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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A 600 VOLT MULTI-STAGE, HIGH REPETITION RATE GAN FET SWITCH

Using recently available GaN FETs, a 600 Volt three- stage, multi-FET switch has been developed having 2 nanosecond rise time driving a 200 Ohm load with the potential of approaching 30 MHz average switching rates. Possible applications include driving particle beam choppers kicking bunch-by-bunch and beam deflectors where the rise time needs to be custom tailored. This paper reports on the engineering issues addressed, the design approach taken and some performance results of this switch.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Accurate prediction of mega-electron-volt electron beam properties from UED using machine learning

To harness the full potential of the ultrafast electron diffraction (UED) and microscopy (UEM), we must know accurately the electron beam properties, such as emittance, energy spread, spatial-pointing jitter, and shot-to-shot energy fluctuation. Owing to the inherent fluctuations in UED/UEM instruments, obtaining such detailed knowledge requires real-time characterization of the beam properties for each electron bunch. While diagnostics of these properties exist, they are often invasive, and many of them cannot operate at a high repetition rate. Here, we present a technique to overcome such limitations. Employing a machine learning (ML) strategy, we can accurately predict electron beam properties for every shot using only parameters that are easily recorded at high repetition rate by the detector while the experiments are ongoing, by training a model on a small set of fully diagnosed bunches. Applying ML as real-time noninvasive diagnostics could enable some new capabilities, e.g., online optimization of the long-term stability and fine single-shot quality of the electron beam, filtering the events and making online corrections of the data for time-resolved UED, otherwise impossible. This opens the possibility of fully realizing the potential of high repetition rate UED and UEM for life science and condensed matter physics applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Enhancement of Distribution System Resilience Through the Application of Volt-Var Regulation Devices

This paper discusses a practical implementation of locating and sizing dynamic reactive compensation using an impedance matrix (Zbus) approach to improve distribution system resilience in scenarios with high penetration of distributed resources. The modeled system is a 14.2 kV radial residential system modified to be fed by a combination of traditional sources and solar resources. Time-varying loads and PV sources are connected along the feeder to simulate the challenging operational voltage regulation scenarios faced by Modern Distribution Systems. Additionally, enhancement of the resilience of the electrical system is demonstrated through analyzing the effect of a topology change to the system. This study uses the GridLAB-D software.

42 ENGINEERING↗
DOE OSTI2018

Diagnosis of ULF Wave-Particle Interactions With Megaelectron Volt Electrons: The Importance of Ultrahigh-Resolution Energy Channels

Electron flux measurements are an important diagnostic for interactions between ultralow-frequency (ULF) waves and relativistic (~1 MeV) electrons. Since measurements are collected by particle detectors with finite energy channel width, they are affected by a phase mixing process that can obscure these interactions. In this paper, we demonstrate that ultrahigh-resolution electron measurements from the Magnetic Electron Ion Spectrometer on the Van Allen Probes mission—obtained using a data product that improves the energy resolution by roughly an order of magnitude—are crucial for understanding ULF wave-particle interactions. In particular, the ultrahigh-resolution measurements reveal a range of complex dynamics that cannot be resolved by standard measurements. Furthermore, the standard measurements provide estimates for the ULF flux modulation amplitude, period, and phase that may not be representative of true flux modulations, potentially leading to ambiguous conclusions concerning electron dynamics.

42 ENGINEERING↗
DOE OSTI2019

PreMevE: New Predictive Model for Megaelectron-volt Electrons inside Earth's Outer Radiation Belt

Here, this work designs a new model called PreMevE to predict storm–time distributions of relativistic electrons within Earth's outer radiation belt. This model takes advantage of the cross–energy, –L–shell, and –pitch–angle coherence associated with wave–electron resonant interactions, ingests observations from belt boundaries—mainly by NOAA POES in low–Earth–orbits (LEOs), and provides high–fidelity nowcast (multiple–hour prediction) and forecast (> ~1 day) of MeV electron fluxes over L–shells between 2.8–7 through linear prediction filters. PreMevE can not only reliably anticipate incoming enhancements of MeV electrons during storms with at least 1–day forewarning time, but also accurately specify the evolving event–specific electron spatial distributions afterwards. The performance of PreMevE is assessed against long–term in situ data from one Van Allen Probe and a LANL geosynchronous satellite. Furthermore, this new model enhances our preparedness for severe MeV electron events in the future, and further adds new science utility to existing and next–generation LEO space infrastructure.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Sub-1 Volt and high-bandwidth visible to near-infrared electro-optic modulators

