Liquid metal-based polarized positron generation benchmark using the GEANT4 toolkit

In this work, we report simulation results for the positron yield and polarization of polarized electron beams incident on GaInSn and PbBi liquid metal targets. One of the proposed upgrades to 12 GeV CEBAF is the use of a continuous wave polarized positron beam for physics experiments. High-$Z$ liquid metal jets are excellent candidates for positron production targets because they can withstand high power beams. Polarized positron beams can be generated from a primary electron beam incident on a thick high-$Z$ target through circular polarized bremsstrahlung conversion to linearly polarized pair production. This polarization transfer from the primary electron beam has been previously demonstrated at Jefferson Lab in the PEPPo experiment with a tungsten target at low energies. Here we report Geant4 simulations for 10 and 120 MeV electron beams incident on GaInSn and PbBi liquid metal targets. These simulations are compared to simulations with a solid tungsten target, as well as with unpolarized simulations using MCNP6.