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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The NASA-LeRC wind turbine sound prediction code

Since regular operation of the DOE/NASA MOD-1 wind turbine began in October 1979 about 10 nearby households have complained of noise from the machine. Development of the NASA-LeRC with turbine sound prediction code began in May 1980 as part of an effort to understand and reduce the noise generated by MOD-1. Tone sound levels predicted with this code are in generally good agreement with measured data taken in the vicinity MOD-1 wind turbine (less than 2 rotor diameters). Comparison in the far field indicates that propagation effects due to terrain and atmospheric conditions may be amplifying the actual sound levels by about 6 dB. Parametric analysis using the code has shown that the predominant contributions to MOD-1 rotor noise are: (1) the velocity deficit in the wake of the support tower; (2) the high rotor speed; and (3) off column operation.

Viterna, L. A.↗
NASA NTRS2013

The Deep Space Network in the Common Platform Era: A Prototype Implementation at DSS-13

To enhance NASA's Deep Space Network (DSN), an effort is underway to improve network performance and simplify its operation and maintenance. This endeavor, known as the "Common Platform," has both short- and long-term objectives. The long-term work has not begun yet; however, the activity to realize the short-term goals has started. There are three goals for the long-term objective: 1. Convert the DSN into a digital network where signals are digitized at the output of the down converters at the antennas and are distributed via a digital IF switch to the processing platforms. 2. Employ a set of common hardware for signal processing applications, e.g., telemetry, tracking, radio science and Very Long Baseline Interferometry (VLBI). 3. Minimize in-house developments in favor of purchasing commercial off-the-shelf (COTS) equipment. The short-term goal is to develop a prototype of the above at NASA's experimental station known as DSS-13. This station consists of a 34m beam waveguide antenna with cryogenically cooled amplifiers capable of handling deep space research frequencies at S-, X-, and Ka-bands. Without the effort at DSS-13, the implementation of the long-term goal can potentially be risky because embarking on the modification of an operational network without prior preparations can, among other things, result in unwanted service interruptions. Not only are there technical challenges to address, full network implementation of the Common Platform concept includes significant cost uncertainties. Therefore, a limited implementation at DSS-13 will contribute to risk reduction. The benefits of employing common platforms for the DSN are lower cost and improved operations resulting from ease of maintenance and reduced number of spare parts. Increased flexibility for the user is another potential benefit. This paper will present the plans for DSS-13 implementation. It will discuss key issues such as the Common Platform architecture, choice of COTS equipment, and the standard for radio frequency (RF) to digital interface.

Space Communications and Navigation (SCaN)↗
DOE OSTI2018

Dynamics of MHD instabilities near a ferromagnetic wall

Prospective fusion component testing and DEMO power reactor concepts are expected to employ low-activation ferritic steels because of their ability to withstand the high neutron flux of the reactor environment. However, theory suggests that ferromagnetic material may amplify certain external MHD instabilities. Using its ferromagnetic-resistive wall mode (FRWM) upgrade, the High Beta Tokamak-Extended Pulse (HBT-EP) experiment has observed approximately doubled growth rates when operating with a close-fitting ferromagnetic first wall, compared to operation with a stainless steel first wall. The presence of a ferromagnetic wall correlates with earlier disruptions, and FRWM growth rates increase with decreasing mode rotation, as expected due to the increased skin depth allowing greater mode interaction with the bulk ferromagnetic material. It is also seen that introducing low-n asymmetries into the toroidal distribution of ferromagnetic material, similar to the ITER test blanket module toroidal asymmetry, changes the phase preference of rotating modes; meanwhile, a similar change in purely conducting material does not significantly change the mode's phase preference.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Status of ProtoDUNE Dual Phase

