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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Mechanism of phase control in a klystron-like relativistic backward wave oscillator by an input signal

Theoretical analyses and particle-in-cell (PIC) simulations are carried out to understand the mechanism of microwave phase control realized by the external RF signal in a klystron-like relativistic backward wave oscillator (RBWO). Theoretical calculations show that a modulated electron beam can lead the microwave field with an arbitrary initial phase to the same equilibrium phase, which is determined by the phase factor of the modulated current, and the difference between them is fixed. Furthermore, PIC simulations demonstrate that the phase of input signal has a close relation to that of modulated current, which initiates the phase of the irregularly microwave during the build-up of oscillation. Since the microwave field is weak during the early time of starting oscillation, it is easy to be induced, and a small input signal is sufficient to control the phase of output microwave. For the klystron-like RBWO with two pre-modulation cavities and a reentrant input cavity, an input signal with 100 kW power and 4.21 GHz frequency can control the phase of 5 GW output microwave with relative phase difference less than 6% when the diode voltage is 760 kV, and beam current is 9.8 kA, corresponding to a power ratio of output microwave to input signal of 47 dB.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Magnetism induced by excess electrons trapped at diamagnetic edge-quantum well in multi-layer graphene

In this paper, we clarified a robust mechanism of magnetism generated by excess electrons captured by edge-quantum well of diamagnetic armchair edges. Consistency between density functional theory calculations and electron cyclotron resonance experiments verified that: (1) Multi-layer armchair nanoribbons are stable with proper amounts of excess electrons which can provide net spin; (2) Since under-coordination induces lattice relaxation and potential well modulation, electrons tend to be trapped at edges; and (3) Neither large amount of excess electrons nor positive charges can induce magnetism. This work shed light on the development of graphene devices in its magnetic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1983

Electron Beam Could Probe Recombination Centers

Electron beam probe technique estimate electron/hole capture cross sections in semiconductors with wide band gaps. Amplitude-modulated electron beam induces short-circuit current collected by ohmic contacts. Phase shift between this current and electron-beam current measured as function of frequency. Results of measurements used to ascertain recombination rates and energy levels.

Vonroos, O.↗
DOE OSTI2014

Microstructure fabrication process induced modulations in CVD graphene

The systematic Raman spectroscopic study of a “mimicked” graphene device fabrication is presented. Upon photoresist baking, compressive stress is induced in the graphene which disappears after it is removed. The indirect irradiation from the electron beam (through the photoresist) does not significantly alter graphene characteristic Raman peaks indicating that graphene quality is preserved upon the exposure. The 2D peak shifts and the intensity ratio of 2D and G band, I(2D)/I(G), decreases upon direct metal deposition (Co and Py) suggesting that the electronic modulation occurs due to sp{sup 2} C-C bond weakening. In contrast, a thin metal oxide film deposited graphene does not show either the significant 2D and G peaks shift or I(2D)/I(G) decrease upon the metal deposition suggesting the oxide protect the graphene quality in the fabrication process.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Performance and Reliability of Bonded Interfaces for High-Temperature Packaging. Annual Report

Current generation automotive power electronics packages utilize silicon devices and lead-free solder alloys. To meet stringent technical targets for 2020 and beyond (for cost, power density, specific power, efficiency and reliability), wide-bandgap devices are being considered since they offer advantages such as operation at higher frequencies, voltages, and temperatures. Traditional power electronics packages must be redesigned to utilize the full potential of wide-bandgap devices, and the die- and substrate-attach layers are key areas where new material development and validation is required. Present solder alloys do not meet the performance requirements for these new package designs while also meeting cost and hazardous substance restrictions. Sintered silver (Ag) promises to meet the needs for die- and substrate-attach interfaces but synthesis optimization and reliability evaluation must be completed. Sintered Ag material was proposed as an alternative solution in power electronics packages almost 20 years back. However, synthesis pressure requirements up 40 MPa caused a higher complexity in the production process and more stringent flatness specifications for the substrates. Recently, several manufacturers have developed sintered Ag materials that require lower (3-5 MPa) or even no bonding pressures. Degradation mechanisms for these sintered Ag materials are not well known and need to be addressed. We are addressing these aspects to some extent in this project. We are developing generalized (i.e., independent of geometry) stress intensity factor versus cycles-to-failure relations for sintered Ag. Because sintered Ag is a relatively new material for automotive power electronics, the industry currently does not have a good understanding of recommended synthesis parameters or expected reliability under prescribed conditions. It is an important deliverable of this project to transfer findings to industry to eliminate barriers to using sintered Ag as a viable and commercialized die- and substrate-attach material. Only a few manufacturers produce sintered Ag pastes and may consider some processing conditions as proprietary. It is the goal of this project to openly explore and define best practices in order to impact the maximum number of power electronics module manufacturers and suppliers.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1985

