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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 1,729 records · Page 96
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Coupling Pulse Radiolysis with Nanosecond Time-Resolved Step-Scan Fourier Transform Infrared Spectroscopy: Broadband Mid-Infrared Detection of Radiolytically Generated Transients

We describe the first implementation of broadband, nanosecond time-resolved step-scan Fourier transform infrared (S 2 -FT-IR) spectroscopy at a pulse radiolysis facility. This new technique allows the rapid acquisition of nano- to microsecond time-resolved infrared (TRIR) spectra of transient species generated by pulse radiolysis of liquid samples at a pulsed electron accelerator. Wide regions of the mid-infrared can be probed in a single experiment, which often takes < 20–30 min to complete. It is therefore a powerful method for rapidly locating the IR absorptions of short-lived, radiation-induced species in solution, and for directly monitoring their subsequent reactions. Time-resolved step-scan FT-IR detection for pulse radiolysis thus complements our existing narrowband quantum cascade laser-based pulse radiolysis-TRIR detection system, which is more suitable for acquiring single-shot kinetics and narrowband TRIR spectra on small-volume samples and in strongly absorbing solvents, such as water. We have demonstrated the application of time-resolved step-scan FT-IR spectroscopy to pulse radiolysis by probing the metal carbonyl and organic carbonyl vibrations of the one-electron-reduced forms of two Re-based CO 2 reduction catalysts in acetonitrile solution. Transient IR absorption bands with amplitudes on the order of 1 × 10 −3 are easily detected on the sub-microsecond timescale using electron pulses as short as 250 ns.

(S2-FT-IR)↗
DOE OSTI2025

Searches for Sub-GeV Dark Matter with NOvA and LDMX and Performance Studies of the Cosmic-Ray Veto for Mu2e

The constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus to within about an MeV to 100 TeV. Most of the stable constituents of known matter have masses in the lower range, and a thermal origin for dark matter works in a simple and predictive manner in this mass range as well. Non-gravitational couplings of dark matter to Standard Model particles would make it possible to produce dark matter at accelerators. Through 120 GeV proton-nucleus collisions, NOvA is effectively a beam dump experiment for producing and detecting dark matter. This thesis presents a search for dark matter – electron scattering in the NOvA near detector from sub-GeV dark matter produced at the target. A future search for sub-GeV dark matter with the Light Dark Matter eXperiment (LDMX) is discussed, along with a study of LDMX's expected sensitivity to visibly decaying dark photons. Additionally, performance studies of the Mu2e cosmic ray veto (CRV) are presented. A calibration procedure for the CRV counters is discussed, along with tests of the efficiency, position resolution, and light yield decline of the CRV counters.

Horoho, Tyler Gregory [Virginia U.] (ORCID:0000000↗
DOE OSTI2021

JLAB LLRF 3.0 Development and Tests

The Jefferson Lab LLRF 3.0 system is being developed to replace legacy LLRF systems in the CEBAF accelerator. The new design builds upon 25 years of design and operational RF control experience, and our recent collaboration in the design of the LCLSII LLRF system. The new cavity control algorithm is a fully functional phase and amplitude locked Self Exciting Loop (SEL). This paper discusses the progress of the LLRF 3.0 hardware design, FPGA firmware development, User Datagram Protocol (UDP) operation, and recent LLRF 3.0 system tests on the CEBAF Booster cryomodule in the Upgrade Injector Test Facility (UITF).

Plawski, T. E.↗
DOE OSTI2023

Lattice design of 250 MeV version of PERLE

The PERLE (Powerful Energy Recovery LINAC for Experiment) collaboration is working on a high power energy recuperation linac facility with three acceleration (up to 500 MeV) and three deceleration passes through two cryomodules with an injection current of 20 mA. Here we present the lattice design of the first phase of this machine, which features a single cryo-module and demonstrates six-pass operation at a maximum energy of 250 MeV at a high current. This initial lattice design boasts a simpler structure with fewer elements, resulting in lower initial costs and faster construction and shorter commissioning time. Furthermore, all magnets and cryo-modules are designed to be compatible with both phases, keeping upgrade costs to a minimum.