The Deep Underground Neutrino Experiment (DUNE) is a dual-site experiment for long baseline neutrino oscillation studies, and for neutrino astrophysics and nucleon decay searches. DUNE will comprise four 10 kton fiducial liquid argon time-projection-chamber (LAr TPC) modules placed at the Sanford Underground Research Facility (South Dakota, USA). One of these modules will profit form the dual phase (DP) technology where the charge is extracted, amplified, and detected in gaseous argon above the liquid surface allowing a fine readout pitch, a low energy threshold, and good pattern reconstruction of the events. To gain experience in building and operating such a large-scale DP LAr detector, a prototype is currently being assembled at the CERN Neutrino Platform. The ProtoDUNE-DP detector consists of a 6x6x6 m3 LAr TPC and commissioning started in Summer 2019.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1979

A study of scattering, production, and stimulated emission of sound by vortex flows

The basic theory of aeroacoustics of homentropic fluid media is applied to the problems of sound scattering, production, and stimulated emission. A general theory of scattering from low speed three-dimensional vortex flows is presented. Specific results are given for the horseshoe vortex and vortex ring. The noise of an elementary corotating vortex pair in various flows is calculated. It is shown that a potential flow and shear flow can substantially increase the basic pair noise. Small reverse shears can annihilate vortex pairs and eliminate the pair noise mechanism. The pair results are used to explain qualitatively the operation of noise suppression devices. The stimulated emission of a single vortex pair and four and six vortex arrays is demonstrated. The results for six vortices illustrate how external pure tones can amplify the broadband noise of a jet in agreement with recent experimental evidence.

Yates, J. E.↗
NASA NTRS1985

60 GHz low noise wideband receiver

The printed circuit and GaAs beam lead technology-based, low noise integrated receiver presented was developed for low cost space communications and operates in the 59-64 GHz range, using a phase-locked Gunn oscillator at 51.5 GHz. An IF output of 7.5-12.5 GHz is obtained. With the exception of the IF amplifier, and of the E-plane technology-based RF preselect filter, all circuits of the device employ suspended stripline construction.

Knust-Graichen, R. A.↗
NASA NTRS1993

Development of a cryogenic hydrogen maser at the NPL

A prototype Cold Hydrogen Maser (CHM) was being developed for the past year. The features of this CHM, which is designed to operate initially at 4.2 K, are the use of low loss alumina, and later sapphire, in the fabrication of the microwave cavity; possible use of superconductors for shielding; use of a cryogenic amplifier; possible coating material; and a reliable RF discharge circuit for the dissociation of hydrogen. A numerical simulation was performed to find the dimensions of the microwave cavity for the TE011 mode and the model was confirmed experimentally. The system will be used to test various wall coatings adsorbed on top of a PTFE buffer underlayer. The CHM is expected to be used as a flywheel frequency standard at the NPL with medium-term stability of one part in 10(exp 14) or better.

Mossavati, R.↗
NASA NTRS2015

Inflatable Antenna for CubeSat: Extension of the Previously Developed S-Band Design to the X-Band

The inflatable antenna for CubeSat is a 1 meter antenna reflector designed with one side reflective Mylar, another side clear Mylar with a patch antenna at the focus. The development of this technology responds to the increasing need for more capable communication systems to allow CubeSats to operate autonomously in interplanetary missions. An initial version of the antenna for the S-Band was developed and tested in both anechoic chamber and vacuum chamber. Recent developments in transceivers and amplifiers for CubeSat at X-band motivated the extension from the S-Band to the X-Band. This paper describes the process of extending the design of the antenna to the X-Band focusing on patch antenna redesign, new manufacturing challenges and initial results of experimental tests.

Babuscia, Alessandra↗
NASA NTRSDate not supplied

Thermally Conductive Melt-Processable Polyimide HBN Micro-Composites for High Temperature Electrical Insulation Applications

Thermoplastic polymers exhibit excellent dielectric properties and manufacturing robustness. These properties mark thermoplastics as competitive material candidates for electrical insulation applications. However, the high-temperature performance of most thermoplastics is insufficient to meet the electrical wiring requirements for next-generation air and space transportation engineering designs, with continuous operation temperature requirements of up to 200 °C among other design requirements. Furthermore, the low thermal conductivity (κ) of polymers as a material class leads to heat trapping within wires which can amplify thermal stresses. As a result, there is a need to investigate candidate thermoplastic systems for their high temperature, dielectric, and κ performance.

