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At least 307 records · Page 17

All sources NASA NTRS DOE OSTI

NASA NTRS2004

Field Effect Transistor Behavior in Electrospun Polyaniline/Polyethylene Oxide Nanofibers

Novel transistors and logic devices based on nanotechnology concepts are under intense development. The potential for ultra-low-power circuitry makes nanotechnology attractive for applications such as digital electronics and sensors. For NASA applications, nanotechnology offers tremendous opportunities for increased onboard data processing, and thus autonomous decision-making ability, and novel sensors that detect and respond to environmental stimuli with little oversight requirements. Polyaniline (PANi) is an intriguing material because its electrical conductivity can be changed from insulating to metallic by varying the doping levels and conformations of the polymer chain, and when combined with polyethylene oxide (PEO), can be formed into nanofibers with diameters ranging from approximately 50 to 500 nm (depending on the deposition conditions). The initial goal of this work was to demonstrate transistor behavior in these nanofibers, thus creating a foundation for future logic devices.

Miranda, Felix A.↗

NASA NTRS1961

A Satellite Borne Cadmium Sulfide Total Corpuscular Energy Detector

The properties of single crystals of cadmium sulfide as radiation detectors are described. It has been found possible to select crystals such that: (a) The ratio of increase of conductivity under irradiation to the rate of absorption of energy in the crystal is substantially independent of particle energy (over the examined ranges of 500 ev to 80 kev for electrons and 5 kev to 180 kev for protons) and of the magnitude of energy flux (over the range from.005 to 10 ergs/cm(sup 2 -sec); and (b) The above ration is substantially the same for protons, electrons, alpha particles, x-rays, and gamma-rays. For a driving voltage of 100 volts, typical crystal yield currents of 10(sup -7) to 10(sup- 6) amperes for each erg/cm(sup 2-sec) of energy absorbed by the crystal. The threshold of such crystal detectors (resulting from dark currents of the order of 10(sup 10 amp) is typically 10(sup -3) ergs/cm(sup 2- sec). For the selected crystals a response-temperature coefficient of -0.25% per degree centigrade is found for the temperature range -50 deg C to + 50 deg C. A description is given of a complete CdS total corpuscular energy detector for the study of geomagnetically trapped radiation by means of a satellite. The detector described has a dynamic range great than 10(sup 4), a solid angle of 10(exp -3) steradian, and a detection threshold of approximately 1 erg/cm(sup 2-sec-sterad). A similar detector employing a small magnet for the selective exclusion of electrons is also described. Noteworthy practical features of these detectors for satellite and space probe experiments are: (a) Use of bare crystals, without covering foils, in order to detect charged particles having energies as low as hundreds of electron volts. (b) Simplicity of electronic auxiliaries. (c) Compactness, lightweight and nechanical ruggedness. (d) Low electrical power requirements; and (e) Conversion of conduction current to the rate of a twostate relaxation oscillator in order to facilitate telemetric transmission of data. A pair of such detectors was flown as part of the s-46 satellite payload on March 23, 1960, but due to vehicular failure an orbit was not achieved and the operation of the CdS detectors was observed for only, six minutes of flight.

Freeman, John W.↗

NASA NTRS1983

Experimental evidence for the acceleration of thermal electrons by ion cyclotron waves in the magnetosphere

Experimental evidence is presented for the acceleration of thermal electrons by large amplitude ion cyclotron waves (ICWs). The wave power in the ULF range near the helium gyrofrequency is compared with the distribution function of low energy electrons measured by GEOS satellite instruments. This comparison shows that electrons are accelerated near the geomagnetic equator along field lines, at times when the ICW energy is large and the cold plasma density is below a threshold value. It is suggested that these accelerated electrons can account for the ELF emissions, modulated at the ICW frequency, observed by Wehrlin (1981). A very efficient acceleration of thermal electrons along field lines results from other ULF events having frequencies close to the proton gyrofrequency. Evidence for this lies in the fact that medium energy protons having large temperature anisotropies in the 100-500 eV range are responsible for the ICW wave generation.

Norris, A. J.↗

DOE OSTI2021

Stabilizing the Power System in 2035 and Beyond: Evolving from Grid-Following to Grid-Forming Distributed Inverter Controllers (Final Technical Report)

Under existing grid operations, large synchronous generators provide sufficient rotational inertia to form a rigid backbone for the bulk power system. With photovoltaics (PV) forecasted to provide more than 600 GW of generation by 2050 under the U.S. Department of Energy’s SunShot Initiative objectives, however, it is clear that power electronic inverters will play a dominant role in future systems, and low-inertia stability must be ensured to maintain system reliability. Today, the risks to system stability can be observed on geographically small islands, such as Hawaii, which contain a relatively large amount of installed PV. These risks stem from a fundamental shortcoming of contemporary control strategies—existing inverter controllers cannot guarantee grid stability. Given that future power systems driven by sustainable resources will be characterized by low inertia, locations such as Hawaii provide a glimpse into the obstacles facing future power systems. Considering these challenges, the aim of this project was to develop and demonstrate distributed inverter controllers that enable the reliable control of low-inertia power systems with hundreds of gigawatts of integrated PV.

