Intense Sub-Femtosecond Optical Radiation from Relativistic Plasmas

来自相对论等离子体的强亚飞秒光辐射

基本信息

批准号：
1619582
负责人：
Howard Milchberg
金额：
$ 46万
依托单位：
University of Maryland, College Park
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：
2016-08-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1619582&HistoricalAwards=false
关键词：
Intense Sub Femtosecond Optical Radiation

项目摘要

This work will explore the shortest duration optical flashes ever generated, produced by accelerating electrons from rest to almost the speed of light over a distance less than one-hundredth the thickness of a human hair. The accelerating charged particles are produced by the interaction of low energy (but very high intensity) laser pulses with dense jets of hydrogen gas. The hydrogen gas has all of its electrons stripped off by the laser pulse, forming a plasma, and radiation pressure from the laser pulse then pushes the free electrons out of the way. This produces an electrostatic disturbance that moves as a wave in the plasma (a 'plasma wave') and is so strong that it can accelerate its own electrons from rest to nearly the speed of light in the form of directed beams. These beams of accelerated electrons are useful for medical and scientific imaging. One of their intriguing, exciting, and potentially useful byproducts is radiation flash emission, which takes place over just one half cycle of the radiation emission itself, making it of sub-femtosecond duration (less than 1/1000000000000000 second long). Such a light source, in addition to its fascinating internal relativistic dynamics, can act as the fastest-ever optical strobe source for capturing images, for example, of electrons in mid-flight in their orbits in an atom.This project will develop and characterize a new source of intense, coherent, sub-femtosecond pulses (or flashes) in the optical range. These pulses arise directly from wave breaking of relativistic plasma waves and are only indirectly driven by a pump laser field. The radiation flash appears to arise purely from classical acceleration of charged particles exposed to the enormous electric and magnetic fields inside relativistic plasma waves. Their spectral and coherence characteristics are strongly affected by the plasma density, which sets the group velocity of the plasma waves, the spatial scale of the radiating bunches, and the laser energy required for relativistic self-focusing of the initiating laser pulse. Such flashes are consistent with unidirectional acceleration of electrons from rest to nearly the speed of light. The project will consist of detailed measurements of flash coherence properties, temporal pulse structure, and exploration of timing control of this radiation. Accompanying the experiments will be extensive 2D and 3D particle-in-cell simulations. A new 1 kHz, 10 mJ laser system will enable experiments at a much higher repetition rate, improving shot-to-shot reproducibility and allowing high data collection rates, both of which lead to better signal-to-noise and more precise measurements.

这项工作将探索产生的最短持续时间光闪光，这是通过将电子从静止加速到几乎距离的光速而产生的，远小于人头发厚度的一百分之一。加速带电的颗粒是由低能（但强度很高）激光脉冲与氢气量密集的射流产生的。氢气使其所有电子被激光脉冲剥离，形成等离子体，并从激光脉冲中辐射压力，然后将自由电子推出。这会产生一种静电干扰，该静电干扰像等离子体中的波动（“等离子体波”），并且非常强，以至于它可以以定向梁的形式将自己的电子从静止速度加速到几乎是光速。这些加速电子光束可用于医学和科学成像。他们有趣，令人兴奋且潜在有用的副产品之一是辐射闪光发射，它发生在辐射发射本身的一半周期中，使其持续时间（小于1/1000000000000000秒长）。除了具有引人入胜的内部相对论动力学外，这种光源还可以充当有史以来最快的光学频率源，用于捕获原子中的轨道中的电子中的电子图像，例如原子中的轨道中的电子。该项目将发展和表征新的强烈，相干，次级，次曲线脉冲（或闪光灯）的新来源。这些脉冲直接来自相对论等离子体波的波浪破裂，仅由泵激光场间接驱动。辐射闪光似乎纯粹是由于经典的带电颗粒的经典加速度，暴露于相对论等离子体波内的巨大电场和磁场。它们的光谱和连贯性特性受到血浆密度的强烈影响，血浆密度设置了等离子体波的组速度，辐射束的空间尺度以及启动激光脉冲相对自我关注所需的激光能量。这样的闪光与电子从静止速度到光速的单向加速度一致。该项目将包括对闪光相干性能，时间脉冲结构的详细测量以及该辐射的时间控制的探索。伴随实验将是广泛的2D和3D粒子模拟。一个新的1 kHz，10 MJ激光系统将以更高的重复速率启用实验，提高射击重现性并允许高数据收集速率，这两者都会导致更好的信噪比噪声和更精确的测量。