Longitudinal phase measurement at the ELI-NP compton gamma source

Virtual bunch length measurement can be carried out by means of ELEGANT code for tracking the bunch particles from RF deflector to the screen. The technique relies on the correlation between the bunch longitudinal coordinate and transverse coordinates induced through a RF deflector. Therefore, the bunch length measurement can be carried out measuring the vertical spot size at the screen, placed after the RF deflector. The deflecting voltage amplitude affects the resolution. Adding a dispersive element, e.g. a magnetic dipole between RF deflector and the screen, the full longitudinal phase space can be measured. In this paper, we discuss some issues relevant for the electron linac of the Compton source at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP).