Engineering Papers⌕ Search

Engineering topics

Massarczyk, Ralph

Publications and source records attributed to Massarczyk, Ralph.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Dark Matter Constraints from Isomeric 178⁢m Hf

In this article, we describe a first measurement of the radiation from a 178⁢m Hf sample to search for dark matter. The $\gamma$ flux from this sample, possessed by Los Alamos National Laboratory nuclear chemistry, was measured with a Ge detector at a distance of 1.2 m due to its high activity. We search for $\gamma$’s that cannot arise from the radioactive decay of 178⁢m Hf but might arise from the production of a nuclear state due to the inelastic scattering with dark matter. The limits obtained on this $\gamma$ flux are then translated into constraints on the parameter space of inelastic dark matter. Finally, we describe the potential reach of future studies with 178⁢m Hf.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Interesting Isomers - From classic nuclear physics to dark matter - [Slides]

The physics of isomers is almost a century old. While a lot of isomers are studied, the most extreme cases remain unexplored. Testing classic nuclear physics in the extrema. A door into dark sector that is allows us to look for DM types that are not accessible in larger efforts.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Modeling backgrounds for the majorana demonstrator

The MAJORANA DEMONSTRATOR is a neutrinoless double-beta decay (0?ß ß ) experiment containing ~30 kg of p-type point contact germanium detectors enriched to 88% in 76Ge and ~14 kg of natural germanium detectors. The detectors are housed in two electroformed copper cryostats and surrounded by a graded passive shield with active muon veto. An extensive radioassay campaign was performed prior to installation to insure the use of ultra-clean materials. The DEMONSTRATOR achieved one of the lowest background rates in the region of the 0?ß ß Q-value, 15.7 ± 1.4 cts/(FWHM t y) from the low-background configuration spanning most of the 64.5 kg-yr active exposure. Nevertheless this background rate is a factor of five higher than the projected background rate. This discrepancy arises from an excess of events from the 232Th decay chain. Background model fits aim to understand this deviation from assay-based projections, potentially determine the source(s) of observed backgrounds, and allow a precision measurement of the two-neutrino double-beta decay half-life. The fits agree with earlier simulation studies, which indicate the origin of the 232Th excess is not from a near-detector component and have informed design decisions for the next-generation LEGEND experiment. Recent findings have narrowed the suspected locations for the excess activity, motivating a final simulation and assay campaign to complete the background model.

Haufe, Christopher R.↗
DOE OSTI2023

Calibration sources for the LEGEND-200 experiment

In the search for a monochromatic peak as the signature of neutrinoless double beta decay an excellent energy resolution and an ultra-low background around the Q-value of the decay are essential. The LEGEND-200 experiment performs such a search with high-purity germanium detectors enriched in 76 Ge immersed in liquid argon. To determine and monitor the stability of the energy scale and resolution of the germanium diodes, custom-made, low-neutron emission 228 Th sources are regularly deployed in the vicinity of the crystals. Here we describe the production process of the 17 sources available for installation in the experiment, the measurements of their alpha- and gamma- activities, as well as the determination of the neutron emission rates with a low-background LiI(Eu) detector operated deep underground. With a flux of ( 4.27 ± 0.60 stat ± 0.92 syst ) × 10 -4 n / (kBq·s), approximately one order of magnitude below that of commercial sources, the neutron-induced background rate, mainly from the activation of 76 Ge, is negligible compared to other background sources in LEGEND-200.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Variable energy X-ray fluorescence source

Here we detail the design of a variable energy, x-ray fluorescence source using a low activity (1.8×10 6 dpm) 99 Tc β source that irradiates thin foils. By rotating the source among foils of Ti, Zn, Nb, Ag, and Au, the device produces x rays between 4 and 70 keV at a rate near 1 Hz. When the source is placed in a storage position, the external radiation is non-detectable. The design of the shielding and rotation mechanism permits use in vacuum and at liquid nitrogen temperature. The design is intended for the study of the low energy response to radiation impinging upon Ge detector surfaces. The source will be useful for understanding the detector response in large-scale Ge arrays such as MAJORANA and LEGEND.

47 OTHER INSTRUMENTATION↗