scholarly journals The Influence of Dimensional Static and Dynamic Charge on the Spectral Parameters and Active Dynamic Conductivity of Resonanse Tunnelling Structures with Constant Electric Field

2016 ◽  
Vol 17 (1) ◽  
pp. 21-30
Author(s):  
I.V. Boyko ◽  
A.M. Gryschyk
Keyword(s):  
Constant Electric Field ◽  
High Energy ◽  
Transmission Factor ◽  
Spectral Parameters ◽  
Dynamic Conductivity ◽  
Shape Dependence ◽  
Dynamic Charge ◽  
Quantum Transitions ◽  
Consistent Solution ◽  
Lorentzian Shape

In the model of effective masses and rectangular potentials obtained self-consistent solution of Poisson and Schrödinger equations for different concentrations of electrons. It has been calculated spectral parameters and active dynamic conductivity for three-well nanostructure as active band of experimental quantum cascade laser. It has been established, that space charge deforms shape dependence of transmission factor of electron energy from Lorentzian shape to quasi-Lorentzian, shifting their maximum value to the high energy region and increasing the lifetimes of electronic quasistationary states. It was shown, that with increasing concentration of electrons energy of laser radiation in quantum transitions  and  decreases, and the total value of active dynamic conductivity increases so, that it increases the partial contribution component of conductivity, determined by electron flux, directed opposite to the exit of nanostructure.

Cathodoluminescence Study of Hydrothermal Zn1-xMgxO Alloy Crystals

2006 ◽  
Vol 957 ◽  
Author(s):  
Julio Mass ◽  
Manuel Avella ◽  
Juan Jiménez ◽  
Michael Callahan ◽  
E. Grant ◽  
...  
Keyword(s):  
Depth Distribution ◽  
Energy Shift ◽  
High Energy ◽  
Growth Sector ◽  
Spectral Parameters ◽  
Luminescence Emission ◽  
Acceleration Voltage ◽  
Marked Dependence ◽  
Excitonic Luminescence ◽  
Cathodoluminescence Study

ABSTRACTHydrothermal ZnMgO crystals were studied by cathodoluminescence. The high energy shift of the excitonic luminescence demonstrates the Mg incorporation in the ZnO lattice in at a few percent. The spectral parameters of the luminescence emission show a marked dependence of the incorporation of defects and Mg on the growth facet. This growth sector selectivity shows similar trends to those observed in hydrothermal ZnO crystals. The in depth distribution of Mg was studied varying the acceleration voltage of the excitation e-beam, showing a slight accumulation of Mg close to the surface.

scholarly journals X-ray Spectral Evolution of High Energy Peaked Blazars

Galaxies ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 62
Author(s):  
Haritma Gaur
Keyword(s):  
High Energy ◽  
Energy Interval ◽  
Spectral Studies ◽  
Parabolic Model ◽  
Spectral Evolution ◽  
Spectral Variability ◽  
Spectral Parameters ◽  
X Ray ◽  
Wide Energy ◽  
Energy Dependent

The synchrotron hump of the high energy peaked blazars generally lies in the 0.1–10 keV range and such sources show extreme flux and spectral variability in X-ray bands. Various spectral studies showed that the X-ray spectra of high energy peaked blazars are curved and better described by the log-parabolic model. The curvature is attributed to the energy dependent statistical acceleration mechanism. In this work, we review the X-ray spectral studies of high energy peaked blazars. It is found that the log-parabolic model well describes the spectra in a wide energy interval around the peak. The log-parabolic model provides the possibility of investigating the correlation between the spectral parameters derived from it. Therefore, we compiled the studies of correlations between the various parameters derived from the log-parabolic model and their implications to describe the variability mechanism of blazars.

scholarly journals Impact of Modifier Oxides on Mechanical and Radiation Shielding Properties of B2O3-SrO-TeO2-RO Glasses (Where RO = TiO2, ZnO, BaO, and PbO)

2021 ◽  
Vol 11 (22) ◽  
pp. 10904
Author(s):  
M. I. Sayyed ◽  
M. Kh. Hamad ◽  
Mohammad Hasan Abu Mhareb ◽  
K. A. Naseer ◽  
K. A. Mahmoud ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Radiation Shielding ◽  
Transmission Factor ◽  
Attenuation Coefficients ◽  
Radiation Attenuation ◽  
Cross Linkage ◽  
Packed Structure ◽  
Shielding Properties ◽  
Hardness Values

