Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ASTROPHYSICS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

AMS-100: The next generation magnetic spectrometer in space – An international science platform for physics and astrophysics at Lagrange point 2

The next generation magnetic spectrometer in space, AMS-100, is designed to have a geometrical acceptance of 100 m 2 sr and to be operated for at least ten years at the Sun–Earth Lagrange Point 2. Compared to existing experiments, it will improve the sensitivity for the observation of new phenomena in cosmic rays, and in particular in cosmic antimatter, by at least a factor of 1000. The magnet design is based on high temperature superconductor tapes, which allow the construction of a thin solenoid with a homogeneous magnetic field of 1 Tesla inside. The inner volume is instrumented with a silicon tracker reaching a maximum detectable rigidity of 100 TV and a calorimeter system that is 70 radiation lengths deep, equivalent to four nuclear interaction lengths, which extends the energy reach for cosmic-ray nuclei up to the PeV scale, i.e. beyond the cosmic-ray knee. In conclusion, covering most of the sky continuously, AMS-100 will detect high-energy gamma-rays in the calorimeter system and by pair conversion in the thin solenoid, reconstructed with excellent angular resolution in the silicon tracker.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Proton decay of 108 I and its significance for the termination of the astrophysical rp -process

Employing the Argonne Fragment Mass Analyzer and the implantation-decay-decay correlation technique, a weak 0.50(21)% proton decay branch was identified in 108 I for the first time. Here the 108 I proton-decay width is consistent with a hindered l = 2 emission, suggesting a d 5/2 origin. Using the extracted 108 I proton-decay Q value of 597(13) keV, and the Q α values of the 108 I and 107 Te isotopes, a proton-decay Q value of 510(20) keV for 104 Sb was deduced. Similarly to the 112,113 Cs proton-emitter pair, the value is lower than that for the less-exotic neighbor 109 I, possibly due to enhanced proton-neutron interactions in N ≈ 2 nuclei. In contrast, the present is higher than that of 105 Sb, suggesting a weaker interaction energy.

104Sb↗
DOE OSTI2023

VarIabiLity seLection of AstrophysIcal sources iN PTF (VILLAIN): I. Structure function fits to 71 million objects

Light-curve variability is well-suited to characterizing objects in surveys with high cadence and a long baseline. This is especially relevant in view of the large datasets to be produced by the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). We aim to determine variability parameters for objects in the Palomar Transient Factory (PTF) and explore differences between quasars (QSOs), stars, and galaxies. We relate variability and colour information in preparation for future surveys. We fit joint likelihoods to structure functions (SFs) of 71 million PTF light curves with a Markov chain Monte Carlo method. For each object, we assume a power-law SF and extract two parameters: the amplitude on timescales of one year, A, and a power-law index, γ. With these parameters and colours in the optical (Pan-STARRS1) and mid-infrared (WISE), we identify regions of parameter space dominated by different types of spectroscopically confirmed objects from SDSS. Candidate QSOs, stars, and galaxies are selected to show their parameter distributions. QSOs show high-amplitude variations in the R band, and the highest γ values. Galaxies have a broader range of amplitudes and their variability shows relatively little dependency on timescale. With variability and colours, we achieve a photometric selection purity of 99.3% for QSOs. Even though hard cuts in monochromatic variability alone are not as effective as seven-band magnitude cuts, variability is useful in characterizing object subclasses. Through variability, we also find QSOs that were erroneously classified as stars in the SDSS. We discuss perspectives and computational solutions in view of the upcoming LSST.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Astrophysical and laboratory constraints for the dense matter equation of state

New measurements of neutron star masses and radii have lead to powerful constraints on the dense matter equation of state. In the vicinity of the nuclear saturation density, the symmetry energy is the least well understood aspect of the nuclear force. Independent constraints from a variety of nuclear experiments are now able to refine the parameters of the symmetry energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

