Light sources are accelerators that circulate electrons around a storage ring, producing very intense beams of photons in a range of useful wavelengths. Photons are produced by synchrotron radiation, which is generated when electrons experience acceleration due to a change in the direction of their trajectory. By shining these photons on a sample to be studied, basic properties of these sample materials can be inferred. Using radiation of different wavelength (e.g, X-rays or ultraviolet) can help elucidate material properties at different distance scales in the samples being studied. Light sources have many applications, including in biology, physics, materials science, and national security.
This proposal aims to develop a new technique to quickly change the direction, or undulate, electrons in a light source. Typically light sources use static magnets that undulate electron beams to generate radiation. However, with current technology it is difficult to obtain short undulator periods needed for shorter radiation wavelengths and reduced electron beam energy operation without compromising the overall beam quality. To overcome these limitations, the PI will develop a novel short-period electromagnetic undulator operating at millimeter-wave with a period of less than 1 millimeter (mm). The scaling laws for this type of undulator predict an aperture, typically, three times the undulator period. This represents a paradigm shift for the design and implementation of undulators for light sources. Because the surface field is very low at the walls of the Radio-Frequency (RF) undulator, the field at the center of the undulator is predicted to be much higher than anything possible with a static magnetic undulator. The design goal is to have an approximately 5 Tesla field for an undulator that has less than 1 mm period. This device will have the added benefit of fast dynamic strength and polarization control of the produced light.
This award will support the training of PhD students and post-doctoral scholars at Stanford University, engaging them in advanced RF/microwave design algorithms and simulation tools. This project has the potential to have a profound impact on many beam-based light sources. Dreams of compact economical free electron lasers, which can be installed at many universities and research institutions, will become closer to reality as RF undulators become a common tool. This applies also to light sources developed for a variety of medical and industrial applications as well as applications related to national security.