Fomin, A.↗
DOE OSTI2023

Simulations of Hypervelocity Impact Plasmas

The space environment is fraught with complex plasmas spanning a wide range of densities and temperatures. Much of space plasma research has focused on large-scale changes in the ambient plasma and fields from the Sun to the Earth’s atmosphere, driven primarily by the solar wind. Yet one particular type of space plasma, which forms from a hypervelocity impact (HVI), remains poorly understood. Hypervelocity impactors include both meteoroids and space debris. Meteoroids are naturally occurring objects in space that travel between 11 and 72.8 km/s and originate primarily from comets and asteroids. In contrast, space debris are human-made objects with speeds typically < 11 km/s. Hypervelocity impactors routinely hit spacecraft, yet the physics behind the formation of the plasma and the dynamics of its expansion remain largely unknown. The complexity of this phenomenon necessitates a research approach that includes both experimental studies and numerical simulation in order to understand the underlying physical processes that occur upon formation and expansion of the impact plasma. Our research has focused on providing a comprehensive understanding of plasma generated by hypervelocity impacts by meteoroids and space debris on spacecraft in order to characterize the behavior of the expanding plasma and its interactions with the ambient environment. Previously. we conducted experimental campaigns at a dust accelerator facility that can accelerate particles up to 60 km/s, which is representative of meteoroid speeds, and at a light gas gun facility that can accelerate larger projectiles up to 7 km/s, which is representative of orbital debris. The experiments included plasma, optical and radio frequency (RF) sensors in order to understand the dynamics and associated RF emission resulting from hypervelocity plasmas. For this research, we developed and applied machine learning algorithms to identify which type of impactor would produce RF and physics-based models to determine the source of the RF. This was a one-year research program that resulted in 2 refereed journal publications (uploaded separately).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1975

Comparison of techniques for measuring +Gz tolerance in man

Two objective methods and one subjective method for measuring +Gz tolerance (inertial vector in a head-to-foot direction) were compared on the human centrifuge. Direct eye-level blood pressure (Pa), blood flow velocity in the superficial temporal artery (Qta), and subjective visual symptoms were used to determine tolerance to rapid-onset acceleration (1 G/s) on the USAFSAM human centrifuge. Seven 'relaxed' subjects with extensive centrifuge experience were exposed to gradually increasing +Gz plateaus until the subject reported 100% loss of peripheral centrifuge gondola lights (PLL) and 50% loss of central light (CLD); viz., blackout. Zero forward Qta occurred 6 s (range 4-9 s) before subjective blackout and when mean eye-level blood pressure had reached 20 + or - 1 mm Hg (SE). The results of this study indicate that flow changes in the superficial temporal artery reflect flow changes in the retinal circulation during +Gz stress.

Krutz, R. W., Jr.↗
NASA NTRS1976

Convection sensitivity and thermal analyses for indium and indium-lead mixing experiment (74-18)

Sounding rocket Experiment 74-18 was designed to demonstrate the effects of the Black Brandt rocket acceleration levels (during the low-g coast phase of its flight) on the motion of a liquid metal system to assist in preflight design. Some post flight analyses were also conducted. Preflight studies consisted of heat transfer analysis and convection sensitivity and convection modeling analyses which aided in the: (1) final selection of fluid materials (indium-lead melts rather than paraffins); (2) design and timing of heater and quench system; and (3) preflight predictions of the degree of lead penetration into the pure indium segment of the fluid. Postflight studies involved: (1) updating the convection sensitivity calculations by utilizing actual flight gravity levels; and (2) modeling the mixing in the flight samples.

Bourgeois, S. V.↗
NASA NTRS1976

A two-gas model of the lunar terminator exosphere

Lunar exospheric ions were accelerated by the solar-wind electric field into the Suprathermal Ion-Detector Experiment (SIDE), which was deployed on the lunar surface during the Apollo missions. Analysis of simultaneous mass and energy spectra from the SIDE indicates that the dominant component of the neutral exosphere at the lunar surface is a gas with mass on the order of 20 amu/q (consistent with Ne-20). The SIDE mass spectra also indicate the presence of gas with a mass of the order of 40 amu/q (consistent with Ar-40). By modeling the lunar exosphere as two exponentially height-distributed gases (Ne-20 and Ar-40), a good fit to the SIDE ion energy spectra can be achieved. The data indicate a surface concentration (n) of the order of 100,000 per cu cm for Ne-20 and 10,000 per cu cm for Ar-40 at a solar zenith angle of about 60 deg. The observed magnitudes of n for neon are consistent with the assumption that the solar wind is the only source of the neon.

Benson, J. L.↗
NASA NTRS1984

A high-resolution study of ultra-heavy cosmic-ray nuclei (A0178)

The main objective of the experiment is a detailed study of the charge spectra of ultraheavy cosmic-ray nuclei from zinc (Z = 30) to uranium (Z = 92) and beyond using solid-state track detectors. Special emphasis will be placed on the relative abundances in the region Z or - 65, which is thought to be dominated by r-process nucleosynthesis. Subsidiary objectives include the study of the cosmic-ray transiron spectrum a search for the postulated long-lived superheavy (SH) nuclei (Z or = 110), such as (110) SH294, in the contemporary cosmic radiation. The motivation behind the search for super-heavy nuclei is based on predicted half-lives that are short compared to the age of the Earth but long compared to the age of cosmic rays. The detection of such nuclei would have far-reaching consequences for nuclear structure theory. The sample of ultraheavy nuclei obtained in this experiment will provide unique opportunities for many tests concerning element nucleosynthesis, cosmic-ray acceleration, and cosmic-ray propagation.

