Machine learning (ML) provides a broad spectrum of tools and architectures that enable the transformation of data from simulations and experiments into useful and explainable science, thereby augmenting domain knowledge. Furthermore, ML-enhanced numerical modelling can revamp scientific computing for real-world complex engineering systems, creating unique opportunities to examine the operation of the technologies in detail and automate their optimization and control. In recent years, ML applications have seen significant growth across various scientific domains, particularly in fluid mechanics, where ML has shown great promise in enhancing computational modeling of fluid flows. In contrast, ML applications in numerical plasma physics research remain relatively limited in scope and extent. Despite this, the close relationship between fluid mechanics and plasma physics presents a valuable opportunity to create a roadmap for transferring ML advances in fluid flow modeling to computational plasma physics. This Perspective aims to outline such a roadmap. We begin by discussing some general fundamental aspects of ML, including the various categories of ML algorithms and the different types of problems that can be solved with the help of ML. With regard to each problem type, we then present specific examples from the use of ML in computational fluid dynamics, reviewing several insightful prior efforts. We also review recent ML applications in plasma physics for each problem type. The paper discusses promising future directions and development pathways for ML in plasma modelling within the different application areas. Additionally, we point out prominent challenges that must be addressed to realize ML's full potential in computational plasma physics, including the need for cost-effective high-fidelity simulation tools for extensive data generation.
机器学习（ML）提供了范围广泛的工具和架构，能够将模拟和实验数据转化为有意义、可解释的科学数据，从而增强领域知识。此外，ML 增强型数值建模能够改造现实世界复杂工程系统的科学计算，为详细研究技术的运行以及自动优化和控制创造独特的机会。近年来，ML 的应用在各个科学领域都有显著增长，尤其是在流体力学领域，ML 在增强流体流动的计算建模方面显示出巨大前景。相比之下，ML 在等离子体数值物理研究中的应用在范围和程度上仍然相对有限。尽管如此，流体力学与等离子体物理之间的密切关系提供了一个宝贵的机会，为将 ML 在流体流动建模方面的进展转移到计算等离子体物理方面绘制路线图。本视角旨在勾勒这样一个路线图。我们首先讨论了 ML 的一些一般基本方面，包括 ML 算法的不同类别以及在 ML 帮助下可以解决的不同类型的问题。然后，针对每种问题类型，我们介绍了 ML 在计算流体力学中应用的具体实例，回顾了之前几项有见地的工作。我们还针对每种问题类型回顾了 ML 在等离子物理学中的最新应用。本文讨论了 ML 在不同应用领域的等离子体建模中的未来发展方向和发展途径。此外，我们还指出了为充分发挥 ML 在计算等离子体物理中的潜力而必须应对的主要挑战，包括需要具有成本效益的高保真仿真工具来生成大量数据。
{"title":"Machine Learning Applications to Computational Plasma Physics and Reduced-Order Plasma Modeling: A Perspective","authors":"Farbod Faraji, Maryam Reza","doi":"arxiv-2409.02349","DOIUrl":"https://doi.org/arxiv-2409.02349","url":null,"abstract":"Machine learning (ML) provides a broad spectrum of tools and architectures\u0000that enable the transformation of data from simulations and experiments into\u0000useful and explainable science, thereby augmenting domain knowledge.\u0000Furthermore, ML-enhanced numerical modelling can revamp scientific computing\u0000for real-world complex engineering systems, creating unique opportunities to\u0000examine the operation of the technologies in detail and automate their\u0000optimization and control. In recent years, ML applications have seen\u0000significant growth across various scientific domains, particularly in fluid\u0000mechanics, where ML has shown great promise in enhancing computational modeling\u0000of fluid flows. In contrast, ML applications in numerical plasma physics\u0000research remain relatively limited in scope and extent. Despite this, the close\u0000relationship between fluid mechanics and plasma physics presents a valuable\u0000opportunity to create a roadmap for transferring ML advances in fluid flow\u0000modeling to computational plasma physics. This Perspective aims to outline such\u0000a roadmap. We begin by discussing some general fundamental aspects of ML,\u0000including the various categories of ML algorithms and the different types of\u0000problems that can be solved with the help of ML. With regard to each problem\u0000type, we then present specific examples from the use of ML in computational\u0000fluid dynamics, reviewing several insightful prior efforts. We also review\u0000recent ML applications in plasma physics for each problem type. The paper\u0000discusses promising future directions and development pathways for ML in plasma\u0000modelling within the different application areas. Additionally, we point out\u0000prominent challenges that must be addressed to realize ML's full potential in\u0000computational plasma physics, including the need for cost-effective\u0000high-fidelity simulation tools for extensive data generation.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196058","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}
We present the first assessment, using hybrid PIC simulations, of the role of non-linear Landau damping in the process of self-generated scattering in a high $beta$ plasma, conditions appropriate for CR scattering in the halo of the Galaxy. This damping process manifests itself in the form of heating of the background plasma and reduction of the drift speed of CRs that yet remains super-Alfvenic. We also show that the damping leads to an inverse cascade process, consisting of producing non-resonant large scale modes, a novel result with many potential phenomenological implications.
