90th Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 9–11, 2023;
Eastern Kentucky University, Richmond, Kentucky
Session E01: Poster Session
6:00 PM,
Thursday, November 9, 2023
Keen Johnson
Room: Walnut Hall
Abstract: E01.00061 : Neutronics work for the BL3 team in OpenMC*
Abstract
Presenter:
Henry W Crumley
(centre college)
Author:
Henry W Crumley
(centre college)
Collaboration:
BL3 Collaboration Team
When neutrons are outside of their typical location (the nuclei of atoms), they have an expiration date (called the neutron lifetime) before decaying into a proton and releasing an electron and antineutrino through the weak force interaction. This is known as Free Neutron Beta Decay. Knowing the exact lifetime of a free neutron is useful across physics, from testing the accuracy of the standard model to developing a deeper understanding of the elemental makeup of the early universe. In recent years, two methods for measuring the free neutron's lifetime have merged. One, nicknamed the "bottle method," stores free neutrons and counts how many are left at certain time periods. The other method is nicknamed the "beam method," and sending linearized neutrons into a magnetic trap, and by measuring the decay products, determines the lifetime. In other words, one process "counts the living," and the other "counts the dead." As the bottle method has improved in precision relative to the beam's, a discrepancy of over four standard deviations in lifetime measurement between the two methods has appeared. BL3 hopes to match the bottle method's level of precision, but with the beam method, and hence shed more light upon this measurement difference. To this end, BL3 will involve a larger neutron beam, with a more accurate proton trap, as well as making other various improvements on the two earlier designs. The final design will be built at NIST in early 2025. Before assembly can take place, however, several simulations need to be performed to test whether or not the design will be both effective and safe. The neutronics simulation in OpenMC will be one of these, focusing primarily on the beam line. When a free neutron is captured in the cross section of some material, a burst of gamma radiation is released (along with secondary neutrons, etc). This radiation is dangerous to both humans and the experimental apparatus, and can give unwanted noise in the measurement. Hence, simulations are required to determine where the capture events will occur, and which materials are best fit to use as shielding. This presentation will detail the current progress of the OpenMC simulation and detail what future steps will be made towards increasing its efficacy.
*NSF grant PHY-2131864