Holographic Imaging of Evolving Laser-Plasma Structures

演化激光等离子体结构的全息成像

• 批准号: 1004321
• 负责人: Michael Downer
• 金额: $ 1.5万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1004321&HistoricalAwards=false
• 关键词: Holographic; Imaging; Evolving; Laser; Plasma

This award is made in response to a proposal submitted to and reviewed under the NSF/DOE Partnership in Basic Plasma Science and Engineering joint solicitation NSF 09-596. The award provides funds to support undergraduate participation in the overall research effort, which is being funded separately by the DOE under contract to University of Texas (Grant DE-FG02-07ER54945). When intense femtosecond laser pulses or electron bunches propagate through an ionized gas, or plasma, they displace plasma electrons from within their envelopes, much like a boat displaces water as it propagates through a lake. As a result, they produce electron density structures that propagate at the speed of light and evolve in shape as they propagate, like the wake behind a boat. In recent years, scientists have developed miniature particle accelerators that work by surfing charged particles on these electron density waves. However, the performance of the accelerators is difficult to optimize because the wave structures are invisible, except indirectly through intensive computer simulations, and challenging to control. This project will develop methods for visualizing and controlling these light-velocity structures. To visualize them, the first of three tasks aims to develop a Frequency Domain Tomography (FDT) system that will take multi-frame "movies" of evolving plasma structures created by a single laser shot. The FDT system will multiplex an existing Frequency Domain Holography system, developed in prior work, that takes slightly blurred "snapshots" using a single probe pulse that co-propagates with and overlaps the evolving structure. The new FDT system adds probes propagating at oblique angles to the plasma structure. Tomographic algorithms similar to those used in medical CAT scans will then reconstruct multiple "frames" depicting the plasma structure at different stages of its evolution. In the second of three tasks, the visualization techniques will be extended to electron-bunch-driven plasma wakes in an experiment at Brookhaven National Laboratory's Advanced Test Facility (ATF) that was recently approved by the ATF Program Advisory Committee after external review. The temporal and radial structure of the plasma wakes will be visualized as the format of the drive bunch train and the plasma density vary. To control evolution of the drive laser pulse and plasma structures it creates, the third of three tasks introduces a secondary drive laser pulse that co-propagates with the main laser pulse and differs in frequency by approximately the electron plasma frequency. Theory developed previously by the co-PI of this project showed that such a secondary pulse can control the intense drive laser pulse's propagation, while a two-color terawatt laser system developed by the lead PI produces temporally synchronized sideband pulses needed to implement such experiments. The project introduces unique approaches to visualizing and controlling rapidly evolving relativistic laser-plasma interactions that the co-PIs pioneered. It will provide the first laboratory visualization of evolving laser- and e-beam driven plasma wakes, and will complement, benchmark and validate computer simulations of these structures. Two-color laser-plasma interactions provide a new approach to controlling plasma wave propagation that is ripe for experimental demonstration.The ability to combat or enhance relativistic self-focusing developed here can impact fast ignition of laser fusion, and lead to more reliable plasma-based accelerators, useful in turn as compact x-ray sources, injectors for conventional accelerators, and medical accelerators. Proposed investigations of two-color laser plasma interactions can lead to a new generation of plasma-based amplifiers and compressors for ultra-intense laser pulses that are free of material damage limits. Finally the proposed research will train a postdoc, three Ph.D. students, and an undergraduate from UT-San Antonio, which ranks 4th in the nation in number of undergraduate degrees awarded to Hispanics.This project is jointly funded by the NSF and the DOE.The NSF support of undergraduate participation adds a broader educational impact through the early-year training of students by introducing them to scientific research as a possible career path.

该奖项是为了响应提交给NSF/DOE基础等离子体科学与工程合作伙伴关系NSF 09-596的提案。该奖项提供资金，以支持本科生参与整体研究工作，这是由美国能源部根据合同单独资助得克萨斯大学（授予DE-FG 02 - 07 ER 54945）。当强烈的飞秒激光脉冲或电子聚束通过电离气体或等离子体传播时，它们会将等离子体电子从其包络中转移出来，就像船在湖中传播时转移水一样。 结果，它们产生了以光速传播的电子密度结构，并在传播过程中演变形状，就像船后的尾流一样。 近年来，科学家们已经开发出微型粒子加速器，其工作原理是在这些电子密度波上冲浪带电粒子。 然而，加速器的性能很难优化，因为波结构是不可见的，除非通过密集的计算机模拟间接进行，并且具有控制挑战性。 该项目将开发可视化和控制这些光速结构的方法。为了使它们可视化，三项任务中的第一项旨在开发一种频域断层扫描（FDT）系统，该系统将拍摄由单次激光照射产生的不断变化的等离子体结构的多帧“电影”。FDT系统将多路复用现有的频域全息系统，在先前的工作中开发的，采取轻微模糊的“快照”使用一个单一的探测脉冲，共同传播和重叠的演变结构。新的FDT系统增加了以斜角传播到等离子体结构的探针。 然后，类似于医学CAT扫描中使用的层析成像算法将重建多个“帧”，描绘等离子体结构在其演变的不同阶段。 在三项任务的第二项中，可视化技术将扩展到布鲁克海文国家实验室高级测试设施（ATF）的实验中的电子束团驱动等离子体尾流，该实验最近由ATF计划咨询委员会在外部审查后批准。等离子体尾流的时间和径向结构将被可视化为驱动聚束列的格式和等离子体密度的变化。为了控制驱动激光脉冲及其产生的等离子体结构的演变，三个任务中的第三个引入次级驱动激光脉冲，该次级驱动激光脉冲与主激光脉冲共同传播并且在频率上相差大约电子等离子体频率。 该项目的合作PI先前开发的理论表明，这样的二次脉冲可以控制强驱动激光脉冲的传播，而由牵头PI开发的双色太瓦激光系统产生实施此类实验所需的时间同步边带脉冲。该项目介绍了独特的方法来可视化和控制快速发展的相对论激光等离子体相互作用，共同PI开创。 它将提供第一个实验室可视化的激光和电子束驱动的等离子体尾流，并将补充，基准和验证这些结构的计算机模拟。双色激光-等离子体相互作用为控制等离子体波的传播提供了一种新的方法，这种方法已经成熟，可以进行实验验证。在这里开发的对抗或增强相对论自聚焦的能力可以影响激光聚变的快速点火，并导致更可靠的等离子体加速器，进而用作紧凑的X射线源，传统加速器的注入器和医疗加速器。双色激光等离子体相互作用的拟议调查可能会导致新一代的基于等离子体的放大器和压缩器的超强激光脉冲，是免费的材料损伤限制。最后提出研究将培养一名博士后、三名博士。该项目由美国国家科学基金会（NSF）和美国能源部（DOE）共同资助。NSF对本科生参与的支持通过向学生介绍科学研究作为一种可能的职业道路，通过对学生的早期培训增加了更广泛的教育影响。