The theory of gauge transformations in linearized gravitation is investigated. After a brief discussion of the fundamentals of the kinetic theory in curved spacetime, the Einstein-Vlasov-Maxwell system of equations in terms of gauge invariant quantities is established without neglecting the equations of motion associated with the dynamics of the non-radiative components of the metric tensor. The established theory is applied to a non-collisional electron-positron plasma, leading to a dispersion relation for gravitational waves in this model system. The problem of Landau damping is addressed and some attention is given to the issue of the energy exchanges between the plasma and the gravitational wave. In a future paper, a more complete set of approximate dispersion relations for waves and oscillations in plasmas will be presented, including the dynamics of non-radiative components of the metric tensor, with special attention to the problems of the Landau damping and of the energy exchanges between matter, the electromagnetic field and the gravitational field.
{"title":"Methodological notes on the gauge invariance in the treatment of waves and oscillations in plasmas $via$ the Einstein-Vlasov-Maxwell system: Fundamental equations","authors":"Lucas Bourscheidt, Fernando Haas","doi":"arxiv-2408.01531","DOIUrl":"https://doi.org/arxiv-2408.01531","url":null,"abstract":"The theory of gauge transformations in linearized gravitation is\u0000investigated. After a brief discussion of the fundamentals of the kinetic\u0000theory in curved spacetime, the Einstein-Vlasov-Maxwell system of equations in\u0000terms of gauge invariant quantities is established without neglecting the\u0000equations of motion associated with the dynamics of the non-radiative\u0000components of the metric tensor. The established theory is applied to a\u0000non-collisional electron-positron plasma, leading to a dispersion relation for\u0000gravitational waves in this model system. The problem of Landau damping is\u0000addressed and some attention is given to the issue of the energy exchanges\u0000between the plasma and the gravitational wave. In a future paper, a more\u0000complete set of approximate dispersion relations for waves and oscillations in\u0000plasmas will be presented, including the dynamics of non-radiative components\u0000of the metric tensor, with special attention to the problems of the Landau\u0000damping and of the energy exchanges between matter, the electromagnetic field\u0000and the gravitational field.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"78 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941377","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}
Jared T. De ChantLawrence Berkeley National Laboratory, Berkeley, CA USA, Kei NakamuraLawrence Berkeley National Laboratory, Berkeley, CA USA, Qing JiLawrence Berkeley National Laboratory, Berkeley, CA USA, Lieselotte Obst-HueblLawrence Berkeley National Laboratory, Berkeley, CA USA, Samuel K. BarberLawrence Berkeley National Laboratory, Berkeley, CA USA, Antoine M. SnijdersLawrence Berkeley National Laboratory, Berkeley, CA USA, Thomas SchenkelLawrence Berkeley National Laboratory, Berkeley, CA USA, Jeroen van TilborgLawrence Berkeley National Laboratory, Berkeley, CA USA, Cameron G. R. GeddesLawrence Berkeley National Laboratory, Berkeley, CA USA, Carl B. SchroederLawrence Berkeley National Laboratory, Berkeley, CA USA, Eric EsareyLawrence Berkeley National Laboratory, Berkeley, CA USA
Laser-driven (LD) ion acceleration has been explored in a newly constructed short focal length beamline at the BELLA petawatt facility (interaction point 2, iP2). For applications utilizing such LD ion beams, a beam transport system is required, which for reasons of compactness be ideally contained within 3 m. The large divergence and energy spread of LD ion beams present a unique challenge to transporting them compared to beams from conventional accelerators. This work gives an overview of proposed compact transport designs that can satisfy different requirements depending on the application for the iP2 proton beamline such as radiation biology, material science, and high energy density science. These designs are optimized for different parameters such as energy spread and peak proton density according to an application's need. The various designs consist solely of permanent magnet elements, which can provide high magnetic field gradients on a small footprint. While the field strengths are fixed, we have shown that the beam size and energy can be tuned effectively by varying the placement of the magnets. The performance of each design was evaluated based on high order particle tracking simulations of typical LD proton beams. A more detailed investigation was carried out for a design to deliver 10 MeV LD accelerated ions for radiation biology applications. With these transport system designs, the iP2 beamline is ready to house various application experiments.
