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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Supernova 1987A

Supernova 1987A (February 23, 1987) in the Large Magellanic Cloud is the brightest supernova to be observed since SN 1604 AD (Kepler). Detection of a burst of neutrinos indicates that a neutron star was formed. Radioactive decay of about 0.07 solar mass of Co-56 is responsible for the observed optical light as well as hard X-rays and gamma-ray lines. Ultraviolet, optical, and infrared 'light echoes' and soft X-rays provide information on the distribution of circumstellar matter and the evolution of the progenitor star.

Mccray, Richard↗
NASA NTRS1994

Lighting considerations in controlled environments for nonphotosynthetic plant responses to blue and ultraviolet radiation

This essay will consider both physical and photobiological aspects of controlled environment lighting in the spectral region beginning in the blue and taken to the normal limit of the solar spectrum in the ultraviolet. The primary emphasis is directed to questions of plant response to sunlight. Measurement and computations used in radiation dosimetry in this part of the spectrum are also briefly treated. Because of interest in the ozone depletion problem, there has been some activity in plant UV-B research and there are several recent reviews available. Some aspects of growth chamber lighting as it relates to UV-B research were covered earlier. Apart from work related to the blue/UV-A receptor, less attention has been given to UV-A responses.

Caldwell, M. M.↗
NASA NTRS2022

Correlated Spatio-temporal Evolution of Extreme-Ultraviolet Ribbons and Hard X-Rays in a Solar Flare

We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet images from the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), magnetic data from the SDO/Helioseismic and Magnetic Imager, hard X-ray (HXR) images from the Reuven Ramaty High Energy Solar Spectroscopic Imager, and light curves from the Fermi/Gamma-ray Burst Monitor, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting nonuniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated nonthermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of nonthermal electrons is highly nonuniform within the flare current sheet. Our results suggest a strong connection between the production of nonthermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects the inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of the reconnecting magnetic flux.

S. J. Naus↗
NASA NTRS2012

The Longitudinal Properties of a Solar Energetic Particle Event Investigated Using Modern Solar Imaging

We use combined high-cadence, high-resolution, and multi-point imaging by the Solar-Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory to investigate the hour-long eruption of a fast and wide coronal mass ejection (CME) on 2011 March 21 when the twin STEREO spacecraft were located beyond the solar limbs. We analyze the relation between the eruption of the CME, the evolution of an Extreme Ultraviolet (EUV) wave, and the onset of a solar energetic particle (SEP) event measured in situ by the STEREO and near-Earth orbiting spacecraft. Combined ultraviolet and white-light images of the lower corona reveal that in an initial CME lateral "expansion phase," the EUV disturbance tracks the laterally expanding flanks of the CME, both moving parallel to the solar surface with speeds of approx 450 km/s. When the lateral expansion of the ejecta ceases, the EUV disturbance carries on propagating parallel to the solar surface but devolves rapidly into a less coherent structure. Multi-point tracking of the CME leading edge and the effects of the launched compression waves (e.g., pushed streamers) give anti-sunward speeds that initially exceed 900 km/s at all measured position angles. We combine our analysis of ultraviolet and white-light images with a comprehensive study of the velocity dispersion of energetic particles measured in situ by particle detectors located at STEREO-A (STA) and first Lagrange point (L1), to demonstrate that the delayed solar particle release times at STA and L1 are consistent with the time required (30-40 minutes) for the CME to perturb the corona over a wide range of longitudes. This study finds an association between the longitudinal extent of the perturbed corona (in EUV and white light) and the longitudinal extent of the SEP event in the heliosphere.

acceleration of particles↗
NASA NTRS1993

Stray-light suppression in a reflecting white-light coronagraph

An analysis of stray-light suppression in the white-light channel of the Ultraviolet Coronagraph Spectrometer experiment for the Solar and Heliospheric Observatory is reported. The white-light channel consists of a reflecting telescope with external and internal occultation and a polarimeter section. Laboratory tests and analytical methods are used to perform the analysis. The various stray-light contributions are classified in two main categories: the contribution from sunlight that passes directly through the entrance aperture and the contribution of sunlight that is diffracted by the edges of the entrance aperture. Values of the stray-light contributions from various sources and the total stray-light level for observations at heliocentric heights from 1.4 to 5 solar radii are derived. Anticipated signal-to-stray-light ratios are presented together with the effective stray-light rejection by the polarimeter, demonstrating the efficacy of the stray-light suppression design.

