Precision Measurements Using Nonlinear Thomson Scattering

使用非线性汤姆逊散射进行精密测量

• 批准号: 2207737
• 负责人: Michael Ware
• 金额: $ 44.91万
• 依托单位: Brigham Young University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2207737&HistoricalAwards=false
• 关键词: Precision; Measurements; Using; Nonlinear; Thomson

High intensity lasers have a wide range of uses in basic science, industry, and national defense applications. To achieve the highest intensities, a laser must be focused to the smallest spot size possible. To achieve a small focus, the structure of the electromagnetic fields within a laser focus must be measured and optimized. In this project, the researchers place electrons within a very high intensity laser focus, and then study the light these electrons emit (nonlinear Thomson scattering) to understand the field structure within the focus. The patterns in the spatial structure and polarization of this nonlinear Thomson scattering contain information about the structure of the fields in a laser focus that is hard to measure in other ways. The researchers will study light emission patterns while varying focal properties of the laser and the distribution of electrons within the focus, with a goal of learning how to measure, understand, and improve the laser focus. These are very challenging measurements to make, and most previous work has been restricted to theoretical and computational predictions. The research project will involve and train approximately a dozen undergraduate students and three graduate students in the challenging blend of high-intensity laser methods used to drive the electrons and the single-photon detection methods used to measure the scattered light. The researchers will incorporate results from this project into a free online optics textbook that is widely used at the university level.This project studies nonlinear Thomson scattering from very diffuse (near-vacuum density) free electrons in a laser focus and enables the study of this fundamental relativistic phenomenon without the confounding influence of plasma dynamics. These measurements will be carried out for several lower-order harmonics in a reference frame that allows the angular structure of the photoemission to be measured. The researchers will: (1) characterize for the first time the polarization-resolved angular emission patterns of individual harmonic orders over virtually the entire emission sphere, (2) investigate the signature of the ponderomotive ejection of electrons from the focus in the angular photoemission patterns and how this is influenced by focal parameters and pulse duration, and (3) study how coherence between electrons emitted from the same atom modifies nonlinear Thomson scattering, both the angular pattern and the strength. Each of these effects has the potential to contributes measurable amounts to the overall nonlinear Thomson scattering signal. Simulations of relativistic electron trajectories within a tight laser focus show that electron trajectories are sensitive to the details of the field vectors. An overarching goal is to be able to better correlate the vector fields of the laser focus with observed nonlinear Thomson scattering.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

高强度激光器在基础科学，工业和国防应用中具有广泛的用途。为了达到最高强度，必须将激光聚焦到可能的最小斑点尺寸上。为了获得较小的焦点，必须测量和优化激光焦点内电磁场的结构。在这个项目中，研究人员将电子放置在非常高的强度激光焦点中，然后研究这些电子发出的光（非线性汤姆森散射），以了解焦点内的场结构。这种非线性汤姆森散射的空间结构和极化中的模式包含有关激光焦点中磁场结构的信息，这些信息很难以其他方式测量。研究人员将研究光发射模式，同时激光的焦点特性以及焦点内的电子分布，以学习如何测量，理解和改善激光焦点的目标。这些都是非常具有挑战性的测量，并且大多数以前的工作都限于理论和计算预测。该研究项目将涉及并培训大约十几个本科生和三名研究生，以挑战用于驱动电子的高强度激光方法和用于测量散射光的单光子检测方法。研究人员将将该项目的结果纳入一个免费的在线光学教科书中，该教科书在大学级别被广泛使用。本项目研究非线性汤姆森（Thomson）从非常漫射（近vacuum密度）的免费电子中的无线散射中，并可以研究这种基本相对论现象的研究，而没有等离子动力学的混乱影响。这些测量将在参考框架中针对几个低阶谐波进行，以允许测量光发射的角结构。研究人员将：（1）首次表征了几乎整个发射球体的单个谐波订单的极化分解的角度发射模式，（2）研究电子从角度弹出电子射精的域名的签名汤姆森散射，既是角模式又有强度。这些效果中的每一个都有可能为整个非线性汤姆森散射信号贡献可衡量的量。在紧密的激光焦点内对相对论电子轨迹的模拟表明，电子轨迹对场矢量的细节敏感。一个总体目标是能够更好地将激光焦点的向量领域与观察到的非线性汤姆森散射相关联。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛的影响来通过评估来获得支持的。