The influence of modifier oxides (TiO2, ZnO, BaO, and PbO) on the mechanical and radiation shielding properties of boro-tellurate glasses is investigated. Samples with a composition of B2O3-SrO-TeO2-RO (RO represents the modifier oxides) were fabricated using the melt quench method, and their physical, mechanical, and radiation attenuation parameters were reported. For this aim, Monte Carlo simulation was employed to predict the radiation attenuation parameters, while the Makishima-Mackenzie model was adopted to determine the mechanical properties. The tightly packed structure with better cross-linkage density is possessed by the Ti-containing glass (SBT-Ti) system among the titled glass batch. The higher Poisson and micro-hardness values of the SBT-Ti glass indicate its structure’s reduced free volume and better compactness. For the glass with PbO, the linear and mass attenuation coefficients are highly increased compared to those glasses doped with TiO2, ZnO, and BaO. The thinner half-value layer was reported at 0.015 MeV, taking values 0.006, 0.005, 0.004, and 0.002 for samples with TiO2, ZnO, BaO, and PbO, respectively. SBT-Pb sample (with PbO) has a thinner HVL compared to other fabricated glass samples. The fabricated glasses’ thickness (Deq) equivalent to 1 cm of lead (Pb) was reported. The results demonstrated that Deq is high at low energy and equals 11.62, 8.81, 7.61, 4.56 cm for SBT-Ti, SBT-Zn, SBT-Ba, and SBT-Pb glass samples, respectively. According to the Deq results, the fabricated glasses have a shielding capacity between 30 and 43% compared to the pure Pb at gamma-ray energy of 1.5 MeV. At high energy (8 MeV), the transmission factor values for a thickness of 1 cm of the fabricated samples reach 88.68, 87.83, 85.95, and 83.11% for glasses SBT-Ti, SBT-Zn, SBT-Ba, and SBT-Pb, respectively.

scholarly journals Dose Measurements around Spallation Neutron Sources

2020 ◽  
Vol 16 ◽  
pp. 53
Author(s):  
M. Fragopoulou ◽  
S. Stoulos ◽  
M. Manolopoulou ◽  
M. Krivopustov ◽  
M. Zamani
Keyword(s):  
High Energy Physics ◽  
High Energy ◽  
Neutron Dose ◽  
Transmission Factor ◽  
Benchmark Analysis ◽  
Energy Proton ◽  
Empirical Relations ◽  
Nuclotron Accelerator ◽  
Dose Measurements ◽  
Energy Physics

Neutron dose measurements and calculations around spallation sources are of importance for an appropriate shielding study. Two spallation sources, consisted of Pb target, have been irradiated by high-energy proton beams, delivered by the Nuclotron accelerator (JINR), Dubna. Dose measurements of the neutrons produced by the two spallation sources were performed using Solid State Nuclear Track Detectors (SSNTDs). In addition, the neutron dose after polyethylene and concrete was calculated using phenomenological model based on empirical relations applied in high energy Physics. Analytical and experimental neutron benchmark analysis has been performed using the transmission factor. A comparison of experimental results with calculations is given.

scholarly journals The Effect of Shallow Impurities on the Light Absorption by the Nanocrystals CdS

2018 ◽  
Vol 63 (12) ◽  
pp. 1088
Author(s):  
V. I. Boichuk ◽  
R. Ya. Leshko ◽  
D. S. Karpyn
Keyword(s):  
Experimental Data ◽  
Absorption Spectra ◽  
Light Absorption ◽  
High Energy ◽  
Quantitative Agreement ◽  
Impurity States ◽  
Quantum Transitions ◽  
Shallow Impurities ◽  
Excitonic States

The energy of quantum transitions of exciton-impurity states in a heterosystem with nanocrystals is calculated. The absorption spectra associated with the indicated transitions are analyzed. It is qualitatively shown that broad luminescence bands in the red region are related to the impurity acceptor states, and the high narrow ones in the violet region to pure excitonic states and excitonic states interacting with the ion of a donor. The satisfactory quantitative agreement of our calculations with experimental data for high energy luminescence bands is obtained.

scholarly journals Theory of Dynamic Conductivity of Three-Barrier Resonance-Tullel Structure with Two-Photon Laser Transitions

2015 ◽  
Vol 16 (1) ◽  
pp. 7-13
Author(s):  
Ju. O. Seti ◽  
I. V. Boyko ◽  
M. V. Pan’kiv
Keyword(s):  
Potential Wells ◽  
Dynamic Conductivity ◽  
Potential Barriers ◽  
Quantum Cascade ◽  
Two Photon ◽  
Geometric Configurations ◽  
Quantum Transitions ◽  
Electron Quantum ◽  
Different Depths ◽  
Resonant Tunneling Structure

Within the approximation of effective mass and rectangular potential barriers for the electron and using the obtained solutions of complete Schrodinger equation, the theory of dynamic conductivity for three-barrier resonant tunneling structure (InGaAs/InAlAs) with different depths of potential wells driven by weak electromagnetic field is developed in one- and two-photon approach. It is shown that varying Ga concentration one can obtain such geometric configurations of nanostructure, being an active region of quantum cascade laser, in which the increasing intensity of laser radiation, produced by electron quantum transitions accompanied by radiation of two photons with equal energy, is observed. It is established that the contribution of two-photon transitions into the complete magnitude of dynamic conductivity is not smaller than 37 %.

