Monte Carlo simulated response of a 4π neutron counter

The paper describes the simulation of 4π neutron counter set up using Monte Carlo codes MCNP4B and FLUKA to estimate its detection efficiency for various neutron energies. The 4pcounter setup consist of 12 BF3 tubes embedded in a paraffin cubical block with the side dimension of 46 cm acting as moderator. The BF3 tubes are mounted in two concentric circles (radius 8 cm and 10.5 cm respectively) containing six tubes each. Each BF3 tube is thin walled brass tubes of 2.5 cm diameter, 46 cm in length and is placed in 1.5 mm thick aluminum tube. 5 cm diameter central hole in the cube will house the neutron producing target. Point isotropic mono energetic neutron source is assumed to be placed at the middle of beam hole. The energy of the source is varied from 100 keV to 5 MeV and 10B(n,a) reaction rate is calculated. The simulations are made for 1 million histories to obtain statistical uncertainty less than 1%