{"title":"The role of non-linear Landau damping for cosmic-ray transport","authors":"Benedikt Schroer, Damiano Caprioli, Pasquale Blasi","doi":"arxiv-2409.02230","DOIUrl":"https://doi.org/arxiv-2409.02230","url":null,"abstract":"We present the first assessment, using hybrid PIC simulations, of the role of\u0000non-linear Landau damping in the process of self-generated scattering in a high\u0000$beta$ plasma, conditions appropriate for CR scattering in the halo of the\u0000Galaxy. This damping process manifests itself in the form of heating of the\u0000background plasma and reduction of the drift speed of CRs that yet remains\u0000super-Alfvenic. We also show that the damping leads to an inverse cascade\u0000process, consisting of producing non-resonant large scale modes, a novel result\u0000with many potential phenomenological implications.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196061","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}
Robert J. Ewart, Michael L. Nastac, Pablo J. Bilbao, Thales Silva, Luís O. Silva, Alexander A. Schekochihin
Generic equilibria are derived for turbulent relaxing plasmas via an entropy-maximization procedure that accounts for the short-time conservation of certain collisionless invariants. The conservation of these collisionless invariants endows the system with a partial `memory' of its prior conditions, but is imperfect on long time scales due to the development of a turbulent cascade to small scales, which breaks the precise conservation of phase volume, making this memory imprecise. The equilibria are still determined by the short-time collisionless invariants, but the invariants themselves are driven to a universal form by the nature of the turbulence. This is numerically confirmed for the case of beam instabilities in one-dimensional electrostatic plasmas, where sufficiently strong turbulence appears to cause the distribution function of particle energies to develop a universal power-law tail, with exponent -2.
{"title":"Relaxation to universal non-Maxwellian equilibria in a collisionless plasma","authors":"Robert J. Ewart, Michael L. Nastac, Pablo J. Bilbao, Thales Silva, Luís O. Silva, Alexander A. Schekochihin","doi":"arxiv-2409.01742","DOIUrl":"https://doi.org/arxiv-2409.01742","url":null,"abstract":"Generic equilibria are derived for turbulent relaxing plasmas via an\u0000entropy-maximization procedure that accounts for the short-time conservation of\u0000certain collisionless invariants. The conservation of these collisionless\u0000invariants endows the system with a partial `memory' of its prior conditions,\u0000but is imperfect on long time scales due to the development of a turbulent\u0000cascade to small scales, which breaks the precise conservation of phase volume,\u0000making this memory imprecise. The equilibria are still determined by the\u0000short-time collisionless invariants, but the invariants themselves are driven\u0000to a universal form by the nature of the turbulence. This is numerically\u0000confirmed for the case of beam instabilities in one-dimensional electrostatic\u0000plasmas, where sufficiently strong turbulence appears to cause the distribution\u0000function of particle energies to develop a universal power-law tail, with\u0000exponent -2.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225089","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}
Richard Nies, Felix Parra, Michael Barnes, Noah Mandell, William Dorland
Strongly driven ion-scale turbulence in tokamak plasmas is shown to be regulated by a new propagating zonal flow mode, the toroidal secondary, which is nonlinearly supported by the turbulence. The mode grows and propagates due to the combined effects of zonal flow shearing and advection by the magnetic drift. Above a threshold in the turbulence level, small-scale toroidal secondary modes become unstable and shear apart turbulent eddies, forcing the turbulence level to remain near the threshold. By including the new zonal flow physics into a theory of turbulence saturation based on the critical balance conjecture, scaling laws for the turbulent heat flux, fluctuation spectra, and zonal flow amplitude are derived and shown to be satisfied in nonlinear gyrokinetic simulations.
