimoreMD21218 United States The Department of Neurology Department of Neuroscience Johns Hopkins University BaltimoreMD21218 United States The Department of Mechanical Engineering Department of Computer Science Department of Orthopaedic Surgery Applied Physics Laboratory Johns Hopkins University BaltimoreMD21218 United States

Hand-eye calibration is the problem of solving the transformation from the end-effector of a robot to the sensor attached to it. Commonly employed techniques, such as AXXB or AXZB formulations, rely on regression methods that require collecting pose data from different robot configurations, which can produce low accuracy and repeatability. However, the derived transformation should solely depend on the geometry of the end-effector and the sensor attachment. We propose Geometry-Based End-Effector Calibration (GBEC) that enhances the repeatability and accuracy of the derived transformation compared to traditional hand-eye calibrations. To demonstrate improvements, we apply the approach to two different robot-assisted procedures: Transcranial Magnetic Stimulation (TMS) and femoroplasty. We also discuss the generalizability of GBEC for camera-in-hand and marker-in-hand sensor mounting methods. In the experiments, we perform GBEC between the robot end-effector and an optical tracker's rigid body marker attached to the TMS coil or femoroplasty drill guide. Previous research documents low repeatability and accuracy of the conventional methods for robot-assisted TMS hand-eye calibration. Applying GBEC to repeated calibrations, we obtain transformations with standard deviations of 0.37mm, 0.65mm, and 0.40mm (translation) along x, y, and z axes of the end-effector, respectively. The tool alignment experiments after using GBEC achieve a mean accuracy around 0.2mm in Euclidean distance. When compared to some existing methods, the proposed method relies solely on the geometry of the flange and the pose of the rigid-body marker, making it independent of workspace constraints or robot accuracy, without sacrificing the orthogonality of the rotation matrix. Our results validate the accuracy and applicability of the approach, providing a new and generalizable methodology for obtaining the transformation from the end-effector to a sensor. © 2024, CC BY-NC-ND.

关键词： Calibration

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Structural properties of hyperuniform Voronoi networks

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Physical Review E 2025年第3期111卷 034123-034123页

作者： Eli Newby Wenlong Shi Yang Jiao Reka Albert Salvatore Torquato Department of Physics Pennsylvania State University University Park Pennsylvania 16802 USA Materials Science and Engineering Arizona State University Tempe Arizona 85287 USA Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Institute of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

Disordered hyperuniform many-particle systems are recently discovered exotic states of matter, characterized by the complete suppression of normalized infinite-wavelength density fluctuations, as in perfect crystals, while lacking conventional long-range order, as in liquids and glasses. In this work, we begin a program to quantify the structural properties of nonhyperuniform and hyperuniform networks. In particular, large two-dimensional (2D) Voronoi networks (graphs) containing approximately 10,000 nodes are created from a variety of different point configurations, including the antihyperuniform hyperplane intersection process (HIP), nonhyperuniform Poisson process, nonhyperuniform random sequential addition (RSA) saturated packing, and both non-stealthy and stealthy hyperuniform point processes. We carry out an extensive study of the Voronoi-cell area distribution of each of the networks by determining multiple metrics that characterize the distribution, including their average areas and corresponding variances as well as higher-order cumulants (i.e., skewness γ1 and excess kurtosis γ2). We show that the HIP distribution is far from Gaussian, as evidenced by a high skewness (γ1=3.16) and large positive excess kurtosis (γ2=16.2). The Poisson (with γ1=1.07 and γ2=1.79) and non-stealthy hyperuniform (with γ1=0.257 and γ2=0.0217) distributions are Gaussian-like distributions, since they exhibit a small but positive skewness and excess kurtosis. The RSA (with γ1=0.450 and γ2=−0.0384) and the highest stealthy hyperuniform distributions (with γ1=0.0272 and γ2=−0.0626) are also non-Gaussian because of their low skewness and negative excess kurtosis, which is diametrically opposite of the non-Gaussian behavior of the HIP. The fact that the cell-area distributions of large, finite-sized RSA and stealthy hyperuniform networks (e.g., with N≈10,000 nodes) are narrower, have larger peaks, and smaller tails than a Gaussian distribution implies that in the thermodynamic limit th

关键词： Gaussian distribution

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Evaluation of the Performance of Wearables’ Inertial Sensors for the Diagnosis of Resting Tremor in Parkinson’s Disease

Evaluation of the Performance of Wearables’ Inertial Sensor...

