Optical Visualization of Beam-Driven Plasma Wakefield Accelerators

目前的粒子加速器技术正处于十字路口——新的发现科学和应用机会就在前面，然而实现它们所需的粒子加速器已经变得过于庞大和昂贵。该项目探索了粒子加速新方法的物理学基础，通过使用等离子体加速粒子，其速度比使用传统加速器快数千倍。目标是使基于等离子体的加速器比传统加速器小几千倍，而且更便宜。该项目解决了目前等离子体粒子加速研究中的两个挑战：(1)频繁产生高能粒子束，每秒数百次；(2)加速反物质粒子，如正电子。该项目将培养包括两名博士生和一名本科生在内的早期职业科学家，并将为为工业和医学创造新的加速器技术铺平道路。该合同支持在第二代SLAC先进加速器科学和实验测试设施（FACET-II）执行E-324实验“光束驱动等离子体尾流场加速器的光学可视化”。实验的具体科学目标是：(1)观察和了解等离子体尾场激发后的恢复时间，这限制了对撞机的重复率和亮度；(2)观察到由计算机模拟预测的在断裂后的强烈非线性电子尾迹所形成的尖锐的轴上离子密度峰；(3)首次观测到延迟小于1皮秒的原始束流驱动电子尾迹。这些研究将为基于等离子体的正电子加速器铺平道路，这是未来正电子对撞机的重要组成部分。他们还将开发可靠的桌面等离子体加速器，为生物、化学和材料研究提供紧凑的相干x射线源，为传统加速器和医疗加速器提供注入器。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Present particle accelerator technology is at a crossroads -- new discovery science and application opportunities lie ahead, yet the particle accelerators needed to realize them have become too large and expensive. This project explores the physics underlying a new approach to particle acceleration by using plasmas to accelerate particles thousands of times faster than can be done using conventional accelerators. The goal is to make plasma-based accelerators thousands of times smaller and less expensive than their conventional counterparts. This project addresses two current challenges in plasma-based particle acceleration research: (1) generating energetic particle bunches frequently, hundreds of times per second; and (2) accelerating anti-matter particles such as positrons. The project will train early career scientists including two Ph.D. students and an undergraduate student, and will help pave the way for creating new accelerator technology for industry and medicine.This award supports execution of the experiment E-324 “Optical visualization of beam-driven plasma wakefield accelerators” at the 2nd generation SLAC Facility for Advanced Accelerator Science and Experimental Tests (FACET-II). Specific scientific goals of the experiment are: (1) to observe and understand the recovery time of a plasma following plasma wakefield excitation, which limits collider repetition rate and luminosity; (2) to observe a sharp on-axis ion-density peak predicted by computer simulations to form as a result of a strongly nonlinear electron wake after it breaks; and (3) to observe the original beam-driven electron wake at delays less than 1 picosecond for the first time. These studies will pave the way for plasma-based positron accelerators, an essential component of future electron-positron colliders. They will also enable development of reliable tabletop plasma-based accelerators which provide compact coherent x-ray sources for biological, chemical, and materials research, injectors for conventional accelerators, and medical accelerators.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.