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Throckmorton, Daniel J.

Publications and source records attributed to Throckmorton, Daniel J..

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Apparatus and methods for sample analysis with multi-gradient microfluidics

A device for analyzing biological samples comprises first, second, third, and fourth layers. The first layer comprises a sample chamber in which a sample is positioned. The second layer comprises first, second, and third channels. A third, porous layer is positioned between the first layer and the second layer. A fourth layer composed of a substantially liquid-impermeable material is positioned between the second layer and the third layer. The fourth layer includes first and second pass-through channels that are aligned with the first and second channel, respectively. Fluids that flow in the first and second channels pass through the pass-through channels and diffuse into the sample chamber, establishing a chemical concentration gradient therein. A gas in the sample chamber can diffuse through the third and fourth layers and interact with a fluid flowing in the third channel, establishing a gas concentration gradient in the sample chamber.

Kim, Peter Wonhee↗
DOE OSTI2017

Plastic scintillators relative gamma-ray light yield measurement

Here we are investigating the inclusion of organotin compounds in polystyrene material to improve plastic scintillators full gamma-ray energy sensitivity with the ultimate goal of achieving spectroscopy. Accurate evaluation of the relative light yield from the newly developed scintillators is crucial to assess merits of compounds and chemical processes used in the scintillators development and assess the scintillation efficiencies of the newly produced scintillators. Full gamma-ray energy peak in the measured gamma-ray spectrum, resulting from total absorption of gamma-ray energy, would be ideal in assessing the relative light yield. However, the significant number of new samples we are producing for investigation lead us to the possibility of using the Compton edge as an alternate spectral feature that can be exploited for expeditious characterization of the relative light yield in plastic scintillators. In this study we present a spectra gain matching approach, using a spectrum rebinning, for accurate relative light yield measurement using the Compton edge.

36 MATERIALS SCIENCE↗
DOE OSTI2016

System Construction of the Stilbene Compact Neutron Scatter Camera

This report documents the construction of a stilbene-crystal-based compact neutron scatter camera. This system is essentially identical to the MINER (Mobile Imager of Neutrons for Emergency Responders) system previously built and deployed under DNN R&D funding,1 but with the liquid scintillator in the detection cells replaced by stilbene crystals. The availability of these two systems for side-by-side performance comparisons will enable us to unambiguously identify the performance enhancements provided by the stilbene crystals, which have only recently become commercially available in the large size required (3” diameter, 3” deep).

36 MATERIALS SCIENCE↗
DOE OSTI2015

Plastic Scintillators Light Yield Energy Calibration.

Currently we are investigating the inclusion of organotin compounds in polystyrene material to improve plastic scintillators full gamma-ray energy sensitivity with the ultimate goal of achieving spectroscopy. Accurate evaluation of light yield from the newly developed scintillators is crucial to assess merits of compounds and chemical process used in the scintillators development. Full gamma-ray energy peak in measured gammaray spectrum, resulting from total absorption of gamma-ray energy, would be ideal in evaluating the light yield from the new scintillators. However, full energy sensitivity achieved thus far is not statistically viable for fast and accurate light yield energy calibration from the new scintillators. The Compton edge in measured gamma-ray spectrum has been found as an alternate gamma-ray spectrum feature that can be exploited for characterizing the light yield energy from the newly developed plastic scintillators. In this study we present technique implemented for accurate light yield energy calibration using the Compton edge. Results obtained were very encouraging and promise the possibility of using the Compton edge for energy calibration in detectors with poor energy resolution such as plastic and liquid scintillators.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Above-ground Antineutrino Detection for Nuclear Reactor Monitoring

Antineutrino monitoring of nuclear reactors has been demonstrated many times, however the technique has not as of yet been developed into a useful capability for treaty verification purposes. The most notable drawback is the current requirement that detectors be deployed underground, with at least several meters-water-equivalent of shielding from cosmic radiation. In addition, the deployment of liquid-based detector media presents a challenge in reactor facilities. We are currently developing a detector system that has the potential to operate above ground and circumvent deployment problems associated with a liquid detection media: the system is composed of segments of plastic scintillator surrounded by 6 LiF/ZnS:Ag. ZnS:Ag is a radio-luminescent phosphor used to detect the neutron capture products of lithium-6. Because of its long decay time compared to standard plastic scintillators, pulse-shape discrimination can be used to distinguish positron and neutron interactions resulting from the inverse beta decay (IBD) of antineutrinos within the detector volume, reducing both accidental and correlated backgrounds. Segmentation further reduces backgrounds by identifying the positron’s annihilation gammas, which are absent for most correlated and uncorrelated backgrounds. This work explores different configurations in order to maximize the size of the detector segments without reducing the intrinsic neutron detection efficiency. We believe this technology will ultimately be applicable to potential safeguards scenarios such as those recently described.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