引用

17th International Joint Conference on Biomedical engineering Systems and Technologies, BIOSTEC 2024

作者： Polvorinos-Fernández, Carlos Sigcha, Luis de Pablo, Laura Pereira Borzí, Luigi Cardoso, Paulo Costa, Nelson Costa, Susana López, Juan Manuel de Arcas, Guillermo Pavón, Ignacio Mechanical Engineering Department ETSI Industriales Universidad Politécnica de Madrid Spain Group University of Limerick LimerickV94 T9PX Ireland ALGORITMI Research Center School of Engineering University of Minho Guimarães Portugal PolitoBIOMed Lab–Biomedical Engineering Lab Politecnico di Torino Turin10129 Italy ANTHEA Lab–Data Analytics and Technologies for Health Lab Department of Control and Computer Engineering Politecnico di Torino Turin10129 Italy Physical Electronics Electrical Engineering and Applied Physics Department ETS de Ingeniería y Sistemas de Telecomunicación Universidad Politécnica de Madrid Spain

Currently, objective monitoring of resting tremor in Parkinson’s disease (PD) involves wearable devices and machine learning. Smartwatches may present an affordable method for remote and unintrusive tremor monitoring. However, the development of optimized systems is necessary to perform accurate monitoring in free-living settings. In this study, the potential of inertial sensors to detect resting tremors is evaluated. A smartwatch was placed on the wrist of six subjects with PD during the execution of MDS-UPDRS motor tasks. Data were collected over eight weeks from triaxial accelerometer and gyroscope simultaneously and used to implement machine learning algorithms to detect resting tremor. The best performance (accuracy 97.0% in tremor detection) was achieved using accelerometer data analysed with a Random Forest classifier, while the gyroscope showed lower performance (93.0%). The results indicates that the use of the accelerometer in commercial smartwatches can offer effective results for detecting resting tremors, while reducing computational workload. These results show opportunities for the development of robust free-living tremor monitoring systems using commodity devices and algorithms using a single sensor. © 2024 by SCITEPRESS–Science and Technology Publications, Lda.

关键词： Gyroscopes

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Longitudinal, Multimodal Tracking Reveals Lasting Neurovascular Impact of Individual Microinfarcts

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Advanced Science 2025年第22期12卷 e2417003页

作者： Jin, Yifu He, Fei Rathore, Haad Sun, Yingchu Zhang, Jia-ao Li, Xinyu Yin, Rongkang Zhu, Hanlin Xie, Chong Luan, Lan Department of Electrical and Computer Engineering Rice University HoustonTX77005 United States Neuroengineering Initiative Rice University HoustonTX77005 United States Applied Physics Program Rice University HoustonTX77005 United States Department of Bioengineering Rice University HoustonTX77005 United States

Microinfarcts, the "invisible lesions", are prevalent in aged and injured brains and associated with cognitive impairments, yet their neurophysiological impact remains largely unknown. Using a multimodal chronic neural platform that combines functional microvasculature imaging with spatially resolved neural recording, the neurovascular effect of a single microinfarct is investigated. Unlike larger strokes, microinfarcts induced only temporary suppression of neural activity with minimal cell death, with recovery paralleling vasculature remodeling at the infarct core. Neural activity is more severely suppressed at the shallower cortical layer despite milder vascular damage compared to deeper layers, and the excitability of fast-spiking interneurons attenuation is accompanied by heightened bursting of regular spiking neurons. Spike phase locking at the low-gamma band is disrupted, indicating a lasting impairment of long-range assembly communication. These results highlight the subtle yet significant neurovascular disruptions of a single microinfarct. © 2025 The Author(s). Advanced Science published by Wiley-VCH GmbH.

关键词： Flexible electronics

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Mechanism of skyrmion condensation and pairing for twisted bilayer graphene

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Physical Review B 2022年第18期105卷 184505-184505页

作者： Dian Jing Alexander Conkey Tyner Pallab Goswami Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Department of Chemical and Biological Engineering Northwestern University Evanston Illinois 60208 USA Integrated Science Program Northwestern University Evanston Illinois 60208 USA Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA

When quantum flavor Hall insulator phases of itinerant fermions are disordered by strong quantum fluctuations, the condensation of skyrmion textures of order parameter fields can lead to superconductivity. In this work, we address the mechanism of skyrmion condensation by considering the scattering between (2+1)-dimensional Weyl fermions and hedgehog-type tunneling configurations of order parameters that violate the skyrmion-number conservation law. We show the quantized, flavor Hall conductivity (σxyf) controls the degeneracy of topologically protected, fermion zero-modes, localized on hedgehogs. The overlap between zero-mode eigenfunctions or 't Hooft vertex is shown to control the nature of the paired states. Employing this formalism for the N=2 model of twisted bilayer graphene, we describe the competition among flavor Hall orders, charge 4e− superconductivity, and various charge 2e− paired states in BCS and paired-density-wave channels. At charge neutrality, we show that the competition between flavor Hall insulators and charge 2e− states can be captured by SO(9) nonlinear sigma models. If the topological pairing mechanism can dominate over the conventional pairing mechanism, our work predicts the flavor-symmetry-preserving charge 4e− superconductivity as a natural candidate for the paired state in the vicinity of the charge neutral point.

关键词： FFLO Multiband superconductivity Pairing mechanisms Superconducting order parameter Superconductivity Topological insulators Topological phase transition Topological phases of matter Topological superconductors

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