SPIROS: Streamlined, Precise, Intuitive, and Rapid Optical Simulator for particle physics detectors

TL;DR

SPIROS is a lightweight, user-friendly optical simulation tool for particle physics detectors, offering faster performance and easy integration with CAD models, validated against GEANT4 and used in multiple neutrino experiments.

Contribution

Developed SPIROS, a fast, intuitive optical simulator tailored for particle physics detectors, with direct CAD import and validated accuracy against GEANT4.

Findings

SPIROS runs over twice as fast as GEANT4 for typical configurations.

Validation shows excellent agreement with GEANT4 in photon behavior.

SPIROS has been successfully used in neutrino experiment design and optimization.

Abstract

This paper presents SPIROS (Streamlined, Precise, Intuitive, and Rapid Optical Simulator), a dedicated optical simulation tool developed for the design and analysis of particle physics detectors. Unlike general-purpose frameworks such as GEANT4, SPIROS offers a lightweight simulation engine and a user-friendly interface optimized for optical processes, including scintillation, Cherenkov emission, and photon transport with reflection, refraction, scattering, absorption, and detection. Detector geometries can be directly imported from 3D CAD models, and all configurations including materials, surfaces, sources, and sensors are specified via a single human-readable input file. Validation against GEANT4 shows excellent agreement in photon generation and propagation behaviors, while benchmark tests demonstrate that SPIROS runs more than two times faster for typical detector configurations. The software has already been applied to multiple neutrino experiments, including T2K, NINJA, and AXEL, for detector design, performance studies, and optimization. SPIROS is open-source and freely available at https://github.com/tkikawa/spiros.