The HIBEAM and NNBAR experiments are a proposed fundamental science
experiments at the European Spallation Source, performing high precision
searches for neutron conversions in several baryon number violating (BNV)
channels. For simulations of the NNBAR beamline, a new sampling method has been
developed. The method is based on probability density evaluation and duct
source biasing and enables the simulations of the entire NNBAR beamline with
high statistics while also preserving correlations of the neutron tracks