scholarly journals An Experiment for Observing VHE Gamma Ray Sources

1987 ◽  
Vol 125 ◽  
pp. 553-553
Author(s):  
Y.L. Jang ◽  
C.X. He ◽  
C.X. Xu ◽  
Y.K. Yuan ◽  
Y.G. Li ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Point Sources ◽  
Hebei Province ◽  
Light Pollution ◽  
Light Detection ◽  
Apparatus Design ◽  
Set Up ◽  
Atmospheric Čerenkov Technique ◽  
Cerenkov Light

An apparatus design is described. It is for detecting VHE gamma ray point sources by means of the atmospheric Cerenkov technique. Obviously, the improvement of flux sensitivity and discrimination between gamma ray and isotropic proton showers is still a key problem. Of course, it is necessary to set up more observatories and to track an object continuously with several facilities. With this in mind, we decided to develop an experiment for observing VHE gamma ray sources in China. As a first step, we will set up an apparatus which consists of three 1.5 m diameter searchlight morrors at Xinglong station of Beijing Observatory, Xinglong county, Hebei province (40°. 4N, 117°.5E, altitude 940 m). The observation will start in 1988. Then, the second apparatus will be set up at Delingha station of Purple Mountain Observatory, Delingha county, Qinghai porvince (37°.22N, altitude 3204 m). Both the sites are far from air and light pollution, and have suitable meteological condition for Cerenkov light detection as well as quite convenient facilities for transportation. Some probable technical improvements are also discussed in this paper.

scholarly journals Modeling Gamma-Ray SEDs and Angular Extensions of Extreme TeV Blazars from Intergalactic Proton-Initiated Cascades in Contemporary Astrophysical EGMF Models

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 220
Author(s):  
Emil Khalikov
Keyword(s):  
Gamma Rays ◽  
Large Scale ◽  
Gamma Ray ◽  
High Energy ◽  
Cascade Model ◽  
Point Sources ◽  
Spectral Energy ◽  
Observation Data ◽  
Cherenkov Telescopes ◽  
The Universe

The intrinsic spectra of some distant blazars known as “extreme TeV blazars” have shown a hint at an anomalous hardening in the TeV energy region. Several extragalactic propagation models have been proposed to explain this possible excess transparency of the Universe to gamma-rays starting from a model which assumes the existence of so-called axion-like particles (ALPs) and the new process of gamma-ALP oscillations. Alternative models suppose that some of the observable gamma-rays are produced in the intergalactic cascades. This work focuses on investigating the spectral and angular features of one of the cascade models, the Intergalactic Hadronic Cascade Model (IHCM) in the contemporary astrophysical models of Extragalactic Magnetic Field (EGMF). For IHCM, EGMF largely determines the deflection of primary cosmic rays and electrons of intergalactic cascades and, thus, is of vital importance. Contemporary Hackstein models are considered in this paper and compared to the model of Dolag. The models assumed are based on simulations of the local part of large-scale structure of the Universe and differ in the assumptions for the seed field. This work provides spectral energy distributions (SEDs) and angular extensions of two extreme TeV blazars, 1ES 0229+200 and 1ES 0414+009. It is demonstrated that observable SEDs inside a typical point spread function of imaging atmospheric Cherenkov telescopes (IACTs) for IHCM would exhibit a characteristic high-energy attenuation compared to the ones obtained in hadronic models that do not consider EGMF, which makes it possible to distinguish among these models. At the same time, the spectra for IHCM models would have longer high energy tails than some available spectra for the ALP models and the universal spectra for the Electromagnetic Cascade Model (ECM). The analysis of the IHCM observable angular extensions shows that the sources would likely be identified by most IACTs not as point sources but rather as extended ones. These spectra could later be compared with future observation data of such instruments as Cherenkov Telescope Array (CTA) and LHAASO.

Design, calibration, and application of an airborne gamma spectrometer system in Switzerland

Geophysics ◽  
1997 ◽  
Vol 62 (5) ◽  
pp. 1369-1378 ◽  
Author(s):  
Georg F. Schwarz ◽  
Ladislaus Rybach ◽  
Emile E. Klingelé
Keyword(s):  
Power Plant ◽  
Nuclear Power ◽  
Power Plants ◽  
Gamma Ray ◽  
Point Sources ◽  
Swiss Alps ◽  
Artificial Radioactivity ◽  
Radiation Level ◽  
Satellite Navigation System ◽  
Emergency Situations

