Determination of the standard deviation on multiplication based on count distributions
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States), J. Verbeke, USDOE · 2010
The multiplication M of a multiplying object can be determined by analyzing the arrival times of thermal neutrons in detectors such as helium tubes. A source emitting neutrons randomly will lead to neutron inter arrival times obeying Poisson process statistics. By observing how the inter arrival times of detected counts differ from Poisson statistics, one can assess properties of the neutron source such as the source intensity and multiplication.The results of this study show that analyzing the data stream using non-overlapping time gates is an improvement over the current analysis using overlapping time gates. The new method enables us to compute the standard deviation on the multiplication parameter M accurately. Also, this standard deviation on M decreases as the largest time gate is about 10 times the characteristic time constant λ -1 of the system.