Beam diagnostics for laser undulator based on compton backward scattering

A low-emittance electron beam is required for the X-ray generation such as the synchrotron radiation and the laser undulator. The laser undulator based on Compton backward scattering has been developed as a compact soft X-ray source for the biological observation at Waseda University. To generate the soft X-ray pulse stably, beam diagnostics is very important. In case of the laser undulator, the energy of the electron beam can be lower than other X-ray source such as synchrotron radiation but it is difficult to measure the beam characteristics about the low energy electron beam like a 5 MeV due to the space charge effect. Consequently, the slit scan technique has been developed to measure the beam emittance precisely. In case of the photocathode rf gun, the beam emittance strongly depends on the laser injection method. To generate the low-emittance beam, the emittance comparison experiments have been performed among three deferent methods, the slanting injection (the standard injection), the slanting injection with profile shaping and the perpendicular injection using the slit scan technique. In this conference, we will report results of the experiments.