{"title":"Design Optimization of Permanent-Magnet Based Compact Transport Systems for Laser-Driven Proton Beams","authors":"Jared T. De ChantLawrence Berkeley National Laboratory, Berkeley, CA USA, Kei NakamuraLawrence Berkeley National Laboratory, Berkeley, CA USA, Qing JiLawrence Berkeley National Laboratory, Berkeley, CA USA, Lieselotte Obst-HueblLawrence Berkeley National Laboratory, Berkeley, CA USA, Samuel K. BarberLawrence Berkeley National Laboratory, Berkeley, CA USA, Antoine M. SnijdersLawrence Berkeley National Laboratory, Berkeley, CA USA, Thomas SchenkelLawrence Berkeley National Laboratory, Berkeley, CA USA, Jeroen van TilborgLawrence Berkeley National Laboratory, Berkeley, CA USA, Cameron G. R. GeddesLawrence Berkeley National Laboratory, Berkeley, CA USA, Carl B. SchroederLawrence Berkeley National Laboratory, Berkeley, CA USA, Eric EsareyLawrence Berkeley National Laboratory, Berkeley, CA USA","doi":"arxiv-2408.01502","DOIUrl":"https://doi.org/arxiv-2408.01502","url":null,"abstract":"Laser-driven (LD) ion acceleration has been explored in a newly constructed\u0000short focal length beamline at the BELLA petawatt facility (interaction point\u00002, iP2). For applications utilizing such LD ion beams, a beam transport system\u0000is required, which for reasons of compactness be ideally contained within 3 m.\u0000The large divergence and energy spread of LD ion beams present a unique\u0000challenge to transporting them compared to beams from conventional\u0000accelerators. This work gives an overview of proposed compact transport designs\u0000that can satisfy different requirements depending on the application for the\u0000iP2 proton beamline such as radiation biology, material science, and high\u0000energy density science. These designs are optimized for different parameters\u0000such as energy spread and peak proton density according to an application's\u0000need. The various designs consist solely of permanent magnet elements, which\u0000can provide high magnetic field gradients on a small footprint. While the field\u0000strengths are fixed, we have shown that the beam size and energy can be tuned\u0000effectively by varying the placement of the magnets. The performance of each\u0000design was evaluated based on high order particle tracking simulations of\u0000typical LD proton beams. A more detailed investigation was carried out for a\u0000design to deliver 10 MeV LD accelerated ions for radiation biology\u0000applications. With these transport system designs, the iP2 beamline is ready to\u0000house various application experiments.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941378","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}
Sugan Durai Murugan, Giorgio Krstulovic, Dario Vincenzi, Samriddhi Sankar Ray
We construct a $d$-dimensional Eddy Damped Quasi-Normal Markovian (EDQNM) Closure Model to study dynamo action in arbitrary dimensions. In particular, we find lower $d_L$ and upper $d_U$ critical dimensions for sustained dynamo action in this incompressible problem. Our model is adaptable for future studies incorporating helicity, compressible effects and a wide range of magnetic Reynolds and Prandtl numbers.
{"title":"An upper critical dimension for dynamo action: A $d$-dimensional closure model study","authors":"Sugan Durai Murugan, Giorgio Krstulovic, Dario Vincenzi, Samriddhi Sankar Ray","doi":"arxiv-2408.01266","DOIUrl":"https://doi.org/arxiv-2408.01266","url":null,"abstract":"We construct a $d$-dimensional Eddy Damped Quasi-Normal Markovian (EDQNM)\u0000Closure Model to study dynamo action in arbitrary dimensions. In particular, we\u0000find lower $d_L$ and upper $d_U$ critical dimensions for sustained dynamo\u0000action in this incompressible problem. Our model is adaptable for future\u0000studies incorporating helicity, compressible effects and a wide range of\u0000magnetic Reynolds and Prandtl numbers.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941381","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}
