From Phase Space Manipulation to First Light from a Laser Plasma Accelerator Powered Free Electron Laser

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

The goal of this project is to develop a table-top x-ray source. High-brightness x-ray light sources are indispensible tools to probe chemical, biological, and physical systems. The x-ray source is driven by electron beams generated in an accelerator that relies on very intense laser beams to excite waves in a cloud of ionized gas, a plasma, on which electrons can surf to reach high energies. This technology has already shown that electron beams can be produced from devices that are only a few inches long compared to several-football-field-long accelerators using conventional technology. In order for a lot of x-rays to be generated, the electron beam quality has to be excellent, and this project will demonstrate that such beams can, in fact, be produced. Success of this project will greatly reduce the size of x-ray sources and bring this tool to individual laboratories and investigators, promoting the advancement of science. This project also supports the education of three graduate students, to be trained in the physics of ultra-short beams, laser-plasma interactions, and advanced accelerator concepts. The project aims at developing a compact, ultra-fast (femtosecond), soft X-ray radiation source using beams produced by a laser-plasma accelerator (LPA). Intense radiation can be generated via the undulator radiation mechanism by coupling the ultra-short laser-plasma-accelerated electron beam into a conventional magnetic undulator. Transport of the electron beams will be performed with two magnetic lenses, incorporating recently-developed ultra-strong active plasma lenses, and a chicane for energy dispersion. The latter is critical to reduce the beam slice energy spread, enabling the observation of free-electron laser gain. By fielding undulator-based radiation diagnostics, the electron beam quality will be measured on every shot and will provide the necessary feedback to understand and control the requirements imposed on the laser plasma accelerator and transport lattice to deliver high quality beams. The project consists of three phases: (1) Operate the LPA in a stable and high-charge mode with the new 100-TW-class laser system. (2) Implement and demonstrate the LPA source-to-undulator transport system, and commission an undulator embedded with strong focusing. Ultra-short incoherent undulator radiation with on the order of 10^8 photons per shot in the 10-100 eV range is expected. (3) By tuning the chicane, coherent enhancement of the undulator radiation will be pursued. This light source is intrinsically synchronized to the laser driver, making such a compact source ideal for pump-probe applications in ultrafast science.