Romoli, Marco↗
DOE OSTI2020

Optically enhanced patternable photosensitivity via oxygen excitation

A method is disclosed for performing a three dimensional (3D) printing process. The method involves generating a primary light beam having a wavelength sufficient to initiate polymerization of a photoresin, and patterning the primary light beam into a patterned primary beam. The patterned primary beam may be directed toward an ultraviolet (UV) or visible light sensitive photoresin to initiate polymerization of select areas of the photoresin. The photoresin may be illuminated with a secondary light beam having a wavelength of about 765 nm to stimulate triplet oxygen into singlet oxygen, to thus control oxygen inhibition in additional areas bordering the select areas, to control polymerization inhibition in the additional areas bordering the select areas.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Ultraviolet spectroscopy of R Coronae Borealis

Observations of the hydrogen-deficient supergiant R CrB were obtained with the IUE over an interval of 54 days in order to study the nature of this star's irregular, small-amplitude variations in light. By chance, the series of observations coincided with a dip in the light intermediate between the normal fluctuations and the deep declines associated with the formation of an obscuring dust cloud. High-resolution spectra have been used to search for radial velocity variations, while low-resolution spectra yield ultraviolet light curves down to 1810 A. Both types of spectra have been analyzed for indications of temperature changes. It is found that a combination of photospheric temperature variation and variable extinction is necessary to account for the details of the observations. A simple, ad hoc, periodic model is presented in which the amount of obscuring dust varies in proportion to the drop in temperature, but at a later time, reproduces the wavelength dependence of both the amplitudes and phase shifts of the light curves. The radial velocities are consistent with pulsation being responsible for the temperature variation.

Holm, A. V.↗
NASA NTRS1982

Chromospheres of classical Cepheids

The International Ultraviolet Explorer spectra of five classical Cepheids were obtained in the short and the long wavelength regions at low dispersion, curves and emission line strengths were obtained from the low resolution spectra. The amplitudes of the light curves increase with decreasing wavelength except around 1550 A where the amplitude is surprisingly small. The emission line fluxes behave differently in the various stars and it appears that bumps in the ultraviolet light curves are related to the behavior of the chromospheres. However, the strengths of the emission lines are roughly comparable to nonvariable stars of similar temperature and luminosity. The high resolution spectra were used to study the fluxes of the emission from the Mg II h and k lines. It is found that the emission components come and go during the cycles and the behavior differs from one star to another, with generally stronger and more persistent emission at longer periods. This is compared with the times of appearance of the Ca II H and K emission features and provides insight into the way in which the chromosphere reacts to shock waves generated by the pulsation of the star.

Schmidt, E. G.↗
NASA NTRS1990

Aspects of the interstellar medium in starburst galaxies

Researchers are engaged in a multifaceted program to investigate the stellar content and star formation history of actively star-forming galaxies. A large body of stellar spectra have been examined to identify spectral features characteristic of specific stellar types. These spectral diagnostics are then calibrated in terms of temperature (spectral type), gravity (luminosity class) and metallicity. The spectral data is compiled into a stellar library whose members represent specific locations in the HR diagram. Through the use of population synthesis techniques, both optimizing and evolutionary approaches, the stellar luminosity function in composite populations can be determined by analysis of their integrated light. Researchers have concentrated on the ultraviolet wavelength region (lambda lambda 1200 to 3200), utilizing the International Ultraviolet Explorer (IUE) archives supplemented by additional observations. In the optical, virtually all stars will contribute to the integrated light. In the ultraviolet however, cool stars will produce negligible flux due to their steep ultraviolet-to-visual continua, greatly simplifying the investigation of the hot component in a composite population. The researchers' initial stellar library has been applied to several blue compact galaxies, (BCGs), a class of starburst galaxy which is UV luminous. BCGs possess a complex interstellar medium which affects the emergent stellar continuum in several ways. This presents a challenge to the stellar analysis but affords insight into the properties of the gas and dust from which the massive OB stars have formed. The optimizing synthesis method solves for the stellar luminosity function and extinction simultaneously. This therefore provides an independent measure of the extinction affecting the hot population component. Despite the rise of the reddening law towards the ultraviolet, BCGs are found to be brighter in the ultraviolet than expected.

Fanelli, Michael N.↗
NASA NTRS1998

Solid-State Laser Source of Tunable Narrow-Bandwidth Ultraviolet Radiation

A solid-state laser source of tunable and narrow-bandwidth UV light is disclosed. The system relies on light from a diode laser that preferably generates light at infrared frequencies. The light from the seed diode laser is pulse amplified in a light amplifier, and converted into the ultraviolet by frequency tripling, quadrupling, or quintupling the infrared light. The narrow bandwidth, or relatively pure light, of the seed laser is preserved, and the pulse amplifier generates high peak light powers to increase the efficiency of the nonlinear crystals in the frequency conversion stage. Higher output powers may be obtained by adding a fiber amplifier to power amplify the pulsed laser light prior to conversion.