Investigations of radiation-induced and carrier-enhanced conductivity

A steady-state carrier computer code, PECK (Parker Enhanced Carrier Kinetics), that predicts the radiation-induced conductivity (RIC) produced in a dielectric by an electron beam was developed. The model, which assumes instantly-trapped holes, was then applied to experimental measurements on thin Kapton samples penetrated by an electron beam. Measurements at high bias were matched in the model by an appropriate choice for the trap-modulated electron mobility. A fractional split between front and rear currents measured at zone bias is explained on the basis of beam-scattering. The effects of carrier-enhanced conductivity (CEC) on data obtained for thick, free-surface Kapton samples is described by using an analytical model that incorporates field injection of carriers from the RIC region. The computer code, LWPCHARGE, modified for carrier transport, is also used to predict partial penetration effects associated with CEC in the unirradiated region. Experimental currents and surface voltages, when incorporated in the appropriate models, provide a value for the trap modulated mobility that is in essential agreement with the RIC results.

Meulenberg, A., Jr.↗
DOE OSTI2019

Low-energy phonons in Bi 2 Sr 2 CaCu 2 O 8 + δ and their possible interaction with electrons measured by inelastic neutron scattering

Electron-phonon interaction in copper oxide superconductors is still enigmatic. Strong coupling for certain optic phonons is now well established experimentally, but theoretical understanding is challenging. Scattering of electrons near the Fermi surface by the longitudinal acoustic (LA) phonons is expected from basic theory because these phonons modulate electron density. We used inelastic neutron scattering on a large single crystal sample of optimally-doped Bi 2 Sr 2 CaCu 2 O 8+δ to show that low-energy LA phonons could couple to electronic density fluctuations only at small phonon wavevectors, which naturally limits any interaction to forward scattering. Such scattering should not be pairbreaking in the case of the d-wave gap. We also found that previously reported low energy phonon spectral weight half-way to the zone boundary is consistent with conventional lattice dynamics and does not reflect incipient charge density wave (CDW).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2012

Distributed Motor Controller (DMC) for Operation in Extreme Environments

This paper presents an extreme environment capable Distributed Motor Controller (DMC) module suitable for operation with a distributed architecture of future spacecraft systems. This motor controller is designed to be a bus-based electronics module capable of operating a single Brushless DC motor in extreme space environments: temperature (-120 C to +85 C required, -180 C to +100 C stretch goal); radiation (>;20K required, >;100KRad stretch goal); >;360 cycles of operation. Achieving this objective will result in a scalable modular configuration for motor control with enhanced reliability that will greatly lower cost during the design, fabrication and ATLO phases of future missions. Within the heart of the DMC lies a pair of cold-capable Application Specific Integrated Circuits (ASICs) and a Field Programmable Gate Array (FPGA) that enable its miniaturization and operation in extreme environments. The ASICs are fabricated in the IBM 0.5 micron Silicon Germanium (SiGe) BiCMOS process and are comprised of Analog circuitry to provide telemetry information, sensor interface, and health and status of DMC. The FPGA contains logic to provide motor control, status monitoring and spacecraft interface. The testing and characterization of these ASICs have yielded excellent functionality in cold temperatures (-135 C). The DMC module has demonstrated successful operation of a motor at temperature.

