Background: In deep penetration application such as well-logging

medical physics and radiation shielding

analog Monte Carlo method will cause long calculation time and large variance. The newly released Monte Carlo code MCNP5 version 1.51 allows almost all of MCNP’s variance reduction techniques to be used with pulse height tally. Purpose: This paper aims to find an optimize pulse height variance reduction technique (PHVRT) to solve low efficiency with pulse-height tallies in deep penetration problems. Methods: A variety of variance reduction techniques including an auto-important sampling method-Mesh-based weight windows were proposed

and all kinds of variance reduction techniques proposed were tested and results with different variance reduction techniques were compared. Results: Mesh-based weight windows used with DXTRAN and forced collision get good calculation efficiency. After optimizing

the efficiency can be improved with large amplitude. Conclusion: Mesh-based weight window used with other variance reduction techniques can resolve deep penetration problem effectively. Abstract