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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Alignment and dissociation of electronically excited molecular hydrogen with intense laser fields

The dissociation of aligned, electronically excited H 2 (E,F 1 Σ g + ), followed by ionization of the produced H atom, is analyzed via the velocity mapped imaging technique. The dissociation and ionization processes are accomplished, respectively, by a two- and a onephoton absorption from a single 532-nm laser pulse, while the alignment is induced by a separate 1064-nm laser pulse. The velocity of the produced H + photofragments shows a weak perpendicular alignment at low alignment laser field values, evolving to strongly parallel for larger fields. We modeled this alignment behavior with a simple two-state model involving the Stark mixing of the initially-prepared J = 0 with the J = 2 rotational state. This model is able to reproduce all of the observed angular distribution, and permits us to extract from the fit the polarizability anisotropy of H 2 (E,F) electronic state. We determine this value to be (3.7 ± 1.2) x 10 3 a.u. As this value is extremely large in comparison to what one would expect from the pure H 2 (E,F) electronic state, we hypothesize that this value comes from the 1064-nm laser beam mixing nearby electronic states with the initially laser prepared (E,F) state generating a mixed state (EF**) with an extremely large polarizability anisotropy.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Tracing magnetic fields by atomic alignment in extended radiation fields

Tracing magnetic field is crucial as magnetic field plays an important role in many astrophysical processes. Earlier studies have demonstrated that ground state alignment (GSA) is an effective way to detect a weak magnetic field (1G≳B≳10{sup −15} G) in a diffuse medium. We explore the atomic alignment in the presence of an extended radiation field for both absorption lines and emission lines. The alignment in the circumstellar medium, binary systems, disks, and the local interstellar medium are considered in order to study the alignment in the radiation field where the pumping source has a clear geometric structure. Furthermore, the multipole expansion method is adopted to study GSA induced in the radiation field with unidentified pumping sources. We study the alignment in the dominant radiation components of the general radiation field: the dipole and quadrupole radiation field. We discuss the approximation of GSA in a general radiation field by summing the contribution from the dipole and quadrupole radiation field. We conclude that GSA is a powerful tool for detecting weak magnetic fields in the diffuse medium in general radiation fields.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

A mathematical model to systematically align superconducting radio frequency cavities employing the serial robot kinematic theory

In Superconducting Radio Frequency (SRF) cryomodules, precise alignment of cavities is necessary to ensure high beam quality and to increase the overall energetic efficiency. In the SSR1 (Single Spoke Resonator 1) cryomodule, the cavities are aligned using a system of seven screws which allows to control five Degree of Freedoms (DOFs). The relation between the rotation of each screw and the movement of the cavity is non-linear, thus the aligning process, currently based on a trial-and-error procedure, can be time consuming and affected by human error. In this paper the design of an alignment mathematical model, based on the serial robot kinematic, is described and tested on a SSR1 cavity. Furthermore, the goal of the proposed model is to give a step by step operational procedure that bring the SSR1 cavity to a desired location reducing the uncertainties related to the current operator-driven alignment process.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Intrinsic alignments of galaxies in the MassiveBlack-II simulation: Analysis of two-point statistics

The intrinsic alignment of galaxies with the large-scale density field in an important astrophysical contaminant in upcoming weak lensing surveys. We present detailed measurements of the galaxy intrinsic alignments and associated ellipticity-direction (ED) and projected shape (w g ₊) correlation functions for galaxies in the cosmological hydrodynamic MassiveBlack-II (MB-II) simulation. We carefully assess the effects on galaxy shapes, misalignment of the stellar component with the dark matter shape and two-point statistics of iterative weighted (by mass and luminosity) definitions of the (reduced and unreduced) inertia tensor. We find that iterative procedures must be adopted for a reliable measurement of the reduced tensor but that luminosity versus mass weighting has only negligible effects. Both ED and w g ₊ correlations increase in amplitude with subhalo mass (in the range of 10¹⁰ – 6.0 X 10¹⁴h⁻¹ M ⊙ ), with a weak redshift dependence (from z = 1 to z = 0.06) at fixed mass. At z ~ 0.3, we predict a w g ₊ that is in reasonable agreement with SDSS LRG measurements and that decreases in amplitude by a factor of ~ 5–18 for galaxies in the LSST survey. We also compared the intrinsic alignment of centrals and satellites, with clear detection of satellite radial alignments within the host halos. Finally, we show that w g ₊ (using subhalos as tracers of density and w δ (using dark matter density) predictions from the simulations agree with that of non-linear alignment models (NLA) at scales where the 2-halo term dominates in the correlations (and tabulate associated NLA fitting parameters). The 1-halo term induces a scale dependent bias at small scales which is not modeled in the NLA model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SU-D-210-07: The Dependence On Acoustic Velocity of Medium On the Needle Template and Electronic Grid Alignment in Ultrasound QA for Prostate Brachytherapy

