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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 217 records · Page 12

All sources NASA NTRS DOE OSTI

NASA NTRS2007

NASA Tech Briefs, April 2007

Topics include: Wearable Environmental and Physiological Sensing Unit; Broadband Phase Retrieval for Image-Based Wavefront Sensing; Filter Function for Wavefront Sensing Over a Field of View; Iterative-Transform Phase Retrieval Using Adaptive Diversity; Wavefront Sensing With Switched Lenses for Defocus Diversity; Smooth Phase Interpolated Keying; Maintaining Stability During a Conducted-Ripple EMC Test; Photodiode Preamplifier for Laser Ranging With Weak Signals; Advanced High-Definition Video Cameras; Circuit for Full Charging of Series Lithium-Ion Cells; Analog Nonvolatile Computer Memory Circuits; JavaGenes Molecular Evolution; World Wind 3D Earth Viewing; Lithium Dinitramide as an Additive in Lithium Power Cells; Accounting for Uncertainties in Strengths of SiC MEMS Parts; Ion-Conducting Organic/Inorganic Polymers; MoO3 Cathodes for High-Temperature Lithium Thin-Film Cells; Counterrotating-Shoulder Mechanism for Friction Stir Welding; Strain Gauges Indicate Differential-CTE-Induced Failures; Antibodies Against Three Forms of Urokinase; Understanding and Counteracting Fatigue in Flight Crews; Active Correction of Aberrations of Low-Quality Telescope Optics; Dual-Beam Atom Laser Driven by Spinor Dynamics; Rugged, Tunable Extended-Cavity Diode Laser; Balloon for Long-Duration, High-Altitude Flight at Venus; and Wide-Temperature-Range Integrated Operational Amplifier.

Source record↗

DOE OSTI2022

Beam-steering system based on a MEMS-actuated vertical-coupler array

An integrated-optics MEMS-actuated beam-steering system is disclosed, wherein the beam-steering system includes a lens and a programmable vertical coupler array having a switching network and an array of vertical couplers, where the switching network can energize of the vertical couplers such that it efficiently emits the light into free-space. The lens collimates the light received from the energized vertical coupler and directs the output beam along a propagation direction determined by the position of the energized vertical coupler within the vertical-coupler array. In some embodiments, the vertical coupler is configured to correct an aberration of the lens. In some embodiments, more than one vertical coupler can be energized to enable steering of multiple output beams. In some embodiments, the switching network is non-blocking.

42 ENGINEERING↗

DOE OSTI2023

Beam-steering system based on a MEMS-actuated vertical-coupler array

Zhang, Xiaosheng↗

NASA NTRS2013

Estimate Low and High Order Wavefront Using P1640 Calibrator Measurements

P1640 high contrast imaging system on the Palomar 200 inch Telescope consists of an apodized-pupil Lyot coronagraph, the PALM-3000 adaptive optics (P3K-AO), and P1640 Calibrator (CAL). Science images are recorded by an integral field spectrograph covering J-H bands for detecting and characterizing stellar companions. With aberrations from atmosphere corrected by the P3K-AO, instrument performance is limited mainly by the quasi-static speckles due to noncommon path wavefront aberrations for the light to propagate to the P3K-AO wavefront sensor and to the coronagraph mask. The non-common path wavefront aberrations are sensed by CAL, which measures the post-coronagraph E-field using interferometry, and can be effectively corrected by offsetting the P3K-AO deformable mirror target position accordingly. Previously, we have demonstrated using CAL measurements to correct high order wavefront aberrations, which is directly connected to the static speckles in the image plane. Low order wavefront, on the other hand, usually of larger amplitudes, causes light to leak through the coronagraph making the whole image plane brighter. Knowledge error in low order wavefront aberrations can also affect the estimation of the high order wavefront. Even though, CAL is designed to sense efficiently high order wavefront aberrations, the low order wavefront front can be inferred with less sensitivity. Here, we describe our method for estimating both low and high order wavefront aberrations using CAL measurements by propagating the post-coronagraph E-field to a pupil before the coronagraph. We present the results from applying this method to both simulated and experiment data.

aberrations↗

NASA NTRS1971

Improvements in Ross type astrometric objectives

It is shown that aspheric deformations of the first and fourth elements of the four element Ross objective can be introduced to permit one to obtain improved color corrections for astrometric purposes. The usual monochromatic aberrations are as well corrected as for the standard Ross lens. In addition, one can eliminate or reduce additional aberrations, such as secondary spectrum, chromatic spherical aberration, chromatic coma and chromatic distortion. The resulting objectives are suitable for use as intermediate and long focus astrometric objectives covering large angle fields.