Airborne radiometric surveys are finding increasingly wider applications in environmental mapping and monitoring. They are the most efficient tool to delimit surface contamination and to locate lost radioactive sources. To secure radiometric capability in survey and emergency situations, a new sensitive airborne system has been built that includes an airborne spectrometer with 256 channels and a sodium iodide detector with a total volume of 16.8 liters. A rack mounted PC with memory cards is used for data acquisition, with a GPS satellite navigation system for positioning. The system was calibrated with point sources using a mathematical correction to take into account the effects of gamma‐ray scattering in the ground and in the atmosphere. The calibration was complemented by high precision ground gamma spectrometry and laboratory measurements on rock samples. In Switzerland, two major research programs make use of the capabilities of airborne radiometric measurements. The first one concerns nuclear power plant monitoring. The five Swiss nuclear installations (four power plants and one research facility) and the surrounding regions of each site are surveyed annually. The project goal is to monitor the dose‐rate distribution and to provide a documented baseline database. The measurements show that all sites (with the exception of the Gösgen power plant) can be identified clearly on the maps. No artificial radioactivity that could not be explained by the Chernobyl release or earlier nuclear weapons tests was detected outside of the fenced sites of the nuclear installations. The second program aims at a better evaluation of the natural radiation level in Switzerland. The survey focused on the crystalline rocks of the Central Massifs of the Swiss Alps because of their relatively high natural radioactivity and lithological variability.

scholarly journals A Search for Gamma-Ray Point Sources

1965 ◽  
Vol 70 (17) ◽  
pp. 4227-4234 ◽  
Author(s):  
C. E. Fichtel ◽  
D. A. Kniffen
Keyword(s):  
Gamma Ray ◽  
Point Sources

scholarly journals Improving the performance of 241Am-Be for PGNAA applications using a proper shielding for neutron source and the NaI detector

2010 ◽  
Vol 25 (3) ◽  
pp. 205-211 ◽  
Author(s):  
Hamed Panjeh ◽  
Hashem Hakimabad ◽  
Lalle Motavalli
Keyword(s):  
Gamma Rays ◽  
Energy Region ◽  
Gamma Ray ◽  
Region Of Interest ◽  
High Rate ◽  
Prompt Gamma ◽  
Peak Resolution ◽  
Set Up ◽  
Gamma Ray Detector

The gamma ray spectrum resolution from a 241Am-Be source-based prompt gamma ray activation analysis set-up has been observed to increase in the energy region of interest with enclosing the NaI detector in a proper neutron and gamma ray shield. We have investigated the tact that the peak resolution of prompt gamma rays in the region of interest from the set-up depends on the source activity to the great extent, size and kind of the detector and the geometry of the detector shield. In order to see the role of a detector shield, five kinds of the detector shield were used and finally the proper kind was introduced. Since the detector shield has an important contribution in the reduction of the undesirable and high rate gamma rays coming to the gamma ray detector, a good design of a proper shield enables the elimination of the unwanted events, such as a pulse pile-up. By improving the shielding design, discrete and distinguishable photoelectric peaks in the energy region of interest have been observed in the spectrum of prompt gamma rays.

scholarly journals Gamma spectrometry technique for the determination of residence time in Submarine Groundwater Discharges

2019 ◽  
Vol 18 ◽  
pp. 155
Author(s):  
G. Eleftheriou ◽  
C. Tsabaris ◽  
D. L. Patiris ◽  
E. Androulakaki ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Residence Time ◽  
Water Samples ◽  
Gamma Ray ◽  
Measuring System ◽  
Gamma Ray Spectrometry ◽  
Reference Source ◽  
Radium Isotopes ◽  
Time Period ◽  
Submarine Groundwater ◽  
Set Up

The evaluation of time period that meteoric water remains in the ground (residence time) before exiting in the open sea can be a valuable information for the submarine groundwater discharges (SGD) in the costal zones. Coastal waters contain elevated dissolved activities of radium isotopes compared to the open ocean, where excess activities are zero. Lately it has been shown by Moore et al., that residence time can be estimated by a model based on radium radioisotopes ratio reduction throughout the coast. However the standard methods for the estimation of radium isotopes concentration in the water are sophisticated, time consuming or require big amount of sample. Hereby, a method based on the direct gamma ray spectrometry of untreated water samples from coastal areas is applied to determine the residence time of the SGD. Efficiency calibration of the spectrometry set up has been performed for two different volumetric sample geometries, using 152Eu/154Eu solution as reference source. In order to ensure the reliability of the method, the background courting rate magnitude and variance through time have been defined for the radioisotopes of interest. Additionally, the minimum detectible activity (MDA) of the measuring system was determined, in Becquerel per cubic meter, as a function of energy in water samples. The developed method was applied and validated for water samples from the submarine spring in Stoupa Bay, southwestern Peloponnesus. The defined residence time varies from 3 to 6 days, being in good agreement with the results of the standard geological pigment-tracer method.

