Research And Development Of An Extended Range Multi-Sphere Neutron Spectrometer

Neutron detection occupies a special position in the nuclear detection techniques, and basic information about the neutron radiation field is the main content of the accelerator radiation protection research. With the development of accelerator, more types of particles can be accelerated, higher energy and intensity can be reached, so the highest energy of secondary neutron produced from nuclear reaction is also rising. Neutron detection at higher energy region is also required.Multi-sphere Neutron Spectrometer is a traditional neutron spectrum detecting technique which usually used in low energy region. Based on the development of extended range neutron dosimeter, design of an extended energy range Multi-sphere neutron spectrometer is presented in this paper.Pure polyethylene moderator ball with thickness of 1.5, 2.0, 2.5, 3.0, 3.5, 5.0, 7.0, 9.0, 13.0 16.0(cm), and moderator ball with auxiliary material of 3C4-6, 3P4-6, 3P4.5-6.5 and 2P5-7(cm), are selected as a set of Multi-sphere neutron spectrometer. A 3He proportional counter tube was placed in the center of each ball as thermal neutron detector, neutron response of each ball was simulated with MCNPX code. The results shows good agreement with those calculated with FLUKA code, it indicate that auxiliary material add in a Bonner ball can increase high energy neutron response significantly.Data acquisition system of the Multi-sphere neutron spectrometer consists of preamplifier, main amplifier, discriminator and shaping circuit was designed in this paper. The neutron energy spectrum of a Pu-Be source were measured, and calculate the ambient dose equivalent rate, compared with a reference value, the deviation is within 10%. For higher energy neutron measurement, such as neutron field of heavy-ion accelerators, more experiment should be performed.