Baker, J.↗

NASA NTRS1997

Spherical mirror grazing incidence x-ray optics

An optical system for x-rays combines at least two spherical or near spherical mirrors for each dimension in grazing incidence orientation to provide the functions of a lens in the x-ray region. To focus x-ray radiation in both the X and the Y dimensions, one of the mirrors focusses the X dimension, a second mirror focusses the Y direction, a third mirror corrects the X dimension by removing comatic aberration and a fourth mirror corrects the Y dimension. Spherical aberration may also be removed for an even better focus. The order of the mirrors is unimportant.

Cash, Jr., Webster C.↗

NASA NTRS2006

Effects of Optical Artifacts in a Laser-Based Spacecraft Navigation Sensor

Testing of the Advanced Video Guidance Sensor (AVGS) used for proximity operations navigation on the Orbital Express ASTRO spacecraft exposed several unanticipated imaging system artifacts and aberrations that required correction to meet critical navigation performance requirements. Mitigation actions are described for a number of system error sources, including lens aberration, optical train misalignment, laser speckle, target image defects, and detector nonlinearity/noise characteristics. Sensor test requirements and protocols are described, along with a summary of test results from sensor confidence tests and system performance testing.

LeCroy, Jerry E.↗

NASA NTRS2007

Effects of Optical Artifacts in a Laser-Based Spacecraft Navigation Sensor

LeCroy, Jerry E.↗

NASA NTRS2007

Effects of Optical Artifacts in a Laser-Based Spacecraft Navigation Sensor

Testing Of the Advanced Video Guidance Sensor (AVGS) used for proximity operations navigation on the Orbital Express ASTRO spacecraft exposed several unanticipated imaging system artifacts and aberrations that required correction, to meet critical navigation performance requirements. Mitigation actions are described for a number of system error sources, including lens aberration, optical train misalignment, laser speckle, target image defects, and detector nonlinearity/noise characteristics. Sensor test requirements and protocols are described, along with a summary ,of test results from sensor confidence tests and system performance testing.

LeCroy, Jerry E.↗

NASA NTRS2003

Optimizing coronagraph designs to minimize their contrast sensitivity to low-order optical aberrations

The presence of optical aberrations in the entrance pupil of a coronagraph causes the stellar light to scatter about the occulting spot, reducing the effective contrast achievable. Even if these aberrations are sufficiently corrected with a deformable mirror to enable planet detection, small drifts in the optical alignment of the telescope introduce additional low-order aberrations.

Shaklan, Stuart B.↗

NASA NTRS2004

On the Fringe Field of Wide Angle LC Optical Phased Array

For free space laser communication, light weighted large deployable optics is a critical component for the transmitter. However, such an optical element will introduce large aberrations due to the fact that the surface figure of the large optics is susceptable to deformation in the space environment. We propose to use a high-resolution liquid crystal spatial light modulator to correct for wavefront aberrations introduced by the primary optical element, and to achieve very fine beam steering and shaping at the same time. A 2-D optical phased array (OPA) antenna based on a Liquid Crystal on Silicon (LCOS) spatial light modulator is described. This device offers a combination of low cost, high resolution, high accuracy, high diffraction efficiency at video speed. To quantitatively understand the influence factor of the different design parameters, a computer simulation of the device is given by the 2-D director simulation and the Finite Difference Time domain (FDTD) simulation. For the 1-D OPA, we define the maximum steering angle to have a grating period of 8 pixel/reset scheme; as for larger steering angles than this criterion, the diffraction efficiency drops dramatically. In this case, the diffraction efficiency of 0.86 and the Strehl ratio of 0.9 are obtained in the simulation. The performance of the device in achieving high resolution wavefront correction and beam steering is also characterized experimentally.

Wang, Xighua↗

DOE OSTI2020

High-resolution cryo-EM reconstructions in the presence of substantial aberrations

Here, an analysis is performed of how uncorrected antisymmetric aberrations, such as coma and trefoil, affect cryo-EM single-particle reconstruction (SPR) results, and an analytical formula quantifying information loss owing to their presence is inferred that explains why Fourier-shell coefficient-based statistics may report significantly overestimated resolution if these aberrations are not fully corrected. The analysis is validated with reference-based aberration refinement for two cryo-EM SPR data sets acquired with a 200 kV microscope in the presence of coma exceeding 40 µm, and 2.3 and 2.7 Å reconstructions for 144 and 173 kDa particles, respectively, were obtained. The results provide a description of an efficient approach for assessing information loss in cryo-EM SPR data acquired in the presence of higher order aberrations, and address inconsistent guidelines regarding the level of aberrations that is acceptable in cryo-EM SPR experiments.

