scholarly journals An Interpretation of De-excitation Gamma Ray Measurements Following the Photodisintegration of 12C, 16O, and 40Ca

1973 ◽  
Vol 26 (3) ◽  
pp. 269 ◽  
Author(s):  
BM Spicer
Keyword(s):  
Gamma Ray ◽  
Ground States ◽  
Radiation Absorption ◽  
Final States ◽  
Photonuclear Reactions ◽  
Absorption Process ◽  
The One

The relative populations of final states in photonuclear reactions for 12C, 160, and 40Ca are examined in the light of information on the known major configurations present in the wavefunctions of those final states, with the assumption that the nucleon excited in the radiation absorption process is in fact the one emitted. This assumption is investigated and found to be reasonable for 12C and 160 but not for 40Ca. The data on relative populations of final states are interpreted to give information on the relative strengths of configurations in the wavefunctions of the ground states of the three nuclei.

THE PHOTONEUTRON CROSS SECTIONS OF Rb87, Zr90, AND Mo92

1953 ◽  
Vol 31 (2) ◽  
pp. 250-261 ◽  
Author(s):  
L. Katz ◽  
R. G. Baker ◽  
R. Montalbetti
Keyword(s):  
Photon Energy ◽  
Cross Sections ◽  
Ground States ◽  
Half Maximum ◽  
Photonuclear Reactions ◽  
Shape Characteristic ◽  
Elementary Analysis ◽  
The Cross

The photoneutron cross sections of the 50-neutron isotopes Rb87, Zr90, and Mo92 have been measured as a function of photon energy. These cross sections exhibit the peaked shape characteristic of photonuclear reactions. Peak values of 0.23, 0.27, and 0.14 barn at 17.5, 18.0, and 18.7 Mev. respectively were found for these nuclei. The widths of all the curves at half maximum were about 6 Mev. In the case of zirconium and molybdenum the cross sections to the isomeric and ground states of the residual nuclei have been determined separately. The ratio of the cross sections, σ ground/σ isomeric, has been examined as a function of photon energy and is discussed in the light of the elementary analysis previously presented.

scholarly journals Gamma-Ray Bursts and Binary Neutron Star Mergers

1996 ◽  
Vol 165 ◽  
pp. 489-502
Author(s):  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Gravitational Radiation ◽  
Gamma Ray ◽  
Indirect Evidence ◽  
Gamma Ray Bursts ◽  
Binary Neutron Star ◽  
Merger Event ◽  
Γ Rays ◽  
Γ Ray ◽  
The One

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

scholarly journals Gamma-Ray Sensitivity to Dark Matter Subhalo Modelling at High Latitudes

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 90 ◽  
Author(s):  
Francesca Calore ◽  
Moritz Hütten ◽  
Martin Stref
Keyword(s):  
Dark Matter ◽  
Gamma Ray ◽  
Detection Threshold ◽  
Point Sources ◽  
Large Set ◽  
Case Scenario ◽  
Tidal Disruption ◽  
Dwarf Spheroidal Galaxies ◽  
Dark Matter Mass ◽  
The One

Searches for “dark” subhaloes in gamma-ray point-like source catalogues are among promising strategies for indirect dark matter detection. Such a search is nevertheless affected by uncertainties related, on the one hand, to the modelling of the dark matter subhalo distribution in Milky-Way-like galaxies, and, on the other hand, to the sensitivity of gamma-ray instruments to the dark matter subhalo signals. In the present work, we assess the detectability of dark matter subhaloes in Fermi-LAT catalogues, taking into accounts uncertainties associated with the modelling of the galactic subhalo population. We use four different halo models bracketing a large set of uncertainties. For each model, adopting an accurate detection threshold of the LAT to dark matter subhalo signals and comparing model predictions with the number of unassociated point-sources in Fermi-LAT catalogues, we derive upper limits on the annihilation cross section as a function of dark matter mass. Our results show that, even in the best-case scenario (i.e., DMonly subhalo model), which does not include tidal disruption from baryons, the limits on the dark matter parameter space are less stringent than current gamma-ray limits from dwarf spheroidal galaxies. Comparing the results obtained with the different subhalo models, we find that baryonic effects on the subhalo population are significant and lead to dark matter constraints that are less stringent by a factor of ∼2 to ∼5. This uncertainty comes from the unknown resilience of dark matter subhaloes to tidal disruption.

