Minisymposium Presentation

Monte Carlo (MC) particle transport simulations are integral to (1) the high-energy physics event reconstruction process, and (2) estimating radiological quantities within nuclear reactors. This method involves tracking individual particles through a computational geometry using a random walk technique. In practice, this requires interweaving ray tracing operations with computationally expensive physics calculations. The Oak Ridge Advanced Nested Geometry Engine (ORANGE) is a state-of-the-art computational geometry library shared by the Celeritas MC high-energy physics code and the Shift MC nuclear reactor simulation code. This presentation will focus on the ray tracing methods within ORANGE that facilitate efficient execution on the GPUs of leadership-class supercomputers. These methods include reordering operations to leverage single instruction, multiple threads (SIMT) parallelism, hierarchical acceleration structure algorithms, and algorithms that exploit the structured configurations of physical systems. Results from production-level simulations on the Frontier supercomputer demonstrate the effectiveness of these methods.