Nuclear Engineering ETDs

Publication Date

Spring 4-30-2020

Abstract

A forward analytic model is required to rapidly simulate the neutron time-of-flight (nToF) signals that result from magnetized liner inertial fusion (MagLIF) experiments at Sandia’s Z Pulsed Power Facility. Various experimental parameters, such as the burn-weighted fuel-ion temperature and liner areal density, determine the shape of the nToF signal and are important for characterizing any given MagLIF experiment. Extracting these parameters from measured nToF signals requires an appropriate analytic model that includes the primary DD neutron peak, once-scattered neutrons in the beryllium liner of the MagLIF target, and direct beamline attenuation. Mathematical expressions for this model were derived from the general geometry time- and energy-dependent neutron transport equation with anisotropic scattering. Assumptions consistent with the time-of-flight technique were used to simplify this linear Boltzmann transport equation into a more tractable form. Models of the un-collided and once-collided neutron scalar fluxes were developed for one of the five nToF detector locations at the Z Machine. Numerical results from these models were produced for a representative MagLIF problem and found to be in good agreement with similar radiation transport simulations. Twenty experimental MagLIF data sets were analyzed using the forward models, which were determined to only be sensitive to the ion temperature. The results of this work were found to be in good agreement with values obtained separately using other low and high fidelity models.

Keywords

neutron time-of-flight, magnetized liner inertial fusion, ion temperature, neutron transport equation, analytical model, Z Pulsed Power Facility

Document Type

Thesis

Language

English

Degree Name

Nuclear Engineering

Level of Degree

Masters

Department Name

Nuclear Engineering

First Committee Member (Chair)

Christopher Perfetti

Second Committee Member

Gary Cooper

Third Committee Member

Mark Gilmore

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