Space charge analysis for photoinjector emittance compensation.
Carillo M., Behtouei M., Bosco F., Chiadroni E., Camacho O., Faillace L., Ficcadenti L., Fukasaway A., Giuliano L., Migliorati M., Mostacci A., Spataro B., Rosenzweig J.B., Palumbo L.
Beam dynamics studies are performed in the context of a C-band hybrid photo-injector project developed by a collaboration between UCLA/Sapienza/INFN-LNF/RadiaBeam. From the analysis of the beam-slice evolution, a more accurate compensation of the beam emittance is obtained. Emittance oscillations are studied by means of the slice analysis, which allows correlation of the position of the emittance minima with the slope of the slices in the transverse phase space. Furthermore, the significant reduction in the normalized emittance observed by varying the transverse shape of the beam while assuming a longitudinal Gaussian distribution has been analytically justified. Indeed, a new method for deriving the expression of space charge forces has shown that the emittance growth is due to nonlinear space-charge fields that occur immediately after the beam emission from the cathode, giving insight into the optimum laser profile needed for minimizing the emittance.