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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

THz Spectroscopy of the Atmosphere

THz spectroscopy of the atmosphere has been driven by the need to make remote sensing measurements of OH. While the THz region can be used for sensitive detection on many atmospheric molecules, the THz region is the best region for measuring the diurnal behavior of stratospheric OH by remote sensing. The infrared region near 3 microns suffers from chemiluminescence and from spectral contamination due to water. The ultraviolet region near 300 nm requires solar illumination. The three techniques for OH emission measurements in the THz region include Fourier Transform interferometry, Fabry-Perot interferometry, and heterodyne radiometry. The first two use cryogenic direct detectors while the last technique uses a local oscillator and a mixer to down convert the THz signal to GHz frequencies. All techniques have been used to measure stratospheric OH from balloon platforms. OH results from the Fabry-Perot based FILOS instrument will be given. Heterodyne measurement of OH at 2.5 THz has been selected to be a component of the Microwave Limb Sounder on the Earth Observing System CHEM-1 polar satellite. The design of this instrument will be described. A balloon-based prototype heterodyne 2.5 THz radiometer had its first flight on, 24 May 1998. Results form this flight will be presented.

Pickett, Herbert M.↗
DOE OSTI2022

High Carrier Lifetimes in Epitaxial Germanium-Tin/Al(In)As Heterostructures with Variable Tin Compositions

Group IV-based germanium-tin (Ge1-ySny) compositional materials have recently shown great promise for infrared detection, light emission and ultra-low power transistors. High carrier lifetimes are desirable for enhancing the detection limit and efficiency of photodetectors, low threshold current density in lasers, and low tunneling barrier height by lowering defects and dislocations at the heterointerface of a source and a channel. Here, carrier lifetimes in epitaxial germanium (Ge) and variable tin (Sn) compositional Ge1-ySny materials were experimentally determined on GaAs substrates using the contactless microwave photoconductive decay (u-PCD) technique at an excitation wavelength of 1500 nm. Sharp (2 x 2) reflection high energy electron diffraction patterns and low surface roughness were observed from the surface of the Ge0.97Sn0.03 epilayer. X-ray rocking curves from Ge0.97Sn0.03 and Ge0.94Sn0.06 layers demonstrated the pseudomorphic and lattice-matched growth on AlAs and In0.12Al0.88As buffers, respectively, further substantiated by reciprocal space maps and abrupt heterointerfaces evident from the presence of Pendellosung oscillations. High effective carrier lifetimes of 150 ns to 450 ns were measured for Ge1-ySny epilayers as a function of Sn composition, surface roughness, growth temperature, and layer thickness. The observed increase in the carrier lifetime with an increasing Ge layer thickness and a reducing surface roughness, by incorporating Sn, were explained. The enhancement of the carrier lifetime with an increasing Sn concentration was achieved by controlling the defects with lattice-matched Ge0.94Sn0.06/In0.12Al0.88As heterointerfaces or the pseudomorphic growth of Ge0.94Sn0.06 on GaAs. Therefore, our monolithic integration of variable Sn alloy compositional Ge1-ySny materials with high carrier lifetimes opens avenues to realize electronic and optoelectronic devices.

carrier lifetimes↗
DOE OSTI2025

DESI 2024: Constraints on physics-focused aspects of dark energy using DESI DR1 BAO data

Baryon acoustic oscillation data from the first year of the Dark Energy Spectroscopic Instrument (DESI) provide near percent-level precision of cosmic distances in seven bins over the redshift range z=0.1–4.2. Here, this paper is the follow-up to the original DESI BAO cosmology paper [A. G. Adame et al. (DESI Collaboration), arXiv:2404.03002], which considered the conventional w 0 w a cold dark matter (CDM) model. We use the novel DESI data, together with other cosmic probes, to constrain the background expansion history using some well-motivated physical classes of dark energy. In particular, we explore three physics-focused behaviors of dark energy from the equation of state and energy density perspectives: the thawing class (matching many simple quintessence potentials), emergent class (where dark energy comes into being recently, as in phase transition models), and mirage class [where phenomenologically the distance to cosmic microwave background (CMB) last scattering is close to that from a cosmological constant Λ despite dark energy dynamics]. All three classes fit the data at least as well as Λ ⁢CDM, and indeed can improve on it by Δ⁢χ 2 ≈ –5 to –17 for the combination of DESI BAO with CMB and supernova data while having one more parameter. The mirage class does essentially as well as w 0 ⁢w a CDM and exhibits moderate to strong Bayesian evidence preference with respect to Λ⁢ CDM. These classes of dynamical behaviors highlight worthwhile avenues for further exploration into the nature of dark energy.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2000