E. TholerusUKAEA, L. GarzottiUKAEA, V. ParailUKAEA, Y. BaranovUKAEA, X. BonninITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, G. CorriganUKAEA, F. ErikssonUKAEA, D. FarinaIstituto per la Scienza e Tecnologia dei Plasmi, CNR, Milan, Italy, L. FiginiIstituto per la Scienza e Tecnologia dei Plasmi, CNR, Milan, Italy, D. M. HartingInstitut für Energie- und Klimaforschung IEK-4, FZJ, TEC, 52425 Jülich, Germany, S. H. KimITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, F. KoechlITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, A. LoarteITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, E. Militello AspUKAEA, H. NordmanAssociation EURATOM-VR, Chalmers University of Technology, Göteborg, Sweden, S. D. PinchesITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, A. R. PolevoiITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, P. StrandAssociation EURATOM-VR, Chalmers University of Technology, Göteborg, Sweden
In the initial stages of ITER operation, ELM mitigation systems need to be commissioned. This requires controlled flat-top operation in type-I ELMy H-mode regimes. Hydrogen or helium plasma discharges are used exclusively in these stages to ensure negligible production of neutrons from fusion reactions. With the expected higher L-H power threshold of hydrogen and helium plasmas compared to corresponding D and D/T plasmas, it is uncertain whether available auxiliary power systems are sufficient to operate in stable type-I ELMy H-mode. This has been investigated using integrated core and edge/SOL/divertor modelling with JINTRAC. Assuming that the L-H power threshold is well captured by the Martin08 scaling law, the presented simulations have found that 30 MW of ECRH power is likely required for the investigated hydrogen plasma scenarios, rather than the originally planned 20 MW in the 2016 Staged Approach ITER Baseline. However, past experiments have shown that a small helium fraction (~10 %) can considerably reduce the hydrogen plasma L-H power threshold. Assuming that these results extrapolate to ITER operation regimes, the 7.5MA/2.65T hydrogen plasma scenario is likely to access stable type-I ELMy H-mode operation also at 20 MW of ECRH.
在热核实验堆运行的初始阶段，需要启用 ELM 减缓系统。这需要在 I 型 ELMy H 模式下进行受控平顶运行。氢或氦等离子体放电仅用于这些阶段，以确保聚变反应产生的中子微乎其微。与相应的 D 和 D/T 等离子体相比，氢和氦等离子体的 L-H 功率阈值较高，因此尚不确定现有的辅助功率系统是否足以在稳定的 I 型 ELMy H 模式下运行。我们使用 JINTRAC 的集成核心和边缘/SOL/分流器建模对这一问题进行了研究。假定马丁08缩放定律能够很好地捕捉到L-H功率阈值，所进行的模拟发现，在所研究的氢等离子体方案中，很可能需要30兆瓦的ECRH功率，而不是2016年分阶段方法ITER基线中最初计划的20兆瓦。然而，过去的实验表明，较小的氦组分（约 10%）可以显著降低氢等离子体的长氢功率阈值。假设这些结果可以推广到热核实验堆的运行机制，那么 7.5MA/2.65T 氢等离子体方案很可能在 20 兆瓦 ECRH 的情况下也能实现稳定的 I 型 ELMy H 模式运行。
{"title":"Access and sustainment of ELMy H-mode operation for ITER Pre-Fusion Power Operation plasmas using JINTRAC","authors":"E. TholerusUKAEA, L. GarzottiUKAEA, V. ParailUKAEA, Y. BaranovUKAEA, X. BonninITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, G. CorriganUKAEA, F. ErikssonUKAEA, D. FarinaIstituto per la Scienza e Tecnologia dei Plasmi, CNR, Milan, Italy, L. FiginiIstituto per la Scienza e Tecnologia dei Plasmi, CNR, Milan, Italy, D. M. HartingInstitut für Energie- und Klimaforschung IEK-4, FZJ, TEC, 52425 Jülich, Germany, S. H. KimITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, F. KoechlITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, A. LoarteITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, E. Militello AspUKAEA, H. NordmanAssociation EURATOM-VR, Chalmers University of Technology, Göteborg, Sweden, S. D. PinchesITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, A. R. PolevoiITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France, P. StrandAssociation EURATOM-VR, Chalmers University of Technology, Göteborg, Sweden","doi":"arxiv-2408.01222","DOIUrl":"https://doi.org/arxiv-2408.01222","url":null,"abstract":"In the initial stages of ITER operation, ELM mitigation systems need to be\u0000commissioned. This requires controlled flat-top operation in type-I ELMy