A new neutron detector designed for (n,2n) and (n,3n) reaction cross section measurements

Abstract A large 4 π liquid scintillator was commonly used as the neutron detector to measure nucleus (n,2n) and (n,3n) reaction cross sections in the past direct neutron counting method. However, this type of detector was often criticized for its high γ -rays background. Hence we constructed a new 4 π 3 He array detector to substitute the large liquid scintillation detector, which can effectively suppress the γ -rays. This work mainly studies the detection efficiency and moderation time of this new detector through experimental and simulational methods. Due to its spherical configuration, a relatively stable and weak angular dependence detection efficiency is obtained for the secondary neutrons from (n,2n) and (n,3n) reactions. In addition, the character that the moderation time is nearly independent of neutron energy guarantees gate width has a same influence on the detection efficiency of the secondary neutrons from different samples. These features make it a good candidate detector for (n,2n) and (n,3n) reaction cross section measurements. At last, the preliminary experiment plan and the corresponding calculation method are briefly described.