CAREER: Microscale Magnetic Devices for Next Generation Coherent X-Ray Sources

概述：本研究将探索新型微尺度磁波动器和四极聚焦磁体，使x射线自由电子激光器（XFELs）实现前所未有的缩放。XFELs加速电子束，使用四极杆聚焦电子束，并使用波动器的磁场将电子能量转换为相干辐射。相衬成像中使用相干x射线，与传统x射线成像相比，其分辨率提高了1000倍。目前，在美国只有一个XFEL。因此，只有少数科学家可以访问它，而潜在的高影响实验在排队等待访问时变得萎靡不振。该项目的成功将导致广泛使用的XFELs能够对非晶体样品进行原子分辨率成像和对动态过程进行飞秒成像。在这个CAREER项目中，PI计划推进最近在3D微磁铁制造方面的创新，他的团队已经率先引入了新一代XFELs。为了实现这一总体目标，CAREER计划将重点实现以下目标：(1)研究微型电磁铁四极体，推动XFELs中使用的电子束聚焦极限。(2)探索利用其正弦磁场的缩放规律从低能量电子束中产生高能光子的可调谐微尺度波动器。(3)引入实验室规模的XFEL，比现有的XFEL小1000倍，比其他同尺寸的相干x射线源亮100万倍。智力优势：本研究将探讨电子束聚焦和高能光子产生的基本限制。传统的四极聚焦磁铁和波动器是厘米级的，通常是手工加工的。三维电磁铁制造的最新进展使微型四极和波动器的大型阵列的平行制造成为可能。设计优化技术将用于探索新颖的四极杆设计，即使四极杆被缩放到电子束光斑尺寸的极限，也可以聚焦电子束。微波动器，比以前建造的任何一个都小，将进入一个运行状态，在那里尾流场效应出现，这种效应还没有在这个规模上进行实验研究。如果成功，这项研究将在高强度四极体和强场、短周期波动器方面创造一个新的艺术状态，这将用于在小型光源中创建具有无与伦比亮度的XFEL。更广泛的影响：拟议的研究为新一代相干x射线源奠定了基础，这将彻底改变科学和医学高速相干x射线成像的途径。对科学家来说，强烈的超短x射线脉冲有可能扩大生物结构和过程的高速成像。对40%不能结晶的蛋白质进行蛋白质结构成像将成为可能，并且可以理解原子运动尺度上的动态过程。此外，XFELs使x射线剂量减少1000倍成为可能，这将减少人们对医用x射线对健康影响的担忧，例如美国每年进行的近4000万次乳房x光检查。PI计划创建一个综合研究、教育和外展项目，其使命是招募和留住STEM中代表性不足的学生。PI将与加州大学洛杉矶分校的CEED多元化中心合作，创建一个名为“设计它，打印它！”的夏季设计挑战赛。在这个为期6周的设计挑战中，代表性不足（UR）的K-12学生将设计，3D打印和测试组件，以对齐四极杆和波动器。K-12学生将由一名工科本科学生指导，他也将在学年期间参加一项有偿研究项目。每年将有4名K-12学生和1名本科生参与，在项目期间为20名K-12学生和5名本科生提供深入的研究经验。每年，PI和本科生还将访问K-12参与者的高中，介绍他们在3D打印方面的工作，在项目的整个生命周期内达到约750名学生。

Overview:This research will explore novel microscale magnetic undulators and quadrupole focusing magnets, enabling unprecedented scaling of x-ray free electron lasers (XFELs). XFELs accelerate a beam of electrons, focus the electron beam using quadrupoles, and convert the electron energy into coherent radiation using the magnetic field of an undulator. Coherent x-rays are used in phase contrast imaging, which offers 1000x better resolution compared to conventional x-ray imaging. Currently, there is only one XFEL in the United States. As such, only a handful of scientists can access it, and potentially high-impact experiments languish as they wait in line for access. Success of this project will lead to broadly accessible XFELs capable of atomic resolution imaging of non-crystalline samples and femtosecond imaging of dynamic processes. In this CAREER project, the PI plans to advance recent innovation in 3D micro-magnet fabrication that his group has pioneered to introduce a new generation of XFELs. To accomplish this overarching goal, the CAREER program will focus on achieving the following goals: (1) Investigate micro-electromagnet quadrupoles that push the limits of focusing for the electron beams used in XFELs. (2) Explore tunable microscale undulators that leverage scaling laws of their sinusoidal magnetic field to create high energy photons from lower energy electron beams. (3) Introduce a lab-scale XFEL that is 1000x smaller than existing XFELs and 1,000,000 times brighter than other coherent x-ray sources of its size.Intellectual Merit :This research will investigate the fundamental limits of electron beam focusing and high-energy photon generation. Conventional quadrupole focusing magnets and undulators are centimeter-scale and individually machined, often by hand. Recent advances in fabrication of 3D electromagnets enable parallel fabrication of large arrays of microscale quadrupoles and undulators. Design optimization techniques will be used to explore novel designs of quadrupoles that focus an electron beam even as the quadrupole is scaled to the limit of the electron beam spot size. Micro-undulators, smaller than any previously built, will access an operating regime where wakefield effects emerge, effects that have not been yet experimentally studied at this scale. If successful, this research will create a new state of the art in high-strength quadrupoles and intense-field, short-period undulators, which will be used to create an XFEL with unmatched brightness among small-scale light sources.Broader Impacts :The proposed research lays the foundation for a new generation of coherent x-ray sources that would revolutionize access to high-speed coherent x-ray imaging for science and medicine. For scientists, intense, ultra-short x-ray pulses have the potential to expand high-speed imaging of biological structure and processes. Imaging of protein structure would become possible for the 40% of proteins that cannot be crystallized, and dynamic processes at the scale of atomic motion could be understood. Also, a 1000x reduction in x-ray dosage made possible by XFELs would diminish concerns about the health effects of medical x-rays, such as for the nearly 40 million mammograms performed in the US each year. The PI plans to create an integrated research, education, and outreach program with the mission of recruiting and retaining underrepresented students in STEM. In collaboration with the CEED diversity center at UCLA, The PI will create a summer design challenge called "Design It, Print It!". In this 6-week design challenge, underrepresented (UR) K-12 students will design, 3D print, and test components to align quadrupoles and undulators. The K-12 students will be guided by an UR undergraduate engineering student, who will also participate in a paid research project during the school year. Four K-12 students and one undergraduate will participate per year, providing an in-depth research experience for twenty K-12 students and five undergraduates during the project. Each year, the PI and undergraduate will also visit the high schools of the K-12 participants to describe their work in 3D printing, reaching ~750 students over the life of the project.