Osullivan, D.↗
NASA NTRS1985

A model for the proton spectrum and cosmic ray anisotropy

The problem of the origin of the cosmic rays is still uncertain. As a theory, it should explain the support of particles and energy, the mechanism of acceleration and propagation as well as some important features obtained directly from cosmic ray experiments, such as the power spectrum and the knee. There are two kinds of models for interpreting the knee of the cosmic ray spectrum. One is the leaky box model. Another model suggests that the cut-off rigidity of the main sources causes the knee. The present paper studies the spectrum and the anisotropy of cosmic rays in an isotropic diffuse model with explosive discrete sources in an infinite galaxy.

Xu, C.↗
NASA NTRS1985

Particle acceleration due to shocks in the interplanetary field: High time resolution data and simulation results

Data were examined from two experiments aboard the Explorer 50 (IMP 8) spacecraft. The Johns Hopkins University/Applied Lab Charged Particle Measurement Experiment (CPME) provides 10.12 second resolution ion and electron count rates as well as 5.5 minute or longer averages of the same, with data sampled in the ecliptic plane. The high time resolution of the data allows for an explicit, point by point, merging of the magnetic field and particle data and thus a close examination of the pre- and post-shock conditions and particle fluxes associated with large angle oblique shocks in the interplanetary field. A computer simulation has been developed wherein sample particle trajectories, taken from observed fluxes, are allowed to interact with a planar shock either forward or backward in time. One event, the 1974 Day 312 shock, is examined in detail.

Kessel, R. L.↗
NASA NTRS1986

Structural analysis of the controlled impact demonstration of a jet transport airplane

An analytical method has been developed for assessing crash dynamics of large transport aircraft, such as in the NASA Controlled Impact Demonstration (CID) jet crash test on December 1, 1984. The DYCAST nonlinear finite-element computer code was used in a series of progressively more difficult tasks to model complete transport aircraft crashes. Single aircraft frames and fuselage section vertical drop tests were modeled and analyzed to obtain comparisons with experimental data and to develop hybrid element crash springs for use in the large CID model. Predictions of crash and acceleration levels from a symmetric CID model agreed well with data from the CID experiment.

Fasanella, E. L.↗
NASA NTRS1987

Turbulence modeling

Recent developments at several levels of statistical turbulence modeling applicable to aerodynamics are briefly surveyed. Emphasis is on examples of model improvements for transonic, two-dimensional flows. Experience with the development of these improved models is cited to suggest methods of accelerating the modeling process necessary to keep abreast of the rapid movement of computational fluid dynamics into the computation of complex three-dimensional flows.

Rubesin, Morris W.↗
NASA NTRS1989

Effects Of Pyrotechnically Generated Shocks

Research program provides better understanding of pyrotechnic phenomenon for design purposes. Evaluating potential for damage to spacecraft by activation of pyrotechnic mechanisms, pyrotechnic-shock tests conducted on three configurations: pin pullers on orthogonal double Hopkinson bar arrangement; pin pullers on mockup of Halogen Occultation Experiment (HALOE) structure; and section of separation joint on single Hopkinson bar. Strains and accelerations measured. Strains converted to output stresses, forces, and moments. Acceleration shock-response spectra obtained for both acceleration and force signals. Results of research useful to designers in making comparison and evaluation tests before committing to costly spacecraft hardware.

Bement, Laurence J.↗
NASA NTRS1989

Tethered variable gravity laboratory study: Low gravity process identification report

Experiments are described performable in the variable gravity environment, and the related compatible/beneficial residual accelerations, both for pure and applied research in the fields of Fluid Mechanics (static and dynamic), Materials Sciences (Crystal Growth, Metal and Alloy Solidification, Glasses, etc.), and Life Sciences, so as to assess the relevance of a variable G-level laboratory.

Briccarello, M.↗
NASA NTRS1992

Plasma effects of active ion beam injections in the ionosphere at rocket altitudes

Data from ARCS rocket ion beam injection experiments are primarily discussed. There are three results from this series of active experiments that are of particular interest in space plasma physics. These are the transverse acceleration of ambient ions in the large beam volume, the scattering of beam ions near the release payload, and the possible acceleration of electrons very close to the plasma generator which produce intense high frequency waves. The ability of 100 ma ion beam injections into the upper E and F regions of the ionosphere to produce these phenomena appear to be related solely to the process by which the plasma release payload and the ion beam are neutralized. Since the electrons in the plasma release do not convect with the plasma ions, the neutralization of both the payload and beam must be accomplished by large field-aligned currents (milliamperes/square meter) which are very unstable to wave growth of various modes.

Arnoldy, R. L.↗