Current Status of Thin Film (Ba,Sr)TiO3 Tunable Microwave Components for RF Communications

The performance of proof-of-concept ferroelectric microwave devices has been moving steadily closer to the level needed for satellite and other rf communications applications. This paper will review recent progress at NASA Glenn in developing thin film Ba(x)Sr(1-x)TiO3 tunable micro-wave components for these applications. Phase shifters for phased array antennas, tunable filters and tunable oscillators employing microstrip and coupled microstrip configurations will be presented. Tunabilities, maximum dielectric constants, and phase shifter parameters will be discussed (e.g., coupled microstrip phase shifters with phase shift over 200 deg at 18 GHz and a figure of merit of 74.3 deg/dB). Issues of post-annealing, Mn-doping and Ba(x)Sr(1-x) TiO3 growth on sapphire and alumina substrates will be covered. The challenges of incorporating these devices into larger systems, such as yield, variability in phase shift and insertion loss, and protective coatings will also be addressed.

VanKeuls, F. W.↗
DOE OSTI2021

On the halo-mass and radial scale dependence of the lensing is low effect

ABSTRACT The canonical Lambda cold dark matter (ΛCDM) cosmological model makes precise predictions for the clustering and lensing properties of galaxies. It has been shown that the lensing amplitude of galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS) is lower than expected given their clustering properties. We present new measurements and modelling of galaxies in the BOSS LOWZ sample. We focus on the radial and stellar mass dependence of the lensing amplitude mismatch. We find an amplitude mismatch of around $35{{\ \rm per\ cent}}$ when assuming ΛCDM with Planck Cosmological Microwave Background (CMB) constraints. This offset is independent of halo mass and radial scale in the range Mhalo ∼ 1013.3−1013.9h−1 M⊙ and $r=0.1\!-\!60 \, h^{-1} \mathrm{Mpc}$ ($k \approx 0.05\!-\!20 \, h \, {\rm Mpc}^{-1}$). The observation that the offset is both mass and scale independent places important constraints on the degree to which astrophysical processes (baryonic effects, assembly bias) can fully explain the effect. This scale independence also suggests that the ‘lensing is low’ effect on small and large radial scales probably have the same physical origin. Resolutions based on new physics require a nearly uniform suppression, relative to ΛCDM predictions, of the amplitude of matter fluctuations on these scales. The possible causes of this are tightly constrained by measurements of the CMB and of the low-redshift expansion history.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1971

Research investigation directed toward extending the useful range of the electromagnetic spectrum

The lifetimes and fine structure of He(-) were studied using time-of-flight techniques and quenching by a static axial magnetic field. Using level-crossing spectroscopy the hyperfine constants A and B and the lifetime of the 3 2P3/2 state of Li-7 were measured. Polarization of the Ru 7S level was created as a first step in determining the hyperfine structure of the alkali excited S state. The parametric interaction between light and microwaves in optically pumped Rb-87 vapor were investigated. Measurements and analyses of transitions in formaldehyde and its isotopic species and in the lowest two excited vibrational states of H2CO were also made, as well as of transitions in furan, pyrrole, formic acid, and cyanoacetylene. The Hanle effect was studied in the NO molecule, and RF oscillators were developed with flat, wideband output to observe excited state hyperfine transitions at zero field. Data was generated on the time-dependent behavior of photon echoes in ruby. Stimulated Raman scattering was studied in atomic Tl vapor. A Q switched, temperature-tuned ruby laser was developed which operates between 6934 and 6938 A. The frequency shift due to resonant interaction between identical radiating atoms was calculated.