scholarly journals Inter-comparison exercise utilizing x- and γ-ray spectrometry

2020 ◽  
Vol 27 ◽  
pp. 121
Author(s):  
Filothei K. Pappa ◽  
Christos Tsabaris ◽  
Dionisis Patiris ◽  
Georgios Eleftheriou ◽  
Effrossini G. Androulakaki ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Natural Radionuclides ◽  
Atomic Spectrometry ◽  
Gamma Ray Spectrometry ◽  
Metal Concentrations ◽  
Activity Concentrations ◽  
Great Divergence ◽  
Set Up ◽  
Comparison Exercise ◽  
Good Agreement

Radionuclides are characterized by their nuclear and chemical behavior. Additionally, the geochemical characteristics of radionuclides result in their accumulation in the sediments via sorption processes. In this work the radionuclide activity concentrations obtained by gamma-ray spectrometry (HPGe detector) were converted to metal concentrations as described in [1]. The results were compared with the measured metal concentrations obtained by atomic spectrometry (X-ray fluorescence system-XRF). The samples originate from the coastal environment of two Greek areas, characterized by elevated values of natural radionuclides (e.g. 226Ra) and metals. The preliminary study revealed a good agreement among the concentrations of potassium calculated via activity concentrations of 40K and those of XRF measurement, while a great divergence was observed for the thorium case. These differences can be attributed to the low statistics, as well as to the calibration set-up of Th XRF measurement.

scholarly journals The Large Magellanic Cloud with the Cherenkov Telescope Array

2019 ◽  
Vol 209 ◽  
pp. 01021
Author(s):  
María Isabel Bernardos ◽  
María Benito ◽  
Fabio Iocco ◽  
Salvatore Mangano ◽  
Olga Sergijenko ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Region Of Interest ◽  
Cosmic Ray ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Point Sources ◽  
Detection Sensitivity ◽  
Telescope Array ◽  
Star Forming ◽  
Cherenkov Telescope

The Large Magellanic Cloud (LMC) is a spiral galaxy, satellite of the Milky way with a high star formation activity. It represents a unique laboratory for studying an extended and spatially resolved star-forming galaxy through gamma-ray observatories. Therefore, the LMC survey is one of the key science projects for the Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray observatory. In this document we present the work performed over the last year by the CTA working group dedicated to the LMC, in order to offer a first characterization of the LMC at TeV energies. We have performed detectability forecasts based on the expected CTA performance for all sources in the region of interest of the LMC with known emission at GeV energies and above. Based on previous observations made by Fermi-LAT and H.E.S.S. we have characterized all point sources, extended sources and diffuse emission produced by cosmic-ray propagation, extrapolating their spectra to CTA energies. Finally, we have characterized the signal expected by different annihilation mechanisms of dark matter (DM) particles within the LMC, computing the detection sensitivity curve for this target in the cross-section-to-mass plane.

Precise volume fraction measurement for three-phase flow meter using 137Cs gamma source and one detector

2020 ◽  
Vol 108 (2) ◽  
pp. 159-164
Author(s):  
S. Z. Islami rad ◽  
R. Gholipour Peyvandi
Keyword(s):  
Neural Network ◽  
Gamma Ray ◽  
Volume Fraction ◽  
Mlp Neural Network ◽  
Three Phase ◽  
Three Phase Flow ◽  
Gamma Ray Attenuation ◽  
Set Up ◽  
Fraction Measurement ◽  
Error Percentage

AbstractThe ability to precisely predict the volume fraction percentage of the different phases flowing in a pipe plays an important role in the oil, petroleum and other industries. In this research, the volume fraction percentage was measured precisely in water-gasoil-air three-phase flows by using a single pencil beam gamma ray attenuation technique and multilayer perceptron (MLP) neural network. The volume fraction percentage determination in three-phase flows requires least two gamma radioactive sources with different energies while in this study, we used just a 137Cs source (with the single energy of 662 keV) and a NaI detector. Also, in this work, the MLP neural network in MATLAB software was implemented to predict the volume fraction percentage. The experimental setup provides the required data for training and testing the network. Using this proposed method, the volume fraction was predicted in water-gasoil-air three-phase flows with mean relative error percentage less than 6.95 %. Also, the root mean square error was calculated 2.60. The set-up used is simpler than other proposed methods and cost, radiation safety and shielding requirements are minimized.

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