Ultrafast coherent XUV radiation from a laser-plasma-accelerated electron beam

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目旨在利用基于激光等离子体的加速器产生的光束，开发一种超快（飞秒）、相干、极紫外（XUV）辐射源。在保证束流质量的前提下，将超短激光等离子体加速电子束耦合到传统的磁波动器中，通过自由电子激光机制产生相干辐射。(1)测量波动辐射来表征电子束的特性（能量扩散和发射度），以证明它们作为FEL驱动器的适用性；(2)开发光束传输系统，以匹配从等离子体加速器到磁波动器的电子束；(3)测量FEL辐射增益。这项工作对紧凑型下一代光源的辐射源开发具有直接意义。这项提议的工作将首次展示由激光等离子体加速电子束驱动的自由电子激光器，从而实现极其紧凑的相干、峰值功率高的辐射源。驱动自由电子激光器的传统方法是使用传统的射频加速器。由于射频直线加速器中的加速梯度通常限制在几十MV/m，因此gev级加速器的尺寸和成本都很大。另一方面，等离子体加速器可以支持大于100 GV/m的加速梯度。因此，激光驱动加速器的尺寸和成本可以相对较小，例如，达到GeV能量所需的加速等离子体结构的尺寸只有几厘米长。此外，从激光等离子体加速器中产生的电子束自然很短（由等离子体波长决定，大约10飞秒），并且本质上与激光驱动器同步，使这种源成为超快科学应用的理想选择。在基本原子时间尺度上理解材料的结构动力学是一个重要的研究前沿。紧凑的飞秒高能XUV辐射源的开发将允许探索化学反应和材料相变的新实验，以及纳米级物理和超快现象。该基金将资助两名研究生和一名博士后研究助理。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project aims toward developing an ultrafast (femtosecond), coherent, extreme ultraviolet (XUV) radiation source using beams produced by a laser-plasma-based accelerator. Coherent radiation can be generated via the free-electron laser (FEL) mechanism by coupling the ultra- short laser-plasma-accelerated electron beam into a conventional magnetic undulator, provided the e-beam quality is sufficientThe project consists of three phases: (1) measurement of undulator radiation to characterize electron beam properties (energy spread and emittance) for demonstrating their suitability as FEL drivers, (2) development of beam transport system to match the electron beam from the plasma accelerator to the magnetic undulator, and (3) measurement of FEL radiation gain. This work has direct implications for radiation source development for, compact, next-generation light sources. The proposed work will demonstrate for the first time an FEL driven by a laser-plasma accelerated electron beam, enabling extremely compact sources of coherent, high peak power, radiation. The traditional approach to drive an FEL is to use a conventional RF accelerator. Since the accelerating gradient in an RF linac is typically limited to tens of MV/m, the size and cost of a GeV-class accelerator is large. Plasma accelerators, on the other hand, can support accelerating gradients greater than 100 GV/m. Consequently, the size and cost of a laser-driven accelerator can be relatively small, e.g., the size of the accelerating plasma structure required to reach GeV energies is only several centimeters in length. In addition, the electron bunches emerging from a laser-plasma accelerator are naturally short (of the order of ten femtoseconds, determined by the plasma wavelength), and intrinsically synchronized to the laser driver, making such a source ideal for ultrafast science applications. Understanding the structural dynamics of materials on fundamental atomic timescale represents an important research frontier. Development of a compact source of femtosecond, energetic XUV radiation would allow novel experiments exploring chemical reactions and phase transitions of materials, as well as nanoscale physics and ultrafast phenomena. The grant will support two graduate students and one post-doctoral Research Associate.