H-mode\u0000regimes. Hydrogen or helium plasma discharges are used exclusively in these\u0000stages to ensure negligible production of neutrons from fusion reactions. With\u0000the expected higher L-H power threshold of hydrogen and helium plasmas compared\u0000to corresponding D and D/T plasmas, it is uncertain whether available auxiliary\u0000power systems are sufficient to operate in stable type-I ELMy H-mode. This has\u0000been investigated using integrated core and edge/SOL/divertor modelling with\u0000JINTRAC. Assuming that the L-H power threshold is well captured by the Martin08\u0000scaling law, the presented simulations have found that 30 MW of ECRH power is\u0000likely required for the investigated hydrogen plasma scenarios, rather than the\u0000originally planned 20 MW in the 2016 Staged Approach ITER Baseline. However,\u0000past experiments have shown that a small helium fraction (~10 %) can\u0000considerably reduce the hydrogen plasma L-H power threshold. Assuming that\u0000these results extrapolate to ITER operation regimes, the 7.5MA/2.65T hydrogen\u0000plasma scenario is likely to access stable type-I ELMy H-mode operation also at\u000020 MW of ECRH.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969131","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}
Lorenzo Martelli, Olena Kononenko, Igor Andriyash, Jonathan Wheeler, Julien Gautier, Jean-Philippe Goddet, Amar Tafzi, Ronan Lahaye, Camilla Giaccaglia, Alessandro Flacco, Vidmantas Tomkus, Migle Mackevičiūtė, Juozas Dudutis, Valdemar Stankevic, Paulius Gečys, Gediminas Račiukaitis, Henri Kraft, Xuan Quyen Dinh, Cédric Thaury
Laser-plasma accelerators represent a promising technology for future compact accelerating systems, enabling the acceleration of tens of pC to above $1,$GeV over just a few centimeters. Nonetheless, these devices currently lack the stability, beam quality and average current of conventional systems. While many efforts have focused on improving acceleration stability and quality, little progress has been made in increasing the beam's average current, which is essential for future laser-plasma-based applications. In this paper, we investigate a laser-plasma acceleration regime aimed at increasing the beam average current with energies up to few-MeVs, efficiently enhancing the beam charge. We present experimental results on configurations that allow reaching charges of $5-30,$nC and a maximum conversion efficiency of around $14,$%. Through comprehensive Particle-In-Cell simulations, we interpret the experimental results and present a detailed study on electron dynamics. From our analysis, we show that most electrons are not trapped in a plasma wave; rather, they experience ponderomotive acceleration. Thus, we prove the laser pulse as the main driver of the particles' energy gain process.
激光等离子体加速器是未来紧凑型加速系统的一项很有前途的技术，它能在几厘米的范围内将几十 pC 的能量加速到 1 美元以上。然而，这些设备目前还缺乏传统系统的稳定性、束流质量和平均电流。虽然许多努力都集中在提高加速稳定性和质量上，但在提高光束平均电流方面却进展甚微，而这对于未来基于激光等离子体的应用是至关重要的。在本文中，我们研究了一种激光等离子体加速机制，旨在提高能量高达数兆电子伏特的光束平均电流，从而有效增强光束充电。通过全面的粒子内电池模拟，我们解释了实验结果，并对电子动力学进行了详细研究。通过分析，我们发现大多数电子并没有被困在等离子体波中；相反，它们经历了动力加速。因此，我们证明激光脉冲是粒子能量增益过程的主要驱动力。
{"title":"Highly-efficient electron ponderomotive acceleration in underdense plasmas","authors":"Lorenzo Martelli, Olena Kononenko, Igor Andriyash, Jonathan Wheeler, Julien Gautier, Jean-Philippe Goddet, Amar Tafzi, Ronan Lahaye, Camilla Giaccaglia, Alessandro Flacco, Vidmantas Tomkus, Migle Mackevičiūtė, Juozas Dudutis, Valdemar Stankevic, Paulius Gečys, Gediminas Račiukaitis, Henri Kraft, Xuan Quyen Dinh, Cédric Thaury","doi":"arxiv-2408.00560","DOIUrl":"https://doi.org/arxiv-2408.00560","url":null,"abstract":"Laser-plasma accelerators represent a promising technology for future compact\u0000accelerating systems, enabling the acceleration of tens of pC to above $1,$GeV\u0000over just a few centimeters. Nonetheless, these devices currently lack the\u0000stability, beam quality and average current of conventional systems. While many\u0000efforts have focused on improving acceleration stability and quality, little\u0000progress has been made in increasing the beam's average current, which is\u0000essential for future laser-plasma-based applications. In this paper, we\u0000investigate a laser-plasma acceleration regime aimed at increasing the beam\u0000average current with energies up to few-MeVs, efficiently enhancing the beam\u0000charge. We present experimental results on configurations that allow reaching\u0000charges of $5-30,$nC and a maximum conversion efficiency of around $14,$%.