Purpose: To analyze the impact on acoustic velocity (AV) of two different media (water and milk) using the needle template/electronic grid alignment test. Water, easily available, makes a good material to test the alignment of the template and grid although water’s AV (1498 m/s at 25°C) is significantly different from tissue (1540 m/s). Milk, with an AV much closer (1548 m/s) to prostate tissue, may be a good substitute for water in ultrasound quality assurance testing. Methods: Tests were performed using a Hitachi ultrasound unit with a mechanical arrangement designed to position needles parallel to the transducer. In this work, two materials – distilled water and homogenized whole milk (AVs of 1498 and 1548 m/s at 25°C) were used in a phantom to test ultrasound needle/grid alignment. The images were obtained with both materials and analyzed for their placement accuracy. Results: The needle template/electronic grid alignment tests showed displacement errors between measured and calculated values. The measurements showed displacements of 2.3mm (water) and 0.4mm (milk), and 1.6mm (water) and 0.3mm (milk) at depths of 7cm and 5cm respectively from true needle positions. The calculated results showed a displacement of 2.36 mm (water); 0.435mm (milk), and 1.66mm (water) and 0.31mm (milk) at a depth of 7cm and 5cm respectively. The displacements in the X and Y directions were also calculated. At depths of 7cm and 5cm, the (ΔX,ΔY) displacements in water were (0.829mm, 2.21mm) and (0.273mm, 1.634mm) and for milk were (0.15mm, 0.44mm) and (0.05mm, 0.302mm) respectively. Conclusion: The measured and calculated values were in good agreement for all tests. They show that milk provides superior results when performing needle template and electronic grid alignment tests for ultrasound units used in prostate brachytherapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-J-181: An Alternative Patient Alignment Tool On TomoTherapy: The First In- Human Megavoltage-Topogram Acquisition

Purpose: To show the first in-human Megavoltage (MV)-Topogram acquisition for the evaluation of the potential for MV-Topogram-based alignment as an alternative to MVCT for reducing dose and imaging time. Methods: A lung cancer patient was enrolled in an ongoing IRB-approved clinical trial at our institute. The patient was set up using the clinical protocol employing positioning lasers. 3.2mm diameter tungsten spheres were placed on the patient’s skin at their alignment tattoos to check surface-based marker concordance between topograms and MVCT. Anterior-Posterior (AP) and lateral (LAT) MV-Topograms were acquired using gantry angles of 0°/90° with a 1mm collimator opening, all MLC leafs open, 4cm/s couch speed, and 12.5s scanning time. The topogram acquisition was immediately followed by the normal MVCT scan acquisition. MV-Topograms were reconstructed from the detector exit-data using in-house developed software. The topograms were also enhanced using contrast-limited adaptive histogram equalization (CLAHE). The MV-Topograms were registered to reference kV-based digitally reconstructed topograms. The localization results were compared against results obtained comparing the clinical MVCT to the kVCT simulation. Results: The shifts using the unenhanced Topograms, enhanced Topograms, and MVCT were (LAT, LONG, VERT, ROLL) (5.8mm, 2.6mm, −5.6mm, 0.34°), (3.9mm, 2.5mm, −2.2mm, 0.65°) and (2.4mm, 1.5mm, −3.0mm, 0.5°), respectively. The magnitude alignment differences between the enhanced Topograms and MVCT were within 1.5 mm and 0.15°. The average MVCT and total Topogram acquisition times were 272.9s ± 31.5s and 46s, respectively. Conclusion: MV-Topograms have the potential for providing equivalent performance with less dose and acquisition time than the traditional MVCT technique. We are evaluating other sites as well as adding patients to develop statistically significant analyses regarding the alignment quality differences. MV-Topograms are likely to be most clinically useful for bony anatomy and radiopaque marker-based alignments. The study was supported by an Accuray Grant.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Alignment of the ATLAS Inner Detector in Run 2

