Abstract
Adjoint Monte Carlo can be an effcient algorithm for solving photon transport problems where the size of the tally is relatively small compared to the source. Such problems are typical in environmental radioactivity calculations, where natural or fallout radionuclides spread over a large area contribute to the air dose rate at a particular location. Moreover photon transport with continuous energy representation is vital for accurately calculating radiation protection quantities. Here we describe the incorporation of an adjoint Monte Carlo capability for continuous energy photon transport into the Particle and Heavy Ion Transport code System (PHITS). An adjoint cross section library for photon interactions was developed based on the JENDL- 4.0 library, by adding cross sections for adjoint incoherent scattering and pair production. PHITS reads in the library and implements the adjoint transport algorithm by Hoogenboom. Adjoint pseudo-photons are spawned within the forward tally volume and transported through space. Currently pseudo-photons can undergo coherent and incoherent scattering within the PHITS adjoint function. Photoelectric absorption is treated implicitly. The calculation result is recovered from the pseudo-photon flux calculated over the true source volume. A new adjoint tally function facilitates this conversion. This paper gives an overview of the new function and discusses potential future developments.
Highlights
The Monte Carlo method can be inefficient for solving radiation transport problems with a small tally relative to the source
Small tally geometries can require long computing times to converge the calculation result to a desired level of precision
We present two example calculations to demonstrate the Particle and Heavy Ion Transport code System (PHITS) adjoint function
Summary
The Monte Carlo method can be inefficient for solving radiation transport problems with a small tally relative to the source. In adjoint Monte Carlo, radiations are generated within the tally region and transported backwards through the geometry, undergoing any physical interactions in reverse. They contribute to the calculation result if they cross the source region. There have only been a few implementations of adjoint Monte Carlo for photons with continuous energy representation in popular transport codes [5, 6]. This paper outlines the addition of a continuous energy photon adjoint function to the Particle and Heavy Ion Transport code System (PHITS) [7]. An adjoint tally function was developed to recover the forward calculation result from the pseudo-photon flux tallied over the real source volume
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