\u0000Through comprehensive Particle-In-Cell simulations, we interpret the\u0000experimental results and present a detailed study on electron dynamics. From\u0000our analysis, we show that most electrons are not trapped in a plasma wave;\u0000rather, they experience ponderomotive acceleration. Thus, we prove the laser\u0000pulse as the main driver of the particles' energy gain process.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883096","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}
Effects of plasma nonuniformity on zero frequency zonal structure (ZFZS) excitation by drift Alfven wave (DAW) instabilities in toroidal plasmas are investigated using nonlinear gyrokinetic theory. The governing equations describing nonlinear interactions among ZFZS and DAWs are derived, with the contribution of DAWs self-beating and radial modulation accounted for on the same footing. The obtained equations are then used to derive the nonlinear dispersion relation, which is then applied to investigate ZFZS generation in several scenarios. In particular, it is found that, the condition for zonal flow excitation by kinetic ballooning mode (KBM) could be sensitive to plasma parameters, and more detailed investigation is needed to understand KBM nonlinear saturation, crucial for bulk plasma transport in future reactors.
{"title":"Effects of plasma nonuniformity on zero frequency zonal structure generation by drift Alfven wave instabilities in toroidal plasmas","authors":"Zhiyong Qiu, Guangyu Wei, Liu Chen, Ruirui Ma","doi":"arxiv-2408.00324","DOIUrl":"https://doi.org/arxiv-2408.00324","url":null,"abstract":"Effects of plasma nonuniformity on zero frequency zonal structure (ZFZS)\u0000excitation by drift Alfven wave (DAW) instabilities in toroidal plasmas are\u0000investigated using nonlinear gyrokinetic theory. The governing equations\u0000describing nonlinear interactions among ZFZS and DAWs are derived, with the\u0000contribution of DAWs self-beating and radial modulation accounted for on the\u0000same footing. The obtained equations are then used to derive the nonlinear\u0000dispersion relation, which is then applied to investigate ZFZS generation in\u0000several scenarios. In particular, it is found that, the condition for zonal\u0000flow excitation by kinetic ballooning mode (KBM) could be sensitive to plasma\u0000parameters, and more detailed investigation is needed to understand KBM\u0000nonlinear saturation, crucial for bulk plasma transport in future reactors.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883098","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}
Plasma turbulence can enhance the diffusion of both magnetic fields and plasmas. But, any theory must be consistent with their evolution equations having the mathematical form of advection-diffusion equations. Advection-diffusion equations have a remarkable feature. When the diffusion is extremely weak but non-zero, its magnitude makes only a small difference even when varied over sixteen orders of magnitude. This is true when the advective velocity is chaotic -- the exponential separation of neighboring streamlines -- as natural flows generally are. Even highly turbulent flows have in addition to eddies large-scale coherent flows, such as the Gulf Stream in the Atlantic, which dominates their transport effects on longest scales. Basic physics and easily understood mathematics place important constraints, which are explained.