Abstract Integrated electro-optic (EO) modulators are fundamental photonics components with utility in domains ranging from digital communications to quantum information processing. At telecommunication wavelengths, thin-film lithium niobate modulators exhibit state-of-the-art performance in voltage-length product ( V π L ), optical loss, and EO bandwidth. However, applications in optical imaging, optogenetics, and quantum science generally require devices operating in the visible-to-near-infrared (VNIR) wavelength range. Here, we realize VNIR amplitude and phase modulators featuring V π L ’s of sub-1 V ⋅ cm, low optical loss, and high bandwidth EO response. Our Mach-Zehnder modulators exhibit a V π L as low as 0.55 V ⋅ cm at 738 nm, on-chip optical loss of ~0.7 dB/cm, and EO bandwidths in excess of 35 GHz. Furthermore, we highlight the opportunities these high-performance modulators offer by demonstrating integrated EO frequency combs operating at VNIR wavelengths, with over 50 lines and tunable spacing, and frequency shifting of pulsed light beyond its intrinsic bandwidth (up to 7x Fourier limit) by an EO shearing method.

42 ENGINEERING↗
DOE OSTI2025

Five-volt-class high-capacity all-solid-state lithium batteries

Advances in battery technology have been impeded by the voltage constraints of electrolytes. Here, in this study, we present a high-energy all-solid-state battery design featuring >5 V operation and an ultrahigh areal capacity of 35.3 mAh cm −2 ; these attributes were enabled by a highly conductive and ultrahigh-voltage stable fluoride solid electrolyte, LiCl–4Li 2 TiF 6 (1.7 × 10 −5 S cm −1 at 30 °C). LiCl–4Li 2 TiF 6 shields high-voltage spinel oxide cathodes, achieving 106 mAh g −1 at 2C with 75.2% retention over 500 cycles for LiNi 0.5 Mn 1.5 O 4 , sharply contrasting with the conventional LiNbO 3 counterpart, which decomposes and fails to prevent detrimental interfacial degradation. The efficacy of LiCl–4Li 2 TiF 6 is validated across various systems, including LiCoMnO 4 , LiFe 0.5 Mn 1.5 O 4 and pouch-type LiNi 0.5 Mn 1.5 O 4 ||Li (or Ag–C) all-solid-state batteries, and further demonstrated by operability down to 2.3 V with 258 mAh g −1 and ultrathick 1.8-mm electrodes. This shielding layer with >5 V stability introduces a transformative design paradigm by revisiting the previously forbidden high-voltage cathodes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Water splitting by electrolysis at high current densities under 1.6 volts

Splitting water into hydrogen and oxygen by electrolysis using electricity from intermittent waste heat, wind, or solar energies is one of the easiest and cleanest methods for high-purity hydrogen production and an effective way to store the excess electrical power. The key dilemma for efficient large-scale production of hydrogen by splitting of water via the hydrogen and oxygen evolution reactions (HER and OER, respectively) is the high overpotential required, especially for the OER. We report an exceptionally active and durable OER catalyst yielding current densities of 500 and 1000 mA cm -2 at overpotentials of only 259 mV and 289 mV in alkaline electrolyte, respectively, fulfilling the commercial criteria of the OER process. Together with a good HER catalyst, we have achieved the commercially required current densities of 500 and 1000 mA cm -2 at 1.586 and 1.657 V, respectively, with very good stability, dramatically lower than any previously reported voltage. This research sets the stage for large-scale hydrogen production by water splitting using excess electrical power whenever and wherever available.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Investigating fusion plasma instabilities in the Mega Amp Spherical Tokamak using mega electron volt proton emissions (invited)

The proton detector (PD) measures 3 MeV proton yield distributions from deuterium-deuterium fusion reactions within the Mega Amp Spherical Tokamak (MAST). The PD’s compact four-channel system of collimated and individually oriented silicon detectors probes different regions of the plasma, detecting protons (with gyro radii large enough to be unconfined) leaving the plasma on curved trajectories during neutral beam injection. From first PD data obtained during plasma operation in 2013, proton production rates (up to several hundred kHz and 1 ms time resolution) during sawtooth events were compared to the corresponding MAST neutron camera data. Fitted proton emission profiles in the poloidal plane demonstrate the capabilities of this new system.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Coherent kilo-electron-volt backscattering from plasma-wave boosted relativistic electron mirrors

A different parameter regime of laser wakefield acceleration driven by sub-petawatt femtosecond lasers is proposed, which enables the generation of relativistic electron mirrors further accelerated by the plasma wave. Integrated particle-in-cell simulation, including both the mirror formation and Thomson scattering, demonstrates that efficient coherent backscattering up to keV photon energy can be obtained with moderate driving laser intensities and high density gas targets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