S. H. Cao, M. J. Rosenberg, A. A. Solodov, H. Wen, C. Ren
Laser-plasma instabilities under ignition conditions for direct-drive inertial confinement fusion are studied using two-dimensional Particle-in-Cell simulations with a combination of in-plane (PP) and out-of-the-plane (SP) lasers. The results show that stimulated Raman side scattering can induce significant pump depletion and form a gap in the Raman scattered light spectra that have been observed in experiments.
{"title":"Pump depletion and the Raman gap in ignition-scale plasmas","authors":"S. H. Cao, M. J. Rosenberg, A. A. Solodov, H. Wen, C. Ren","doi":"arxiv-2409.05232","DOIUrl":"https://doi.org/arxiv-2409.05232","url":null,"abstract":"Laser-plasma instabilities under ignition conditions for direct-drive\u0000inertial confinement fusion are studied using two-dimensional Particle-in-Cell\u0000simulations with a combination of in-plane (PP) and out-of-the-plane (SP)\u0000lasers. The results show that stimulated Raman side scattering can induce\u0000significant pump depletion and form a gap in the Raman scattered light spectra\u0000that have been observed in experiments.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196035","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}
Allan N. Kaufman, Bruce I. Cohen, Alain J. Brizard
Presented here is a transcription of the lecture notes from Professor Allan N. Kaufman's graduate statistical mechanics course at Berkeley from the 1972-1973 academic year. Part 1 addresses equilibrium statistical mechanics with topics: fundamentals, classical fluids and other systems, chemical equilibrium, and long-range interactions. Part 2 addresses non-equilibrium statistical mechanics with topics: fundamentals, Brownian motion, Liouville and Klimontovich equations, Landau equation, Markov processes and Fokker-Planck equation, linear response and transport theory, and an introduction to non-equilibrium quantum statistical mechanics.
{"title":"Lectures on Statistical Mechanics","authors":"Allan N. Kaufman, Bruce I. Cohen, Alain J. Brizard","doi":"arxiv-2409.04899","DOIUrl":"https://doi.org/arxiv-2409.04899","url":null,"abstract":"Presented here is a transcription of the lecture notes from Professor Allan\u0000N. Kaufman's graduate statistical mechanics course at Berkeley from the\u00001972-1973 academic year. Part 1 addresses equilibrium statistical mechanics\u0000with topics: fundamentals, classical fluids and other systems, chemical\u0000equilibrium, and long-range interactions. Part 2 addresses non-equilibrium\u0000statistical mechanics with topics: fundamentals, Brownian motion, Liouville and\u0000Klimontovich equations, Landau equation, Markov processes and Fokker-Planck\u0000equation, linear response and transport theory, and an introduction to\u0000non-equilibrium quantum statistical mechanics.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196032","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}
Diogo R. Ferreira, Alexandre Lança, Luís Lemos Alves
Low-temperature plasmas are partially ionized gases, where ions and neutrals coexist in a highly reactive environment. This creates a rich chemistry, which is often difficult to understand in its full complexity. In this work, we develop a machine learning model to identify the most important reactions in a given chemical scheme. The training data are an initial distribution of species and a final distribution of species, which can be obtained from either experiments or simulations. The model is trained to provide a set of reaction weights, which become the basis for reducing the chemical scheme. The approach is applied to $text{N}_2-text{H}_2$ plasmas, created by an electric discharge at low pressure, where the main goal is to produce $text{NH}_3$. The interplay of multiple species, as well as of volume and surface reactions, make this chemistry especially challenging to understand. Reducing the chemical scheme via the proposed model helps identify the main chemical pathways.
