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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Optically pumped polarized 3 He ++ ion source development for RHIC/EIC

The proposed polarized 3 He ++ acceleration in RHIC and the future Electron-Ion Collider will require about 2×10 11 ions in the source pulse. A new technique had been proposed for production of high intensity polarized 3 He ++ ion beams. It is based on ionization and accumulation of the 3 He gas (polarized by metastability-exchange optical pumping and in the 5T high magnetic field) in the existing Electron Beam Ion Source (EBIS). A novel 3 He cryogenic purification and storage technique was developed to provide the required gas purity. An original gas refill and polarized 3 He gas injection to the EBIS long drift tubes, (which serves as the storage cell) were developed to ensure polarization preservation. An infrared laser system for optical pumping and polarization measurements in the high 3–5 T field has been developed. The 3 He polarization 80–85% (and sufficiently long ~30 min relaxation time) was obtained in the “open” cell configuration with refilling valve tube inlet and isolation valve closed. The development of the spin-rotator and 3 He 4 He absolute nuclear polarimeter at 6 MeV 3 He ++ beam energy is also presented here in this work.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Tin removal by an annular surface wave plasma antenna in an extreme ultraviolet lithography source

Tin contamination of the collector mirror surface remains one of the crucial issues of EUV (Extreme Ultraviolet) sources, directly impacting the availability of the tool. Hydrogen plasma-based tin removal processes employ hydrogen radicals and ions to interact with tin deposits to form gaseous tin hydride (SnH 4 ), which can be removed through pumping. An annular surface wave plasma (SWP) source developed at the University of Illinois—Urbana Champaign is integrated into the cone and perimeter of the collection mirror for in situ tin removal. The SWP is characterized by high ion and radical densities, low electron temperature, and local generation where etching is needed. This method has the potential to significantly reduce downtime and increase mirror lifetime. Radical probe measurements show hydrogen radical densities in the order of 10 19 m -3 , while Langmuir probe measurements show electron temperatures of up to 6 eV and plasma densities on the order of 10 17–18 m -3 . The generated ions are essential to the tin cleaning and have sufficiently low energy to cause no damage to the collector capping layer. Tin etch rates of up to 270 nm/min were observed in a variety of experimental conditions, including various powers, pressures, flowrates, and temperatures. In conclusion, the high etch rates demonstrated in this study exceed the expected contamination rate of the EUV source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2000

Cloudy 94 and Applications to Quasar Emission Line Regions

This review discusses the most recent developments of the plasma simulation code Cloudy and its application to the, emission-line regions of quasars. The longterm goal is to develop the tools needed to determine the chemical composition of the emitting gas and the luminosity of the central engine for any emission line source. Emission lines and the underlying thermal continuum are formed in plasmas that are far from thermodynamic equilibrium. Their thermal and ionization states are the result of a balance of a vast set of microphysical processes. Once produced, radiation must, propagate out of the (usually) optically thick source. No analytic solutions are possible, and recourse to numerical simulations is necessary. I am developing the large-scale plasma simulation code Cloudy as an investigative tool for this work, much as an observer might build a spectrometer. This review describes the current version of Cloudy, version 94. It describes improvements made since the, release of the previous version, C90. The major recent, application has been the development of the "Locally Optimally-Emitting Cloud" (LOC) model of AGN emission line regions. Powerful selection effects, introduced by the atomic physics and line formation process, permit individual lines to form most efficiently only near certain selected parameters. These selection effects, together with the presence of gas with a wide range of conditions, are enough to reproduce the spectrum of a typical quasar with little dependence on details. The spectrum actually carries little information to the identity of the emitters. I view this as a major step forward since it provides a method to handle accidental details at the source, so that we can concentrate on essential information such as the luminosity or chemical composition of the quasar.

Ferland, Gary J.↗
DOE OSTI2021

Polarization-Insensitive Medium-Switchable Holographic Metasurfaces

The adoption of metasurfaces has led to revolutionary advances in holography due to improved compactness, integrability, and performance. Switchable meta-holograms projecting different replay field images in a controllable manner are highly desirable. Still, existing technologies generally rely on the use of polarized light and additional optics to facilitate switching. Consequently, the potential benefits afforded through the use of metasurfaces are limited both by the system complexity and a fixed relationship between the optical input and output. In this manuscript, we demonstrate polarization-insensitive metasurfaces encoding arbitrary and independent holograms, which can be switched between by changing the refractive index of the infiltration medium while maintaining identical illumination conditions. Finally, by sidestepping the requirements for high-performance light sources, switching optics, or delicate alignment, this approach points toward ultracompact and cost-effective switchable meta-holograms for various practical applications, such as holographic image projection, eye-perceptible sensors, optical information storage, processing, and security.

