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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Proposal to detect emergent gauge field and its Meissner effect in spin liquids using NV centers

Here, we show that nitrogen-vacancy (NV) centers could provide distinct signatures of emergent gauge fields in certain phase transitions in spin liquids. We consider the relaxation rate 1/ T 1 of a diamond NV center placed a distance z 0 above a crystal consisting of two-dimensional layers which hosts a U(1) quantum spin liquid with spinon Fermi surface. We show that, during a spinon pairing transition from a U(1) to a Z2 spin liquid, the relaxation rate exhibits a rapid fall just below the pairing transition. The drop is much faster than what can be accounted for by the opening of the energy gap. Instead, the rapid fall with a unique z 0 dependence of its height and width is the signature of the Meissner effect of the gauge field. We identify the organic ET compound which has a phase transition at 6 K as a candidate for the experimental observation of this phenomenon.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Sensitivity of Proposed Search for Axion-induced Magnetic Field using Optically Pumped Magnetometers

We investigate the sensitivity of a search for the oscillating current induced by axion dark matter in an external magnetic field using optically pumped magnetometers. This experiment is based upon the LC circuit (circuit with inductor and capacitor) axion detection concept of Sikivie et al. [Phys. Rev. Lett. 112, 131301 (2014)]. The modification of Maxwell’s equations caused by the axion-photon coupling results in a minute magnetic field oscillating at a frequency equal to the axion mass, in the presence of an external magnetic field. The axion-induced magnetic field could be searched for using a LC circuit amplifier with an optically pumped magnetometer, the most sensitive cryogen-free magnetic-field sensor, in a room-temperature experiment, avoiding the need for a complicated and expensive cryogenic system. Here, we discuss how an existing magnetic resonance imaging experiment can be modified to search for axions in a previously unexplored part of the parameter space. Our existing detection setup, optimized for magnetic resonance imagining, is already sensitive to an axion-photon coupling of 10 -7 GeV -1 for an axion mass near 3 × 10 -10 eV, which is already limited by astrophysical processes and solar axion searches. We show that realistic modifications, and optimization of the experiment for axion detection, can probe the axion-photon coupling up to 4 orders of magnitude beyond the current best limit, for axion masses between 10 -1 and 10 -7 eV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Absence of Low-Energy Shape Coexistence in 80 Ge: The Nonobservation of a Proposed Excited 0 2 + Level at 639 keV

The 80 Ge structure was investigated in a high-statistics β-decay experiment of 80 Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through γ, β-e, e-γ and γ-γ spectroscopy. No evidence was found for the recently reported 0 2 + 639-keV level suggested as evidence for low-energy shape coexistence in 80Ge. Large-scale shell model calculations performed in 78,80,82 Ge place the 0 2 + level in 80 Ge at 2 MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in 80 Ge.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Evaluation of models determined by neutron diffraction and proposed improvements to their validation and deposition

The Protein Data Bank (PDB) contains a growing number of models that have been determined using neutron diffraction or a hybrid method that combines X-ray and neutron diffraction. The advantage of neutron diffraction experiments is that the positions of all atoms can be determined, including H atoms, which are hardly detectable by X-ray diffraction. This allows the determination of protonation states and the assignment of H atoms to water molecules. Because neutrons are scattered differently by hydrogen and its isotope deuterium, neutron diffraction in combination with H/D exchange can provide information on accessibility, dynamics and chemical lability. In this study, the deposited data, models and model-to-data fit for all PDB entries that used neutron diffraction as the source of experimental data have been analysed. In many cases, the reported R work and R free values were not reproducible. In such cases, the model and data files were analysed to identify the reasons for this mismatch. The issues responsible for the discrepancies are summarized and explained. The analysis unveiled limitations to the annotation, deposition and validation of models and data, and a lack of community-wide accepted standards for the description of neutron models and data, as well as deficiencies in current model refinement tools. Most of the issues identified concern the handling of H atoms. Since the primary use of neutron macromolecular crystallography is to locate and directly visualize H atoms, it is important to address these issues, so that the deposited neutron models allow the retrieval of the maximum amount of information with the smallest effort of manual intervention. A path forward to improving the annotation, validation and deposition of neutron models and hybrid X-ray and neutron models is suggested.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Error Correction: a Proposal for a Standard

Some of the errors in transducers such as instrument transformers can be corrected as part of the digital processing for the measurement. The transducer can be characterized on such a way that allows the TEDS of IEEE Std 1451 to transfer the information to the measurement system. A modification would allow the measurement system to perform a high-quality self-calibration whenever a transducer was replaced.

error correction.↗