Using a clinical linac to determine the energies of gamma-ray transitions and half-lives of barium nuclei

2020 ◽  
Vol 35 (10) ◽  
pp. 2050062
Author(s):  
Abdullah Engin Çalık ◽  
Kaan Manisa ◽  
Ahmet Biçer ◽  
Mehmet Erdoğan ◽  
Mürsel Şen ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Linear Accelerator ◽  
Nuclear Physics ◽  
Hpge Detector ◽  
Gamma Ray ◽  
Energy Levels ◽  
Photonuclear Reactions ◽  
High Purity Germanium ◽  
Physics Experiment ◽  
First Time

Photonuclear reactions have great importance in understanding the structure of the nuclei. These reactions, performed using the gamma rays obtained by way of bremsstrahlung, are a standard nuclear physics experiment. In this study, a non-enriched barium sample was activated for the first time by using a clinical linear accelerator (cLINACs). The spectrum of barium radioisotopes was obtained by using a gamma spectrometry with a high purity germanium (HPGe) detector. The obtained spectroscopic data were analyzed and energy levels and half-life values together with their uncertainties were obtained. Some energy levels and half-lives of [Formula: see text]Ba were determined with more precision than those of literature values.

scholarly journals The Effect of Magnetic Fields Upon Cosmic X-ray Spectra

1990 ◽  
Vol 115 ◽  
pp. 70-77
Author(s):  
P. Mészáros
Keyword(s):  
Magnetic Fields ◽  
Gamma Ray ◽  
Line Emission ◽  
Atomic Line ◽  
Photon Scattering ◽  
Theoretical Understanding ◽  
Strong Magnetic Fields ◽  
X Ray ◽  
Two Photon ◽  
The One

AbstractThe effect of strong magnetic fields (B ≳ 1011Gauss) upon various atomic line emission mechanisms in the X-ray range is considered, in particular for H and H-like or He-like ions, and a discussion of the detectability and significance of possible measurements is given. The cyclotron mechanism, the one- and two-photon scattering and the bremsstrahlung effects in a strong B are reviewed, as well as the role they play in determining X-ray spectra. These considerations are applied to typical models of X-ray pulsars and Gamma-ray bursters, contrasting observations of magnetic related features to the present theoretical understanding of these objects.

CO2 Emission Abatement in IGCC Power Plants by Semiclosed Cycles: Part B—With Air-Blown Combustion and CO2 Physical Absorption

1999 ◽  
Vol 121 (4) ◽  
pp. 642-648 ◽  
Author(s):  
P. Chiesa ◽  
G. Lozza
Keyword(s):  
Power Plants ◽  
Pressure Ratio ◽  
Co2 Concentration ◽  
Absorption Process ◽  
Combustion Gases ◽  
Additional Equipment ◽  
Physical Absorption ◽  
Previous Solution ◽  
The One ◽  
The Impact

This paper analyzes the fundamentals of IGCC power plants with carbon dioxide removal systems, by a cycle configuration alternative to the one discussed in Part A (with oxygen-blown combustion). The idea behind this proposal is to overcome the major drawbacks of the previous solution (large oxygen consumption and re-design of the gas turbine unit), by means of a semiclosed cycle using air as the oxidizer. Consequently, combustion gases are largely diluted by nitrogen and cannot be simply compressed to produce liquefied CO2 for storage or disposal. However, CO2 concentration remains high enough to make separation possible by a physical absorption process. It requires a re-pressurization of the flow subtracted from the cycle, with relevant consequences on the plant energy balance. The configuration and the thermodynamic performance of this plant concept are extensively addressed in the paper. As in the first part, the influence of the pressure ratio is discussed, but values similar to the ones adopted in commercial heavy-duty machines provided here acceptable performance. Proper attention was paid to the impact of the absorption process on the energy consumption. The resulting net overall efficiency is again in the 38–39 percent range, with assumptions fully comparable to the ones of Part A. Finally, we demonstrated that the present scheme enables the use of unmodified machines, but large additional equipment is required for exhausts treatment and CO2 separation. A final comparison between the two semiclosed cycle concepts was therefore addressed.

scholarly journals Kinetic beaming in radiative relativistic magnetic reconnection: a mechanism for rapid gamma-ray flares in jets

2020 ◽  
Vol 498 (1) ◽  
pp. 799-820 ◽  
Author(s):  
J M Mehlhaff ◽  
G R Werner ◽  
D A Uzdensky ◽  
M C Begelman
Keyword(s):  
Magnetic Reconnection ◽  
Gamma Ray ◽  
Critical Role ◽  
High Energy ◽  
Particle In Cell ◽  
Pair Plasma ◽  
Spectrum Radio ◽  
Inverse Compton ◽  
Emission Models ◽  
The One

