Weighting and Biasing of a Monte Carlo Calculation for Very Deep Penetration of Radiation

Starting with the solution of the adjoint to the transport equation, a weighting and biasing system is developed permitting one to obtain a constant variance in every point of the phase space which is strict in a particular case and nearly strict in the general case by means of the Monte Carlo method. Neutron spectra at a very great distance from the source were thus derived with good precision.