Miniature Magnetic Devices-based Chip-scale Panofksy Quadrupoles for Focusing Electron Beams

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

The project will investigate a new class of miniature magnetic devices that can focus beams of electrons, similar to the way that lenses focus light. Magnetic fields are highly effective for focusing beams of electrons, but current magnets are bulky and expensive. The proposed work aspires to create a new class of magnetic focusing devices that are at least one hundred times smaller than their existing counterparts. Steering electron beams has a broad range of applications. They are used in the world's most powerful microscopes, free electron lasers, which can study the motion of individual atoms. These laser microscopes can provide insight into the fundamental behavior of atoms and molecules, which can have impact in everyday life, such as discovery of new drugs. Additionally, electron beams are also used in treating cancer, with electron beam therapy having the benefit that it can be targeted much more precisely than radiation therapy. Miniaturizing magnetic focusing devices would not only allow broader access to these electron beams for use as laser microscopes, it would also allow electron beams to be put into places previously inaccessible, such as catheters for cancer therapy. The fundamental issues that will be studied in this work are the limits of miniaturization of these devices (i.e., how small can these magnets be made while still effectively focusing electron beams). To address the challenge of miniaturization, new designs, fundamentally different from the current state-of-the-art, must be pursued. Fabrication of these devices will require a combination of methods currently used by microchip manufacturers with custom methods developed especially for this work. Students at universities will be able to perform hands-on experiments that were previously limited to beamline scientists at a handful of facilities. The proposed activities will include being a faculty lead for "Santa Monica College/UCLA" Summer Scholar Research Program, development of high-school curriculum on magnetic devices, writing one article per year covering women in science and engineering. To provide more detail, the proposed research will create a new class of microfabricated electromagnet quadrupoles for focusing electron beams. Electron beams have made profound impacts in many application areas, ranging from the world's most precise microscopes to targeted ablation of cancer. Until recently, all these applications relied on large, expensive pieces of laboratory equipment to generate and accelerate electron beams. For example, storage rings and linear coherent light sources that allow for imaging with unprecedented temporal (femtosecond) and spatial (Angstrom) resolution are often housed in facilities on the scale of kilometers. Recent advances have enabled centimeter-scale accelerators on-chip with the potential to accelerate electron beams to relativistic velocities, comparable to those at kilometer-scale facilities. While these results are promising, there remains a critical barrier: there is currently no chip-scale method that can focus the beams produced by these next-generation accelerators. Inspired by asymmetric quadrupoles, which use magnetic field gradients to focus electron beams in a rectangular aperture, this work proposes to design, fabricate, and characterize a new class of miniature rectangular quadrupoles. However, the large-scale rectangular quadrupoles cannot simply be directly miniaturized. New designs must be developed to adapt to the fabrication constraints particular to small scale fabrication, and new fabrication methods must be developed to build devices at a mesoscale size range that falls between the regions where microfabrication and standard fabrication can comfortably operate. The proposed devices will provide 20 times greater focusing gradient and fit in a volume seven orders of magnitude smaller than the current state-of-the-art rectangular quadrupoles. If successful, this will be the first-ever focusing demonstration of a relativistic electron beam using a chip-scale device. 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.