Preliminary Results on Beam Dynamics of Laser Pulse Shaping Effects in SPARC

Electron beams with different initial pulse characteristics have been transported along the SPARC photoinjector. The differences we considered come from the possible profiles of the laser pulse driving the radiofrequency (rf) electron gun. Realistic deviations from the ideal flat-top pulse give for example a ramp or multi-peaks shape with a relative rise time, plateau deformation and roughness. The beam quality of the electron source is essential for the production of high brightness beams. The role played by the laser pulse is crucial, as it determines the electron beam pulse shape. The study presented here gives some indications on the tolerances of the laser beam characteristics for the electron beam quality preservation. The different beam current profiles are transported along the injector with the PARMELA [1] code. The electron pulse as external input to PARMELA is generated directly from a laser pulse resulting from certain configurations of the SPARC laser system. The variations of normalized emittance (ENX) and envelope are discussed for the different cases. Spectral and shaping requirements on the laser pulse temporal profile for the SPARC injector are found.