Nuclear Engineering ETDs

Publication Date

Summer 7-15-2023

Abstract

Sandia National Laboratories conducts Magnetized Liner Inertial Fusion (MagLIF) experiments at the Z Pulsed Power Facility. Their objective is to study the burning plasma formed under magnetic direct drive Inertial Confinement Fusion (ICF) conditions and use the inferred information to reduce uncertainty in computational models and improve experimental designs. The Z machine has five neutron time-of-flight (nToF) detectors that measure the fusion neutron time spectrum from three lines-of-sight. Together, these signals are used to infer the ion temperature, target liner mass density, and the burn history of the MagLIF experiment from measured data. These parameters are a few used by ICF scientists to determine if a plasma has achieved ignition or satisfies the Lawson net energy gain criterion. In this work, the computational resources of MCNP were utilized to simulate nToF signals for a user specified Impulse Response Function (IRF) and calculate the sensitivity of the nToF detector response to perturbations in the ion temperature, liner density, bang time, burn width, and IRF shape parameters. These sensitivity profiles are calculated using the CLUTCH methodology, which was implemented in MCNP as a standalone library that is called directly from the source code. The seven novel sensitivity coefficients presented in this work are used in conjunction with the generalized linear least squares Bayesian inference formalism to perform full uncertainty quantification of three simplified models of the Z machine and extract unknown fusion source conditions from synthetic data. It should be noted that while the techniques developed in this work are used to improve our understanding of MagLIF ICF experiments, these same techniques are more general and can be used to address any other fixed source neutron transport problem.

Keywords

Sensitivity Analysis, Uncertainty Quantification, Monte Carlo Neutron Transport, Inertial Confinement Fusion, MagLIF, Bayesian Statistics

Document Type

Dissertation

Language

English

Degree Name

Nuclear Engineering

Level of Degree

Doctoral

Department Name

Nuclear Engineering

First Committee Member (Chair)

Christopher Perfetti

Second Committee Member

Gary Cooper

Third Committee Member

Forrest Brown

Fourth Committee Member

Mark Gilmore

Fifth Committee Member

Michael Rising and Patrick Knapp

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