Estimation of Confidence Intervals for Multiplication and Efficiency

Verbeke, J

关键词: CHARGE COLLECTION;    DETECTION;    DISTRIBUTION;    EFFICIENCY;    FISSION;    HELIUM 3;    NEUTRONS;    PLUTONIUM ISOTOPES;    THERMAL NEUTRONS;    URANIUM;   

DOI  :  10.2172/964524
RP-ID  :  LLNL-TR-415482
PID  :  OSTI ID: 964524
Others  :  TRN: US0903618

美国|英语

来源: SciTech Connect

【 摘 要 】

Helium-3 tubes are used to detect thermal neutrons by charge collection using the {sup 3}He(n,p) reaction. By analyzing the time sequence of neutrons detected by these tubes, one can determine important features about the constitution of a measured object: Some materials such as Cf-252 emit several neutrons simultaneously, while others such as uranium and plutonium isotopes multiply the number of neutrons to form bursts. This translates into unmistakable signatures. To determine the type of materials measured, one compares the measured count distribution with the one generated by a theoretical fission chain model. When the neutron background is negligible, the theoretical count distributions can be completely characterized by a pair of parameters, the multiplication M and the detection efficiency {var_epsilon}. While the optimal pair of M and {var_epsilon} can be determined by existing codes such as BigFit, the uncertainty on these parameters has not yet been fully studied. The purpose of this work is to precisely compute the uncertainties on the parameters M and {var_epsilon}, given the uncertainties in the count distribution. By considering different lengths of time tagged data, we will determine how the uncertainties on M and {var_epsilon} vary with the different count distributions.