The performance of the ATLAS Inner Detector alignment has been studied using pp collision data at s√=13TeV collected by the ATLAS experiment during Run 2 (2015–2018) of the Large Hadron Collider (LHC). The goal of the detector alignment is to determine the detector geometry as accurately as possible and correct for time-dependent movements. The Inner Detector alignment is based on the minimization of track-hit residuals in a sequence of hierarchical levels, from global mechanical assembly structures to local sensors. Subsequent levels have increasing numbers of degrees of freedom; in total there are almost 750,000. The alignment determines detector geometry on both short and long timescales, where short timescales describe movements within an LHC fill. The performance and possible track parameter biases originating from systematic detector deformations are evaluated. Momentum biases are studied using resonances decaying to muons or to electrons. The residual sagitta bias and momentum scale bias after alignment are reduced to less than ~0.1 TeV -1 and 0.9×10 -3 , respectively. Impact parameter biases are also evaluated using tracks within jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Determining tolerance requirements for spray-duct alignment in ducted fuel injection

Several ducted fuel injection (DFI) studies have highlighted the importance of accuracy in aligning the duct axis with that of its corresponding spray for optimal effectiveness, as misalignment adversely impacts the method’s performance. The need for accurate alignment could lead to added manufacturing complexity via tighter tolerances. This study systematically explores cases of horizontal, vertical, and rotational misalignment, analyzing their respective effects on DFI performance. Vertical and horizontal misalignments at the duct inlet plane were varied at magnitudes of 6.25%, 12.5%, and 25.0% of the duct diameter, corresponding to 0.125, 0.25, and 0.5 mm, respectively. Rotational misalignments were set at 1°, 2°, and 4°, corresponding to 3.65%, 7.30%, and 14.6%, respectively, of the duct diameter at its inlet plane. The investigation yields spray-duct alignment tolerance limits and highlights the influence of misalignment direction on emissions due to the interactions with swirl and squish inside the combustion chamber. The results indicate that the tolerance limits for the alignment are within 4° and 0.5 mm relative to the geometrically aligned position. If the misalignment exceeds 4°of rotation or 0.5 mm in the horizontal direction, the beneficial effects on soot reduction using this method are no longer observed. The findings contribute to an understanding that can be used to optimize DFI for cleaner and more efficient combustion in compression-ignition engines.

Şener, Ramazan↗
DOE OSTI2019

Design and alignment of an all-spherical unobscured four-mirror image relay for an ultra-broadband sub-petawatt laser

We describe the design and alignment of an unobscured reflective image relay for use in an ultra-broadband half-petawatt laser system in development at the University of Rochester’s Laboratory for Laser Energetics. The design consists of four spherical mirrors in an unobscured configuration. We show the theoretical basis for such a four-mirror design using first-order optical matrix methods and nodal aberration theory. We also describe the process of aligning this design in a test bed and show the results of this alignment method. We were able to achieve a diffraction-limited nominal design. Furthermore, upon aligning the design in our test bed, we were able to successfully align the design to achieve our target wavefront error of less than 0.3 waves p–v and 0.07 waves rms at the central laser-operating wavelength of 910 nm.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Joint iterative reconstruction and 3D rigid alignment for X-ray tomography

X-ray tomography is widely used for three-dimensional structure determination in many areas of science, from the millimeter to the nanometer scale. The resolution and quality of the 3D reconstruction is limited by the availability of alignment parameters that correct for the mechanical shifts of the sample or sample stage for the images that constitute a scan. In this paper we describe an algorithm for marker-free, fully automated and accurately aligned and reconstructed X-ray tomography data. Our approach solves the tomographic reconstruction jointly with projection data alignment based on a rigid-body deformation model. We demonstrate the robustness of our method on both synthetic phantom and experimental data and show that our method is highly efficient in recovering relatively large alignment errors without prior knowledge of a low resolution approximation of the 3D structure or a reasonable estimate of alignment parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2018

