Optimisation of importance sampling implementation in rare-event shielding simulations using Geant4
Abstract
Rare-event search experiments demand ever-lower backgrounds, and the resulting radio-pure materials and suppressive shielding make related background simulations computationally expensive without event biasing. We present a method for optimising the widely used importance splitting and Russian roulette technique for rare-event searches, in which a whole number of equal-width importance layers fill the shielding geometry. Balancing relative uncertainty against execution time, we optimise the layer thickness for both γ-rays and neutrons, and across different shielding materials and thicknesses. Expressed as a multiple of the primary particle's mean free path, the optimal thickness generalises across energies for a given particle type and yields a physics-based prediction applicable to any shielding design. The same trend reveals that over-biasing is possible, with relative uncertainty worsening at high layer counts for fixed execution time. The optimal configuration gives an 𝒪(20) gain in computational efficiency over the unbiased case.
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BibTeX
@misc{knights2026optimisation,
title = {{Optimisation of importance sampling implementation in rare-event shielding simulations using Geant4}},
author = {P. Knights and L. J. Milligan and K. Nikolopoulos},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03822},
eprint = {2609.03822},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03822},
note = {CC BY-SA 4.0},
}
RIS
TY - UNPB
TI - Optimisation of importance sampling implementation in rare-event shielding simulations using Geant4
AU - P. Knights
AU - L. J. Milligan
AU - K. Nikolopoulos
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03822
UR - https://arxiv.org/abs/2609.03822
AB - Rare-event search experiments demand ever-lower backgrounds, and the resulting radio-pure materials and suppressive shielding make related background simulations computationally expensive without event biasing. We present a method for optimising the widely used importance splitting and Russian roulette technique for rare-event searches, in which a whole number of equal-width importance layers fill the shielding geometry. Balancing relative uncertainty against execution time, we optimise the layer thickness for both γ-rays and neutrons, and across different shielding materials and thicknesses. Expressed as a multiple of the primary particle's mean free path, the optimal thickness generalises across energies for a given particle type and yields a physics-based prediction applicable to any shielding design. The same trend reveals that over-biasing is possible, with relative uncertainty worsening at high layer counts for fixed execution time. The optimal configuration gives an 𝒪(20) gain in computational efficiency over the unbiased case.
ER -