14 SOLAR ENERGY↗

NASA NTRSDate not supplied

Qualification of a Pulsed, Millinewton Class Metal Plasma Thruster for Broad Mission Applications

In the field of low power (<100W) electric propulsion, all thruster options demand significant trade-offs between operating parameters, reliability and scalable cost. With many systems on the market there are concerns with reliability, the need for extra considerations such as electron neutralizers for pure ion plumes, and the cost or craft compatibility of propellants. The Metal Plasma Thruster (MPT) is a new type of electric propulsion technology intended for low power applications. The system imparts momentum using inert, solid metal pucks as a propellant by using pulsed power to convert the metal into high velocity (~17km/s for Mo) jets of quasi-neutral plasma. The MPT technology does not require gas or liquid propellants, neutralizers, standby heaters, high voltage electronics, high electric or magnetic fields to operate. This comparatively simple pulsed operation is amenable to closed loop control, which provides for fine thrust control and S/C directed impulse on demand. Furthermore, the technology can use any metal as propellant, opening up unique opportunities for In-Situ Resource Utilization (ISRU) as well as customizability of performance for meeting specific mission needs. This paper describes implementation and direct measurement of this closed loop control mode as well as impulse measurement of multiple metals consistent with the aim of ISRU at NASA Glenn Research Center (GRC).

Electric Propulsion↗

NASA NTRSDate not supplied

Qualification of a Pulsed, Millinewton Class Metal Plasma Thruster for Broad Mission Applications

Electric Propulsion↗

DOE OSTI2020

Ultra-Low SWaP CO 2 Sensing for Demand Control Ventilation (Final Report)

In this project PARC and Energy ETC aimed to develop an ultra-low cost, size, weight, and power (SWaP) printed CO 2 sensor system for occupancy detection to enable Demand Control Ventilation (DCV) on a per-room basis. The CO 2 sensor technology is based on the temperature variation when CO 2 reversibly physisorbs to a highly conductive and high surface area sorbent surface, and is compatible with integration with PARC innovations in printed sensors and flexible electronics, for which PARC is a globally leading research center. The printed CO 2 sensor itself is designed to be compatible with PARC’s “peel-and-stick” platform of ultra-low power, low-cost, distributed sensors, and to facilitate real-time DCV based on overall indoor air quality (IAQ). Previously, PARC has developed flexible hybrid electronics (FHE) compatible materials to measure humidity, temperature, light, strain, and gases such as carbon monoxide, methane, ammonia, and hydrogen sulfide. Through this project, PARC developed FHE-compatible materials to measure CO 2 . Thus, with one <$15 FHE “peel-and-stick” based sensor node, a building management system (BMS) will be able to capture a complete picture of the indoor environment. This includes IAQ, light, temperature, and other comfort factors that impact building operations. Combined with optimized DCV, this low-cost sensor capability can be a key enabler of annual primary energy savings of ~ 0.3-0.4 Quad in commercial buildings while ensuring healthy IAQ. Energy ETC is a leader in supplier-agnostic BMS deployments and will design the commissioning and deployment procedures to maximize system interoperability.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2004

Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation Using Superconducting Tunnel Junctions with Integrated Radio Frequency Single-Electron Transistors

For high resolution imaging and spectroscopy in the FIR and submillimeter, space observatories will demand sensitive, fast, compact, low-power detector arrays with 104 pixels and sensitivity less than 10(exp -20) W/Hz(sup 0.5). Antenna-coupled superconducting tunnel junctions with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique. The device consists of an antenna to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure current through junctions contacting the absorber. We describe optimization of device parameters, and results on fabrication techniques for producing devices with high yield for detector arrays. We also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

Stevenson, T. R.↗

DOE OSTI2021

Endpoint Use Efficiency Comparison for AC and DC Power Distribution in Commercial Buildings

Advances in power electronics and their use in Miscellaneous Electric Loads (MELs) in buildings have resulted in increased interest in using low-voltage direct current (DC) power distribution as a replacement for the standard alternating current (AC) power distribution in buildings. Both systems require an endpoint converter to convert the distribution system voltage to the MELs voltage requirements. This study focused on the efficiency of these endpoint converters by testing pairs of AC/DC and DC/DC power converters powering the same load profile. In contrast to prior studies, which estimated losses based on data sheet efficiency and rated loads, in this study, we used part load data derived from real-world time-series load measurements of MELs and experimentally characterized efficiency curves for all converters. The measurements performed for this study showed no systematic efficiency advantage for commercially available DC/DC endpoint converters relative to comparable, commercially available AC/DC endpoint converters. For the eight appliances analyzed with the pair of converters tested, in 50%, the weighted energy efficiency of the DC/DC converter was higher, while, for the other 50%, the AC/DC converter was. Additionally, the measurements indicated that the common assumption of using either data sheet efficiency values or efficiency at full load may result in substantial mis-estimates of the system efficiency.