{"title":"Machine Learning for Chemistry Reduction in $text{N}_2-text{H}_2$ Low-Temperature Plasmas","authors":"Diogo R. Ferreira, Alexandre Lança, Luís Lemos Alves","doi":"arxiv-2409.05914","DOIUrl":"https://doi.org/arxiv-2409.05914","url":null,"abstract":"Low-temperature plasmas are partially ionized gases, where ions and neutrals\u0000coexist in a highly reactive environment. This creates a rich chemistry, which\u0000is often difficult to understand in its full complexity. In this work, we\u0000develop a machine learning model to identify the most important reactions in a\u0000given chemical scheme. The training data are an initial distribution of species\u0000and a final distribution of species, which can be obtained from either\u0000experiments or simulations. The model is trained to provide a set of reaction\u0000weights, which become the basis for reducing the chemical scheme. The approach\u0000is applied to $text{N}_2-text{H}_2$ plasmas, created by an electric discharge\u0000at low pressure, where the main goal is to produce $text{NH}_3$. The interplay\u0000of multiple species, as well as of volume and surface reactions, make this\u0000chemistry especially challenging to understand. Reducing the chemical scheme\u0000via the proposed model helps identify the main chemical pathways.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196028","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}
Matteo Moscheni, Erik Maartensson, Matthew Robinson, Chris Marsden, Adrian Rengle, Travis Kelly Gray, Andrea Scarabosio, Elena Vekshina, Xin Zhang
A new tool for infra-red thermographic inversion on Tokamak Energy's spherical tokamak, ST40, is developed in-house and here presented. Functional Analysis of Heat Flux (FAHF) is written in Python, and configured for multi-2D thermographic inversions, solving the heat conduction equation within the divertor tiles via the finite difference method, and leveraging an explicit time-marching scheme. Using infra-red camera data of the highest effective spatial resolution available, FAHF ultimately outputs the plasma perpendicular heat flux on the divertor, crucial quantity in any edge plasma investigation. In the present work, the internal numerics of the tool is first successfully verified by formal time and space convergence analyses, and corroborated by an energy balance assessment. A significant sensitivity of the perpendicular heat flux computed by FAHF to the user-selected spatial resolution is then evidenced. However, a precise heat flux is proved to be recoverable by ensuring a sufficiently high resolution. Last, the appropriateness of the model/geometry simplifications adopted in FAHF is successfully confirmed, by means of comparison against COMSOL Multiphysics simulations. FAHF is hence conclusively proven to qualify as a precise and accurate tool for infra-red thermographic inversions.
{"title":"Infra-red thermographic inversion in ST40","authors":"Matteo Moscheni, Erik Maartensson, Matthew Robinson, Chris Marsden, Adrian Rengle, Travis Kelly Gray, Andrea Scarabosio, Elena Vekshina, Xin Zhang","doi":"arxiv-2409.04278","DOIUrl":"https://doi.org/arxiv-2409.04278","url":null,"abstract":"A new tool for infra-red thermographic inversion on Tokamak Energy's\u0000spherical tokamak, ST40, is developed in-house and here presented. Functional\u0000Analysis of Heat Flux (FAHF) is written in Python, and configured for multi-2D\u0000thermographic inversions, solving the heat conduction equation within the\u0000divertor tiles via the finite difference method, and leveraging an explicit\u0000time-marching scheme. Using infra-red camera data of the highest effective\u0000spatial resolution available, FAHF ultimately outputs the plasma perpendicular\u0000heat flux on the divertor, crucial quantity in any edge plasma investigation.\u0000In the present work, the internal numerics of the tool is first successfully\u0000verified by formal time and space convergence analyses, and corroborated by an\u0000energy balance assessment. A significant sensitivity of the perpendicular heat\u0000flux computed by FAHF to the user-selected spatial resolution is then\u0000evidenced. However, a precise heat flux is proved to be recoverable by ensuring\u0000a sufficiently high resolution. Last, the appropriateness of the model/geometry\u0000simplifications adopted in FAHF is successfully confirmed, by means of\u0000comparison against COMSOL Multiphysics simulations. FAHF is hence conclusively\u0000proven to qualify as a precise and accurate tool for infra-red thermographic\u0000inversions.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196036","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}
Jesse M. Snelling, Gregory R. Werner, John R. Cary
Numerical solutions to the 1D steady-state Vlasov-Poisson system are used to develop a straightforward empirical formula for the electric current density transmitted through a vacuum diode (voltage gap) as a function of gap distance, gap voltage, the injected current density, and the average velocity and temperature of injected particles, as well as their charge and mass. This formula generalizes the 1D cold beam Child-Langmuir law (which predicts the maximum transmitted current for mono-energetic particles in a planar diode as a function of gap voltage and distance) to the case where particles are injected with a finite velocity spread. Though this case is of practical importance, no analytical solution is known. Found by a best-fit to results from particle-in-cell (PIC) simulations, the empirical formula characterizes the current transmitted across the diode for an injected velocity distribution of a drifting Maxwellian. It is not meant to yield a precise answer, but approximately characterizes the effect of space charge on transmitted current density over a large input space. The formula allows quick quantitative estimation of the effect of space charge in diode-like devices, such as gate-anode gaps in nanoscale vacuum channel transistors.
