Advanced Modeling and Simulation Methods for Evaluation of Thermal Neutron Scattering Materials

With the rise of interest in thermal neutron scattering data for advanced reactor, criticality safety, and shielding applications, new experimental are required evaluation materials or re-evaluation (or validations) previously evaluated materials. New a three-step process: (1) computing phonon characteristics, (2) dynamic structure factor (DSF) from data, (3) using setup to simulate data. All three steps have challenges, ranging need suffciently general material simulation code—a processing code that can compute corresponding DSF—to having detailed layout instrument/beamline/facility where were measured. Whereas characteristics be computed various methods (molecular dynamics, density functional theory, etc.), high-fidelity computation DSF experiment based on is vital accuracy evaluation. The latter two achieved by systems developed instrument scientists at Spallation Neutron Source (SNS) Oak Ridge National Laboratory: OCLIMAX, program calculates DFT MD results, MCViNE, Monte Carlo ray-tracing designed experiments. Recently, polyethylene yttrium hydride measured Wide Angular-Range Chopper (ARCS) SEQUOIA stations SNS. These experiments simulated theory code, Cambridge Serial Total Energy Package (CASTEP), its (eigenvalues/vectors PDOS), which then processed OCLIMAX yield DSF, finally each station MCViNE comparison For conventional methods, compared against those LEAPR module NJOY, results simulations used simplified beamline models implemented N-Particle (MCNP) code.