{"title":"Saturation of magnetised plasma turbulence by propagating zonal flows","authors":"Richard Nies, Felix Parra, Michael Barnes, Noah Mandell, William Dorland","doi":"arxiv-2409.02283","DOIUrl":"https://doi.org/arxiv-2409.02283","url":null,"abstract":"Strongly driven ion-scale turbulence in tokamak plasmas is shown to be\u0000regulated by a new propagating zonal flow mode, the toroidal secondary, which\u0000is nonlinearly supported by the turbulence. The mode grows and propagates due\u0000to the combined effects of zonal flow shearing and advection by the magnetic\u0000drift. Above a threshold in the turbulence level, small-scale toroidal\u0000secondary modes become unstable and shear apart turbulent eddies, forcing the\u0000turbulence level to remain near the threshold. By including the new zonal flow\u0000physics into a theory of turbulence saturation based on the critical balance\u0000conjecture, scaling laws for the turbulent heat flux, fluctuation spectra, and\u0000zonal flow amplitude are derived and shown to be satisfied in nonlinear\u0000gyrokinetic simulations.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196059","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}
Accurate modeling in the warm dense matter regime is a persistent challenge with the most detailed models such as quantum molecular dynamics and path integral Monte Carlo being immensely computationally expensive. Density functional theory (DFT)-based average atom models (AAM) offer significant speed-ups in calculation times while still retaining fair accuracy in evaluating equations of state, mean ionizations, and more. Despite their success, AAMs struggle to precisely account for electronic interactions -- in particular, they do not account for effects on the kinetic energy arising from overlaps in neighboring atom densities. We aim to enhance these models by including such interactions via the non-additive kinetic potential $v^{rm nadd}$ as in DFT embedding theories. $v^{rm nadd}$ can be computed using Thomas-Fermi, von Weizs"acker, or more sophisticated kinetic energy functionals. The proposed model introduces $v^{rm nadd}$ as a novel interaction term in existing ion-correlation models, which include interactions beyond the central atom. We have applied this model to hydrogen at 5 eV and densities ranging 0.008 to 0.8 g/cm$^3$, and investigated the effects of $v^{rm nadd}$ on electron densities, Kohn-Sham energy level shifts, mean ionization, and total energies.