{sup 3}He+{sup 4}He astrophysical factor study using activation method

In 1998, [2] pointed out the big difference for the S{sub 34}(0) ('old' experimental data) when experimental results were grouped starting from the main two methods: S{sub 34}(0) = 0.507(16)keVb for the direct capture and S{sub 34}(0) = 0.572(26)keVb for the activation. Its importance for the Standard Solar Model was the reason to ask for new measurements to understand the discrepancy. 'New' results solved this issue by equalizing the above values, but introduced a new situation to clarify: a discrepancy between the S{sub 34}(E) variations for 'old' and 'new' data at higher energies than E{sub CM} 1.0MeV. 'Old' theoretical models, used for extrapolating the S{sub 34}(E) to the stellar energies, couldn't explain this new behavior. New experimental data was required, again, by theorists. We started this project with the main goal to clarify the situation. Here are the results.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Possible explanation for the low flux of high energy astrophysical muon neutrinos

I consider the possibility that some exotic neutrino property is responsible for reducing the muon neutrino flux at high energies from distant sources; specifically, (i) neutrino decay and (ii) neutrinos being pseudo-Dirac particles. This would provide a mechanism for the lack of high energy muon events in the Icecube detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Selected topics in nuclear astrophysics

In this lectures after a brief introduction to stellar reaction rates and its implementation in nuclear networks, I discuss the nuclear physics aspects of core collapse supernova and explosive nucleosynthesis and their significance for the production of heavy elements by the rapid neutron capture process and potentially also by the recently discovered {nu}p process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Determination of astrophysical thermonuclear rates with a bubble chamber: The {sup 12}C(αγ){sup 16}O reaction case

The {sup 12}C(αγ){sup 16}O reaction rate is considered one of the most important unknown parameters in the physics of structure and evolution of massive stars. While extensive experimental campaigns have been performed trying to improve the quality of the measurements, the rate still holds very large uncertainties. Here we discuss a new experimantal scheme to measure the cross section of this reaction with a bubble chamber and a bremsstrahlung beam. The main advantage of the technique is a gain in the luminosity of several orders of magnitude when compared to other ongoing experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Astrophysical S-factor for destructive reactions of lithium-7 in big bang nucleosynthesis

One of the most prominent success with the Big Bang models is the precise reproduction of mass abundance ratio for {sup 4}He. In spite of the success, abundances of lithium isotopes are still inconsistent between observations and their calculated results, which is known as lithium abundance problem. Since the calculations were based on the experimental reaction data together with theoretical estimations, more precise experimental measurements may improve the knowledge of the Big Bang nucleosynthesis. As one of the destruction process of lithium-7, we have performed measurements for the reaction cross sections of the {sup 7}L({sup 3}He,p){sup 9}Be reaction.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

The universe in the laboratory - Nuclear astrophysics opportunity at the facility for antiproton and ion research

In the next years the Facility for Antiproton and Ion Research FAIR will be constructed at the GSI Helmholtzze-ntrum für Schwerionenforschung in Darmstadt, Germany. This new accelerator complex will allow for unprecedented and pathbreaking research in hadronic, nuclear, and atomic physics as well as in applied sciences. This manuscript will discuss some of these research opportunities, with a focus on supernova dynamics and nucleosynthesis.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Comparison of two HPGe counting system used in activation studies for nuclear astrophysics

The activation method is a widely used technique to measure charged-particle induced cross sections for astrophys-ical applications. This two step technique is used for example to measure alpha-induced cross sections in γ-process related studies. The first step – in which a target is irradiated with a proton/alpha beam – is followed by the determination of the produced activity. Especially in p-process related studies in the heavier mass range, the produced radioactive nuclei decays mainly with electron-capture, resulting intense x-rays. The activity of the reaction products hence can be determine via the counting of these x-rays, and not only by counting the usually much weaker γ-rays. In this paper we compare the minimum detectable activity (MDA) of two High Purity Germanium (HPGe) detectors used for x- and γ-ray counting in activation experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