Optimizing beam dynamics in the EuPRAXIA@ SPARCLAB RF injector

. - The EuPRAXIA@SPARC LAB RF injector provides highbrightness electron beams accelerated and longitudinally manipulated in the velocity bunching regime (VB). The RF injector works in the so-called comb configuration. It foresees a 30 pC witness and a 200 pC driver longitudinally compressed in the first two accelerating structures both operated in the VB regime. The beam stability can be improved by adding a High Harmonic Cavity (HHC), interposed between the Gun and the first accelerating structure, to shorten and flatter the charge distribution and manipulate the beams to reach proper transverse and longitudinal parameters. The paper reports on beam dynamics studies performed with the insertion of the X-band RF cavity that is proposed to shape the beam current distribution, linearize the longitudinal phase space, and stabilize it with respect to RF jitters.