Improved Monte Carlo Methods with Application to Borehole Logging Simulations


Légrády, D.

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Delft University Press


This thesis covers the development and assessment of the time dependent Monte Carlo Midway method for application to nuclear borehole logging with the primary aim of providing an acceleration tool for simulating responses on a detailed model parameter space.

The basic concept of the Midway method is the estimation of the detector response at a surface bounding completely either the source or the detector. In a conventional Monte Carlo simulation, particles arriving at this surface would proceed, and depending on the probability of reaching the detector, possibly yield a score. This probability could be estimated by an adjoint calculation: a transport in reverse; by particles originating from the detector, flying backwards in space and time, while gaining instead of loosing energy at collisions. Scoring could be relocated then to this surface, and the response estimation would include a forward and an adjoint calculation. When this technique is applied to enhance the efficiency of the calculation, it forms the Midway method.