PATENTS↗
NASA NTRS2012

Photoacoustic Optical Properties at UV, VIS, and near IR Wavelengths for Laboratory Generated and Winter Time Ambient Urban Aerosols

We present the laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet wavelength (i.e., 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009 and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM (sub 2.5) and PM( sub 10) (particulate matter with aerodynamic diameters less than 2.5 micrometers and 10 micrometers, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Angstrom exponent of absorption (AEA), and Angstrom exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.

absorptivity↗
NASA NTRS1973

Ultraviolet proximity focussed converters for use in a satellite SEC-TV system.

Performance characteristics of Bendix type BX08025-4522 proximity-focussed vacuum-ultraviolet to visible-light image converters are presented. The converters are to be used with SEC vidicons as detectors for an echelle spectrograph on the International Ultraviolet Explorer astronomical satellite. Magnesium fluoride input windows with Cs-Te photocathodes are used in the converters, with P-11 phosphors on the fiber optic output windows. Quantum efficiencies, modulation transfer function, background, geometric distortion, and environmental test results are presented for the wavelength region from 1150 to 3500 A.-

Feibelman, W. A.↗
NASA NTRS2016

Type II Supernova Energetics and Comparison of Light Curves to Shock-Cooling Models

During the first few days after explosion, Type II supernovae (SNe) are dominated by relatively simple physics. Theoretical predictions regarding early-time SN light curves in the ultraviolet (UV) and optical bands are thus quite robust. We present, for the first time, a sample of 57 R-band SN II light curves that are well-monitored during their rise, with greater than 5 detections during the first 10 days after discovery, and a well-constrained time of explosion to within 13 days. We show that the energy per unit mass (E/M) can be deduced to roughly a factor of five by comparing early-time optical data to the 2011 model of Rabinak Waxman, while the progenitor radius cannot be determined based on R-band data alone. We find that SN II explosion energies span a range of EM = (0.2-20) x 10(exp 51) erg/(10 M stellar mass), and have a mean energy per unit mass of E/ M = 0.85 x 10(exp 51) erg(10 stellar mass), corrected for Malmquist bias. Assuming a small spread in progenitor masses, this indicates a large intrinsic diversity in explosion energy. Moreover, E/M is positively correlated with the amount of Ni-56 produced in the explosion, as predicted by some recent models of core-collapse SNe. We further present several empirical correlations. The peak magnitude is correlated with the decline rate (Delta m(sub15), the decline rate is weakly correlated with the rise time, and the rise time is not significantly correlated with the peak magnitude. Faster declining SNe are more luminous and have longer rise times. This limits the possible power sources for such events.

supernovae: general↗
NASA NTRS1979

Ultraviolet photometry with the Astronomical Netherlands Satellite /ANS/ Observations of Beta Canis Majoris variables

The paper deals with detailed ANS observations of three Beta Canis Majoris variables: Xi-1 CMa, HD 61068 (whose discovery is reported here) and 15 CMa. Light curves at five ultraviolet wavelengths are presented, and the periods and amplitudes are discussed. The ultraviolet colors are used to derive temperatures and temperature variations, which are compared with the MK spectral types. The anomalously high luminosity found for Xi-1 CMa on the basis of certain line strengths is also discussed.

Lesh, J. R.↗
DOE OSTI2022

Near-infrared spectra and molar absorption coefficients of trivalent lanthanides dissolved in molten LiCl–KCl eutectic