Hartmann, S. R.↗
NASA NTRS1998

Baseline Observations of Hemispheric Sea Ice with the Nimbus 7 Scanning Multichannel Microwave Radiometer

The Scanning Multichannel Microwave Radiometer (SMMR) on board the NASA Nimbus 7 satellite was designed to obtain data for sea surface temperatures (SSTs), near-surface wind speeds, sea ice coverage and type, rainfall rates over the oceans, cloud water content, snow water equivalent, and soil moisture. In this paper, I shall emphasize the sea ice observations and mention briefly some important SST observations. A prime factor contributing to the importance of SMMR sea ice observations lies in their successful integration into a long-term time series, presently being extended by observations from the series of Special Sensor Microwave/Imager (SSMI) on board the DOD/DMSP F8, Fl1, and F12 satellites. This currently constitutes a 19-year data set. Almost half of this was provided by the SMMR. Unfortunately, the 4-year data set produced earlier by the single-channel Electrically Scanned Microwave Radiometer (ESMR) was not successfully integrated into the SMMR/SSMI data set. This resulted primarily from the lack of an overlap period to provide intersensor adjustment, but also because of the large difference between the algorithms to produce ice concentrations and large temporal gaps in the ESMR data. The lack of overlap between the SeaSat and Nimbus 7 SMMR data sets was an important consideration for also excluding the SeatSat one, but the spatial gaps especially in the Southern Hemisphere daily SeaSat observations was another. The sea ice observations will continue into the future by means of the Advanced Microwave Scanning Radiometer (AMSR) on board the ADEOS II and EOS satellites due to be launched in mid- and late-2000, respectively. Analysis of the sea ice data has been carried out by a number of different techniques. Long-term trends have been examined by means of ordinary least squares and band-limited regression. Oscillations in the data have been examined by band-limited Fourier analysis. Here, I shall present results from a novel combination of Principal Component analysis and the recently-developed Empirical Mode Decomposition (EMD). In this method, the data are first separated into spatial and temporal parts, and then the temporal parts of the first few PCs are broken into intrinsic modes by the EMD method.

Gloersen, Per↗
DOE OSTI2026

Nonequilibrium dynamics of two-level systems directly after cryogenic alternating bias

Two-level systems (TLSs) are a dominant decoherence mechanism in superconducting qubits, microwave kinetic inductance detectors, and quantum dots. TLSs are tunneling states commonly found in amorphous materials and interfaces, which interact electromechanically, leading to energy loss. Fluctuations in the frequency of the TLSs are a significant problem for qubit operation and force recalibration every few hours. In this study, we probe the effect of alternating bias at cryogenic temperatures on TLSs in a purpose-built LC oscillator. When an in situ alternating bias is applied, the steady-state spectra of the TLSs disappear. Spectroscopy reveals transient behavior, in which the TLS frequency fluctuates on the order of minutes. Thermal cycling above 10 K reverses these effects, restoring the TLS spectrum to its original state. Importantly, the intrinsic loss tangent of the LC oscillator remains unchanged before and after the application of the alternating bias. We propose that the disappearance of the steady-state spectrum is caused by nonequilibrium energy buildup from strain in the oxide film introduced by the pulsed voltage-bias sequence. Understanding this nonequilibrium energy could shed light on TLS fluctuations and reduce the calibration requirements for qubits.