scholarly journals Open Universe for Blazars: a new generation of astronomical products based on 14 years of Swift-XRT data

2019 ◽  
Vol 631 ◽  
pp. A116 ◽  
Author(s):  
P. Giommi ◽  
C. H. Brandt ◽  
U. Barres de Almeida ◽  
A. M. T. Pollock ◽  
F. Arneodo ◽  
...  
Keyword(s):  
Data Analysis ◽  
Data Science ◽  
High Energy ◽  
Space Mission ◽  
Science Data ◽  
Spectral Parameters ◽  
Data Set ◽  
X Ray ◽  
Research Education ◽  
Open Universe

Aims. Open Universe for Blazars is a set of high-transparency multi-frequency data products for blazar science, and the tools designed to generate them. Blazars are drawing growing interest following the consolidation of their position as the most abundant type of source in the extragalactic very high-energy γ-ray sky, and because of their status as prime candidate sources in the nascent field of multi-messenger astrophysics. As such, blazar astrophysics is becoming increasingly data driven, depending on the integration and combined analysis of large quantities of data from the entire span of observational astrophysics techniques. The project was therefore chosen as one of the pilot activities within the United Nations Open Universe Initiative, whose objective is to stimulate a large increase in the accessibility and ease of utilisation of space science data for the worldwide benefit of scientific research, education, capacity building, and citizen science. Methods. Our aim is to deliver innovative data science tools for multi-messenger astrophysics. In this work we report on a data analysis pipeline called Swift-DeepSky based on the Swift XRTDAS software and the XIMAGE package, encapsulated into a Docker container. Swift-DeepSky downloads and reads low-level data, generates higher level products, detects X-ray sources, and estimates several intensity and spectral parameters for each detection, thus facilitating the generation of complete and up-to-date science-ready catalogues from an entire space-mission data set. Results. As a first application of our innovative approach, we present the results of a detailed X-ray image analysis based on Swift-DeepSky that was run on all Swift-XRT observations including a known blazar, carried out during the first 14 years of operations of the Neil Gehrels Swift Observatory. Short exposures executed within one week of each other have been added to increase sensitivity, which ranges between ∼1 × 10−12 and ∼1 × 10−14 erg cm−2 s−1 (0.3–10.0 keV). After cleaning for problematic fields, the resulting database includes over 27 000 images integrated in different X-ray bands, and a catalogue, called 1OUSXB, that provides intensity and spectral information for 33 396 X-ray sources, 8896 of which are single or multiple detections of 2308 distinct blazars. All the results can be accessed online in a variety of ways, from the Open Universe portal through Virtual Observatory services, via the VOU-Blazar tool and the SSDC SED builder. One of the most innovative aspects of this work is that the results can be easily reproduced and extended by anyone using the Docker version of the Swift-DeepSky pipeline, which runs on Linux, Mac, and Windows machines, and does not require any specific experience in X-ray data analysis.

scholarly journals Deeper H.E.S.S. observations of Vela Junior (RX J0852.0−4622): Morphology studies and resolved spectroscopy

2018 ◽  
Vol 612 ◽  
pp. A7 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Power Law ◽  
Spectral Characteristics ◽  
Direct Determination ◽  
High Energy ◽  
Spectral Parameters ◽  
Data Set ◽  
Spatially Resolved ◽  
Particle Population ◽  
Spatially Resolved Spectroscopy

Aims. We study γ-ray emission from the shell-type supernova remnant (SNR) RX J0852.0−4622 to better characterize its spectral properties and its distribution over the SNR.Methods. The analysis of an extended High Energy Spectroscopic System (H.E.S.S.) data set at very high energies (E > 100 GeV) permits detailed studies, as well as spatially resolved spectroscopy, of the morphology and spectrum of the whole RX J0852.0−4622 region. The H.E.S.S. data are combined with archival data from other wavebands and interpreted in the framework of leptonic and hadronic models. The joint Fermi-LAT-H.E.S.S. spectrum allows the direct determination of the spectral characteristics of the parent particle population in leptonic and hadronic scenarios using only GeV-TeV data.Results. An updated analysis of the H.E.S.S. data shows that the spectrum of the entire SNR connects smoothly to the high-energy spectrum measured by Fermi-LAT. The increased data set makes it possible to demonstrate that the H.E.S.S. spectrum deviates significantly from a power law and is well described by both a curved power law and a power law with an exponential cutoff at an energy of Ecut = (6.7 ± 1.2stat ± 1.2syst) TeV. The joint Fermi-LAT-H.E.S.S. spectrum allows the unambiguous identification of the spectral shape as a power law with an exponential cutoff. No significant evidence is found for a variation of the spectral parameters across the SNR, suggesting similar conditions of particle acceleration across the remnant. A simple modeling using one particle population to model the SNR emission demonstrates that both leptonic and hadronic emission scenarios remain plausible. It is also shown that at least a part of the shell emission is likely due to the presence of a pulsar wind nebula around PSR J0855−4644.

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