AC/DC converters↗

DOE OSTI2022

CONGO²: Scalable Online Anomaly Detection and Localization in Power Electronics Networks

Rapid and accurate detection and localization of electronic disturbances simultaneously are important for preventing its potential damages and determining potential remedies. Existing anomaly detection methods are severely limited by the low accuracy, the expensive computational cost and the need for highly trained personnel. There is an urgent need for a scalable online algorithm for in-field analysis of large-scale power electronics networks. Here in this paper, we propose a fast and accurate algorithm for anomaly detection and localization of power electronics networks: stratified colored-node graph (CONGO2). This algorithm hierarchically models the change of correlated waveforms and then correlated sensors using the colored-node graph. By aggregating the change of each sensor with its neighbors’ inputs, we can spontaneously identify and localize the anomaly that cannot be detected by data collected from a single sensor. As our proposed method only focuses on the changes within a short time frame, it is highly computational efficient and only needs small data storage. Thus, our method is ideal for online and reliable anomaly detection and localization of large-scale power electronic networks. Compared to existing anomaly detection methods, our method is entirely data-driven without training data, highly accurate and reliable for wide-spectrum anomalies detection, and more importantly, capable of both detection and localization. Thus, it is ideal for infield deployment for large-scale power electronic networks. As illustrated by a distributed energy resources (DERs) power grid with 37-node, our method can effectively detect and localize various cyber and physical attacks.

42 ENGINEERING↗

NASA NTRS1985

Propagation of energetic electron streams in solar flares

The microscopic stability of an electron stream flowing down to the photosphere from the corona is examined. It is found that, while a power-law distribution is stable in the low-density corona, it is unstable against the generation of magnetized electron plasma waves in the high-density photosphere. The scattering of these energetic electrons may alter their radiation signatures.

Mok, Y.↗

DOE OSTI2020

Ferroelectric Switching of Pure Spin Polarization in Two-Dimensional Electron Gas

Two-dimensional electron gas (2DEG) created at compound interfaces can exhibit a broad range of exotic physical phenomena, including quantum Hall phase, emergent ferromagnetism, and superconductivity. Although electron spin plays key roles in these phenomena, the fundamental understanding and application prospects of such emergent interfacial states have been largely impeded by the lack of purely spin-polarized 2DEG. In this paper, by first-principles calculations of the multiferroic superlattice GeTe/MnTe, we find the ferroelectric polarization of GeTe is concurrent with the half-metallic 2DEG at interfaces. Remarkably, the pure spin polarization of the 2DEG can be created and annihilated by polarizing and depolarizing the ferroelectrics and can be switched (between pure spin-up and pure spin-down) by flipping the ferroelectric polarization. Given the electric-field amplification effect of ferroelectric electronics, we envision multiferroic superlattices could open up new opportunities for low-power, high-efficiency spintronic devices such as spin field-effect transistors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRSDate not supplied

On the Moon to Stay: Challenges Presented to Power Electronics Technology by Sustained Operations on the Lunar Surface

NASA’s Artemis Program seeks not only to return humans to the Moon for the first time since the 1970’s but also to provide the technological basis for infrastructure that will enable permanent and expanding scientific and industrial exploitation of the Lunar surface. The primary purpose of this infrastructure is to generate and distribute power to a diverse and growing range of scientific and industrial assets, and the keys to success for this function are power management and control circuits that are highly reliable and maintainable for a decade of operation in the extreme thermal, radiation, and dust environment of the Lunar surface. While various combinations of wide band gap semiconductors, electronic devices, circuit topologies, and shielding schemes have been successfully developed for mission environments ranging from low Earth orbit to the Jovian system, power management technology has not been optimized to meet the full combination of mission requirements for the Lunar surface. To accomplish this, NASA requests the dedicated focus of the power electronics industry.