general physics↗
DOE OSTI2025

Millimeter-Wave Superconducting Qubit

Manipulating the electromagnetic spectrum at the single-photon level is fundamental for quantum experiments. In the visible and infrared ranges, this can be accomplished with atomic quantum emitters, and with superconducting qubits such control is extended to the microwave range (below 10 GHz). Meanwhile, the region between these two energy ranges presents an unexplored opportunity for innovation. We bridge this gap by scaling up a superconducting qubit to the millimeter-wave range (near 100 GHz). Working in this energy range greatly reduces sensitivity to thermal noise compared to microwave devices, enabling operation at significantly higher temperatures, up to 1 K. This has many advantages by removing the dependence on rare 3⁢ He for refrigeration, simplifying cryogenic systems, and providing orders-of-magnitude higher cooling power, lending the flexibility needed for novel quantum sensing and hybrid experiments. Using low-loss niobium trilayer junctions, we realize a qubit at 72 GHz cooled to 0.87 K using only 4 ⁢He. We perform Rabi oscillations to establish control over the qubit state, and measure relaxation and dephasing times of 15.8 and 17.4 ns, respectively. This demonstration of a millimeter-wave quantum emitter offers exciting prospects for enhanced sensitivity thresholds in high-frequency photon detection, provides new options for quantum transduction and for scaling up and speeding up quantum computing, enables integration of quantum systems where 3 ⁢He refrigeration units are impractical, and, importantly, paves the way for quantum experiments exploring a novel energy range.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

DESI 2024 VII: cosmological constraints from the full-shape modeling of clustering measurements

We present cosmological results from the measurement of clustering of galaxy, quasar and Lyman-α forest tracers from the first year of observations with the Dark Energy Spectroscopic Instrument (DESI Data Release 1). We adopt the full-shape (FS) modeling of the power spectrum, including the effects of redshift-space distortions, in an analysis which has been thoroughly validated in a series of supporting papers as summarised in [1]. We combine the full-shape information with DESI's DR1 constraints from the baryon acoustic oscillations (BAO) of these tracers. In the flat ΛCDM cosmological model, DESI (FS+BAO), combined with a baryon density prior from Big Bang Nucleosynthesis and a weak prior on the scalar spectral index, determines matter density to Ω m = 0.2962 ± 0.0095, and the amplitude of mass fluctuations to σ 8 = 0.842 ± 0.034. The addition of the cosmic microwave background (CMB) data tightens these constraints to Ω m = 0.3056 ± 0.0049 and σ 8 = 0.8121 ± 0.0053, while further addition of the joint clustering and lensing analysis from the Dark Energy Survey Year-3 (DESY3) data further improves these measurements, and leads to a 0.4% determination of the Hubble constant, H 0 = (68.40 ± 0.27) km s -1 Mpc -1 . In models with a time-varying dark energy equation of state parametrised by w 0 and w a , combinations of DESI (FS+BAO) with CMB and type Ia supernovae continue to show the preference, previously found in the DESI DR1 BAO analysis, for w 0 > -1 and w a < 0 with similar levels of significance. DESI data, in combination with the CMB, improve the upper limits on the sum of the neutrino masses relative to the case when only the DR1 BAO was available, giving ∑m ν < 0.071 eV at 95% confidence. We finally constrain deviations from general relativity represented by two modified gravity parameters. DESI (FS+BAO) data alone measure the parameter that controls the clustering of massive particles, μ 0 = 0.11 +0.45 -0.54 , in agreement with the zero value predicted by general relativity. The combination of DESI with the CMB and the clustering and lensing analysis from DESY3 constrains both modified-gravity parameters, giving μ 0 = 0.04 ± 0.22 and Σ 0 = 0.044 ± 0.047, again in agreement with general relativity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

GALILEO: Galactic Axion Laser Interferometer Leveraging Electro-Optics

We propose a novel experimental method for probing light dark matter candidates. We show that an electro-optical material’s refractive index is modified in the presence of a coherently oscillating dark matter background. A high-precision resonant Michelson interferometer can be used to read out this signal. The proposed detection scheme allows for the exploration of an uncharted parameter space of dark matter candidates over a wide range of masses—including masses exceeding a few tens of microelectronvolts, which is a challenging parameter space for microwave cavity haloscopes. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1993