{"title":"Embedding theory contributions to average atom models for warm dense matter","authors":"Sameen Yunus, David A. Strubbe","doi":"arxiv-2409.02105","DOIUrl":"https://doi.org/arxiv-2409.02105","url":null,"abstract":"Accurate modeling in the warm dense matter regime is a persistent challenge\u0000with the most detailed models such as quantum molecular dynamics and path\u0000integral Monte Carlo being immensely computationally expensive. Density\u0000functional theory (DFT)-based average atom models (AAM) offer significant\u0000speed-ups in calculation times while still retaining fair accuracy in\u0000evaluating equations of state, mean ionizations, and more. Despite their\u0000success, AAMs struggle to precisely account for electronic interactions -- in\u0000particular, they do not account for effects on the kinetic energy arising from\u0000overlaps in neighboring atom densities. We aim to enhance these models by\u0000including such interactions via the non-additive kinetic potential $v^{rm\u0000nadd}$ as in DFT embedding theories. $v^{rm nadd}$ can be computed using\u0000Thomas-Fermi, von Weizs\"acker, or more sophisticated kinetic energy\u0000functionals. The proposed model introduces $v^{rm nadd}$ as a novel\u0000interaction term in existing ion-correlation models, which include interactions\u0000beyond the central atom. We have applied this model to hydrogen at 5 eV and\u0000densities ranging 0.008 to 0.8 g/cm$^3$, and investigated the effects of\u0000$v^{rm nadd}$ on electron densities, Kohn-Sham energy level shifts, mean\u0000ionization, and total energies.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"94 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225090","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}
This paper presents a kinetic model for the coupled evolution of radiation, electrons, and ions in a radiation plasma system. The model is solved using two methods. The gas-kinetic scheme (GKS) for electron and ion hydrodynamics and the unified gas-kinetic scheme (UGKS) for non-equilibrium radiative transfer. The UGKS accurately captures multiscale photon transport from free streaming to diffusion across varying fluid opacities. This approach enables the scheme to model equilibrium plasma with non-equilibrium radiation transport. The model is validated through several test cases, including radiative transfer in kinetic and diffusion regimes, Marshak wave, Radiative shock, 3T double lax shock tube problem, two-dimensional Sedov blast wave, and two-dimensional tophat based problem. These tests demonstrate the current scheme's capability to handle diverse radiation plasma scenarios.
{"title":"Radiative hydrodynamic equations with nonequilibrium radiative transfer","authors":"Mingyu Quan, Xiaojian Yang, Yufeng Wei, Kun Xu","doi":"arxiv-2409.01827","DOIUrl":"https://doi.org/arxiv-2409.01827","url":null,"abstract":"This paper presents a kinetic model for the coupled evolution of radiation,\u0000electrons, and ions in a radiation plasma system. The model is solved using two\u0000methods. The gas-kinetic scheme (GKS) for electron and ion hydrodynamics and\u0000the unified gas-kinetic scheme (UGKS) for non-equilibrium radiative transfer.\u0000The UGKS accurately captures multiscale photon transport from free streaming to\u0000diffusion across varying fluid opacities. This approach enables the scheme to\u0000model equilibrium plasma with non-equilibrium radiation transport. The model is\u0000validated through several test cases, including radiative transfer in kinetic\u0000and diffusion regimes, Marshak wave, Radiative shock, 3T double lax shock tube\u0000problem, two-dimensional Sedov blast wave, and two-dimensional tophat based\u0000problem. These tests demonstrate the current scheme's capability to handle\u0000diverse radiation plasma scenarios.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142195855","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}
Danika Nimlos, Alejandro Arellano, Scott Kevin Cushing
