Seminar Details

MCNPX-PoliMi Variance Reduction Techniques for Neutron Scintillation Detector Response

Shikha Prasad, University of Michigan
Monday, March 4, 11:00 AM - Special Seminar
NSCL Lecture Hall

Organic scintillation detectors are capable of detecting both gamma-rays and fast neutrons, therefore, they can be helpful in characterization and identification of special nuclear material. Simulations of nuclear nonproliferation and safeguards measurements done with scintillation detectors require detailed modeling of various physical phenomena. Scintillation detectors convert energy-deposited into light-emitted. These detectors are also coupled with photo-multiplier tubes to convert the scintillation light-emitted into charge that can be recorded by instrumentation. The Monte Carlo Code MCNPX-PoliMi and its associated post-processor simulate and record not only detailed event-by-event collision information within the detector, but also carefully model the nonlinear processes of energy-to light conversion based on the nuclei of collision, energy-deposited, et cetera. Presently, it is important to run MCNPX-PoliMi in the analog mode in order to capture the detailed physics which prevents the user from utilizing existing MCNP variance reduction techniques. Thus, complex yet typical nonproliferation scenarios that comprise of thick shielding or large source detector distances require long simulation run-times. To mitigate this user-expense, a method is formulated which allows post-processing of non-analog MCNPX-PoliMi simulations and lets the user implement standard MCNP variance reduction techniques. Even time-dependent simulations of measurement using organic scintillation detectors can have significantly reduced computation-times with non-analog MCNPX-PoliMi. In this work, time-dependent cross-correlation EJ-309 liquid scintillation detector response using analog and non-analog MCNPX-PoliMi is simulated. Good agreement between non-analog and analog MCNPX-PoliMi simulations for bare 252Cf source and shielded cases are shown.