Collimated beams of fast neutrons at the NPI CAS

The Nuclear Physics Institute of the Czech Academy of Sciences operates multiple neutron sources that can produce neutrons with energies up to 33 MeV. Recently, a segmented collimator was constructed to facilitate research on collimated beams of fast neutrons. In front of the collimator, a new quasi-monoenergetic neutron source was built using accelerated protons interacting with a 2.5 mm thick beryllium target. The collimated beam provides a neutron flux of approximately 10${}^6$ n/cm${}^2$/s at the standard measurement position.

To determine the parameters of the collimated neutron beam, various measurement techniques were employed, including scintillator-based time-of-flight mode, proton recoil telescope, and activation detection through the (n,2-3n) reaction on a yttrium sample. Furthermore, Monte Carlo simulations were conducted to model the neutron transport through the collimator, and the results were subsequently compared to the experimental data obtained.