High Aspect Ratio Electron Beam Generation in KEK-STF

Phase-space manipulation on the beam gives a way to optimize the beam phase space distribution for a specific purpose. It is realized by beam optics components which have couplings between degree of freedoms. In this article, a high aspect ratio beam generation with a photo-cathode in a solenoid field is described. In International Linear Col-lider (ILC) project, a high aspect ratio electron beam is em-ployed for high luminosity up to several 1034cm−2s−1 by keeping “beam-beam effects ” reasonably low. In the cur-rent design of ILC, a high aspect ratio beam which corre-sponds to 250 in transverse emittance ratio, is generated by radiation damping in a 3km storage ring prior to the main acceleration. If such high aspect ratio beam is directly gen-erated from an injector linac, the 3km damping ring, a cou-ple of long transport lines, and a part of the bunching sec-tion can be omitted and the system becomes much simpler and cost-effective. We give a result of a simulation study of the high aspect ratio beam generation. Here, we assume a test experiment in STF (Super conducting Test Facility) in KEK. At last, an ILC design based on this method is discussed