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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

LOW-FREQUENCY OBSERVATIONS OF LINEARLY POLARIZED STRUCTURES IN THE INTERSTELLAR MEDIUM NEAR THE SOUTH GALACTIC POLE

We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg{sup 2} centered on α = 0{sup h}and δ = −27°. The sensitivity available in our deep observations allows an in-band, frequency-dependent analysis of polarized structure for the first time at long wavelengths. Our analysis suggests that the polarized structures are dominated by intrinsic emission but may also have a foreground Faraday screen component. At these wavelengths, the compactness of the MWA baseline distribution provides excellent snapshot sensitivity to large-scale structure. The observations are sensitive to diffuse polarized emission at ∼54′ resolution with a sensitivity of 5.9 mJy beam{sup −1} and compact polarized sources at ∼2.′4 resolution with a sensitivity of 2.3 mJy beam{sup −1} for a subset (400 deg{sup 2}) of this field. The sensitivity allows the effect of ionospheric Faraday rotation to be spatially and temporally measured directly from the diffuse polarized background. Our observations reveal large-scale structures (∼1°–8° in extent) in linear polarization clearly detectable in ∼2 minute snapshots, which would remain undetectable by interferometers with minimum baseline lengths of >110 m at 154 MHz. The brightness temperature of these structures is on average 4 K in polarized intensity, peaking at 11 K. Rotation measure synthesis reveals that the structures have Faraday depths ranging from −2 to 10 rad m{sup −2} with a large fraction peaking at approximately +1 rad m{sup −2}. We estimate a distance of 51 ± 20 pc to the polarized emission based on measurements of the in-field pulsar J2330–2005. We detect four extragalactic linearly polarized point sources within the field in our compact source survey. Based on the known polarized source population at 1.4 GHz and non-detections at 154 MHz, we estimate an upper limit on the depolarization ratio of 0.08 from 1.4 GHz to 154 MHz.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

WIYN Open Cluster Study LXXIX. M48 (NGC 2548) I. Radial Velocities, Rotational Velocities, and Metallicities of Stars in the Open Cluster M48 (NGC 2548)

WIYN/Hydra spectra (R ∼ 13,500, signal-to-noise pixel{sup −1} = 50–1000) of a 400 Å region around Li 6708 Å are used to determine radial and rotational velocities for 287 photometrically selected candidate members of the open cluster M48. The sample ranges from turnoff A stars to late-K dwarfs and eight giants. We combine our V {sub RAD} measurements and power spectrum analysis with parallax and proper motion data from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as single cluster members, 11 as binary members, 16 as members of uncertain multiplicity, 56 as single nonmembers, 28 as single “likely” nonmembers, two as single “likely” members, one as a binary “likely” member, five as binary nonmembers, 10 as “likely” members of uncertain multiplicity, three as nonmembers of uncertain multiplicity, and three as “likely” nonmembers of uncertain multiplicity. From a subsample of 95 single members, we derive V {sub RAD} = 8.512 ± 0.087 km s{sup −1} (σ {sub μ}, and σ = 0.848 km s{sup −1}). Using 16 isolated Fe I lines for a subsample of 99 single members (that have σ{sub T{sub e{sub f{sub f}}}}<75 K (from 10 colors from UBVRI), v sin i < 25 km s{sup −1}, and well-behaved Fe I lines), [Fe/H]{sub M48} = −0.063 ± 0.007 dex (σ {sub μ}). [Fe/H] is independent of T {sub eff} over an unprecedentedly large range of 2500 K. The minimum cluster binary fraction is 11%–21%. M48 exhibits a clear but modest broadening of the main-sequence turnoff, and there is no correlation between color and v sin i.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Jets with a Twist: The Emergence of FR0 Jets in a 3D GRMHD Simulation of Zero-angular-momentum Black Hole Accretion

Abstract Spinning supermassive black holes (BHs) in active galactic nuclei magnetically launch relativistic collimated outflows, or jets. Without angular momentum supply, such jets are thought to perish within 3 orders of magnitude in distance from the BH, well before reaching kiloparsec scales. We study the survival of such jets at the largest scale separation to date, via 3D general relativistic magnetohydrodynamic simulations of rapidly spinning BHs immersed into uniform zero-angular-momentum gas threaded by a weak vertical magnetic field. We place the gas outside the BH sphere of influence, or the Bondi radius, chosen to be much larger than the BH gravitational radius, R B = 10 3 R g . The BH develops dynamically important large-scale magnetic fields, forms a magnetically arrested disk (MAD), and launches relativistic jets that propagate well outside R B and suppress BH accretion to 1.5% of the Bondi rate, M ̇ B . Thus, low-angular-momentum accretion in the MAD state can form large-scale jets in Fanaroff–Riley (FR) type I and II galaxies. Subsequently, the disk shrinks and exits the MAD state: barely a disk (BAD), it rapidly precesses, whips the jets around, globally destroys them, and lets 5%–10% of M ̇ B reach the BH. Thereafter, the disk starts rocking back and forth by angles 90°–180°: the rocking accretion disk (RAD) launches weak intermittent jets that spread their energy over a large area and suppress BH accretion to ≲2% M ̇ B . Because the BAD and RAD states tangle up the jets and destroy them well inside R B , they are promising candidates for the more abundant, but less luminous, class of FR0 galaxies.