polyimide↗
DOE OSTI2022

Fully differential rail-to-rail output amplifier with inverter-based input pair

A fully differential rail-to-rail-output amplifier includes a differential input inverter pair, folded cascode pair, class AB control pair, and class AB output rail-to-rail pair. A drain associated with the folded cascode pair is operatively coupled to the class AB control pair, and the drain associated with the folded cascode pair is unconnected to the current source associated with the class AB control pair. A method of providing fully differential rail-to-rail-output amplification includes coupling a folded cascode pair operatively to a differential input inverter pair, coupling a drain associated with the folded cascode pair operatively to a class AB control pair, and coupling a class AB output rail-to-rail pair operatively to the class AB control pair.

Dabrowski, Mieczyslaw M.↗
NASA NTRS2001

The HP 85192B EEFet3 GaAs FET Nonlinear Model Used in the High Efficiency Microwave Power Amplifier (HEMPA)

Most nonlinear circuit analysis programs that exist today were designed primarily for transient analysis. By incorporating more accurate models in simulation programs, accurate predictions of GaAs field effect transistors (FET) behavior can be accomplished. However, should the designer need to simulate GaAs FETs that operate at high DC-to-RF conversion efficiencies, a more sophisticated model is needed. A relevant and appropriate method is called harmonic-balance, as described by Quere et al.

Sims, William Herbert, III↗
NASA NTRS1987

Advanced Components for Spaceborne Infrared Astronomy

Basic improvements in the technology of low noise read-out systems for low background detectors were demonstrated. Using discrete JFET integrating amplifiers at their optimum temperature of 55 K, read noise less than 7.5 electrons in 128 seconds of integration was obtained. Two models of single channel integrators are now available, the JF-77 for use between 50 and 80 K and the JF-4 for lower temperatures. A 1 x 15 linear array of complete integrators on a single integrated circuit was developed and will be made available in the near future. The successful operation of a superconducting stepper motor was demonstrated. The motor shows a three fold increase in torque over conventional motors operating at room temperature. The success of the motor stems from the use of superconducting coils in conjunction with developments in bearings for cryogenic use, rare-earth rotors, and motor cooling techniques. The current state of development will allow the rapid development of motors optimized for specific applications. An electronic switch capable of resetting cooled JFET integrating amplifiers was developed. The JFET integrating amplifiers that use this switch have demonstrated read noise of less than 10 electrons. The JFET reset device exhibits an extremely high open impedance and low leakage current. Capacitance is sufficiently low so as not to impair amplifier sensitivity. The effects of transient switching charges are minimized by a compensation technique and variable transient current problems inherent to devices of this type are overcome by external circuity.

Davidson, Arnold W.↗
DOE OSTI2017

The electronics, trigger and data acquisition system for the liquid argon time projection chamber of the DarkSide-50 search for dark matter

The DarkSide-50 experiment at the Laboratori Nazionali del Gran Sasso is a search for dark matter using a dual phase time projection chamber with 50 kg of low radioactivity argon as target. Light signals from interactions in the argon are detected by a system of 38 photo-multiplier tubes (PMTs), 19 above and 19 below the TPC volume inside the argon cryostat. We describe the electronics which processes the signals from the photo-multipliers, the trigger system which identifies events of interest, and the data-acquisition system which records the data for further analysis. The electronics include resistive voltage dividers on the PMTs, custom pre-amplifiers mounted directly on the PMT voltage dividers in the liquid argon, and custom amplifier/discriminators (at room temperature). After amplification, the PMT signals are digitized in CAEN waveform digitizers, and CAEN logic modules are used to construct the trigger, the data acquisition system for the TPC is based on the Fermilab "artdaq" software. The system has been in operation since early 2014.

