Design Optimizations of X-Ray FEL Facility at MIT

In recent years, a number of short wavelength FEL experiments have demonstrated key technologies and obtained good agreement between experiment and theory. The x-ray FEL at MIT[1] is one example of a design for a new generation linac-based light source. Such a new machine requires very high quality electron beams. Besides the usual requirements on beam quality such as emittance, energy spread, peak current, etc., there are new challenges emerging in the design studies, e.g., the precise arrival timing of electron beam at lower tens of femtoseconds level to ensure the laser seed overlap the desired sections of electron bunch in the multiple-stage HGHG process. In this paper we report the progress on design optimization towards high quality and low sensitivity beams