The increasing popularity of time-resolved X-ray absorption measurements for understanding dynamics in molecular and material systems has led to many advances in table-top sources for pulsed X-rays. We report on a table top laser-produced plasma (LPP) source that can perform soft X-ray (SXR), near edge X-ray absorption fine structure (NEXAFS) measurements using a laser source with 23 ps pulse duration. The spectrometer's key specifications, such as brilliance, resolution, and stability, are characterized against the more commonly used longer-pulse-duration LPP sources. The 23 ps laser produced approximately an order of magnitude weaker SXR flux than the 8 ns laser for a higher power density due to the smaller total energy absorbed by the plasma. The increased repetition rate and an implemented self-referencing scheme still allowed for high-resolution, synchrotron-like NEXAFS measurements of Si3N4 and TiO2 thin films with 2.5 minute acquisition times. It was observed that degradation of the gas jet nozzle led to long-term instability of the source, which can be remediated using alternative nozzle designs. This work demonstrates the feasibility of achieving higher temporal resolution in future time-resolved X-ray absorption measurements using table-top laser-produced plasma sources
为了解分子和材料系统的动力学而进行的时间分辨 X 射线吸收测量越来越受欢迎，这促使台式脉冲 X 射线源取得了许多进展。我们报告了一种台式激光产生的等离子体（LPP）源，它可以使用 23 ps 脉冲持续时间的激光源进行软 X 射线（SXR）、近边缘 X 射线吸收精细结构（NEXAFS）测量。该光谱仪的主要技术指标，如亮度、分辨率和稳定性等，都是根据更常用的长脉冲持续时间 LPP 源来确定的。由于等离子体吸收的总能量较小，在较高功率密度下，23 ps 激光产生的 SXR 流量比 8 ns 激光产生的 SXR 流量弱大约一个数量级。据观察，气体喷射喷嘴的退化导致了光源的长期不稳定性，这可以通过使用替代喷嘴设计来解决。这项工作证明了在未来使用台式激光等离子体源进行时间分辨 X 射线吸收测量时实现更高的时间分辨率的可行性。
{"title":"Approaching the Lower Temporal Limit of Laser-Produced Plasma Sources for Table-Top Soft X-ray NEXAFS Measurements","authors":"Danika Nimlos, Alejandro Arellano, Scott Kevin Cushing","doi":"arxiv-2409.02280","DOIUrl":"https://doi.org/arxiv-2409.02280","url":null,"abstract":"The increasing popularity of time-resolved X-ray absorption measurements for\u0000understanding dynamics in molecular and material systems has led to many\u0000advances in table-top sources for pulsed X-rays. We report on a table top\u0000laser-produced plasma (LPP) source that can perform soft X-ray (SXR), near edge\u0000X-ray absorption fine structure (NEXAFS) measurements using a laser source with\u000023 ps pulse duration. The spectrometer's key specifications, such as\u0000brilliance, resolution, and stability, are characterized against the more\u0000commonly used longer-pulse-duration LPP sources. The 23 ps laser produced\u0000approximately an order of magnitude weaker SXR flux than the 8 ns laser for a\u0000higher power density due to the smaller total energy absorbed by the plasma.\u0000The increased repetition rate and an implemented self-referencing scheme still\u0000allowed for high-resolution, synchrotron-like NEXAFS measurements of Si3N4 and\u0000TiO2 thin films with 2.5 minute acquisition times. It was observed that\u0000degradation of the gas jet nozzle led to long-term instability of the source,\u0000which can be remediated using alternative nozzle designs. This work\u0000demonstrates the feasibility of achieving higher temporal resolution in future\u0000time-resolved X-ray absorption measurements using table-top laser-produced\u0000plasma sources","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196063","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}
Paul Huslage, Elisabeth J. Paul, Mohammed Haque. Pedro F. Gil, Nicolo Foppiani, Jason Smoniewsk, Eve. V. Stenson
This work provides an optimization mechanism to ensure the compatibility of ReBCO (Rare-earth Barium Copper Oxide) high-temperature superconducting (HTS) tapes with non-planar stellarator coils. ReBCO coils enable higher field strengths and operating temperatures for the magnet systems of future fusion reactors but are sensitive to strain due to their brittle, ceramic functional layer. We have implemented a metric to optimize strain on stellarator coils made from ReBCO superconductors into the stellarator optimization framework texttt{SIMSOPT} and used it to design new stellarator coil configurations. To ensure structural integrity of coils wound with HTS tape, we introduce a penalty on binormal curvature and torsion along a coil. It can be used to optimize the orientation of the winding path for a given coil filament or to jointly optimize orientation and coil filament. We apply the strain optimization to three cases. For the EPOS (Electrons and Positrons in an Optimized Stellarator) design, we combine the strain penalty with an objective for quasisymmetry into a single-stage optimization; this enables us to find a configuration with excellent quasisymmetry at the smallest possible size compatible with the use of ReBCO tape. For CSX (Columbia Stellarator eXperiment), in addition to HTS strain, we add a penalty to prevent net tape rotation to ease the coil winding process. If the strain is calculated for a coil at reactor scale, we find a considerable variation of the binormal and torsional strain over the cross section of the large winding pack (0.5,m x 0.5,m). By exploiting the overall orientation of the winding pack as a degree of freedom, we can reduce binormal and torsional strains below limits for every ReBCO stack.
