Review of the worldwide SASE FEL development

Three major X-ray FELs are now under construction: LCLS[1] at SLAC Stanford, XFEL/SPring-8[2] in Japan and Euro-XFEL[3] at DESY Hamburg. They are all aiming at generating 1 Å wavelength coherent X-ray radiation, which possess special feature: very high peak power and short pulse length. It will provide powerful tool to study non-linear dynamics of condensed matter, multi-photon ionization process of gases, and also it will realize the X-ray microscope of Angstrom resolving power, and instantaneous photography of femto-second time slicing capability. All of those XFELs rely on the same principle of SASE: Self-Amplified Spontaneous Emission, which does not require the cavity mirrors, thus wavelength is widely tuneable. This paper reviews basic configuration of each machine and project status.