Astronomy & Astrophysics↗
DOE OSTI2017

What Is the Hidden Depolarization Mechanism in Low-luminosity AGNs?

Millimeter-wavelength polarimetry of accreting black hole systems can provide a tomographic probe of the accretion flow on a wide range of linear scales. We searched for linear polarization in two low-luminosity active galactic nuclei (LLAGNs), M81 and M84, using the Combined Array for Millimeter Astronomy and the Submillimeter Array. We find upper limits of ∼1%–2% averaging over the full bandwidth and with a rotation measure (RM) synthesis technique. These low polarization fractions, along with similarly low values for LLAGNs M87 and 3C 84, suggest that LLAGNs have qualitatively different polarization properties than radio-loud sources and Sgr A*. If the sources are intrinsically polarized and then depolarized by Faraday rotation, then we place lower limits on the RM of a few times 10{sup 7} rad m{sup −2} for the full bandwidth case and ∼10{sup 9} rad m{sup −2} for the RM synthesis analysis. These limits are inconsistent with or marginally consistent with expected accretion flow properties. Alternatively, the sources may be depolarized by cold electrons within a few Schwarzschild radii from the black hole, as suggested by numerical models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

The effect of inverse Compton losses on particle acceleration in three-dimensional relativistic reconnection

Relativistic magnetic reconnection is a key mechanism for dissipating magnetic energy and accelerating particles in astrophysics. In the absence of radiative cooling, recent particle-in-cell (PIC) simulations have shown that high-energy particles gain most of their energy in the upstream region, during a short-lived "free phase" where they meander between the two sides of the layer; when they get captured/trapped by the downstream flux ropes, they undergo a "trapped phase", where no significant energization occurs. Here, we perform a suite of 3D PIC simulations of relativistic reconnection including inverse Compton (IC) losses in the weakly cooled regime in which the radiation-reaction-limited Lorentz factor $γ_{\rm rad}$ exceeds the magnetization $σ$. We show that electron cooling losses do not appreciably alter the reconnection rate, the structure of the layer, and the physics of particle acceleration in the free phase, so the spectrum of free electrons is $dN_{\rm free}/dγ\propto γ^{-1}$, as in the uncooled case. The spectrum of trapped electrons above the cooling break $γ_{\rm cool}$ (in the range $γ_{\rm cool}<γ<γ_{\rm rad}$) is $dN/dγ\propto γ^{-3}$, steeper than the scaling $dN/dγ\propto γ^{-2}$ of uncooled simulations. This confirms that no significant particle energization occurs during the trapped phase. Our results validate the model by arXiv:2302.12269 for particle acceleration in 3D relativistic reconnection, and imply that radiative emission models of reconnection-powered astrophysical sources should employ a two-zone structure, that differentiates between free, rapidly accelerating particles and trapped, passively cooling particles.

FOS: Physical sciences↗
DOE OSTI2019

MDSplus Yesterday, Today and Tomorrow

MDSplus is a data acquisition and analysis system used worldwide predominantly in the fusion research community. Development began 31 years ago by a collaboration of software developers who were charged with providing a data acquisition system for three new fusion experiments under construction: CMOD at MIT, ZTH at LANL and RFX at Padova, Italy. The design of MDSplus combined the functionality of MDS (MIT/Model Data System developed at MIT for the Alcator and Tara fusion experiments) with new features suggested by the developers from the other laboratories. The development of MDSplus used a RAD (rapid application development) approach before RAD became a mainstream methodology. MDSplus was implemented and ready for the initial operation of CMOD in 1991. Since that time, many other fusion facilities started using MDSplus for data acquisition and/or for exporting their data to other sites. Today MDSplus is still used around the world for fusion energy research, space exploration and other fields of science and technology. Work on MDSplus continues to enhance its capabilities, support more platforms, and improve its reliability. It is anticipated that MDSplus will continue to provide valuable tools for the fusion energy research community. This paper describes some of the history of the MDSplus software, the work that is currently underway, and the plans to enable MDSplus to continue to be available and supported long into the future.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1964

