First Emission of Novel Photocathode Gun Gated by Z-polarized Laser Pulse

We have developed a laser-induced Schottky-effect-gated photocathode gun since 2006. This new type of gun utilizes a laser¿s coherency to realize a compact laser source using Z-polarization of the IR laser on the cathode. This Z-polarization scheme reduces the laser pulse energy by reducing the cathode work function due to Schottky effect. Before this epoch-making scheme, photocathode guns had never utilized laser¿s coherency. A hollow laser incidence is applied with a hollow convex lens that is focused after passing the beam through a radial polarizer. According to our calculations (convex lens: NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fundamental wavelength (792 nm) and 0.316 MW for the SHG (396 nm). Therefore, we expect that this laser-induced Schottky emission requires just a compact femtosecond laser oscillator as a laser source. Besides, a dichromatic laser scheme (photo-exciting: 780 nm; gating: 30 um) should be applied to polarized electron sources for International Linear Collider (ILC). We report the first feasibility study of this laser-induced Schottky-effect on several metal photocathodes by comparing radial and azimuthal polarizations.
Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan