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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Fast event-based electron counting for small-molecule structure determination by MicroED

Electron counting helped realize the resolution revolution in single-particle cryoEM and is now accelerating the determination of MicroED structures. Its advantages are best demonstrated by new direct electron detectors capable of fast (kilohertz) event-based electron counting (EBEC). This strategy minimizes the inaccuracies introduced by coincidence loss (CL) and promises rapid determination of accurate structures. We used the Direct Electron Apollo camera to leverage EBEC technology for MicroED data collection. Given its ability to count single electrons, the Apollo collects high-quality MicroED data from organic small-molecule crystals illuminated with incident electron beam flux densities as low as 0.01–0.045 e − /Å 2 /s. Under even the lowest flux density (0.01 e − /Å 2 /s) condition, fast EBEC data produced ab initio structures of a salen ligand (268 Da) and biotin (244 Da). Each structure was determined from a 100° wedge of data collected from a single crystal in as few as 50 s, with a delivered fluence of only ∼0.5 e − /Å 2 . Fast EBEC data collected with a fluence of 2.25 or 3.33 e − /Å 2 also facilitated a 1.5 Å structure of thiostrepton (1665 Da). While refinement of these structures appeared unaffected by CL, a CL adjustment applied to EBEC data further improved the distribution of intensities measured from the salen ligand and biotin crystals. However, CL adjustment only marginally improved the refinement of their corresponding structures, signaling the already high counting accuracy of detectors with counting rates in the kilohertz range. Overall, by delivering low-dose structure-worthy data, fast EBEC collection strategies open new possibilities for high-throughput MicroED.

EBEC↗
DOE OSTI2025

Combining MicroED and native mass spectrometry for structural discovery of enzyme–small molecule complexes

With the goal of accelerating the discovery of small molecule–protein complexes, we leverage fast, low-dose, event-based electron counting microcrystal electron diffraction (MicroED) data collection and native mass spectrometry. This approach, which we term electron diffraction with native mass spectrometry (ED-MS), allows assignment of protein target structures bound to ligands with data obtained from crystal slurries soaked with mixtures of known inhibitors and crude biosynthetic reactions. This extends to libraries of printed ligands dispensed directly onto TEM grids for later soaking with microcrystal slurries, and complexes with noncovalent ligands. ED-MS resolves structures of the natural product, epoxide-based cysteine protease inhibitor E-64, and its biosynthetic analogs bound to the model cysteine protease, papain. It further identifies papain binding to its preferred natural products, by showing that two analogs of E-64 outcompete others in binding to papain crystals, and by detecting papain bound to E-64 and an analog from crude biosynthetic reactions, without purification. ED-MS also resolves binding of the CTX-M-14 β-lactamase, a target of active drug development, to the non-β-lactam inhibitor, avibactam, alone or in a cocktail of unrelated compounds. These results illustrate the utility of ED-MS for natural product ligand discovery and for structure-based screening of small molecule binders to macromolecular targets, promising utility for drug discovery.

MicroED↗
NASA NTRS1985

Electrons and cosmic ray produced protons in Saturn's inner magnetosphere

The Cerenkov detector on Pioneer 11 previously observed Crand protons above 600 MeV in Saturn's inner magnetosphere, mixed with a poorly understood background of energetic electrons. The electron count is separated from the proton counts and the first-order angular distributions are established for each species. To do this the theoretical relationships among the harmonic coefficients of the count rate is used as a function of spacecraft roll angle. The majority of the counts were electrons with energy above several MeV; i.e., with drift periods shorter than the satellite orbital resonance. The electrons have isotropic pitch angle distributions, and the protons pancake over most of the region between Mimas and the rings, although there is a small region of dumbbell proton distributions in the vicinity of Janus and epimetheus.

Northrop, T. G.↗
NASA NTRS1985

Electrons and Cosmic Ray Produced Protons in Saturn's Inner Magnetosphere

The Cerenkov detector on Pioneer 11 previously observed Crand protons above 600 MeV in Saturn's inner magnetosphere, mixed with a poorly understood background of energetic electrons. The electron count is separated from the proton counts and the first-order angular distributions are established for each species. To do this the theoretical relationships among the harmonic coefficients of the count rate is used as a function of spacecraft roll angle. The majority of the counts were electrons with energy above several MeV; i.e., with drift periods shorter than the satellite orbital resonance. The electrons have isotropic pitch angle distributions, and the protons pancake over most of the region between Nimas and the rings, although there is a small region of dumbbell proton distributions in the vicinity of Janus and Epimetheus.

Northrop, T. G.↗
NASA NTRS1985

Electrons and cosmic ray produced protons in Saturn's inner magnetosphere

The Cerenkov detector on Pioneer 11 previously observed Crand protons above 600 MeV in Saturn's inner magnetosphere, mixed with a poorly understood background of energetic electrons. The electron count is separated from the proton counts and the first-order angular distributions are established for each species. To do this the theoretical relationships among the harmonic coefficients of the count rate is used as a function of spacecraft roll angle. The majority of the counts were electrons with energy above several MeV; i.e., with drift periods shorter than the satellite orbital resonance. The electrons have isotropic pitch angle distributions, and the protons pancake over most of the region between Nimas and the rings, although there is a small region of dumbbell proton distributions in the vicinity of Janus and Epimetheus.

Northrop, T. G.↗
DOE OSTI2026

Pb-Apatite Framework as a Generator of Novel Flat-Band CuO-Based Physics

Based upon density functional theory (DFT) calculations, we present the basic electronic structure of CuPb 9 (PO 4 ) 6 O (Cu-doped lead apatite, aka LK-99), in two scenarios: (1) where the structure is constrained to the P3 symmetry and (2) where no symmetry is imposed. At the DFT level, the former is predicted to be metallic while the latter is found to be a charge-transfer insulator. In both cases the filling of these states is nominally d 9 , consistent with the standard Cu 2+ valence state, and Cu with a local magnetic moment of order 0.7 μ B . In the metallic case we find these states to be unusually flat (∼0.2 eV dispersion), giving a very high density of electronic states (DOS) at the Fermi level that we argue can be a host for novel electronic physics. The flatness of the bands is the likely origin of symmetry-lowering gapping possibilities that would remove the spectral weight from E F . Motivated by some initial experimental observations of metallic or semiconducting behavior, we propose that disorder (likely structural) is responsible for closing the gap. Here, we consider a variety of possibilities that could possibly close the charge-transfer gap but limit consideration to kinds of disorder that preserve electron count. Of the possible kinds we considered (spin disorder, O populating vacancy sites, and Cu on less energetically favorable Pb sites), the local Cu moment, and consequently the charge-transfer gap, remains robust. We conclude that disorder responsible for metallic behavior entails some kind of doping where the electron count changes. Further, we claim that the emergence of the flat bands should be due to weak wave function overlap between the orbitals on Cu and O sites, owing to the directional character of the constituent orbitals. Therefore, finding an appropriate host structure for minimizing hybridization between Cu and O while allowing them to still weakly interact should be a promising route for generating flat bands at E F which can lead to interesting electronic phenomena, regardless of whether LK-99 is a superconductor.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Readout optimization of multi-amplifier sensing charge-coupled devices for single-quantum measurement

The non-destructive readout capability of the Skipper Charge Coupled Device (CCD) has been demonstrated to reduce the noise limitation of conventional silicon devices to levels that allow single-photon or single-electron counting. The noise reduction is achieved by taking multiple measurements of the charge in each pixel. These multiple measurements come at the cost of extra readout time, which has been a limitation for the broader adoption of this technology in particle physics, quantum imaging, and astronomy applications. This work presents recent results of a novel sensor architecture that uses multiple non-destructive floating-gate amplifiers in series to achieve sub-electron readout noise in a thick, fully-depleted silicon detector to overcome the readout time overhead of the Skipper-CCD. This sensor is called the Multiple-Amplifier Sensing Charge-Coupled Device (MAS-CCD) can perform multiple independent charge measurements with each amplifier, and the measurements from multiple amplifiers can be combined to further reduce the readout noise. We will show results obtained for sensors with 8 and 16 amplifiers per readout stage in new readout operations modes to optimize its readout speed. The noise reduction capability of the new techniques will be demonstrated in terms of its ability to reduce the noise by combining the information from the different amplifiers, and to resolve signals in the order of a single photon per pixel. The first readout operation explored here avoids the extra readout time needed in the MAS-CCD to read a line of the sensor associated with the extra extent of the serial register. The second technique explore the capability of the MAS-CCD device to perform a region of interest readout increasing the number of multiple samples per amplifier in a targeted region of the active area of the device.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Magnetic Properties Tuning via Broad Range Site Deficiency in Square Net Material UCu x Bi 2

HfCuSi 2 -type pnictogen compounds have recently been shown to be a versatile platform for designing materials with topologically nontrivial band structures. However, these phases require strict control over the electron count to tune the Fermi level, which can only be achieved in compositions with A 2+ M 2+ Pn 2 and A 3+ M + Pn 2 (A = lanthanides, M = transition metals, Pn = pnictogens P–Bi) charge distribution. While such lanthanide compounds have been thoroughly studied as candidate magnetic topological materials, their heavy element analogs with uranium and bismuth remain largely underexplored. In this report, we present the synthesis of UCu x Bi 2 single crystals and study their magnetic properties. Detailed structural analysis revealed that flux-grown crystals always form as a site-deficient UCu x Bi 2 composition, where x varies between 0.20 and 0.64. Magnetic property measurements revealed a dependence of the magnetic coupling on the Cu site deficiency, linearly changing the Néel temperature from 51 K for UCu 0.60 Bi 2 to 118 K for UCu 0.30 Bi 2 . Moreover, higher Cu concentration promotes a metamagnetic transition in highly magnetically anisotropic UCu 0.60 Bi 2 single crystals. We show that DFT calculations can successfully model site deficiency in the UCu x Sb 2 and UCu x Bi 2 systems. This work paves the way toward using the site deficiency to tune the Fermi level in more ubiquitous A 3+ M 2+ x Pn 2 phases, which previously have not been considered topological candidate materials due to unfavorable electron count.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Machine learning pipeline for denoising low signal-to-noise ratio and out-of-distribution transmission electron microscopy datasets

High-resolution transmission electron microscopy (HRTEM) is crucial for observing material’s structural and morphological evolution at Angstrom scales, but the electron beam can alter these processes. Devices such as CMOS-based direct-electron detectors operating in electron-counting mode can be utilized to substantially reduce the electron dosage. However, the resulting images often lead to a low signal-to-noise ratio, which requires frame integration that sacrifices temporal resolution. Several machine learning (ML) models have been recently developed to successfully denoise HRTEM images. Yet, these models are often computationally expensive, and their inference speeds on GPUs are outpaced by the imaging speed of advanced detectors, precluding in situ analysis. Furthermore, the performance of these denoising models on datasets with imaging conditions that deviate from the training datasets has not been evaluated. To mitigate these gaps, we propose a new self-supervised ML denoising pipeline specifically designed for time-series HRTEM images. This pipeline integrates a blind-spot convolution neural network with pre-processing and post-processing steps, including drift correction and low-pass filtering. Results demonstrate that our model outperforms various other ML and non-ML denoising methods in noise reduction and contrast enhancement, leading to improved visual clarity of atomic features. Additionally, the model is drastically faster than U-Net-based ML models and demonstrates excellent out-of-distribution generalization. The model’s computational inference speed is in the order of milliseconds per image, rendering it suitable for application in in-situ HRTEM experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Towards a quantum realization of the ampere using single-electron resolution Skipper-CCDs

