Design and simulation of a pulsed positron beam at ELI-NP

The design of the pulsing system for the slow e+ beam at ELI-NP is presented. It will deliver narrow time width e+ pulses, achieved by a combination of prebuncher, chopper and buncher. The effect of the different components on the pulse compression is simulated by a Matlab program. The results show that the best compression of the e+ pulses, which can be achieved by the proposed pulsing system, is limited to about 100 ps (FWHM). The most effective solution, applied up to now, for minimizing the influence of the backscattered e+ on the PALS spectra by using a bent tube filter is simulated by Comsol Multiphysics.