Spectral distribution of SPARC photo injector electrons

SPARC is a photo-injector for production of high-brightness low emittance electron beams to drive a FEL experiment in various configurations, including SASE-FEL radiation of 1-10nm (SPARCX project). Due to a high-brightness source, the SPARC facility can be used to study the physics of ultrashort beams, plasma-wave based acceleration, production of X-rays by means of Compton backscattering, channeling of electron beams and other experiments. The initial process of electron beam generation inside the RF gun determines the main parameters of the electron beam. Interaction of electrons with high-frequency laser beam leads to modulation of the electron beam. In this paper we present electron beam spectral distribution for SPARC photo injector parameters. The estimate of electron beam energy loss for such electron distribution also is given.