{"title":"Empirically extending 1D Child-Langmuir theory to a finite temperature beam","authors":"Jesse M. Snelling, Gregory R. Werner, John R. Cary","doi":"arxiv-2409.04355","DOIUrl":"https://doi.org/arxiv-2409.04355","url":null,"abstract":"Numerical solutions to the 1D steady-state Vlasov-Poisson system are used to\u0000develop a straightforward empirical formula for the electric current density\u0000transmitted through a vacuum diode (voltage gap) as a function of gap distance,\u0000gap voltage, the injected current density, and the average velocity and\u0000temperature of injected particles, as well as their charge and mass. This\u0000formula generalizes the 1D cold beam Child-Langmuir law (which predicts the\u0000maximum transmitted current for mono-energetic particles in a planar diode as a\u0000function of gap voltage and distance) to the case where particles are injected\u0000with a finite velocity spread. Though this case is of practical importance, no\u0000analytical solution is known. Found by a best-fit to results from\u0000particle-in-cell (PIC) simulations, the empirical formula characterizes the\u0000current transmitted across the diode for an injected velocity distribution of a\u0000drifting Maxwellian. It is not meant to yield a precise answer, but\u0000approximately characterizes the effect of space charge on transmitted current\u0000density over a large input space. The formula allows quick quantitative\u0000estimation of the effect of space charge in diode-like devices, such as\u0000gate-anode gaps in nanoscale vacuum channel transistors.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"182 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196033","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}
The growth of streamers is determined at their heads, for individual streamers as well as in collective phenomena, such as streamer trees or coronas or streamer bursts ahead of lighting leaders. Some properties of the streamer heads, such as velocity v and radius R now can be measured quite well, but this is very challenging for others such as the maximal electric field, the charge content at the streamer head and the degree of chemical excitation and ionization in the streamer channel. Here we develop, test and evaluate a macroscopic approximation for positive streamer heads in air that relates macroscopic streamer head properties to each other. In particular, we find that velocity v, radius R and background field E_bg determine the complete profile of streamer heads with photoionization, if they propagate steadily. We also revisit Naidis' approximate relation between v, R and the maximal field E_max. The approximate head model consists of three first-order ordinary differential equations along the streamer axis. It is derived from the classical fluid model for streamer discharges by assuming axisymmetry, steady streamer propagation (with constant velocity and shape), and a (semi-)spherical shape of the charge layer. The model shows good agreement with solutions of the classical fluid model, even when it is applied to accelerating streamers. Therefore the model can be used for evaluations of experiments, like measurements of the maximal electric field, and it could be a valuable tool in constructing reduced models for the collective dynamics of many streamer discharges.
流线体的生长取决于其头部，对于单个流线体以及集体现象，如流线体树或冠状流线体，或流线体在照明领导者前方的爆发。现在可以很好地测量流线头的某些特性，如速度 v 和半径 R，但对于其他特性，如最大电场、流线头的电荷含量以及流线通道中的化学激发和电离程度，测量则非常具有挑战性。在这里，我们开发、测试并评估了空气中正流头的微观近似值，该近似值将流头的微观特性相互联系起来。特别是，我们发现如果流头稳定地传播，速度 v、半径 R 和背景场 E_bg 将决定流头光电离的完整轮廓。我们还考察了奈迪斯提出的 v、R 和最大场 E_max 之间的近似关系。该近似水头模型由沿流束轴线的三个一阶常微分方程组成。它是从流束放电的经典流体模型推导出来的，假定流束具有轴对称性、稳定的流束传播（具有恒定的速度和形状）以及荷电层（半）球形。该模型与经典流体模型的解显示出很好的一致性，即使将其应用于加速流体时也是如此。因此，该模型可用于实验评估，如最大电场的测量，并可作为构建许多流体放电集体动力学简化模型的重要工具。
{"title":"Macroscopic parameterization of positive streamer heads in air","authors":"Dennis Bouwman, Jannis Teunissen, Ute Ebert","doi":"arxiv-2409.04282","DOIUrl":"https://doi.org/arxiv-2409.04282","url":null,"abstract":"The growth of streamers is determined at their heads, for individual\u0000streamers as well as in collective phenomena, such as streamer trees or coronas\u0000or streamer bursts ahead of lighting leaders. Some properties of the streamer\u0000heads, such as velocity v and radius R now can be measured quite well, but this\u0000is very challenging for others such as the maximal electric field, the charge\u0000content at the streamer head and the degree of chemical excitation and\u0000ionization in the streamer channel. Here we develop, test and evaluate a\u0000macroscopic approximation for positive streamer heads in air that relates\u0000macroscopic streamer head properties to each other. In particular, we find that\u0000velocity v, radius R and background field E_bg determine the complete profile\u0000of streamer heads with photoionization, if they propagate steadily. We also\u0000revisit Naidis' approximate relation between v, R and the maximal field E_max.