Optimizing Positron Converter and Particle Spectrometer Shielding Design Using FLUKA Simulations

Recent experiments exploring positron generation using the electron beam from the OMEGA EP self-modulated laser wakefield acceleration (SMLWFA) platform struggle with insufficient positron signal relative to background using the existing particle spectrometer. To address this challenge, a new particle spectrometer is being designed with a larger aperture and specially designed magnetic optics to increase particle collection and enhance signal strength. FLUKA Monte-Carlo simulations were applied to optimize the positron converter for the next round of experiments and to design a shielding configuration for the new particle spectrometer. For the electron beam from the OMEGA EP SMLWFA platform, a 0.8cm thick tungsten converter maximizes positron yield. The optimized shielding design places the high-Z shield 2cm downstream of the converter to effectively scatter secondary particles and suppress background; this shielding achieves signal-to-noise ratios exceeding 3:1 in the modeling.