The MRIS feasibility study

The Microwave Reflectometer Ionization Sensor (MRIS) is an instrument being developed for use in detecting and ranging of electron density layers in the reentry plasma of a space transfer vehicle. The rationale for the selection of the Double Sideband Suppressed Carrier (DSBSC) system used in the feasibility study for the MRIS is presented. A 25 GHz single-oscillator system and a 220 GHz double-oscillator system are described. The 25 GHz system was constructed and tested in the laboratory and test results are presented. As developed, the system employs a sideband spacing of 160 MHz. Based on an estimated electromagnetic wave velocity in the plasma, a round-trip phase shift measurement accuracy of +/- 7.6 degrees was required for the desired +/- 1/2 cm distance measurement accuracy. The interaction of parallel ground and reflecting planes produces interference that prevents the basic DSBSC system from meeting the accuracy goal so a frequency modulation was added to the system to allow averaging of the measured phase deviation. With an FM deviation of +/- 1 GHz, laboratory measurements were made for distances from 5 to 61 cm tip free space. Accounting for the plasma velocity factor, 82 percent of the data were equal to or better than the desired accuracy. Based on this measured result a sideband spacing to 250 MHz could be expected to yield data approximately 96 percent within the accuracy goal.

Neece, Robert T.↗
NASA NTRS1998

Variablility of Fram Strait Ice Flux

We estimate the winter sea ice export through the Fram Strait using ice motion from satellite passive microwave data. Sea ice motion (October through May)is obtained by tracking the displacement of common features in sequential 85 GHz and 37 GHz brightness temperature fields.

Fram Strait Ice Flux North Atlantic Oscillation↗
NASA NTRS2013

Improved Understanding of the Modeled QBO Using MLS Observations and MERRA Reanalysis

The Quasi-Biennial Oscillation (QBO) dominates the variability of the tropical stratosphere on interannual time scales. The QBO has been shown to extend its influence into the chemical composition of this region through dynamical mechanisms. We have started our analysis using the realistic QBO internally generated by the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 33 years. We will show targeted comparisons with observations from NASAs Aura satellite Microwave Limb Sounder (MLS) and the Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis to provide insight into the simulation of the primary and secondary circulations associated with the QBO. Using frequency spectrum analysis and multiple linear regression we can illuminate the resulting circulations and deduce the strengths and weaknesses in their modeled representation. Inclusion of the QBO in our simulation improves the representation of the subtropical barriers and overall tropical variability. The QBO impact on tropical upwelling is important to quantify when calculating trends in sub-decadal scale datasets.

MERRA↗
DOE OSTI2021

Singling out modified gravity parameters and data sets reveals a dichotomy between Planck and lensing

ABSTRACT An important route to testing general relativity (GR) at cosmological scales is usually done by constraining modified gravity (MG) parameters added to the Einstein perturbed equations. Most studies have analysed so far constraints on pairs of MG parameters, but here, we explore constraints on one parameter at a time while fixing the other at its GR value. This allows us to analyse various models while benefiting from a stronger constraining power from the data. We also explore which specific data sets are in tension with GR. We find that models with (μ = 1, η) and (μ, η = 1) exhibit a 3.9σ and 3.8σ departure from GR when using Planck18 + Supernovae type Ia (SNe) + Baryon acoustic oscillation (BAO), while (μ, η) shows a tension of 3.4σ. We find no tension with GR for models with the MG parameter Σ fixed to its GR value. Using a Bayesian model selection analysis, we find that some one-parameter MG models are moderately favoured over ΛCDM when using all data set combinations except Planck cosmic microwave background lensing and dark energy survey data. Namely, Planck18 shows a moderate tension with GR that only increases when adding any combination of redshift space distortion, SNe, or BAO. However, adding lensing diminishes or removes these tensions, which can be attributed to the ability of lensing in constraining the MG parameter Σ. The two overall groups of data sets are found to have a dichotomy when performing consistency tests with GR, which may be due to systematic effects, lack of constraining power, or modelling. These findings warrant further investigation using more precise data from ongoing and future surveys.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2019

Tropopause Laminar Cirrus and Its Role in the Lower Stratosphere Total Water Budget