\u0000The approximate head model consists of three first-order ordinary differential\u0000equations along the streamer axis. It is derived from the classical fluid model\u0000for streamer discharges by assuming axisymmetry, steady streamer propagation\u0000(with constant velocity and shape), and a (semi-)spherical shape of the charge\u0000layer. The model shows good agreement with solutions of the classical fluid\u0000model, even when it is applied to accelerating streamers. Therefore the model\u0000can be used for evaluations of experiments, like measurements of the maximal\u0000electric field, and it could be a valuable tool in constructing reduced models\u0000for the collective dynamics of many streamer discharges.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196034","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}
White dwarfs are stellar remnants devoid of a nuclear energy source, gradually cooling over billions of years and eventually freezing into a solid state from the inside out. Recently, it was discovered that a population of freezing white dwarfs maintains a constant luminosity for a duration comparable to the age of the universe, signaling the presence of a powerful yet unknown energy source that inhibits the cooling. For certain core compositions, the freezing process is predicted to trigger a solid-liquid distillation mechanism, due to the solid phase being depleted in heavy impurities. The crystals thus formed are buoyant and float up, thereby displacing heavier liquid downward and releasing gravitational energy. Here we show that distillation interrupts the cooling for billions of years and explains all the observational properties of the unusual delayed population. With a steady luminosity surpassing that of some main-sequence stars, these white dwarfs defy their conventional portrayal as dead stars. Our results highlight the existence of peculiar merger remnants and have profound implications for the use of white dwarfs in dating stellar populations.
{"title":"Buoyant crystals halt the cooling of white dwarf stars","authors":"Antoine Bédard, Simon Blouin, Sihao Cheng","doi":"arxiv-2409.04419","DOIUrl":"https://doi.org/arxiv-2409.04419","url":null,"abstract":"White dwarfs are stellar remnants devoid of a nuclear energy source,\u0000gradually cooling over billions of years and eventually freezing into a solid\u0000state from the inside out. Recently, it was discovered that a population of\u0000freezing white dwarfs maintains a constant luminosity for a duration comparable\u0000to the age of the universe, signaling the presence of a powerful yet unknown\u0000energy source that inhibits the cooling. For certain core compositions, the\u0000freezing process is predicted to trigger a solid-liquid distillation mechanism,\u0000due to the solid phase being depleted in heavy impurities. The crystals thus\u0000formed are buoyant and float up, thereby displacing heavier liquid downward and\u0000releasing gravitational energy. Here we show that distillation interrupts the\u0000cooling for billions of years and explains all the observational properties of\u0000the unusual delayed population. With a steady luminosity surpassing that of\u0000some main-sequence stars, these white dwarfs defy their conventional portrayal\u0000as dead stars. Our results highlight the existence of peculiar merger remnants\u0000and have profound implications for the use of white dwarfs in dating stellar\u0000populations.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196040","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}
Pedro Pons-Villalonga, Álvaro Cappa, José Martínez-Fernández
A synthetic Mirnov coils diagnostic is presented and used to study the capabilities of the poloidal array of single-axis coils and the two helical arrays of tri-axial coils installed in the TJ-II stellarator. This tool integrates the plasma currents induced by Alfv'en-like perturbations of the electric potential inside the plasma and provides the induced magnetic field oscillations anywhere outside of it. The simulated signals can then be analyzed in the same manner as the experimental ones, and a scan on the radial position and width of the potential perturbation is conducted to find the limiting values that produce identifiable signals. We find, not surprisingly, that core-localized modes are indistinguishable from one another; and that the identification of low-n, low-m modes is often subject to off-by-one errors. We also determine the optimal polarization basis in which to analyze the tri-axial coils signals and address the diagnostic performance when resolving components of gap modes such as HAEs. Additionally, selected cases have been analyzed with a simplified plasma response model, showing that plasma shielding of the mode currents may further deteriorate the accuracy of the mode identification method. The code for this synthetic diagnostic, that can be easily used to conduct similar analysis for other devices, is publicly available in http://github.com/pponsv/synth_mirnov .
