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Hoover, Andrew S.

Publications and source records attributed to Hoover, Andrew S..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

The Mini Astrophysical MeV Background Observatory (MAMBO) CubeSat mission

The origin of the cosmic diffuse gamma-ray (CDG) background in the 0.3 – 30 MeV energy range is a mystery that has persisted for over 40 years. The Mini Astrophysical MeV Background Observatory (MAMBO) is a CubeSat mission concept motivated by the fact that, since the MeV CDG is relatively bright, only a small detector is required to make highquality measurements of it. Indeed, the sensitivity of space-based gamma-ray instruments to the CDG is limited not by size, but by the locally generated instrumental background produced by interactions of energetic particles in spacecraft materials. Comparatively tiny CubeSat platforms provide a uniquely quiet environment relative to previous gamma-ray science missions. The MAMBO mission will provide the best measurements ever made of the MeV CDG spectrum and angular distribution, utilizing two key innovations: 1) low instrumental background on a 12U CubeSat platform; and 2) an innovative shielded spectrometer design that simultaneously measures signal and background. We describe the MAMBO instrument and mission concept in detail, including simulations and laboratory measurements demonstrating the key measurement concept.

Astronomy and astrophysics↗
DOE OSTI2015

Measurement of the 240 Pu/ 239 Pu mass ratio using a transition-edge-sensor microcalorimeter for total decay energy spectroscopy

In this study, we have developed a new category of sensor for measurement of the 240 Pu/ 239 Pu mass ratio from aqueous solution samples with advantages over existing methods. Aqueous solution plutonium samples were evaporated and encapsulated inside of a gold foil absorber, and a superconducting transition-edge-sensor microcalorimeter detector was used to measure the total reaction energy (Q-value) of nuclear decays via heat generated when the energy is thermalized. Since all of the decay energy is contained in the absorber, we measure a single spectral peak for each isotope, resulting in a simple spectral analysis problem with minimal peak overlap. We found that mechanical kneading of the absorber dramatically improves spectral quality by reducing the size of radioactive inclusions within the absorber to scales below 50 nm such that decay products primarily interact with atoms of the host material. Due to the low noise performance of the microcalorimeter detector, energy resolution values of 1 keV fwhm (full width at half-maximum) at 5.5 MeV have been achieved, an order of magnitude improvement over α-spectroscopy with conventional silicon detectors. We measured the 240 Pu/ 239 Pu mass ratio of two samples and confirmed the results by comparison to mass spectrometry values. These results have implications for future measurements of trace samples of nuclear material.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Development of processing algorithms to enable high-rate microcalorimeter array operation

The millisecond-scale decay constants of microcalorimeter gamma-ray pulses present challenges for operation at high count rates needed to compete with semiconductor HPGe detectors. If using conventional optimal filtering methods, pulse records with pileup events are simply discarded, leading to a large fraction of data unused when count rates are large. For single pixel rates exceeding 1-2 Hz, improved pulse processing algorithms are needed to better deal with pileup and increase the filter throughput. A 256-pixel array operating at 10 Hz per pixel would provide a total counting rate of 2.5 kHz.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