{"title":"Magnetic reconnection and plasma transport in the presence of plasma turbulence","authors":"Allen H Boozer","doi":"arxiv-2408.00875","DOIUrl":"https://doi.org/arxiv-2408.00875","url":null,"abstract":"Plasma turbulence can enhance the diffusion of both magnetic fields and\u0000plasmas. But, any theory must be consistent with their evolution equations\u0000having the mathematical form of advection-diffusion equations.\u0000Advection-diffusion equations have a remarkable feature. When the diffusion is\u0000extremely weak but non-zero, its magnitude makes only a small difference even\u0000when varied over sixteen orders of magnitude. This is true when the advective\u0000velocity is chaotic -- the exponential separation of neighboring streamlines --\u0000as natural flows generally are. Even highly turbulent flows have in addition to\u0000eddies large-scale coherent flows, such as the Gulf Stream in the Atlantic,\u0000which dominates their transport effects on longest scales. Basic physics and\u0000easily understood mathematics place important constraints, which are explained.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941380","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}
A. Picksley, J. Stackhouse, C. Benedetti, K. Nakamura, H. E. Tsai, R. Li, B. Miao, J. E. Shrock, E. Rockafellow, H. M. Milchberg, C. B. Schroeder, J. van Tilborg, E. Esarey, C. G. R. Geddes, A. J. Gonsalves
We measure the high intensity laser propagation throughout meter-scale, channel-guided LPAs by adjusting the length of the plasma channel on a shot-by-shot basis, showing high quality guiding of 500 TW laser pulses over 30 cm in a hydrogen plasma of density $n_0 approx 1 times 10^{17} , mathrm{cm^{-3}}$. We observed transverse energy transport of higher-order modes in the first $approx 12 , mathrm{cm}$ of the plasma channel, followed by quasi-matched propagation, and the gradual, dark-current-free depletion of laser energy to the wakefield. We quantify the laser-to-wake transfer efficiency limitations of currently available PW-class laser systems, and demonstrate via simulation how control over the laser mode can significantly improve accelerated beam parameters. Using just 21.3 J of laser energy, and triggering localized electron injection into the accelerator, we observed electron bunches with single, quasimonoenergetic peaks, relative energy spreads as low as 3 % and energy up to 9.2 GeV with charge extending beyond 10 GeV.
{"title":"Matched Guiding and Controlled Injection in Dark-Current-Free, 10-GeV-Class, Channel-Guided Laser Plasma Accelerators","authors":"A. Picksley, J. Stackhouse, C. Benedetti, K. Nakamura, H. E. Tsai, R. Li, B. Miao, J. E. Shrock, E. Rockafellow, H. M. Milchberg, C. B. Schroeder, J. van Tilborg, E. Esarey, C. G. R. Geddes, A. J. Gonsalves","doi":"arxiv-2408.00740","DOIUrl":"https://doi.org/arxiv-2408.00740","url":null,"abstract":"We measure the high intensity laser propagation throughout meter-scale,\u0000channel-guided LPAs by adjusting the length of the plasma channel on a\u0000shot-by-shot basis, showing high quality guiding of 500 TW laser pulses over 30\u0000cm in a hydrogen plasma of density $n_0 approx 1 times 10^{17} ,\u0000mathrm{cm^{-3}}$. We observed transverse energy transport of higher-order\u0000modes in the first $approx 12 , mathrm{cm}$ of the plasma channel, followed\u0000by quasi-matched propagation, and the gradual, dark-current-free depletion of\u0000laser energy to the wakefield. We quantify the laser-to-wake transfer\u0000efficiency limitations of currently available PW-class laser systems, and\u0000demonstrate via simulation how control over the laser mode can significantly\u0000improve accelerated beam parameters. Using just 21.3 J of laser energy, and\u0000triggering localized electron injection into the accelerator, we observed\u0000electron bunches with single, quasimonoenergetic peaks, relative energy spreads\u0000as low as 3 % and energy up to 9.2 GeV with charge extending beyond 10 GeV.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"216 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883095","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}
Jeffersson Andres Agudelo Rueda, Yi-Hsin Liu, Kai Germaschewski, Michael Hesse, Naoki Bessho
Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic reconnection can occur as a product of the turbulent cascade. In this study, we perform 2D particle-in-cell simulations of a reconnecting Harris current sheet in the presence of turbulent fluctuations to explore the effect of turbulence on the reconnection process in collisionless non-relativistic pair-plasmas. We find that the presence of a turbulent field can affect the onset and evolution of magnetic reconnection. Moreover, we observe the existence of a scale dependent amplitude of magnetic field fluctuations above which these fluctuations are able to disrupt the growing of magnetic islands. These fluctuations provide thermal energy to the particles within the current sheet and preferential perpendicular thermal energy to the background population.