36 MATERIALS SCIENCE↗
DOE OSTI2023

AutoFocus: AI-driven alignment of nanofocusing X-ray mirror systems

We describe the application of an AI-driven system to autonomously align complex x-ray-focusing mirror systems, including mirrors systems with variable focus spot sizes. The system has been developed and studied on a digital twin of nanofocusing X-ray beamlines, built using advanced optical simulation tools calibrated with wavefront sensing data collected at the beamline. We experimentally demonstrated that the system is reliably capable of positioning a focused beam on the sample, both by simulating the variation of a beamline with random perturbations due to typical changes in the light source and optical elements over time, and by conducting similar tests on an actual focusing mirror system.

47 OTHER INSTRUMENTATION↗
NASA NTRSDate not supplied

Optical and Near-Infrared Coronagraphy of the Quasar 3C 273

We present preliminary results of our observations of the ultraluminous quasar 3C 273 using the HST/STIS coronagraph and the Keck/NIRC2 vortex coronagraph to provide high-contrast imaging of the inner regions of the host galaxy in the optical and near-infrared. We use reference star differential imaging (RDI) techniques developed for high-contrast imaging of exoplanets and circumstellar disks to observe the morphology of features down to the inner few tenths of arcseconds (inner few 100s of pc) around the quasar point source. Broadband optical (50CORON) coronagraphy with STIS reveals the inner structure of jets and shocks, while Ks-band coronagraphy with NIRC2 suggests the presence of a candidate kpc-scale circumnuclear disk. If confirmed, this disk plays a potentially important role in driving the extreme feedback state of 3C 273 by up-regulating accretion, and its presence is consistent with recent observations of atomic and molecular gas in this system at larger spatial scales. We conclude by discussing potential applications of the observing techniques we applied to 3C 273 to other PSF-dominated systems at moderate redshifts to detect features such as circumnuclear disks and multiple nuclei with direct imaging.

Kevin Fogarty↗
NASA NTRS2011

Contribution of X/Ka VLBI to Multi-Wavelength Celestial Frame Studies

This paper is an update of Sotuela et al. (2011) which improves their simulated Gaia frame tie precision by approximately 10% by adding three additional VLBI observing sessions. Astrometry at X/Ka-band (8.4/32 GHz) using NASAs Deep Space Network has detected 466 quasars with accuracies of 200-300 micro-arc seconds. A program is underway to reduce errors by a factor of 2-3. From our sample, 245 sources have optical magnitudes V less than 20 and should also be detectable by Gaia. A covariance study using existing X/Ka data and simulated Gaia uncertainties for the 345 objects yields a frame tie precision of 10-15 micro-arc seconds (1 - sigma). The characterization of wavelength dependent systematic from extended source morphology and core shift should benefit greatly from adding X/Ka-band measurements to S/X-band (2.3/8.4 GHz) measurements thus helping to constrain astrophysical models of the wavelength dependence of positions.

galaxies↗
NASA NTRS1988

Simultaneous IUE, EXOSAT and optical observations of the unusual AM Her type variable H058+608

Simultaneous observations of the AM Her type variable H0538+608 made with IUE, EXOSAT, and a 1.3 m ground based telescope, and subsequent optical spectrophotometry at high and low resolution are discussed. The X-ray and optical data show clear evidence of a 3.30 + or - 0.03 hr period. Three SWP spectra were taken outside of eclipse and during overlapping phase intervals. The UV spectra contain strong emission lines characteristic of this class of objects and a flat continuum which appears to be deficient, given the brightness of source at optical and X-ray wavelengths. There is evidence for intensity variations in emission lines, particularly C IV. The X-ray light curves for H0538+608 reveal behavior which may be related to irregularities in its accretion flow.

Shrader, C. R.↗
NASA NTRS2012

Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications

The design and initial demonstration of a laser pump module (LPM) incorporating single-mode, grating-stabilized 808-nm diode lasers and a low-loss, high-port-count optical combiner are completed. The purpose of the developed LPM is to reliably pump an Nd:YAG crystal in the laser head (LH), which serves as the optical metrology source for SIMLite mission. Using the narrow-linewidth, single-mode laser diodes enables placement of the pump power near Nd adsorption peak, which enhances pumping efficiency. Grating stabilization allows for stable pump spectra as diode operating temperature and bias current change. The low-loss, high-port-count optical combiner enables efficient combining of tens of pumps. Overall, the module supports 5+ years of continuous operation at 2 W of pump power with reliability approaching 100 percent. The LPM consists of a laser diode farm (LDF) and a pump beam combiner (PBC). An array of 807- to 808-nm fiber-pigtailed laser diodes makes up the LDF. A Bragg grating in each 5- m core single-mode (SM) fiber pigtail acts to stabilize the lasing spectra over a range of diode operating conditions. These commercially available single-mode laser diodes can deliver up to 150 mW of optical power. The outputs from the multiple pumps in the LDF are routed to the PBC, which is a 37-input by 1-output all-fiber device. The input ports consist of 5- m core SM fiber, while the output port consists of 105- m core, 0.15 NA (numerical aperture) multi-mode (MM) fiber. The combiner is fabricated by fusing the 37 input fibers while simultaneously tapering the fused region. At the completion of this process, the MM fiber is spliced to the end of the adiabatic taper, and, for protection, the combiner is sheathed by a capillary tube. A compact and robust metal housing was designed and fabricated to protect the PBC during space deployment.