Agnes, P.↗
DOE OSTI2026

The critical role of soil moisture in compound hazards

Soil moisture regulates the exchange of energy, water, and carbon across land–vegetation–atmosphere interfaces. Extremes in soil moisture can amplify natural hazards through interactions with diverse Earth system processes. Despite its mechanistic importance, soil moisture remains underrepresented in hazard research and predictive frameworks. Here, in this study, we review our current understanding of the role of soil moisture in the evolution and onset of diverse compound hazards by synthesizing the latest findings from observational and modelling studies. We highlight key soil moisture mechanisms, including atmospheric feedbacks that amplify drought–heatwave–wildfire events, precipitation couplings that promote clustered storms, and threshold responses that drive vegetation die-offs, trigger landslides, and induce flooding. Persistent challenges in observational data, model representation and operational implementation have limited the integration of soil moisture into hazard early-warning systems. Addressing these gaps through advances in observations, data assimilation, and physics-based and data-driven modelling will enhance hazard prediction and preparedness in a rapidly changing world.

Li, Chuxuan [University of California, Los Angeles↗
DOE OSTI2017

Cross-plane Thermoelectric and Thermionic Transport across Au/ h -BN/Graphene Heterostructures

Here, the thermoelectric voltage generated at an atomically abrupt interface has not been studied exclusively because of the lack of established measurement tools and techniques. Atomically thin 2D materials provide an excellent platform for studying the thermoelectric transport at these interfaces. Here, we report a novel technique and device structure to probe the thermoelectric transport across Au/ h -BN/graphene heterostructures. An indium tin oxide (ITO) transparent electrical heater is patterned on top of this heterostructure, enabling Raman spectroscopy and thermometry to be obtained from the graphene top electrode in situ under device operating conditions. Here, an AC voltage V(ω) is applied to the ITO heater and the thermoelectric voltage across the Au/ h -BN/graphene heterostructure is measured at 2ω using a lock-in amplifier. We report the Seebeck coefficient for our thermoelectric structure to be –215 μV/K. The Au/graphene/ h -BN heterostructures enable us to explore thermoelectric and thermal transport on nanometer length scales in a regime of extremely short length scales. The thermoelectric voltage generated at the graphene/ h -BN interface is due to thermionic emission rather than bulk diffusive transport. As such, this should be thought of as an interfacial Seebeck coefficient rather than a Seebeck coefficient of the constituent materials.

42 ENGINEERING↗
DOE OSTI2020

III/V silicon hybrid laser based on a resonant Bragg structure

We demonstrate a laser tunable in intensity with gigahertz tuning speed based on a III/V reflective semiconductor optical amplifier (RSOA) coupled to a silicon photonic chip. The silicon chip contains a Bragg-based Fabry–Perot resonator to form a passive bandpass filter within its stopband to enable single-mode operation of the laser. We observe a side mode suppression ratio of 43 dB, linewidth of 790 kHz, and an optical output power of 1.65 mW around 1530 nm. We also investigate using a micro-ball lens as an alternative coupling method between the RSOA and the silicon chip.

Davis, Jordan A. (ORCID:0000000343483295)↗
DOE OSTI2024

On Forced RF Generation of CW Magnetrons for SRF Accelerators

CW magnetrons, initially developed for industrial RF heaters, were suggested to power RF cavities of superconducting accelerators due to their higher efficiency and lower cost than traditionally used klystrons, IOTs or solid-state amplifiers. RF amplifiers driven by a master oscillator serve as coherent RF sources. CW magnetrons are regenerative RF generators with a huge regenerative gain. This causes regenerative instability with a large noise when a magnetron operates with the anode voltage above the threshold of self-excitation. Traditionally for stabilization of magnetrons is used injection locking by a quite small signal. Then the magnetron except the injection locked oscillations may generate noise. This may preclude use of standard CW magnetrons in some SRF accelerators. Recently we developed briefly described below a mode for forced RF generation of CW magnetrons when the magnetron startup is provided by the injected forcing signal and the regenerative noise is suppressed. The mode is most suitable for powering high Q-factor SRF cavities.

43 PARTICLE ACCELERATORS↗