Determining the concentration of the dissolved lanthanide species in LiCl–KCl eutectic salt is important to the development of pyrochemical reprocessing of used nuclear fuel. In this process, lanthanide fission products are found dissolved in the electrorefiner electrolyte in their trivalent oxidation state. The presence of dissolved trivalent lanthanides increases the liquidus temperature of the electrolyte mixture and can lead to the formation of insoluble oxide or oxychloride phases and must therefore be continuously monitored and controlled during the operation. Absorbance spectroscopy is a promising method for continuous measurement of the concentration of lanthanides and other elements dissolved in the electrolyte. The absorption of light by elements is linearly proportional to the concentration of the element for relatively dilute solutions according to the Beer-Lambert law. Although measurement of the absorption of ultraviolet and visible range light by lanthanides in LiCl–KCl eutectic molten salt have been explored previously, near infrared (NIR) absorption spectroscopy has received far less attention. It may, however, provide a better analytical signal when insoluble phases are present due to less Raleigh scattering compared to shorter wavelength radiation. Additionally, it may allow for concentration determination for certain elements using NIR absorption features where UV and visible range features are overlapping with features from other species. In this study, we report the UV–Vis–NIR spectra of the trivalent lanthanide chlorides of neodymium, samarium, and dysprosium in LiCl–KCl eutectic. Molar absorption coefficients are reported for analytically useful absorption maxima, with a focus on the molar absorption coefficients for NIR absorption maxima which have not been reported previously. Additionally, we observe a NIR-range absorption band of Nd3+ which was previously predicted but never experimentally observed. Here, we compare the calculated crystal field levels to the newly observed absorbance band and find them to be in good agreement with previous predictions.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Optically enhanced patternable photosensitivity via oxygen excitation

The present disclosure relates to a method for performing a three dimensional (3D) printing process. A primary light beam having a wavelength sufficient to initiate polymerization of a photoresin is generated and patterned into a patterned primary beam. The patterned primary beam is directed toward an ultraviolet (UV) or visible light sensitive photoresin to initiate polymerization of select areas of the photoresin. The photoresin is also illuminated with a secondary light beam having a wavelength of at least one of about 765 nm, 1064 nm, or 1273 nm. The secondary light beam stimulates triplet oxygen into singlet oxygen, which controls oxygen inhibition in additional areas bordering the select areas, to enable controlled polymerization inhibition in the additional areas bordering the select areas.

Hensleigh, Ryan↗
DOE OSTI2022

High speed ultraviolet digital image correlation (UV-DIC) for dynamic strains at extreme temperatures

Digital Image Correlation (DIC) is a camera-based method of measuring full-field displacements and strains from the surface of a deforming object. It can be applied at any length scale (determined by the lenses) and any time scale (determined by the camera), and because it is non-contacting, it can also be used at temperatures much higher than can be withstood by bonded strain gauges. At extreme temperatures, materials emit light in the form of blackbody radiation, which can saturate the camera sensor. It has previously been shown that the emitted light can be effectively screened by using ultraviolet (UV) cameras, lenses, and filters; however, commercially available UV cameras are relatively slow, which limits the speed of combined UV-DIC measurements. In this study, a UV intensifier was paired with a high-speed camera, and its ability to perform UV-DIC at high temperature and high speed was investigated. The system was compared over three different experiments: (A) a quasi-static thermal expansion test at high temperature, (B) a vibration test at room temperature, and (C) the same vibration test repeated at high temperature. The system successfully performed DIC up to at least 1600 °C at frame rates of 5000 fps, which is more than 100 times faster than other examples of UV-DIC in the literature. In all cases, measurements made using the UV intensifier were much noisier than those made without the intensifier, but the intensifier enabled measurements at temperatures well above those which an unfiltered high-speed camera otherwise saturates.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Investigating the Nature of the Luminous Ambiguous Nuclear Transient ASASSN-17jz

Abstract We present observations of the extremely luminous but ambiguous nuclear transient (ANT) ASASSN-17jz, spanning roughly 1200 days of the object’s evolution. ASASSN-17jz was discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in the galaxy SDSS J171955.84+414049.4 on UT 2017 July 27 at a redshift of z = 0.1641. The transient peaked at an absolute B -band magnitude of M B ,peak = −22.81, corresponding to a bolometric luminosity of L bol,peak = 8.3 × 10 44 erg s −1 , and exhibited late-time ultraviolet emission that was still ongoing in our latest observations. Integrating the full light curve gives a total emitted energy of E tot = (1.36 ±0.08) × 10 52 erg, with (0.80 ± 0.02) × 10 52 erg of this emitted within 200 days of peak light. This late-time ultraviolet emission is accompanied by increasing X-ray emission that becomes softer as it brightens. ASASSN-17jz exhibited a large number of spectral emission lines most commonly seen in active galactic nuclei (AGNs) with little evidence of evolution. It also showed transient Balmer features, which became fainter and broader over time, and are still being detected >1000 days after peak brightness. We consider various physical scenarios for the origin of the transient, including supernovae (SNe), tidal disruption events, AGN outbursts, and ANTs. We find that the most likely explanation is that ASASSN-17jz was a SN IIn occurring in or near the disk of an existing AGN, and that the late-time emission is caused by the AGN transitioning to a more active state.

79 ASTRONOMY AND ASTROPHYSICS↗