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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Experimental setup for high-resolution characterization of crystal optics for coherent X-ray beam applications

Stanford Synchrotron Radiation Lightsource serves a wide scientific community with its variety of X-ray capabilities. Recently, a wiggler X-ray source located at beamline 10-2 has been employed to perform high-resolution rocking curve imaging (RCI) of diamond and silicon crystals. X-ray RCI is invaluable for the development of upcoming cavity-based X-ray sources at SLAC, including the cavity-based X-ray free-electron laser and X-ray laser oscillator. In this paper, the RCI apparatus is described and experimental results are provided to validate its design. Future improvements of the setup are also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Design and Characterization of an Optically Segmented Single Volume Scatter Camera Module

Here, the optically segmented single volume scatter camera (OS-SVSC) aims to image neutron sources for nuclear nonproliferation applications using the kinematic reconstruction of elastic double-scatter events. We report on the design, construction, and calibration of one module of a new prototype. The module includes 16 EJ-204 organic plastic scintillating bars individually wrapped in Teflon tape, each measuring 0.5cx0.5cmx20cm . The scintillator array is coupled to two custom silicon photomultiplier (SiPM) boards consisting of a 2x8 array of SensL J-Series-60035 SiPMs, which are read out by a custom 16 channel DRS4 based digitizer board. The electrical crosstalk between SiPMs within the electronics chain is measured as 0.76%±0.11% among all 16 channels. We report the detector response of one module including interaction position, time, and energy, using two different optical coupling materials: EJ-560 silicone rubber optical coupling pads and EJ-550 optical coupling grease. We present results in terms of the overall mean and standard deviation of the z -position reconstruction and interaction time resolutions for all 16 bars in the module. We observed the 1σz -position resolution for gamma interactions in the 0.3–0.4 MeVee range to be 2.24 cm ± 1.10 cm and 1.45 cm ± 0.19 cm for silicone optical coupling pad and optical grease, respectively. The observed 1σ interaction time resolution is 265 ps ± 29 ps and 235 ps ± 10 ps for silicone optical coupling pad and optical grease, respectively.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1986

Optical technique to characterize heavy rain

A technique to measure the size and velocity of raindrops is presented and experimental and numerical results discussed. The technique bases the droplet size on the absolute intensity of the light scattered when the droplets cross a laser-based probe volume. The velocity is obtained from the Doppler frequency. A size range of 0.1 mm to 9 mm was covered with overlapping ranges. Experiments were conducted with simulated rain sprays except that the local LWC was much larger than the values encountered in natural rain. The accuracy of the size measurement was not strongly affected by spray interference, but it showed a clear dependence with the droplet shape. A simple numerical model based on the light reflected from ellipsoids attempts to explain the relationship between droplet shape and absolute scattered light.

Hess, C. F.↗
NASA NTRS1991

New optical approaches to the quantitative characterization of crystal growth, segregation and defect formation

Elemental and compound semiconductors were characterized using new optical approach based on NIR microscopy in conjunction with computational image analysis and contrast enhancement. The approach made it possible to perform a quantitative microsegregation analysis of GaAs and InP. NIR dark file illumination in transmission mode makes it possible to detect submicron precipitates in semiinsulating GaAs.

Carlson, D. J.↗
NASA NTRS2011

Orbital Debris Characterization via Laboratory Optical Measurements

Optical observations of orbital debris offer insights that differ from radar measurements (specifically the size parameter,wavelength regime,and altitude range). For example, time-dependent photometric data yield lightcurves in multiple bandpasses that aid in material identification and possible periodic orientations. These data can also be used to help identify shapes and optical properties at multiple phase angles. Capitalizing on optical data products and applying them to generate a more complete understanding of orbital objects is a key objective of NASA's Optical Measurement Program, and the primary reason for the creation of the Optical Measurements Center(OMC). The OMC attempts to emulate space-based illumination conditions using equipment and techniques that parallel telescopic observations and source-target-sensor orientations.