This paper presents a proof-of-concept demonstration of the Skipper-charge coupled device (CCD), a sensor with single-electron counting capability, as a promising technology for implementing an electron-pump-based current source. Relying on its single-electron resolution and built-in charge sensing, it allows self-calibration of the charge packets. This article presents an initial discussion of the uncertainty in the charge measurement and achievable currents levels with this technology. Here, we report experimental results that illustrate the key functionalities in manipulating both small and large electron charge packets, including a comparison of the charge generated, self-measured, and drained by the sensor against measurements from an electrometer. These results were obtained using a standard sensor and readout electronics without specific optimizations for this application. The objective is to explore the potential of Skipper-CCD for realizing an electron-based current source.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1977

Active experiments in modifying spacecraft potential: Results from ATS-5 and ATS-6

Instruments on ATS-5 and ATS-6 were operated to study the phenomena of spacecraft charging. The ion engine neutralizers were operated in attempts to modify the spacecraft potentials. The neutralizer on ATS-5 is a hot filament emitting electrons, while the neutralizer on ATS-6 is a low energy plasma bridge. The diagnostics used were particle detectors, counting electrons and protons as a function of energy. Operations were conducted in daylight and eclipse. This report describes the processing data from these and other operations. Only preliminary analysis of some of this data has been carried out, with the following results: (1) electron emission does not perturb the status of a low potential satellite by more than 50 volts, (2) emission of a low energy plasma does not change low potentials by more than a few volts, (3) when ATS-6 enters eclipse in the presence of a high energy plasma, the neutralizer suppresses any rise in (within a few volts resolution), (4) when the electron emitter on ATS-5 is operated, it serves to discharge negative potentials from thousands to hundreds of volts.

Olsen, R.↗
NASA NTRS1977

A general study of techniques for ultraviolet astrophysical studies on space vehicles

Recent accomplishments in three areas of UV instrumentation for space astronomy are discussed. These areas include reliable UV photometry, sensitive photon-detection techniques, and precise telescope pointing. Calibration facilities for spectrometers designed to operate in the spectral regions above 1200 A and down to 400 A are described which employ a series of diodes calibrated against electron synchrotron radiation as well as other radiometric standards. Improvements in photon-detection sensitivity achieved with the aid of pulse-counting electronics and multispectral detectors are reported, and the technique of precise subarcsecond telescope pointing is briefly noted. Some observational results are presented which demonstrate the advantages and precision of the instruments and techniques considered.

Moos, H. W.↗
NASA NTRS1991

Precipitating relativistic electrons - Their long-term effect on stratospheric odd nitrogen levels

Using electron count rate data at geostationary orbit, daily energy spectra, extending from 30 keV to 15 MeV, have been developed for trapped relativistic electrons at 6.6 earth radii. These spectra have been used to model the flux of these electrons into the atmosphere at 120 km. Energy deposition calculations permit daily sources of HO(x) and NO(y) to be calculated at auroral and subauroral latitudes due to relativistic electron precipitation (REP) for the period June 13, 1979, through June 4, 1988. Both short-term and long-term source variations are quite large over the period considered. The results suggest that a significant contribution to the anomalously large and unexplained global O3 declines between 1979 and 1985 has been made by the catalytic destruction of O3 by odd nitrogen in the lower stratosphere at mid to high latitudes. The results also provide evidence for a clear and strong linkage between solar variability, the state of the magnetosphere, and the chemical climatological state of the middle and lower atmosphere.

Callis, Linwood B.↗
NASA NTRS1986

The development and test of multi-anode microchannel array detector systems. Part 2: Soft X-ray detectors

Detector systems based on the high gain microchannel plate (MCP) electron multiplier were used extensively for imaging at soft X-ray wavelengths both on the ground and in space. The latest pulse counting electronic readout systems provide zero readout noise, spatial resolutions (FWHM) of 25 microns or better and can determine the arrival times of detected photons to an accuracy of the order of 100 ns. These systems can be developed to produce detectors with active areas of 100 nm in diameter or greater. The use of CsI photocathodes produces very high detective quantum efficiencies at wavelengths between about 100 and 1A (approximately 0.1 to 10 keV) with moderate energy resolution. The operating characteristics of the different types of soft X-ray MCP detector systems are described and the prospects for future developments are discussed.

Timothy, J. G.↗