The X-Irradiation of Hydrazine and 1,1- Dimethylhydrazine

Hydrazine and 1,1-dimethylhydrazine were radiolyzed at room temperature by using about 1 gram of liquid or 1/2 to 2 liters of vapor at room-temperature vapor pressure. A tungsten-target X-ray source operating at 300 kilovolts and 6 to 8 milliamperes (0.1 to 1.0 A) was used at intensities of 1 times 10 (sup 2) to 1 times 10 (sup 3) roentgens per minute to give total doses of 4.1 rads to 2.3 times 10 (sup 6) rads. The amounts of decomposition were dependent on total dose and independent of dose rate. In the case of hydrazine vapor, the decomposition was also directly related to surface area. There was a lesser surface effect with liquid hydrazine, but this variable was not studied for 1,1-dimethylhydrazine. The order of decreasing sensitivity to X-radiation is as follows: hydrazine vapor, 1,1-dimethylhydrazine vapor, 1,1-dimethylhydrazine liquid, and hydrazine liquid. The decomposition products of hydrazine were nitrogen, hydrogen, ammonia, and unidentified products. The same products plus methylamine, dimethylamine, and hydrazine were found from the decomposition of 1,1-dimethylhydrazine. In addition, the 1,1-dimethylhydrazine underwent post-irradiation changes. Values for G (number of molecules of sample decomposed per 100 electronvolts of absorbed energy) of the order of 10 (sup 6) suggest that the vapor-phase decompositions are chain reactions.

X-RAY IRRADIATION↗
NASA NTRS1972

Brain tumors in irradiated monkeys.

A study was made of 32 monkeys which survived one to seven years after total body exposure to protons or to high-energy X rays. Among these 32 monkeys there were 21 which survived two years or longer after exposure to 200 to 800 rad. Glioblastoma multiforme developed in 3 of the 10 monkeys surviving three to five years after receiving 600 or 800 rad 55-MeV protons. Thus, the incidence of tumor development in the present series was far higher than the incidence of spontaneously developing brain tumors in monkeys cited in the literature. This suggests that the tumors in the present series may have been radiation-induced.

Haymaker, W.↗
NASA NTRS1972

Film type SO-168 radiation study

Investigations were performed to determine optimum exposure and processing procedures necessary to partially offset the effect of radiation to which film type SO-168 will be exposed during the Skylab Mission. This task became necessary when it was determined that original predictions of 2 to 3 RADS of radiation to which the film will be exposed were too low, and that levels as high as 3.5 to 4.0 RADS may be incurred, thus reducing image quality below an acceptable level. Tests results show that forced processing of type SO-168 film tended to reduce the density range to an unusable level, and that processing to a lower ASA value would provide greater image quality for the user.

Pierce, W. N.↗
NASA NTRS1975

Histological analysis of the influence of certain extremal factors on the postradiational changes in the tissues of experimental animals

Protons with energies of 120 MeV at a dose of 640 rads or gamma-neutron radiation at a dose of 300 rads produce radiation sickness of moderate severity in rats. The significance of toxemia and disturbances to the endocrine regulatory system in the development of metabolic processes in various stages of radiation sickness are discussed.

Sutulov, L. S.↗
NASA NTRS1976

Fiber composite fan blade impact improvement

The improved foreign object damage resistance of a metal matrix advanced composite fan blade was demonstrated. The fabrication, whirl impact test and subsequent evaluation of nine advanced composite fan blades of the "QCSEE" type design were performed. The blades were designed to operate at a tip speed of 282 m/sec. The blade design was the spar/shell type, consisting of a titanium spar and boron/aluminum composite airfoils. The blade retention was designed to rock on impact with large birds, thereby reducing the blade bending stresses. The program demonstrated the ability of the blades to sustain impacts with up to 681 g slices of birds at 0.38 rad with little damage (only 1.4 percent max weight loss) and 788 g slices of birds at 0.56 rad with only 3.2 percent max weight loss. Unbonding did not exceed 1.1 percent of the post-test blade area during any of the tests. All blades in the post-test condition were judged capable of operation in accordance with the FAA guidelines for medium and large bird impacts.

Graff, J.↗
NASA NTRS1976

Linear polarimeter with rapid modulation, achromatic in the 0.3-1.1-micron range

A polarimeter is described, which provides achromatic modulation over the spectral range 0.3 to 1.1 microns, with very small light losses. The instrument is the first one to use superachromatic half-wave plates; such a plate is made of three achromatic half-wave plates of quartz and magnesium fluoride cemented with the optical axis of the central plate making an angle of 1.00 rad with the axes of the parallel-oriented outer half-wave plates. Wavelength dependence of the axis direction of the optical axis was eliminated by using two identical such plates in front of a Wollaston prism. The plate closer to the prism is stationary, while the other is continuously rotated by a stepper motor. In the polarimeter constructed, the range of instrumentally induced wavelength dependence of the plane of polarization did not exceed 0.002 rad. Using the polarimeter on a 228-cm telescope, a 10-min integration through the blue filter of the UBV photometric system for a star of magnitude 10.0 gives the percentage polarization with a mean error of + or - 0.014%.

