Simulations of Laser Experiments to Study the Origin of Cosmic Magnetic Fields

模拟激光实验研究宇宙磁场的起源

基本信息

批准号：
1619573
负责人：
Petros Tzeferacos
金额：
$ 1.5万
依托单位：
University of Chicago
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-08-15 至 2019-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1619573&HistoricalAwards=false
关键词：
Simulations Laser Experiments Study Origin

项目摘要

Magnetic fields are ubiquitous in the universe. However, their origin is not fully understood. While cosmologists and astrophysicists have proposed a variety of ways in which small seed magnetic fields could be created, the significantly larger values of cosmic magnetic fields we observe are believed to be the result of the amplification of these seed fields by a turbulent flow of plasma, the so-called turbulent dynamo mechanism. This mechanism has not yet been demonstrated in a controlled laboratory environment. Experiments to demonstrate and study turbulent dynamo in the laboratory are now being planned using the high-intensity lasers at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory and the Laser Megajoule (LMJ) facility in France - the two largest laser facilities in the world. The effort supported by this award consists of designing and modeling these highly demanding experiments through simulation campaigns using a highly capable code to run large-scale 3D simulations. The simulations are vital to ensuring the experiments achieve the conditions required for the turbulent dynamo mechanism to operate and are crucial to interpreting the results of the experiments. This work will further the transformation of the academic community's ability to design and analyze High Energy Density Physics experiments at large laser facilities and will train junior scientists to design and interpret such experiments using validated simulations - a critical national need.The experiments to be modeled build on pathfinder experiments that have been conducted on the Vulcan laser at the Rutherford-Appleton Laboratory in the UK and the Omega laser at Laboratory for Laser Energetics at the University of Rochester. They also build on the experience that has been gained designing and interpreting these experiments using validated simulations done with the FLASH code, a highly capable radiation-MHD code developed by the group. The configurations to be used for the NIF and LMJ experiments are based on the platform deployed for the Omega laser, adapted for the large laser facilities using FLASH simulations. The NIF experiment will probe dynamo in the regime of large magnetic Prandtl numbers, the ratio of magnetic-to-fluid Reynolds numbers (Pm = Rm / Re 1), while the LMJ experiment will focus on magnetic field amplification for Pm 1. The dynamo mechanism is expected to operate differently in each regime and FLASH simulations will ensure the experiments reach the required plasma states. These experiments promise to characterize the distribution of turbulent energy among the velocity, magnetic field, and density fluctuations, providing a comprehensive picture of the energy cascade in a magnetized, turbulent plasma. Since the number of laser shots per shot day is only two at NIF and three at LMJ, there is no room for error: numerical modeling to design and analyze the experiments is imperative to accomplish the scientific goals of demonstrating and characterizing the turbulent dynamo mechanism.

磁场在宇宙中无处不在。但是，它们的起源尚未完全理解。尽管宇宙学家和天体物理学家提出了可以产生小种子磁场的多种方式，但我们观察到的宇宙磁场值显着较大，这被认为是由于等离子体的湍流流动，即所谓的湍流功能机制。在受控的实验室环境中尚未证明这种机制。现在，正在计划使用在法国劳伦斯·利弗莫尔国家实验室（Lawrence Livermore National Laboratory）的国家点火设施（NIF）和法国的激光巨人（LMJ）设施的国家点火设施（NIF）的高强度激光器（NIF）进行实验中的湍流动力学的实验。该奖项支持的努力包括设计和建模这些高度要求的实验通过使用高度强大的代码运行大规模3D模拟的模拟广告系列。模拟对于确保实验达到操作湍流发电机机制所需的条件至关重要，并且对于解释实验结果至关重要。这项工作将进一步转变学术界在大型激光设施中设计和分析高能量密度物理学实验的能力，并将训练初级科学家使用经过验证的模拟设计和解释此类实验 - 一个关键的国家需求 - 建立在探路者实验的探路者实验的实验，该实验是在Rutter -applets -applets -applets -applets -applets -applets -applets -applets -applets -appleton实验室进行的实验。罗切斯特大学的能量学。他们还建立在已经获得设计和解释这些实验的经验的基础上，该实验是使用闪存代码进行的经过验证的模拟，该模拟是该小组开发的高功能强大的辐射MHD代码。用于NIF和LMJ实验的配置基于为Omega激光部署的平台，使用Flash模拟适用于大型激光器设施。 NIF实验将在大型磁性prandTL数字的状态下进行探测发电机，磁性与流体雷诺数的比率（PM = Rm / re 1），而LMJ实验将集中在PM 1的磁场扩增上。预期在每个制度和闪光灯模拟中，Dynamo机制都可以不同，确保了所需的Plassments Plassmy的Plassma demando机制。这些实验有望表征湍流能量在速度，磁场和密度波动之间的分布，从而在磁化，湍流等离子体中提供了能量级联的全面图片。由于每次射击日的激光射击数量仅为NIF的两个，在LMJ处只有三个，因此没有错误的余地：设计和分析实验的数值建模必须实现证明和表征湍流的发电机机制的科学目标。