SiGe↗
DOE OSTI2019

UV/Near-IR Aerosol Absorption Monitor

In this DOE SBIR Phase I study, we have designed and constructed two prototypes demonstrating proof of concept for a new aerosol measurement instrument: a UV/near-IR aerosol absorption monitor. One prototype operates at 360nm and the other at 1064nm. From the laboratory testing and evaluation, we obtained the following technical specifications for the two prototypes: (A) Photoacoustic measurements of aerosol light absorption at 360nm and 1064 nm; (B) Detection limit of 1.0 Mm-1 in 10s-averaging and 0.36 Mm-1 in 100s at 1064nm; (C) Detection limit of 9 Mm-1 in 10s at 360nm; (D) Time response of 4.3 ± 0.6 s, using the 90% criteria; (E) Linear dynamic range from 0.36 Mm to 250 Mm-1 at 1064nm; (F) Sample flow rate of 0.5-2.0 liter per minute; (G) Continuous measurement at 1s sampling rate; (H) An aerosol-based calibration approach; (I) Dimension of 56cm×43cm×25cm and 25kg for the near-IR prototype; while 66cm×43cm×38cm and 30kg for the UV prototype. In this Phase I study, we changed the modulation approach applied to the UV prototype to improve its detection sensitivity. Using an optical chopper to chop the laser beam instead of the electronic modulation on its power supply, we were able to increase the effective laser power and thereby improve the sensitivity by a factor of 2.1. However there is a tradeoff of utilizing a chopper. This approach can only produce a single modulation frequency, presenting an obstacle to combining the UV and near-IR aerosol absorption monitors into a single two-wavelength measurement instrument. Given that the near-IR prototype meets all the desired technical specifications from the DoE SBIR program, this instrument will be ready to be commercialized in the Phase II program. On the other hand, in addition to a different modulation scheme from the near-IR model, the UV aerosol absorption monitor needs some improvements to achieve the desired technical objective in measurement sensitivity. Thus the future Phase II program would primarily focus on improving the UV model and developing both the UV and near-IR aerosol absorption monitors into standalone commercial products.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Heterometallic Actinide‐Containing Photoresponsive Metal‐Organic Frameworks: Dynamic and Static Tuning of Electronic Properties

Abstract Acquiring fundamental knowledge of properties of actinide‐based materials is a necessary step to create new possibilities for addressing the current challenges in the nuclear energy and nuclear waste sectors. In this report, we established a photophysics–electronics correlation for actinide‐containing metal‐organic frameworks (An‐MOFs) as a function of excitation wavelength, for the first time. A stepwise approach for dynamically modulating electronic properties was applied for the first time towards actinide‐based heterometallic MOFs through integration of photochromic linkers. Optical cycling, modeling of density of states near the Fermi edge, conductivity measurements, and photoisomerization kinetics were employed to shed light on the process of tailoring optoelectronic properties of An‐MOFs. Furthermore, the first photochromic MOF‐based field‐effect transistor, in which the field‐effect response could be changed through light exposure, was constructed. As a demonstration, the change in current upon light exposure was sufficient to operate a two‐LED fail‐safe indicator circuit.

Martin, Corey R.↗
DOE OSTI2015

MODULATION OF GALACTIC ELECTRONS IN THE HELIOSPHERE DURING THE UNUSUAL SOLAR MINIMUM OF 2006–2009: A MODELING APPROACH

The last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. The highest levels of Galactic protons were recorded at Earth in late 2009 in contrast to expectations. A comprehensive model was used to study the proton modulation for the period from 2006 to 2009 in order to determine what basic processes were responsible for solar modulation during this period and why it differs from proton modulation during previous solar minimum modulation periods. This established model is now applied to studying the solar modulation of electron spectra as observed for 80 MeV–30 GeV by the PAMELA space detector from mid-2006 to the end of 2009. Over this period the heliospheric magnetic field had decreased significantly until the end of 2009 while the waviness of the heliospheric current sheet decreased moderately and the observed electron spectra increased by a factor of ∼1.5 at 1.0 GeV to ∼3.5 at 100 MeV. In order to reproduce the modulation evident from seven consecutive semesters, the diffusion coefficients had to increase moderately while maintaining the basic rigidity dependence. It is confirmed that the main diffusion coefficients are independent of rigidity below ∼0.5 GV, while the drift coefficient had to be reduced below this value. The 2006–2009 solar minimum epoch indeed was different than previously observed minima, at least since the beginning of the space exploration era. This period could be called “diffusion-dominated” as was also found for the modulation of protons.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Heterogeneous Integration Technologies for High-temperature, High-density, Low-profile Power Modules of Wide Bandgap Devices in Electric Drive Applications (Final Technical Report)