Laminar cirrus are thin, extensive, isolated layers of ice clouds frequently observed in the tropical tropopause layer. Widespread laminar cirrus significantly affects tropical tropopause layer total water and thermal budget. In this study, we extract laminar cirrus from the Cloud‐Aerosol Lidar with Orthogonal Polarization Level 1 attenuated total backscatter images for January 2009, in order to characterize statistical properties of laminar cirrus cloud length, base, thickness, optical depth, and layer partial ice water path. These characteristics are used to develop an algorithm identifying laminar cirrus automatically from the Cloud‐Aerosol Lidar with Orthogonal Polarization Level 2 layer product for 2008–2017. The nearly 10‐year records reveal that tropopause laminar cirrus occurrence (30–40% of total cirrus) is strongly anticorrelated with the tropopause temperatures in that colder tropopause in frequent (super)saturation during boreal winter favors in situ formation of clouds. Interannually, anomalously warmer troposphere temperature (ΔT), easterly shear of the quasi‐biennial oscillation, and stronger upwelling branch of the Brewer‐Dobson circulation enhance laminar cirrus formation via cooling of the tropopause. The tropopause laminar cirrus carries ~0.05 mg/m(exp 3) (~0.5 ppmv) of ice water content during boreal winter and <0.01 mg/m(exp 3) during summer, which is anticorrelated with the seasonal variations of water vapor (H2O) observed by the Microwave Lime Sounder, indicating a temperature‐regulated partition between vapor and ice. Interannually, in cirrus‐rich region 1 ppmv decrease in H2O corresponds to 0.2–0.3 ppmv increase in ice water content. Frequently situated in (super)saturated air, tropopause laminar cirrus are likely to survive multiple lifecycles of the sublimation‐deposition processes, and may contribute up to 10% to the total water budget in the lower stratosphere. Satellites constantly observe thin, isolated, extensive layer of cirrus around the tropopause. The so‐called “laminar” cirrus occurrence and their ice amount are strongly regulated by temperature, such that colder temperatures favor more frequent (super)saturation, which results in more frequent laminar cirrus with more ice amount and therefore less water vapor. In this study we analyze laminar cirrus and water vapor from the Cloud‐Aerosol Lidar with Orthogonal Polarization and Microwave Lime Sounder observations, and hypothesize that laminar cirrus could act as an important transient water storage and contribute to the total water budget in the lower stratosphere.

Tao Wang↗
NASA NTRS1977

Low-noise receivers: Microwave maser development

An S-Band traveling-wave maser with a 2260- to 2400-MHz tuning capability has been built and installed on the 26-m antenna. The traveling-wave maser closed cycle refrigerator package was assembled within a limited time schedule and at low cost to meet the requirements of the very long baseline interferometry validation task. The maser uses a superconducting magnet with a field staggering coil for gain/bandwidth adjustment. The maser pump source is a Gunn effect oscillator with the capability of continuous tuning throughout the entire maser tuning range. The package was assembled from surplus components that have been used previously in the Deep Space Network in a variety of applications.

Quinn, R.↗
NASA NTRS2007

Compact Microwave Mercury Ion Clock for Deep-Space Applications

We have recently completed a breadboard ion-dock physics package based on Kg ions shuttled between a quadrupole and a 16-pole rf trap. With this architecture we have demonstrated short-term stability -1-2xl0-13 at 1 second, averaging to 10-15 at 1 day. This development shows that 8- maser quality stabilities can be produced in a small clock package, comparable in size to an oItra-stable quartz oscillator required for holding 1-2xl0-13 at 1 second. This performance was obtained in a sealed vacuum configuration where only agetter pump was used to maintain vacuum. The vacuum tube containing the traps has now been onder sealed vacuum conditions for nearly two years with no measurable degradation of ion trapping lifetimes or clock short-term performance. We have fabricated the vacuum tube, ion trap and UV windows from materials that will allow a - 400 C tube bake-out to prepare for tube sealoff. This approach to the vacuum follows the methods used in mght vacuum tube electronics, such as flight TWTA's where tube operation lifetime and shelf life of up to 15 years is achieved. We use neon as a buffer gas with 2-3 times less pressure induced frequency pulling than helium and, being heavier, negligable diffusion losses will occur over the operation lifetime.

space clock↗