提出了一种合成米尔诺夫线圈诊断法，用于研究安装在TJ-II恒星器中的单轴线圈极性阵列和两个三轴线圈螺旋阵列的能力。该工具整合了等离子体内部电势的Alfv'en 类扰动所诱发的等离子体电流，并提供了等离子体外部任意位置的诱导磁场振荡。然后，可以用与实验信号相同的方式分析模拟信号，并对电势扰动的径向位置和宽度进行扫描，以找到产生可识别信号的极限值。我们毫不奇怪地发现，核心定位模式是无法相互区分的；而低 n、低 m 模式的识别往往会出现偏差。我们还确定了分析三轴线圈信号的最佳极化基础，并解决了解析 HAE 等间隙模式成分时的诊断性能问题。此外，还利用简化的等离子体响应模型分析了部分案例，结果表明等离子体对模态电流的屏蔽可能会进一步降低模态识别方法的准确性。这种合成诊断的代码可以很容易地用于对其他设备进行类似的分析，可在http://github.com/pponsv/synth_mirnov。
{"title":"Exploring the operational limits of Mirnov coil arrays in stellarators by means of a synthetic diagnostic","authors":"Pedro Pons-Villalonga, Álvaro Cappa, José Martínez-Fernández","doi":"arxiv-2409.04221","DOIUrl":"https://doi.org/arxiv-2409.04221","url":null,"abstract":"A synthetic Mirnov coils diagnostic is presented and used to study the\u0000capabilities of the poloidal array of single-axis coils and the two helical\u0000arrays of tri-axial coils installed in the TJ-II stellarator. This tool\u0000integrates the plasma currents induced by Alfv'en-like perturbations of the\u0000electric potential inside the plasma and provides the induced magnetic field\u0000oscillations anywhere outside of it. The simulated signals can then be analyzed\u0000in the same manner as the experimental ones, and a scan on the radial position\u0000and width of the potential perturbation is conducted to find the limiting\u0000values that produce identifiable signals. We find, not surprisingly, that\u0000core-localized modes are indistinguishable from one another; and that the\u0000identification of low-n, low-m modes is often subject to off-by-one errors. We\u0000also determine the optimal polarization basis in which to analyze the tri-axial\u0000coils signals and address the diagnostic performance when resolving components\u0000of gap modes such as HAEs. Additionally, selected cases have been analyzed with\u0000a simplified plasma response model, showing that plasma shielding of the mode\u0000currents may further deteriorate the accuracy of the mode identification\u0000method. The code for this synthetic diagnostic, that can be easily used to\u0000conduct similar analysis for other devices, is publicly available in\u0000http://github.com/pponsv/synth_mirnov .","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196038","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}
Emanuele Sobacchi, Masanori Iwamoto, Lorenzo Sironi, Tsvi Piran
We study the propagation of electromagnetic waves in tenuous plasmas, where the wave frequency, $omega_0$, is much larger than the plasma frequency, $omega_{rm P}$. We show that in pair plasmas nonlinear effects are weak for $a_0 ll omega_0/omega_{rm P}$, where $a_0$ is the wave strength parameter. In electron-proton plasmas a more restrictive condition must be satisfied, namely either $a_0ll 1/omega_{rm P}tau_0$, where $tau_0$ is the duration of the radiation pulse, or $a_0ll 1$. We derive the equations that govern the evolution of the pulse in the weakly nonlinear regime. Our results have important implications for the modeling of fast radio bursts. We argue that: (i) Millisecond duration bursts with a smooth profile must be produced in a proton-free environment, where nonlinear effects are weaker. (ii) Propagation through an electron-proton plasma near the source can imprint a sub-microsecond variability on the burst profile.