NSLS-II Booster Survey and Alignment Systems

This section outlines the survey and alignment requirements and the technology and tools for achieving the NSLS-II equipment positioning goals. The required alignment tolerances are defined primarily by the physics requirements of the accelerator. The tight tolerances dictated by the physics requirements are an order of magnitude tighter than the tolerances of second generation light sources (NSLS) and on level with those at third generation light sources (Soleil, Diamond). These extraordinary position requirements necessitate a concerted R&D engineering effort to identify and develop the survey methodology needed to meet these requirements. As of this date, the methodology is still evolving to balance cost and time constraints while still maintaining the integrity of the survey and alignment systems. State-of-the art equipment including Laser Trackers and Laser Arms have been purchased and used extensively in the pursuit of meeting the NSLS-II survey tolerances. No new technology will need to be developed to meet the alignment requirements but new techniques will be pursued and developed. Survey and alignment provides the foundation for positioning the beam-guiding magnet structures in all 6 degrees of freedom within the required tolerances. Although the tools and instrumentation available for this task have changed over the years and faster and more accurate measurements are possible, only limited control of the environmental conditions is possible. This ultimately sets an upper limit for the achievable measurement and subsequent control network accuracy. At the same time, the control of environmental variables (temperature, humidity) will be fully taken advantage of during the building of NSLS-II , opening up the possibility of ever-increasing accuracy unheard of only five years ago.

42 ENGINEERING↗
DOE OSTI2023

New alignment method for remote protein sequences by the direct use of pairwise sequence correlations and substitutions

Understanding protein sequences and how they relate to the functions of proteins is extremely important. One of the most basic operations in bioinformatics is sequence alignment and usually the first things learned from these are which positions are the most conserved and often these are critical parts of the structure, such as enzyme active site residues. In addition, the contact pairs in a protein usually correspond closely to the correlations between residue positions in the multiple sequence alignment, and these usually change in a systematic and coordinated way, if one position changes then the other member of the pair also changes to compensate. In the present work, these correlated pairs are taken as anchor points for a new type of sequence alignment. The main advantage of the method here is its combining the remote homolog detection from our method PROST with pairwise sequence substitutions in the rigorous method from Kleinjung et al. We show a few examples of some resulting sequence alignments, and how they can lead to improvements in alignments for function, even for a disordered protein.

Jia, Kejue↗
DOE OSTI2021

Mechanical and Dielectric Properties of Aligned Electrospun Fibers

This review paper examines the current state-of-the-art in fabrication of aligned fibers via electrospinning techniques and the effects of these techniques on the mechanical and dielectric properties of electrospun fibers. Molecular orientation, system configuration to align fibers, and post-drawing treatment, like hot/cold drawing process, contribute to better specific strength and specific stiffness properties of nanofibers. The authors suggest that these improved, aligned nanofibers, when applied in composites, have better mechanical and dielectric properties for many structural and multifunctional applications, including advanced aerospace applications and energy storage devices. For these applications, most fiber alignment electrospinning research has focused on either mechanical property improvement or dielectric property improvement alone, but not both simultaneously. Relative to many other nanofiber formation techniques, the electrospinning technique exhibits superior nanofiber formation when considering cost and manufacturing complexity for many situations. Even though the dielectric property of pure nanofiber mat may not be of general interest, the analysis of the combined effect of mechanical and dielectric properties is relevant to the present analysis of improved and aligned nanofibers. A plethora of nanofibers, in particular, polyacrylonitrile (PAN) electrospun nanofibers, are discussed for their mechanical and dielectric properties. In addition, other types of electrospun nanofibers are explored for their mechanical and dielectric properties. An exploratory study by the author demonstrates the relationship between mechanical and dielectric properties for specimens obtained from a rotating mandrel horizontal setup.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Radiative Grain Alignment in Protoplanetary Disks: Implications for Polarimetric Observations