3D reconstruction and image processing↗

NASA NTRS2011

Autonomous Phase Retrieval Calibration

The Palomar Adaptive Optics System actively corrects for changing aberrations in light due to atmospheric turbulence. However, the underlying internal static error is unknown and uncorrected by this process. The dedicated wavefront sensor device necessarily lies along a different path than the science camera, and, therefore, doesn't measure the true errors along the path leading to the final detected imagery. This is a standard problem in adaptive optics (AO) called "non-common path error." The Autonomous Phase Retrieval Calibration (APRC) software suite performs automated sensing and correction iterations to calibrate the Palomar AO system to levels that were previously unreachable.

Estlin, Tara A.↗

NASA NTRS1992

HST image restoration: A comparison of pre- and post-servicing mission results

A variety of image restoration techniques (e.g., Wiener filter, Lucy-Richardson, MEM) have been applied quite successfully to the aberrated HST images. The HST servicing mission (scheduled for late 1993 or early 1994) will install a corrective optics system (COSTAR) for the Faint Object Camera and spectrographs and replace the Wide Field/Planetary Camera with a second generation instrument (WF/PC-II) having its own corrective elements. The image quality is expected to be improved substantially with these new instruments. What then is the role of image restoration for the HST in the long term? Through a series of numerical experiments using model point-spread functions for both aberrated and unaberrated optics, we find that substantial improvements in image resolution can be obtained for post-servicing mission data using the same or similar algorithms as being employed now to correct aberrated images. Included in our investigations are studies of the photometric integrity of the restoration algorithms and explicit models for HST pointing errors (spacecraft jitter).

Hanisch, R. J.↗

DOE OSTI2022

A comparison of carbon impurities in pre- and post-melt uranium Part 2: Scanning/Transmission electron microscopy analysis

We report the speciation and morphology of U carbide inclusions in pre- and post-melt U metal have been explored using high-resolution analytical electron microscopy (AEM). This report presents Part 2 of our study, in which aberration (C s ) corrected transmission and scanning transmission electron microscopy (S)TEM was used to elementally and crystallographically characterize C-containing impurities and defect features in U samples for comparison with results obtained by scanning electron microscopy (SEM) in Part 1, previously published by this journal. Elemental mapping and unit cell matching of inclusions by (S)TEM are consistent with phases observed by SEM, and new dislocations can be observed associating with some inclusion morphologies and not others.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Meter-scale plasma waveguides for multi-GeV laser wakefield acceleration

Here, we present results from two new techniques for the generation of meter-scale, low density (~10 17 cm -3 on axis) plasma waveguides, the “two-Bessel” technique, and the “self-waveguiding” technique. Plasma waveguides of this density and length range are needed for demonstration of a ~10 GeV laser wakefield accelerator module, key for future staging for a ~TeV lepton collider. Both techniques require the use of high quality ultrashort pulse Bessel beams to efficiently and uniformly ionize hydrogen gas in meter-scale supersonic gas jets via optical field ionization. We review these two techniques, describe our meter-scale gas jets, and present a new method for correction of optical aberrations in Bessel beams. Finally, we briefly present results from recent experiments employing one of our techniques, demonstrating quasi-monoenergetic acceleration of ~5 GeV electron bunches in 20 cm long, low density plasma waveguides.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Single Electron Self-coherence and Its Wave/Particle Duality in the Electron Microscope

Intensities in high-resolution phase-contrast images from electron microscopes build up discretely in time by detecting single electrons. A wave description of pulse-like coherent-inelastic interaction of an electron with matter implies a time-dependent coexistence of coherent partial waves. Their superposition forms a wave package by phase decoherence of 0.5 - 1 radian with Heisenbergs energy uncertainty ΔE H = $\hbar$/2 Δt -1 matching the energy loss ΔE of a coherent-inelastic interaction and sets the interaction time Δt. In these circumstances, the product of Planck's constant and the speed of light hc is given by the product of the expression for temporal coherence λ 2 /Δλ and the energy loss ΔE. Experimentally, the self-coherence length was measured by detecting the energy-dependent localization of scattered, plane matter waves in surface proximity exploiting the Goos–Hänchen shift. Chromatic-aberration Cc-corrected electron microscopy on boron nitride (BN) proves that the coherent crystal illumination and phase contrast are lost if the self-coherence length shrinks below the size of the crystal unit cell at ΔE > 200 eV. Finally, in perspective, the interaction time of any matter wave compares with the lifetime of a virtual particle of any elemental interaction, suggesting the present concept of coherent-inelastic interactions of matter waves might be generalizable.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Z-Petawatt Laser Highlights for FY21

We’re happy to report that the full-aperture upgrade project, started in FY18, is now complete and short-pulse target experiments are underway. The table below lists the present performance level of ZPW. Additional laser improvements are in progress to increase the laser energy and pulse contrast along with implementing a correction for achromatic aberrations to reduce the focused spot size and pulse width.

47 OTHER INSTRUMENTATION↗