{"title":"Strain Optimization for ReBCO High-Temperature Superconducting Stellarator Coils in SIMSOPT","authors":"Paul Huslage, Elisabeth J. Paul, Mohammed Haque. Pedro F. Gil, Nicolo Foppiani, Jason Smoniewsk, Eve. V. Stenson","doi":"arxiv-2409.01925","DOIUrl":"https://doi.org/arxiv-2409.01925","url":null,"abstract":"This work provides an optimization mechanism to ensure the compatibility of\u0000ReBCO (Rare-earth Barium Copper Oxide) high-temperature superconducting (HTS)\u0000tapes with non-planar stellarator coils. ReBCO coils enable higher field\u0000strengths and operating temperatures for the magnet systems of future fusion\u0000reactors but are sensitive to strain due to their brittle, ceramic functional\u0000layer. We have implemented a metric to optimize strain on stellarator coils\u0000made from ReBCO superconductors into the stellarator optimization framework\u0000texttt{SIMSOPT} and used it to design new stellarator coil configurations. To\u0000ensure structural integrity of coils wound with HTS tape, we introduce a\u0000penalty on binormal curvature and torsion along a coil. It can be used to\u0000optimize the orientation of the winding path for a given coil filament or to\u0000jointly optimize orientation and coil filament. We apply the strain\u0000optimization to three cases. For the EPOS (Electrons and Positrons in an\u0000Optimized Stellarator) design, we combine the strain penalty with an objective\u0000for quasisymmetry into a single-stage optimization; this enables us to find a\u0000configuration with excellent quasisymmetry at the smallest possible size\u0000compatible with the use of ReBCO tape. For CSX (Columbia Stellarator\u0000eXperiment), in addition to HTS strain, we add a penalty to prevent net tape\u0000rotation to ease the coil winding process. If the strain is calculated for a\u0000coil at reactor scale, we find a considerable variation of the binormal and\u0000torsional strain over the cross section of the large winding pack (0.5,m x\u00000.5,m). By exploiting the overall orientation of the winding pack as a degree\u0000of freedom, we can reduce binormal and torsional strains below limits for every\u0000ReBCO stack.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196062","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}
C. A. McAnespie, P. Chaudhary, M. J. V. Streeter, S. W. Botchway, N. Bourgeois, L. Calvin, N. Cavanagh, K. Fleck, D. Jaroszynski, B. Kettle, A. M. Lupu, S. P. D. Mangles, S. J. McMahon, J. Mill, S. R. Needham, P. P. Rajeev, K. M. Prise, G. Sarri
We report on the first experimental characterization of a laser-wakefield accelerator able to deliver, in a single pulse, doses in excess of 1 Gy on timescales of the order of tens of femtoseconds, reaching unprecedented average dose-rates above $10^{13}$ Gy/s. The irradiator is demonstrated to deliver doses tuneable up to 2.2 Gy in a cm$^2$ area and with a high degree of longitudinal and transverse uniformity in a single irradiation. In this regime, proof-of-principle irradiation of patient-derived glioblastoma stem-like cells and human skin fibroblast cells show indications of a differential cellular response, when compared to reference irradiations at conventional dose-rates. These include a statistically significant increase in relative biological effectiveness ($1.40pm0.08$ at 50% survival for both cell lines) and a significant reduction of the relative radioresistance of tumour cells. Data analysis provides preliminary indications that these effects might not be fully explained by induced oxygen depletion in the cells but may be instead linked to a higher complexity of the damages triggered by the ultra-high density of ionising tracks of femtosecond-scale radiation pulses. These results demonstrate an integrated platform for systematic radiobiological studies at unprecedented beam durations and dose-rates, a unique infrastructure for translational research in radiobiology at the femtosecond scale.