We apply the theory of radiative torque (RAT) alignment for studying protoplanetary disks around a T-Tauri star and perform 3D radiative transfer calculations to provide the expected maps of polarized radiation to be compared with observations, such as with ALMA. We revisit the issue of grain alignment for large grains expected in the protoplanetary disks and find that mm-sized grains at the midplane do not align with the magnetic field since the Larmor precession timescale for such large grains becomes longer than the gaseous damping timescale. Hence, for these grains the RAT theory predicts that the alignment axis is determined by the grain precession with respect to the radiative flux. As a result, we expect that the polarization will be in the azimuthal direction for a face-on disk. It is also shown that if dust grains have superparamagnetic inclusions, magnetic field alignment is possible for (sub-)micron grains at the surface layer of disks, and this can be tested by mid-infrared polarimetric observations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

Simultaneous particle and field observations of field-aligned currents

Simultaneous measurements of low energy precipitating electrons and magnetic fluctuations from the low altitude polar orbiting satellite OGO-4 have been compared. Analysis of the two sets of experimental data for isolated events led to the classification of high latitude field-aligned currents as purely temporal or purely spatial variations. Magnetic field disturbances calculated using these simple current models and the measured particle fluxes were in good agreement with measured field values. While fluxes of greater than 1 keV electrons are detected primarily on the nightside, magnetometer disturbances indicative of field-aligned currents were seen at all local times, both in the visual auroral regions and dayside polar cusp. Thus electrons with energies less than approximately 1 keV are the prime charge carriers in high latitude dayside field-aligned currents. The satellite measurements are in good agreement with previously measured field-aligned current values and with values predicted from several models involving magnetospheric field-aligned currents.

Berko, F. W.↗
NASA NTRS1974

Field-aligned auroral electron fluxes

Out of a series of five auroral sounding rocket flights, electron fluxes in three of the flights were observed to be sharply field-aligned. The electrons were detected with an array of electrostatic analyzers making 50-point spectral samples from 0 to 15 keV. The field-aligned fluxes resulted in a peak in the spectrum at a lower energy than that of another monoenergetic peak in the spectrum seen consistently when it was conjugate to bright auroral forms giving multiply peaked spectra. The field-aligned peak in the spectrum is apparently a phenomenon distinct from the isotropic peak and was observed to occur at various times in the energy range from a few hundred electron volts to 5 keV. The field-aligned electrons were highly collimated, having pitch angles less than 20 deg and at times less than 10 deg. The high degree of field alignment and the monoenergetic character support the model that these events can be attributed to relatively cool plasma falling through an electric potential at altitudes not too far removed from the rocket.

Arnoldy, R. L.↗
NASA NTRS1977

Development of a method of alignment between various SOLAR MAXIMUM MISSION experiments

Results of an engineering study of the methods of alignment between various experiments for the solar maximum mission are described. The configuration studied consists of the instruments, mounts and instrument support platform located within the experiment module. Hardware design, fabrication methods and alignment techniques were studied with regard to optimizing the coalignment between the experiments and the fine sun sensor. The proposed hardware design was reviewed with regard to loads, stress, thermal distortion, alignment error budgets, fabrication techniques, alignment techniques and producibility. Methods of achieving comparable alignment accuracies on previous projects were also reviewed.

Source record↗
NASA NTRS1978

Relations between transverse electric fields and field-aligned currents

A model for the field-aligned propagation of transverse electric fields and associated field-aligned sheet currents is presented which takes into account the wave nature of the process. The model is applied to the separate cases of ionospheric and magnetospheric sources, and the resulting ionospheric electric field to field-aligned sheet current ratios are determined for comparison with experimental observations. It is found that the magnetospheric wave 'conductivity' for shear mode Alfven waves is small with respect to typical values of the height-integrated ionospheric Pedersen conductivity. For plasma convecting across a stationary disturbance a dynamic equilibrium is achieved in which field-aligned currents flow continuously away from the source on convecting field lines. Consistency with typical ionospheric electric fields requires that the field-aligned sheet currents are limited to around 0.1 A/m for ionospheric polarization sources, while magnetospheric sources are easily capable of 1 A/m or more.

Mallinckrodt, A. J.↗