Erlig, Herman↗
NASA NTRS1991

An X-ray and radio study of steep-spectrum radio sources. II - Four fields from a 22 MHz polar cap survey

Four fields containing radio sources with spectral indices greater than unity at low frequencies have been observed over a wide range of radio wavelengths and at X-ray wavelengths. For most of the steep-spectrum sources no optical identifications have been found to the detection limit of the Palomar Schmidt prints, even with the positional precision of about 1 arcsec from VLA maps. This implies that the associated galaxies or clusters lie at a great distance. X-ray emission was not detected from any of the steep-spectrum radio sources. In one case, an extended source appears to be a radio halo in an uncataloged cluster of galaxies at a redshift of 0.125, and it is suggested that this object is a promising candidate for the detection of inverse Compton X-rays, since it is not a high-luminosity source of thermal X-rays.

Dewdney, P. E.↗
DOE OSTI2021

Functional Principal Component Analysis of Radio–Optical Reference Frame Tie

The Gaia optical reference frame is intrinsically undefined with respect to global orientation and spin, so it needs to be anchored in the radio-based International Celestial Reference Frame (ICRF) to provide a referenced and quasi-inertial celestial coordinate system. The link between the two fundamental frames is realized through two samples of distant extragalactic sources, mostly active galactic nuclei and quasars, but only the smaller sample of radio-loud ICRF sources with optical counterparts is available to determine the mutual orientation. The robustness of this link can be mathematically formulated in the framework of functional principal component analysis using a set of vector spherical harmonics to represent the differences in celestial positions of the common objects. The weakest eigenvectors are computed, which describe the greatest deficiency of the link. The deficient or poorly determined terms are specific vector fields on the sphere that carry the largest errors of absolute astrometry using Gaia in reference to the ICRF. This analysis provides guidelines for the future development of the ICRF maximizing the accuracy of the link over the entire celestial sphere. A measure of the robustness of a least-squares solution, which can be applied to any linear model fitting problem, is introduced to help discriminate between reference frame tie models of different degrees.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2013

Aeronet-based Microphysical and Optical Properties of Smoke-dominated Aerosol near Source Regions and Transported over Oceans, and Implications for Satellite Retrievals of Aerosol Optical Depth

Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad families of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA 0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA 0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savanna at Mongu (Zambia), with average SSA 0.85 in the midvisible. These can serve as candidate sets of aerosol microphysicaloptical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

AERONET↗
NASA NTRS1983

Time-resolved ultraviolet and optical spectroscopy of the pulsating X-ray source H2252-035

UV spectrophotometry and and optical spectroscopy of H2252-035, a close binary featuring a spinning, magnetized star, were carried out with instrumentation on the IUE satellite, in addition to ground-based observations from the Lick Observatory. An excess reddening was determined, with E(B-V) equal to 0.10. The spectrum from 1200-22,000 A was decomposed into a blackbody with a temperature of 13,400 K and a power law wavelength component, where the exponent is 2.74, which fits the excess UV and IR excesses. The exponent value is noted to be amenable to a disk model with a slight curvature because of its finite extent. The emission-line intensities were found to vary by a factor of two, with some of the variations accountable by a modulation in-phase with the optical continuum binary modulation.

Cordova, F. A.↗
DOE OSTI2020

Evaluation of high-stability optical beats in laser chaos by plasmonic photomixing

The stability of optical beats in a chaotically oscillating laser is compared to that of a free-running continuous-wave laser using a highly efficient plasmonic photomixer. Using a chaotically oscillating laser diode, stable optical beats are observed over an operation current range of 60-90 mA. The optical spectra are stable even with frequent mode hopping. In contrast, optical beats in a free-running continuous-wave laser are not stable compared to those of a chaotically oscillating laser, because of intermittent hopping of the laser modes. The high stability of chaotically oscillating lasers makes these lasers promising candidates for optical pump sources in terahertz time-domain spectroscopy systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1981

