Use of CAD to CSG Conversion Tool for MCNP Simulation of Gamma Detector Arrays

The magnitude of fundamental symmetry violation (P- or P- and T-) effects increases near p-resonance when polarized neutrons pass through a nucleus target [1]. This was confirmed for heavy nuclei, including a 10^6 P-violation enhancement in 139La [2]. As p-resonance neutron widths are extremely narrow, the total width is dominated by radiative capture, making gamma-ray capture asymmetry measurements viable for studying P-violation in compound nuclei. To study the gamma detector efficiency, we simulate the experimental setup using MCNP code [3]. The problem arises in the creation of MCNP constructive solid geometry (CSG) files due to the tedious process required. We present the preliminary results showing a workflow to study designs for a new gamma ray array. In this workflow, the gamma array is 1) modeled using the SolidWorks, 2) converted to the CSG MCNP file using GEOUNED Python library, [4] , 3) the MCNP simulation with particle track output (PTRAC) performed, and 4) obtaining realistic detector response using Detector Response Function Toolkit, [5].

1. Bunakov VE, Gudkov VP., Zeitschrift für Physik A., 321(2):271-41,1985

2. G. M. Mitchell, et al, Phys. Rep. 354, 157 (2001).

3. Kulesza, Joel A., et al. MCNP® code version 6.3. theory & user manual.LA-UR-22-30006. LANL, 2022

4. Harb, M., at al, J. Nucl. Eng. 2023, 4, 436-447.

5. M.T. Andrews, et al., NIM A, 830, 2016, pp 466-472