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

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

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.