Laser Pulse Shaping for Low Emittance Photo-Injector.

摘要

Fourth generation light sources are pushing the boundaries of high intensity, coherent, short wavelength light sources for the scientific community. In the step from the 3rd generation to the 4th, a Free Electron Laser (FEL) amplifier is used to generate the light over the synchrotron rings of the past. To get to the short wavelengths of an X-ray FEL the emittance of the electron beam must be tightly controlled to match the emittance of the short wavelength photons they are interacting with. The emittance is an intrinsic property of an electron beam and can only be harmed as it propagates through a beam line. Due to this, it is important to start with as low as emittance as possible. Minimizing the electron beam emittance has the added benefit of decreasing the gain length needed to get up to higher power. For this reason low emittance is important for all types of FEL schemes. Most injector schemes use a photo-cathode as the electron beam source. A way to keep the emittance low is to shape the laser beam that generates the electrons as it imparts energy into the photo-cathode. Research was done in shaping the drive laser using a set of birefringent crystals for the APEX project at Lawrence Berkeley National Lab. The thesis discusses the light sources as a whole, the physics behind the pulse shaping technique as well as results obtained.