Optical identification of serendipitous Einstein sources - 19 X-ray-selected active galactic nuclei

The identification of counterparts to 19 serendipitous Einstein Observatory X-ray sources at high galactic latitude is reported. The counterparts are identified as previously uncataloged active galactic nuclei (AGNs) - quasars or Seyfert galaxies - with redshifts varying from z = 0.036 through z = 1.40. The success rate, that is, the fraction of X-ray sources that are identified as AGNs, is approximately 50%, an order of magnitude larger than for traditional ultraviolet surveys. It is expected that this method will produce a large number of X-ray-selected AGNs for statistical studies. For the 19 AGNs in this sample, which is free from the radio selection effects that have complicated previous studies, the X-ray-to-optical-flux slope is found to be 1.30 + or - 0.05.

Chanan, G. A.↗
DOE OSTI2021

High-performance photonic transformers for DC voltage conversion

Abstract Direct current (DC) converters play an essential role in electronic circuits. Conventional high-efficiency DC voltage converters, especially step-up type, rely on switching operation, where energy is periodically stored within and released from inductors and/or capacitors connected in a variety of circuit topologies. Since these energy storage components, especially inductors, are fundamentally difficult to scale down, miniaturization of switching converters proves challenging. Furthermore, the resulting switching currents produce significant electromagnetic noise. To overcome the limitations of switching converters, photonic transformers, where voltage conversion is achieved through light emission and detection processes, have been demonstrated. However, the demonstrated efficiency is significantly below that of the switching converter. Here we perform a detailed balance analysis and show that with a monolithically integrated design that enables efficient photon transport, the photonic transformer can operate with a near-unity conversion efficiency and high voltage conversion ratio. We validate the theory with a transformer constructed with off-the-shelf discrete components. Our experiment showcases near noiseless operation and a voltage conversion ratio that is significantly higher than obtained in previous photonic transformers. Our findings point to the possibility of a high-performance optical solution to miniaturizing DC power converters and improving the electromagnetic compatibility and quality of electrical power.

42 ENGINEERING↗
NASA NTRS1994

Discovery of Be/x-ray stars in two supernova remnants in the Small Magellanic Cloud

We present ROSAT high resolution x-ray images of two previously cataloged supernova remnants in the Small Magellanic Cloud (SMC): 0101-72.4 and 0104-72.3. These remnants were known to show optical, x-ray, and radio emission based on earlier observations: the present data show the first evidence for arcsecond-scale x-ray structure. There is no diffuse x-ray emission associated with the optically emitting shell in 0101-72.4; we set a 3 sigma upper limit of 7 x 10(exp 34) erg s(exp -1) on the 0.02-2 keV luminosity from the region. The x-ray emission comes instead from a weak pointlike object near the limb of the remnant. Optical observations of this source reveal a m(sub v) = 14.8 blue star with H alpha and H beta in emission; we identify this as a Be star in the SMC. No evidence for variability down to time scales of about 1 s was found in the ROSAT data; however, a comparison of the ROSAT and Einstein fluxes indicates possible long term variability by a factor of approximately 2 over several years. The other SNR, 0104-72.3, also contains a pointlike x-ray source with a blue optical counterpart (m(sub v) = 16.7) and H alpha emission. We tentatively identify this as a Be star as well. In addition to the point source there is weak diffuse x-ray emission from 0104-72.3 (L(sub x) approximately 1.4 x 10(exp 35) erg s(exp -1)), but the remnant's appearance in the x-ray band is considerably different from that in either the radio or optical band. We argue for a physical association between the supernova remnants (SNRs) and Be/x-ray stars. A large space velocity (greater than or approximately 100 km s(exp -1)) for the Be/x-ray binaries is required if the explosions that produced the remnants also formed the neutron stars in the binaries. Alternatively, the associations could be the result of common membership in OB associations in the SMC.

Hughes, John P.↗
NASA NTRS1989

The optical counterpart of the X-ray source H0253+193 - A distant, high-luminosity RS Canum Venaticorum system

Optical and near-infrared photometry in the VRIJHK and CO (2.35 microns) bands and optical spectroscopy and polarimetry reveal that the optical counterpart of the X-ray source H0253+193 is most likely a RS CVn binary system. The results show a visual extinction of 11.3 mag to the star, with an IR excess possibly due a cooler binary companion or circumstellar material. It is suggested that the I-band polarization of 8.1 + or - 1.8 may be induced in the starlight by passage through the molecular cloud. The lack of strong H-alpha emission in the optical spectrum argues against the possibility of a classical T Tauri star, and the IR excess argues against a naked T Tauri star. The wide energy spectrum found in the dereddened optical and near-infrared photometry supports the binary star model.

Clemens, Dan P.↗