ABSTRACT Rapid gamma-ray flares pose an astrophysical puzzle, requiring mechanisms both to accelerate energetic particles and to produce fast observed variability. These dual requirements may be satisfied by collisionless relativistic magnetic reconnection. On the one hand, relativistic reconnection can energize gamma-ray emitting electrons. On the other hand, as previous kinetic simulations have shown, the reconnection acceleration mechanism preferentially focuses high energy particles – and their emitted photons – into beams, which may create rapid blips in flux as they cross a telescope’s line of sight. Using a series of 2D pair-plasma particle-in-cell simulations, we explicitly demonstrate the critical role played by radiative (specifically inverse Compton) cooling in mediating the observable signatures of this ‘kinetic beaming’ effect. Only in our efficiently cooled simulations do we measure kinetic beaming beyond one light crossing time of the reconnection layer. We find a correlation between the cooling strength and the photon energy range across which persistent kinetic beaming occurs: stronger cooling coincides with a wider range of beamed photon energies. We also apply our results to rapid gamma-ray flares in flat-spectrum radio quasars, suggesting that a paradigm of radiatively efficient kinetic beaming constrains relevant emission models. In particular, beaming-produced variability may be more easily realized in two-zone (e.g. spine-sheath) set-ups, with Compton seed photons originating in the jet itself, rather than in one-zone external Compton scenarios.

Beta Backscattering and Gamma Radiation Absorption Characteristics of Carbon Nanoparticles Contained Concrete Composite

2017 ◽  
Vol 17 ◽  
pp. 31-36 ◽  
Author(s):  
B. Gopal Krishna ◽  
Pooja Prasad ◽  
Vibha Sahu ◽  
Jyoti Prabha Sahu ◽  
Akansha Agarwal
Keyword(s):  
Gamma Radiation ◽  
Carbon Nanoparticles ◽  
Power Plants ◽  
Gamma Ray ◽  
Nuclear Research ◽  
Radiation Absorption ◽  
Particle Accelerators ◽  
Building Structures ◽  
Back Scattering ◽  
Absorption Characteristics

Concrete is a very important composite for making different building structures to absorb different levels of radiation. Nuclear power plants, nuclear research reactors, particle accelerators and linear accelerator in medical institution use concrete in building construction. Nanoparticles or nanocrystals have different properties than their bulk counterparts. The gamma radiation absorption characteristics and beta back scattering by nanoparticles is also different than their counterparts. In this paper, carbon nanoparticles are mixed in the concrete composite during its preparation. The concrete composite with carbon nanoparticles as admixture were analyzed to provide radiation protection. The gamma radiation absorption characteristics and beta back scattering in ordinary and carbon nanoparticles contained concretes have been studied by GM counter. The results show that using carbon nanoparticles as an admixture in the concrete is one of the solutions for gamma ray shielding and beta back scattering. Therefore, it is good to use carbon nanoparticles as admixtures in concrete composites for beta and gamma radiation scattering and absorption respectively.

scholarly journals MOMENTUM DISTRIBUTION OF ITINERANT ELECTRONS IN THE ONE-DIMENSIONAL FALICOV–KIMBALL MODEL

2003 ◽  
Vol 17 (27) ◽  
pp. 4897-4911 ◽  
Author(s):  
PAVOL FARKAŠOVSKÝ
Keyword(s):  
Momentum Distribution ◽  
Ground States ◽  
Local Maximum ◽  
Singular Behavior ◽  
Coulomb Interactions ◽  
Unusual Behavior ◽  
One Dimensional ◽  
Itinerant Electrons ◽  
Half Filling ◽  
The One

The momentum distribution nk of itinerant electrons in the one-dimensional Falicov–Kimball model is calculated for various ground-state phases. In particular, we examine the periodic phases with period two, three and four (that are ground-states for all Coulomb interactions) as well as the phase separated states (that are ground states for small Coulomb interactions). For all periodic phases examined the momentum distribution is a smooth function of k with no sign of any discontinuity or singular behavior at the Fermi surface k=kF. An unusual behavior of nk (a local maximum) is found at k=3kF for electron concentrations outside half-filling. For the phase separated ground states the momentum distribution nk exhibits discontinuity at k=k0<kF. This behavior is interpreted in terms of a Fermi liquid.

scholarly journals SYMMETRIC GROUND STATES FOR A STATIONARY RELATIVISTIC MEAN-FIELD MODEL FOR NUCLEONS IN THE NON-RELATIVISTIC LIMIT

2012 ◽  
Vol 24 (10) ◽  
pp. 1250025 ◽  
Author(s):  
MARIA J. ESTEBAN ◽  
SIMONA ROTA NODARI
Keyword(s):  
Nuclear Physics ◽  
Field Model ◽  
Mean Field ◽  
Ground States ◽  
Good Choice ◽  
Coupling Constants ◽  
Mean Field Model ◽  
Relativistic Limit ◽  
Relativistic Mean Field ◽  
The One

In this paper, we consider a model for a nucleon interacting with the ω and σ mesons in the atomic nucleus. The model is relativistic, but we study it in the nuclear physics non-relativistic limit, which is of a very different nature from the one of the atomic physics. Ground states with a given angular momentum are shown to exist for a large class of values for the coupling constants and the mesons' masses. Moreover, we show that, for a good choice of parameters, the very striking shapes of mesonic densities inside and outside the nucleus are well described by the solutions of our model.

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