Frecker, J. E.↗
NASA NTRS1977

Effects of radiation upon the light-sensing elements of the retina as characterized by scanning electron microscopy

A model system using Necturus maculosus, the common mudpuppy, was established for evaluating effects of radiation upon the light-sensing elements of the retina. Accelerated heavy ions of helium and neon from the Berkeley Bevalac were used. A number of criteria were chosen to characterize radiation damage by observing morphological changes with the scanning electron microscope. The studies indicated retina sensitivity to high-LET (neon) particles at radiation levels below 10 rads (7 particles per visual element) whereas no significant effects were seen from fast helium ions below 50 rads.

Malachowski, M. J.↗
NASA NTRS1978

Evaluation of radiation interference in the Voyager Sun Sensor's cadmium sulfide detector

The simulation of radiation interference effects and the results of a radiation interference test on two Voyager Sun Sensor prototype detector assemblies are reported. The derivation of test levels and requirements are discussed and show that cobalt 60 gamma radiation is an effective and practical simulator of the ionization dose rate effects induced by high-energy electron flux incident on the spacecraft at a rate of 3.7 x 10 to the 8th e/sq cm-sec (10 rad(Si)/s) during closest approach to Jupiter. The test results provide information that is used to confirm an analytic correlation, and to predict satisfactory performance of a spacecraft sun sensing device having stringent angular resolution requirements. The measured detector response shows that at dose rates incident on the detector elements of 2 rad(Si)/sec, which is four times that expected during Jupiter encounter, the radiation-induced angle error is almost an order of magnitude less than that allowed by the acceptance criteria.

Clarke, T. C.↗
NASA NTRS1980

Radiation Exposure of Selected Composites and Thin Films

The effect of electron radiation on selected candidate composite materials was investigated. Radiation damage mechanisms were identified and the coefficient of thermal expansion were measured for each type composite material. It was concluded that the threshold for major physical and mechanical property changes in the polysulfone films and in the polysulfone and epoxy composites is in excess of 1 x 10 to the 9th power rads of electrons. Based upon these data, the 5208 and 934 epoxies and the P1700 polysulfone composites would be acceptable for 5 to 10 year geosynchronous Earth environment missions receiving 1 x 10 to the 9th power rads of electron radiation.

Wayne S Slemp↗
NASA NTRS1981

Solid state microelectronics tolerant to radiation and high temperature

The 300 C electronics technology based on JFET thick film hybrids was tested up to 10 to the 9th power rad gamma (Si) and 10 to the 15th power neutrons/sq cm. Circuits and individual components from this technology all survived this total dose although some devices required 1 hour of annealing at 200 or 300 C to regain functionality. This technology used with real time annealing should function to levels greater than 10 to the 10th power rad gamma and 10 to the 16th power n/sq cm.

Draper, B. L.↗
NASA NTRS1982

Calibration of the active radiation detector for Spacelab-One

The flight models of the active radiation detector (ARD) for the ENV-01 environmental monitor were calibrated using gamma radiation. Measured sensitivities of the ion chambers were 6.1 + or - 0.3 micron rad per count for ARD S/N1, and 10.4 + or - 0.5 micron rad per count for ARD S/N2. Both were linear over the measured range 0.10 to 500 m/rad hour. The particle counters (proportional counters) were set to respond to approximately 85% of minimum ionizing particles of unit charge passing through them. These counters were also calibrated in the gamma field.

Source record↗
NASA NTRS1982

Nuclear reactor system study for NASA/JPL

Reactor shielding, safety studies, and heat pipe development work are described. Monte Carlo calculations of gamma and neutron shield configurations show that substantial weight penalties are incurred if exposure at 25 m to neutrons and gammas must be limited to 10 to the 12th power nvt and 10 to the 6th power rad, instead of the 10 to the 13th power nvt and 10 to the 7th power rad values used earlier. For a 1.6 MW sub t reactor, the required shield weight increases from 400 to 815 kg. Water immersion critically calculations were extended to study the effect of water in fuel void spaces as well as in the core heat pipes. These show that the insertion into the core of eight blades of B4C with a mass totaling 2.5 kg will guarantee subcriticality. The design, fabrication procedure, and testing of a 4m long molybdenum/lithium heat pipe are described. It appears that an excess of oxygen in the wick prevented the attainment of expected performance capability.

Palmer, R. G.↗