{"title":"Exploring the effect of turbulent fluctuations on the onset of reconnection","authors":"Jeffersson Andres Agudelo Rueda, Yi-Hsin Liu, Kai Germaschewski, Michael Hesse, Naoki Bessho","doi":"arxiv-2408.00894","DOIUrl":"https://doi.org/arxiv-2408.00894","url":null,"abstract":"Energy dissipation in collisionless plasmas is one of the most outstanding\u0000open questions in plasma physics. Magnetic reconnection and turbulence are two\u0000phenomena that can produce the conditions for energy dissipation. These two\u0000phenomena are closely related to each other in a wide range of plasmas.\u0000Turbulent fluctuations can emerge in critical regions of reconnection events,\u0000and magnetic reconnection can occur as a product of the turbulent cascade. In\u0000this study, we perform 2D particle-in-cell simulations of a reconnecting Harris\u0000current sheet in the presence of turbulent fluctuations to explore the effect\u0000of turbulence on the reconnection process in collisionless non-relativistic\u0000pair-plasmas. We find that the presence of a turbulent field can affect the\u0000onset and evolution of magnetic reconnection. Moreover, we observe the\u0000existence of a scale dependent amplitude of magnetic field fluctuations above\u0000which these fluctuations are able to disrupt the growing of magnetic islands.\u0000These fluctuations provide thermal energy to the particles within the current\u0000sheet and preferential perpendicular thermal energy to the background\u0000population.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941379","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}
Christopher G. Albert, Craig D. Beidler, Gernot Kapper, Sergei V. Kasilov, Winfried Kernbichler
Bootstrap current in stellarators can be presented as a sum of a collisionless value given by the Shaing-Callen asymptotic formula and an off-set current, which non-trivially depends on plasma collisionality and radial electric field. Using NEO-2 modelling, analytical estimates and semi-analytical studies with help of a propagator method, it is shown that the off-set current in the $1/nu$ regime does not converge with decreasing collisionality $nu_ast$ but rather shows oscillations over $lognu_ast$ with an amplitude of the order of the bootstrap current in an equivalent tokamak. The convergence to the Shaing-Callen limit appears in regimes with significant orbit precession, in particular, due to a finite radial electric field, where the off-set current decreases as $nu_ast^{3/5}$. The off-set current strongly increases in case of nearly aligned magnetic field maxima on the field line where it diverges as $nu_ast^{-1/2}$ in the $1/nu$ regime and saturates due to the precession at a level exceeding the equivalent tokamak value by ${v_E^ast}^{-1/2}$ where $v_E^ast$ is the perpendicular Mach number. The latter off-set, however, can be minimized by further aligning local magnetic field maxima and by fulfilling an extra integral condition of "equivalent ripples" for the magnetic field. A criterion for the accuracy of this alignment and of ripple equivalence is derived. In addition, the possibility of the bootstrap effect at the magnetic axis caused by the above off-set is also discussed.
{"title":"On the convergence of bootstrap current to the Shaing-Callen limit in stellarators","authors":"Christopher G. Albert, Craig D. Beidler, Gernot Kapper, Sergei V. Kasilov, Winfried Kernbichler","doi":"arxiv-2407.21599","DOIUrl":"https://doi.org/arxiv-2407.21599","url":null,"abstract":"Bootstrap current in stellarators can be presented as a sum of a\u0000collisionless value given by the Shaing-Callen asymptotic formula and an\u0000off-set current, which non-trivially depends on plasma collisionality and\u0000radial electric field. Using NEO-2 modelling, analytical estimates and\u0000semi-analytical studies with help of a propagator method, it is shown that the\u0000off-set current in the $1/nu$ regime does not converge with decreasing\u0000collisionality $nu_ast$ but rather shows oscillations over $lognu_ast$\u0000with an amplitude of the order of the bootstrap current in an equivalent\u0000tokamak. The convergence to the Shaing-Callen limit appears in regimes with\u0000significant orbit precession, in particular, due to a finite radial electric\u0000field, where the off-set current decreases as $nu_ast^{3/5}$. The off-set\u0000current strongly increases in case of nearly aligned magnetic field maxima on\u0000the field line where it diverges as $nu_ast^{-1/2}$ in the $1/nu$ regime and\u0000saturates due to the precession at a level exceeding the equivalent tokamak\u0000value by ${v_E^ast}^{-1/2}$ where $v_E^ast$ is the perpendicular Mach number.\u0000The latter off-set, however, can be minimized by further aligning local\u0000magnetic field maxima and by fulfilling an extra integral condition of\u0000\"equivalent ripples\" for the magnetic field. A criterion for the accuracy of\u0000this alignment and of ripple equivalence is derived. In addition, the\u0000possibility of the bootstrap effect at the magnetic axis caused by the above\u0000off-set is also discussed.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869416","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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