semiconductors↗

NASA NTRS2004

High Power Light Gas Helicon Plasma Source For VASMIR

The VASIMR space propulsion development effort relies on a high power (greater than 10kW) helicon source to produce a dense flowing plasma (H, D and He) target for ion cyclotron resonance (ICR) acceleration of the ions. Subsequent expansion in an expanding magnetic field (magnetic nozzle) converts ion lunetic energy to directed momentum. This plasma source must have critical features to enable an effective propulsion device. First, it must ionize most of the input neutral flux of gas, thus producing a plasma stream with a high degree of ionization for application of ICR power. This avoids propellant waste and potential power losses due to charge exchange. Next, the plasma stream must flow into a region of high magnetic field (approximately 0.5 T) for efficient ICR acceleration. Third, the ratio of input power to plasma flux must be low, providing an energy per ion-electron pair approaching 100 eV. Lastly, the source must be robust and capable of very long life-times (years). In our helicon experiment (VX-10) we have measured a ratio of input gas to plasma flux near 100%. The plasma flows from the helicon region (B approximately 0.1 T) into a region with a peak magnetic field of 0.8 T. The energy input per ion-electron pair has been measured at 300 plus or minus 100 eV. Recent results at Oak Ridge National Laboratory (ORNL) show an enhanced efficiency mode of operation with a high power density, over 5 kW in a 5 cm diameter tube. Our helicon is presently 9 cm in diameter and operates up to 3.5 kW of input power. An upgrade to a power level of 10 kW is underway. Much of our recent work has been with a Boswell double-saddle antenna design. We are also converting the antenna design to a helical type. With these modifications, we anticipate an improvement in the ionization efficiency. This paper presents the results from scaling the helicon in the VX-10 device from 3.5 to 10 kW. We also compare the operation with a double-saddle to a helical antenna design. Finally, we discuss modeling of these configurations using ORNL's EMIR code.

Squire, J. P.↗

NASA NTRS2012

Lidar Electro-Optic Beam Switch with a Liquid Crystal Variable Retarder

A document discusses a liquid crystal variable retarder, an electro-optic element that changes the polarization of an optical beam in response to a low-voltage electronic signal. This device can be fabricated so that the element creates, among other states, a half-wave of retardance that can be reduced to a very small retardance. When aligned to a polarized source, this can act to rotate the polarization by 90 in one state, but generate no rotation in the other state. If the beam is then incident on a polarization beam splitter, it will efficiently switch from one path to the other when the voltage is applied. The laser beam switching system has no moving parts, improving reliability over mechanical switching. It is low cost, tolerant of high laser power density, and needs only simple drive electronics, minimizing the required system resources.

Baer, James↗

DOE OSTI2022

The Synchrotron Low-energy Spectrum Arising from the Cooling of Electrons in Gamma-Ray Bursts

This work is a continuation of a previous effort (Panaitescu) to study the cooling of relativistic electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses, with application to the spectra and light curves of the synchrotron gamma-ray burst (GRB) produced by such cooling electrons. Here, we derive the low-energy slope β LE of a GRB pulse-integrated spectrum and quantify the implications of the measured distribution of β LE . Radiative processes that produce soft integrated spectra can accommodate the harder slopes measured by CGRO/BATSE and Fermi/GBM only if the magnetic field lifetime t B is shorter than the time during which the typical GRB electrons cool to radiate below 1–10 keV, which is less than (at most) 10 radiative cooling timescales t rad of the typical GRB electron. In this case, there is a one-to-one correspondence between t B and β LE . To account for low-energy slopes β LE > -3/4, the adiabatic electron-cooling requires a similar restriction on t B . In this case, the diversity of slopes arises mostly from how the electron-injection rate varies with time (temporal power-law injection rates yield power-law low-energy GRB spectra) and not from the magnetic field timescale.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1987

A possible energy source to power stable auroral red arcs - Precipitating electrons

Results of coincident measurements by ground-based photometers and the low-altitude plasma instrument on board the Dynamics Explorer 2 satellite are presented that demonstrate the association of precipitating low-energy electrons with stable auroral red (SAR) arcs. A search of available data has yielded 23 instances of DE 2 overflights during the presence of SAR arcs being monitored by the photometers. For each case, downward fluxes of electrons are found to be enhanced along field lines penetrating the arcs in relation to regions both north and south of the features. Modeling of the atmospheric response to these influxes indicates that these electrons can represent a major source of the energy required to establish temperature profiles within the ionospheric electron gas that are sufficient to produce the recorded 6300-A emission rates. The sensitivity of these results to uncertainties of the assumed spacecraft potential and thermospheric composition has been investigated and found to be important, but does not alter the conclusion that precipitating electrons are a fundamental link in the production of SAR arcs.

Slater, D. W.↗

NASA NTRS1981

Electric vehicle motors and controllers

Improved and advanced components being developed include electronically commutated permanent magnet motors of both drum and disk configuration, an unconventional brush commutated motor, and ac induction motors and various controllers. Test results on developmental motors, controllers, and combinations thereof indicate that efficiencies of 90% and higher for individual components, and 80% to 90% for motor/controller combinations can be obtained at rated power. The simplicity of the developmental motors and the potential for ultimately low cost electronics indicate that one or more of these approaches to electric vehicle propulsion may eventually displace presently used controllers and brush commutated dc motors.

Secunde, R. R.↗