Neutron Monitors for High Energy Accelerators

Thermal neutron counters inside moderating shells are used widely at high energy accelerators. Response of these detectors to neutrons of different energy depends on material, size and shape of moderator. Radiators and absorbers can also modify this response significantly. The main application of counters in moderators is neutron dosimetry. Some dedicated sets of these detectors Bonner spheres) are even used sometimes to estimate neutron spectra. Monitoring of fast neutrons at modern accelerator and experimental facilities is very important to keep radiation damage of electronic components under control. One more step towards fast neutron measurements with thermal neutron counters in moderators is reported here. A set of neutron transport simulations is done to optimize moderator/radiator/absorber assemblies for higher sensitivity to neutrons with energies above 100 kev along with much lower sensitivity at lower energies. The resulting pair of the main and complementary monitors is designed.