{"title":"Propagation of strong electromagnetic waves in tenuous plasmas","authors":"Emanuele Sobacchi, Masanori Iwamoto, Lorenzo Sironi, Tsvi Piran","doi":"arxiv-2409.04127","DOIUrl":"https://doi.org/arxiv-2409.04127","url":null,"abstract":"We study the propagation of electromagnetic waves in tenuous plasmas, where\u0000the wave frequency, $omega_0$, is much larger than the plasma frequency,\u0000$omega_{rm P}$. We show that in pair plasmas nonlinear effects are weak for\u0000$a_0 ll omega_0/omega_{rm P}$, where $a_0$ is the wave strength parameter.\u0000In electron-proton plasmas a more restrictive condition must be satisfied,\u0000namely either $a_0ll 1/omega_{rm P}tau_0$, where $tau_0$ is the duration\u0000of the radiation pulse, or $a_0ll 1$. We derive the equations that govern the\u0000evolution of the pulse in the weakly nonlinear regime. Our results have\u0000important implications for the modeling of fast radio bursts. We argue that:\u0000(i) Millisecond duration bursts with a smooth profile must be produced in a\u0000proton-free environment, where nonlinear effects are weaker. (ii) Propagation\u0000through an electron-proton plasma near the source can imprint a sub-microsecond\u0000variability on the burst profile.","PeriodicalId":501274,"journal":{"name":"arXiv - PHYS - Plasma Physics","volume":"71 23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142196041","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}
Sergey S. Makarov, Sergey A. Grigoryev, Vasily V. Zhakhovsky, Petr Chuprov, Tatiana A. Pikuz, Nail A. Inogamov, Victor V. Khokhlov, Yuri V. Petrov, Eugene Perov, Vadim Shepelev, Takehisa Shobu, Aki Tominaga, Ludovic Rapp, Andrei V. Rode, Saulius Juodkazis, Mikako Makita, Motoaki Nakatsutsumi, Thomas R. Preston, Karen Appel, Zuzana Konopkova, Valerio Cerantola, Erik Brambrink, Jan-Patrick Schwinkendorf, István Mohacsi, Vojtech Vozda, Vera Hajkova, Tomas Burian, Jaromir Chalupsky, Libor Juha, Norimasa Ozaki, Ryosuke Kodama, Ulf Zastrau, Sergey A. Pikuz
Sub-picosecond optical laser processing of metals is actively utilized for modification of a heated surface layer. But for deeper modification of different materials a laser in the hard x-ray range is required. Here, we demonstrate that a single 9-keV x-ray pulse from a free-electron laser can form a um-diameter cylindrical cavity with length of ~1 mm in LiF surrounded by shock-transformed material. The plasma-generated shock wave with TPa-level pressure results in damage, melting and polymorphic transformations of any material, including transparent and non-transparent to conventional optical lasers. Moreover, cylindrical shocks can be utilized to obtain a considerable amount of exotic high-pressure polymorphs. Pressure wave propagation in LiF, radial material flow, formation of cracks and voids are analyzed via continuum and atomistic simulations revealing a sequence of processes leading to the final structure with the long cavity. Similar results can be produced with semiconductors and ceramics, which opens a new pathway for development of laser material processing with hard x-ray pulses.
金属的亚皮秒光学激光加工主要用于加热表面层的改性。但要对不同材料进行更深层次的改性，则需要硬 X 射线范围内的激光。在这里，我们证明了来自自由电子激光器的单个 9-keV X 射线脉冲可以在被冲击转化材料包围的 LiF 中形成一个直径为 um、长度为 ~1 mm 的圆柱形空腔。等离子体产生的具有 TPa 级压力的冲击波可导致任何材料的损坏、熔化和多晶体转变，包括对传统光学激光器透明和不透明的材料。此外，利用圆柱形冲击波还可以获得大量奇特的高压多晶体。通过连续和原子模拟分析了 LiF 中的压力波传播、径向材料流动、裂缝和空隙的形成，揭示了导致最终形成长空腔结构的一系列过程。半导体和陶瓷也能产生类似的结果，这为利用硬 X 射线脉冲进行激光材料加工的发展开辟了一条新途径。
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