{"title":"Single-pulse Gy-scale irradiation of biological cells at average dose-rates above $10^{13}$ Gy/s from a laser-wakefield accelerator","authors":"C. A. McAnespie, P. Chaudhary, M. J. V. Streeter, S. W. Botchway, N. Bourgeois, L. Calvin, N. Cavanagh, K. Fleck, D. Jaroszynski, B. Kettle, A. M. Lupu, S. P. D. Mangles, S. J. McMahon, J. Mill, S. R. Needham, P. P. Rajeev, K. M. Prise, G. Sarri","doi":"arxiv-2409.01717","DOIUrl":"https://doi.org/arxiv-2409.01717","url":null,"abstract":"We report on the first experimental characterization of a laser-wakefield\u0000accelerator able to deliver, in a single pulse, doses in excess of 1 Gy on\u0000timescales of the order of tens of femtoseconds, reaching unprecedented average\u0000dose-rates above $10^{13}$ Gy/s. The irradiator is demonstrated to deliver\u0000doses tuneable up to 2.2 Gy in a cm$^2$ area and with a high degree of\u0000longitudinal and transverse uniformity in a single irradiation. In this regime,\u0000proof-of-principle irradiation of patient-derived glioblastoma stem-like cells\u0000and human skin fibroblast cells show indications of a differential cellular\u0000response, when compared to reference irradiations at conventional dose-rates.\u0000These include a statistically significant increase in relative biological\u0000effectiveness ($1.40pm0.08$ at 50% survival for both cell lines) and a\u0000significant reduction of the relative radioresistance of tumour cells. Data\u0000analysis provides preliminary indications that these effects might not be fully\u0000explained by induced oxygen depletion in the cells but may be instead linked to\u0000a higher complexity of the damages triggered by the ultra-high density of\u0000ionising tracks of femtosecond-scale radiation pulses. These results\u0000demonstrate an integrated platform for systematic radiobiological studies at\u0000unprecedented beam durations and dose-rates, a unique infrastructure for\u0000translational research in radiobiology at the femtosecond scale.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196068","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}
Simulating gas flow within the divertor, which is a crucial component in nuclear fusion reactors, is essential for assessing and enhancing its design and performance. Traditional methods, such as the direct simulation Monte Carlo and the discrete velocity method, often fall short in efficiency for these simulations. In this study, we utilize the general synthetic iterative scheme to simulate a simplified Tokamak divertor model, demonstrating its fast convergence and asymptotic-preserving properties in complex three-dimensional scenarios. A conservative estimate of speedup by three orders of magnitude is achieved by the general synthetic iterative scheme when compared to the direct simulation Monte Carlo method. We further investigate the relationship between pumping efficiency and factors like temperature, absorptivity, and the Knudsen number, providing valuable insights to guide the design and optimization of divertor structures.
{"title":"Multiscale simulation of rarefied gas flows in Divertor Tokamak Test facility","authors":"Wei Li, Yanbing Zhang, Jianan Zeng, Lei Wu","doi":"arxiv-2409.05895","DOIUrl":"https://doi.org/arxiv-2409.05895","url":null,"abstract":"Simulating gas flow within the divertor, which is a crucial component in\u0000nuclear fusion reactors, is essential for assessing and enhancing its design\u0000and performance. Traditional methods, such as the direct simulation Monte Carlo\u0000and the discrete velocity method, often fall short in efficiency for these\u0000simulations. In this study, we utilize the general synthetic iterative scheme\u0000to simulate a simplified Tokamak divertor model, demonstrating its fast\u0000convergence and asymptotic-preserving properties in complex three-dimensional\u0000scenarios. A conservative estimate of speedup by three orders of magnitude is\u0000achieved by the general synthetic iterative scheme when compared to the direct\u0000simulation Monte Carlo method. We further investigate the relationship between\u0000pumping efficiency and factors like temperature, absorptivity, and the Knudsen\u0000number, providing valuable insights to guide the design and optimization of\u0000divertor structures.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196070","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}
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