James Bevins, Rachel Slaybaugh
The goal of this project is to modify properties of existing neutron sources to make them more desirable for high-impact applications. Neutron sources are broadly classified by their intensity and energy distribution. For many applications, such as medical treatments, radiation damage studies in epi-thermal or fast reactors, neutron radiation effects studies on semiconducting devices, or nuclear forensics, no current neutron source has the characteristic intensity and energy distribution required to meet many of test or operational objectives. Historically, surrogate methods and equivalencies were developed to provide calibration metrics that enabled the use of existing sources even though they did not have the correct intensity and energy characteristics. However, these methods often result in large design margins and experimental uncertainties. Fundamentally, many applications do not have the ability to test across the complete range desired and there is a high-order mismatch between the experiment and the desired physics and conditions.
This research proposes instead to use existing, high intensity sources with a custom energy tuning assembly (ETA) to tailor the neutron spectrum to address neutron source capability. Neutron filters, screens, and moderation have been used in the past to alter a neutron source’s spectral characteristics, but these tended to be simple in objective and construction. To generically tailor a spectrum, many different materials and geometric configurations have to be explored rapidly. Because of the sheer size of the possible phase space, designing by hand will only explore a small subset of that space and is unlikely to arrive at consistently valid solutions. This research is developing a metaheuristic optimization tool to customize ETAs for any application. The ETA design will be tested using D-T neutron generators and the LBNL 88” Cyclotron facilities. The goal will be to demonstrate the ability to model, measure, and experimentally validate the design of an ETA to achieve a desired spectrum.