The goal of this project is to develop packaging technologies for making high-temperature, high-density, and low-profile wide-bandgap (WBG) power electronics modules for electric drives. These modules are aimed at enabling the DOE’s University Consortium to reach its 2025 inverter targets of ≥ 100 kW/L and ≤ 2.7 $/kW. The specific objectives are to: design and fabricate SiC half-bridge power modules with double-sided cooling and parasitic inductances < 5 nH, heat flux density > 400 W/cm 2 , and working junction temperature of 200 o C; design, fabricate, and deliver a gate driver with double-sided cooled modules for the construction of a 100 kW/L inverter at Oak Ridge National Lab; and design and prototype intelligent gate drivers with integrated current sensor and a low-profile DC-DC power supply with air-core transformer for testing power modules at 200 o C junction temperature. We followed an iterative technical approach of design, simulation, fabrication, and testing of various versions of modules, current sensors, and power supply. The state-of-the-art silicon carbide devices rated at 1.2 kV and 149 A were packaged by sintered-silver bonding on an aluminum nitride direct-bond-copper substrate for high thermal conductivity, high working temperature, and high joint reliability. Porous silver posts were used to interconnect the device’s source pads to the other direct-bond-copper substrate for low mechanical stresses, ease of manufacturing, and double-sided cooling. A current sensor based on package parasitic inductance was developed to measure switching current. A dynamic feedback scheme was developed to compensate the effect of parasitic resistance and temperature variation. A constant-current class-E dc-dc converter with air-core transformer was developed. Air-core transformer was used due to the unavailability of magnetic core at high temperatures. Gate driver and power supply were integrated with the double-side cooled, high temperature SiC power modules for testing the modules at 200 o C junction temperature. Double-pulse and continuous testing of the integrated technologies validated the design and fabrication of the three component technologies. Throughout the project, we overcame the challenge for design verification caused by low prototyping yield, which then helped train the graduate students, the future workforce, to learn the engineering know-how for low-cost manufacturing of reliable products. Below is a summary of the major accomplishments of this project: development of a prototyping process for fabricating double-side cooled (1200 V, 149 A) SiC phase-leg modules capable of working to 200 o C Tj; simulation and experimental verification of the improvement of thermo-mechanical reliability of the double-side cooled SiC phase-leg module by using rigid encapsulant; design and experimental validation of a current sensor based on package parasitic inductance and a compensation solution for eliminating the effect of parasitic resistance; design and experimental validation of a low-profile power supply with six-output air-core transformer for gate driver; functional demonstration of a SiC phase-leg module integrated with its gate driver, current sensor, and an air-core power supply at 200 o C Tj in a double-pulse switching test setup and Buck converter continuous test setup; successful completion of six PhD and two MS students who are or will work at Apple Inc., Tesla Inc., Wolfspeed Inc., Microchip Inc., Monolithic Power Systems Inc., and LG Magna Inc.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Heterometallic Actinide-Containing Photoresponsive Metal-Organic Frameworks: Dynamic and Static Tuning of Electronic Properties

Acquiring fundamental knowledge of properties of actinide-based materials is a necessary step to create new possibilities for addressing the current challenges in the nuclear energy and nuclear waste sectors. Here in this report, we established a photophysics–electronics correlation for actinide-containing metal-organic frameworks (An-MOFs) as a function of excitation wavelength, for the first time. A stepwise approach for dynamically modulating electronic properties was applied for the first time towards actinide-based heterometallic MOFs through integration of photochromic linkers. Optical cycling, modeling of density of states near the Fermi edge, conductivity measurements, and photoisomerization kinetics were employed to shed light on the process of tailoring optoelectronic properties of An-MOFs. Furthermore, the first photochromic MOF-based field-effect transistor, in which the field-effect response could be changed through light exposure, was constructed. As a demonstration, the change in current upon light exposure was sufficient to operate a two-LED fail-safe indicator circuit.

36 MATERIALS SCIENCE↗
NASA NTRS1984

A balloon-borne high-resolution spectrometer for observations of gamma-ray emission from solar flares

The design, development, and balloon-flight verification of a payload for observations of gamma-ray emission from solar flares are reported. The payload incorporates a high-purity germanium semiconductor detector, standard NIM and CAMAC electronics modules, a thermally stabilized pressure housing, and regulated battery power supplies. The flight system is supported on the ground with interactive data-handling equipment comprised of similar electronics hardware. The modularity and flexibility of the payload, together with the resolution and stability obtained throughout a 30-hour flight, make it readily adaptable for high-sensitivity, long-duration balloon fight applications.

