Two kinds of sources were considered in this work, a point isotropic source in order to obtain the 3He pulse height spectrum, and a point source collimated into a cone of directions in order to obtain the count values.
In the MCNPX calculations the FT8 PHL and F8 tallies were used. The FT option allows the F8 tally to be based on energy deposition in one region via one F6 tally. Thus the F8 tally is dependent on results from another tally, which works because the F8 tally is posted at the end of the particle history where the F6 tally is accumulated along each track of the particle history [4]. The energy output from one region is used to subdivide the pulse height tally (F8). As a result, the anticoincidence is considered.