  The multiplexing capabilities of superconducting X-ray free-electron lasers
(FELs) have gained much attention in recent years. The demanding requirements
for photon properties from multiple undulator lines necessitate more flexible
beam manipulation techniques to achieve the goal of "beam on demand". In this
paper, we investigate a multiplexed configuration for the photoinjector of
high-repetition-rate FELs that aims to simultaneously provide low-emittance
electron beams of different charges. A parallel, multi-objective genetic
algorithm is implemented for the photoinjector parameter optimization. The
proposed configuration could drastically enhance the flexibility of beam
manipulation to improve multiplexing capabilities and realize the full
potential of the facility.