Cowardin, Healther↗
NASA NTRS2013

Characterization of the Optical and X-ray Properties of the Northwestern Wisps in the Crab Nebula

We have studied the variability of the Crab Nebula both in the visible and in X -rays. Optical observations were obtained using the Nordic Optical Telescope in La Palma and X -ray observations were made with the Chandra X -Ray Observatory. We observe wisps forming and peeling off from the region commonly associated with the termination shock of the pulsar wind. We measure a number of properties of the wisps to the Northwest of the pulsar. We find that the exact locations of the wisps in the optical and in X-rays are similar but not coincident, with the X-ray wisp preferentially located closer to the pulsar. Our measurements and their implications are interpreted in terms of a MHD model. We find that the optical wisps are more strongly Doppler boosted than X-ray wisps, a result inconsistent with current MHD simulations. Indeed the inferred optical boosting factors exceed MHD simulation values by about one order of magnitude. These findings suggest that the optical and X-ray wisps are not produced by the same particle distribution, a result which is consistent with the spatial differences. Further, the X -ray wisps and optical wisps are apparently developing independently from each other, but every time a new X ]ray wisp is born so is an optical wisp, thus pointing to a possible common cause or trigger. Finally, we find that the typical wisp formation rate is approximately once per year, interestingly at about the same rate of production of the large gamma-ray flares.

Weisskopf, M. C.↗
NASA NTRS2013

Characterization of the Optical and X-ray Properties of the Northwestern Wisps in the Crab Nebula

We have studied the wisps to the northwest of the Crab pulsar as part of a multi-wavelength campaign in the visible and in X-rays. Optical observations were obtained using the Nordic Optical Telescope in La Palma and X-ray observations were made with the Chandra X-ray Observatory. The observing campaign took place from October 2010 until September 2012. About once per year we observe wisps forming and peeling off from (or near) the region commonly associated with the termination shock of the pulsar wind. We find that the exact locations of the northwestern wisps in the optical and in X-rays are similar but not coincident, with X-ray wisps preferentially located closer to the pulsar. This suggests that the optical and X-ray wisps are not produced by the same particle distribution. It is also interesting to note that the optical and radio wisps are also separated from each other (Bietenholz et al. 2004). Our measurements and their implications are interpreted in terms of a Doppler-boosted ring model that has its origin in MHD modeling. While the Doppler boosting factors inferred from the X-ray wisps are consistent with current MHD simulations of PWNe, the optical boosting factors are not, and typically exceed values from MHD simulations by about a factor of 4.

Weisskopf, M. C.↗
NASA NTRS2022

Polarization as a Discriminator of Light-Absorbing Impurities in or Above Snow

This conceptual study presents advanced radiative transfer computations of light polarization originating from a snowpack consisting of nonspherical grains and variable content of light-absorbing impurities, either embedded in the snowpack or (with the same optical properties) lofted above it in the form of atmospheric aerosols. The results highlight the importance of considering shapes other than spherical for the snow grains, which otherwise can lead to non-negligible errors in the retrieval of snow albedo from remote sensing observations. More importantly, it is found that polarimetric measurements provide a means to partition light-absorbing impurities embedded in the snowpack from absorbing aerosols aloft, a task traditionally prohibitive for sensors capable exclusively of measurements of total reflectance. Heritage techniques to obtain snow grain size from shortwave infrared observations of total reflectance are well established, as are those that leverage polarimetric, multiangular observations across the entire optical spectrum to characterize the optical and microphysical properties of atmospheric aerosols. The polarization signatures of near-infrared (e.g., 864 nm) observations carry critical information on snow grain shape. The prospected launch of space-borne polarimeters with proven accuracy, therefore, advocates for the development of data inversion schemes, to boost the accuracy of simultaneous retrievals of atmospheric and surface parameters in the polar and snow-covered regions, critical to climate studies.

light polarization↗
NASA NTRS1991

Characterization of magneto-optical media

Amorphous rare earth-transition metal (RE-TM) alloys and compositionally modulated TM/TM films were characterized in terms of their magnetic, magneto-optic, and galvanomagnetic properties. The loop tracer, vibrating sample magnetometer (VSM), and Rutherford Backscattering (RBS) facility were used to characterize and analyze the various properties of these magneto-optical storage media. Kerr effect, ellipticity, coercivity, and anisotropy at various temperatures, magnetoresistance, and resistivity are among the properties measured in Co/Pt films, Co/Pd films, and TbFeCo films.

Hajjar, Roger A.↗
NASA NTRS1977

An optical profilometer for spatial characterization of three-dimensional surfaces

The design concept and system operation of an optical profilometer are discussed, and a preliminary evaluation of a breadboard system is presented to demonstrate the feasibility of the optical profilometer technique. Measurement results are presented for several test surfaces; and to illustrate a typical application, results are shown for a cleft palate cast used by dental surgeons. Finally, recommendations are made for future development of the optical profilometer technique for specific engineering or scientific applications.

Kelly, W. L., IV↗