Analysis of the sampling distribution in Monte Carlo Radiation Transport calculations

Undersampling conditions can often lead to an estimated solution which can be significantly smaller than the true solution-but the estimate of the standard deviation may seem acceptably small. Various techniques devised to flag undersampling in Monte Carlo calculations were investigated. The calculation of F values, of the variance of the variance, and of the figure of merit, can be helpful but were not conclusive. A particle contribution distribution histogram which is output at the end of each batch provided a very effective way of detecting undersampling