Crannell, C. J.↗
DOE OSTI2015

Building America Case Study: Photovoltaic Systems with Module-Level Power Electronics

Direct current (DC) power optimizers and microinverters (together known as module-level power electronics, or MLPE) are one of the fastest growing market segments in the solar industry. According to GTM Research in The Global PV Inverter Landscape 2015, over 55% of all residential photovoltaic (PV) installations in the United States used some form of MLPE in 2014.

14 SOLAR ENERGY↗
DOE OSTI2021

Doping-modulated strain control of bifunctional electrocatalysis for rechargeable zinc–air batteries

Changes in the local atomic arrangement in a crystal caused by lattice-mismatch-induced strain can efficiently regulate the performance of electrocatalysts for zinc–air batteries (ZABs) in many manners, mainly due to modulated electronic structure configurations that affect the adsorption energies for oxygen-intermediates formed during oxygen reduction and evolution reactions (ORR and OER). However, the application of strain engineering in electrocatalysis has been limited by the strain relaxation caused by structural instability such as dissolution and destruction, leading to insufficient durability towards the ORR/OER. In this work, we propose a doping strategy to modulate the phase transition and formation of self-supported cobalt fluoride–sulfide (CoFS) nanoporous films using a low amount of copper (Cu) as a dopant. This well-defined Cu–CoFS heterostructure overcomes the obstacle of structural instability. Our study of the proposed Cu–CoFS also helps establish the structure–property relationship of strained electrocatalysts by unraveling the role of local strain in regulating the electronic structure of the catalyst. As a proof-of-concept, the Cu–CoFS electrocatalyst with doping-modulated strain exhibited superior onset potentials of 0.91 V and 1.49 V for the ORR and OER, respectively, surpassing commercial Pt/C@RuO 2 and benchmarking non-platinum group metal (non-PGM) catalysts. ZABs with the Cu–CoFS catalyst delivered excellent charge/discharge cycling performance with an extremely low voltage gap of 0.5 V at a current density of 10 mA cm –2 and successively 0.93 V at a high current density of 100 mA cm –2 and afforded an outstanding peak power density of 255 mW cm –2 .

25 ENERGY STORAGE↗
DOE OSTI2018

Validation study of GENE on ASDEX Upgrade using perturbative thermal diffusivity measured with partial sawtooth heat pulses

Perturbative thermal diffusivity is measured with partial sawtooth-generated heat pulses on ASDEX Upgrade for the first time, and these measurements are used to validate the first nonlinear ion-scale gyrokinetic simulation that agrees with experimentally measured perturbative diffusivity. Recent work on Alcator C-Mod and DIII-D has shown that ion-scale gyrokinetics cannot adequately describe certain plasma conditions, and that in these instances multi-scale simulations may resolve the observed discrepancies. This work presents the first measurements of electron perturbative thermal diffusivity with partial sawteeth on ASDEX Upgrade (measuring values between 2 and 9 m 2 s -1 ), and compares these measurements to those made with more established modulated electron cyclotron heating measurements, finding good agreement within experimental uncertainty. Perturbative diffusivity is found to scale inversely with collisionality across ASDEX Upgrade and Alcator C-Mod plasmas. Finally, perturbative diffusivity is used as a validation constraint in a study with the gyrokinetic code GENE, showing the first instance where an ion-scale gyrokinetic simulation can simultaneously match the experimental ion and electron heat fluxes and the perturbative thermal diffusivity. Here these results indicate that multi-scale effects may only be important in some plasmas, and the collisionality and ratio of high to low wavenumber linear growth rates may distinguish these cases.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2022

Development of LISA Laser System at NASA

NASA Goddard Space Flight Center (GSFC) is developing a master oscillator power amplifier (MOPA) laser transmitter for the Laser Interferometer Space Antenna (LISA) mission. The laser transmitter is one of the potential contributions to the LISA mission from NASA. Our development effort has included a master oscillator (MO), a power amplifier (PA), a frequency reference system (FRS), a power monitor detector (PMON), and laser electronics module (LEM). We are working on their design, performance evaluation, environmental testing, and reliability testing for space flight. We have built TRL 4 laser optical modules based on the MO and PA, which meets most performance requirements. One of the TRL 4 laser optical modules has been delivered to ESA for independent evaluation. TRL 6 versions of MO and PA are being built and evaluated at GSFC. TRL 5 and 6 versions of laser electronics are under development. In this paper, we will describe our progress to date and plans to demonstrate and deliver a TRL 6 laser demonstrator system to ESA by 2024.

LISA, Space Lasers↗