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Information can be obtained from the main sites of providers, such as Ortec, Canberra and others [5-7]. To increase the sensitivity of gamma-ray spectrometry, samples containing water can be freeze-dried.

Table 1. Common used emission lines for the detection of natural radionuclides with gamma‐ray spectrometry
Table 1. Common used emission lines for the detection of natural radionuclides with gamma‐ray spectrometry

Gamma nuclides in the environment

Swiss monitoring programme

Tritium emissions are regularly detected in KVA Basel's air filter wash water. This is evidenced by the activities found in the air filter wash water.

Figure 3. Activity trends of radiocaesium in soil, vegetation and cow
Figure 3. Activity trends of radiocaesium in soil, vegetation and cow's milk on a farm in Basel‐Country

Special applications/projects

Nevertheless, we believe that tree bark monitoring is comparable to soil monitoring and can provide adequate pollution data for emergencies. Despite the great diversity of moss species and the difficulty of age determination, mosses can monitor plants for radioactive fallout if they are carefully normalized (Figure 5).

Figure 5. Correlations of radiocaesium between moss, tree bark and the corresponding soil activity.
Figure 5. Correlations of radiocaesium between moss, tree bark and the corresponding soil activity.

Gamma nuclides in food

Radio contamination of food

Healing earths

Gamma spectrometry as an important analytical tool for emergency cases with ionising radiation

In Basel, drinking water is extracted from groundwater, which is enriched with river water through soil filtration. After an earthquake, when the drinking water production site is no longer operable, plans exist for public emergency supply with water pumped from the ground and from rivers.

Table 5. Extract of possible fission and activation products released at an NPP accident or from a bomb.
Table 5. Extract of possible fission and activation products released at an NPP accident or from a bomb.

Acknowledgements

They give an order to take samples to assess the contamination/radiation level outdoors and to control the level of food contamination. It is important to prevent polluted river water from entering this filter system.

Author details

With a gamma analysis of a 1 L water sample in a Marinelli beaker, it is possible to limit the analysis time to 15 minutes for the investigation of threshold values.

Radioactivity in Food: Experiences of the Basel Food Control Authority since the Chernobyl Accident. All references related to reports of the State Laboratory of the City of Basel are online, available at: http://www.kantonslabor.bs.ch/berichte.html.

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Dead Time in the Gamma‐Ray Spectrometry

  • Introduction
  • General characteristics of photon detectors
  • Gamma-ray spectrometry system components
  • The dead-time detection methods
  • Some models for the dead-time correction
  • Conclusion

The dead time due to the observed count rate due to exponential decay of the source is determined. However, the eating time is important for counting losses due to system dead time calculations. Therefore, the dead time of the system is determined by adding the peak time to the ADC conversion time.

To determine the dead time of the system, the minimum solution time must first be established [14]. In addition, the peak time of the amplifier increases both the dead time and the counting losses. This saturation point is determined by the size of the dead time of the counting system.

Figure 1. General appearance of the gamma-ray spectrometry system.
Figure 1. General appearance of the gamma-ray spectrometry system.

Pseudo-gamma Spectrometry in Plastic Scintillators

Plastic scintillator modifications

  • Introduction to plastic scintillators
  • Plastic scintillator loading
  • Theory
  • Heavy metal loading 1. Organometallic complex

This can be illustrated in Figure 3, where you can see the appearance of the full energy peak on the black signal. Basically, an organometallic complex is a molecule that embeds a metal core surrounded by one or more organic ligands, their number depending on the valence of the metal. The choice of both metal and ligand(s) is of particular importance, as it will directly affect the scintillation properties of the plastic scintillator.

13–15] successfully observed for the first time a distinct photopeak arising from the full absorption of 662 keV energy 137Cs gamma rays. Significant improvements were also achieved by adding a polymerization bond to the organic part of the organometallic complex. Interestingly, a linear increase of the photoelectric and Compton counting rates, obtained by appropriate region integration, was observed from 0 to 9 wt. %.

Figure 2. Schematic representations of molecules involved in the preparation of a plastic scintillator.
Figure 2. Schematic representations of molecules involved in the preparation of a plastic scintillator.

Algorithms

  • Context and motivations
  • Standard approach for gamma-ray spectrometry analysis and associated limitations Gamma-ray spectrometry is a technique based on the detection of Gamma-rays emitted by
  • Analysis of a gamma-ray spectrum as an inverse problem
  • Analysis on simulated and experimental data
  • Current status and future developments

Example of a gamma ray spectrum obtained with a plastic scintillator (type EJ-200), 137Cs and 60Co signatures (Monte Carlo simulation using MCNPX). The nbe_channels parameter corresponds to the number of channels of the gamma ray spectrum. The S-matrix corresponds to the measurement result, i.e. the gamma-ray spectrum to be processed.

For example, the element hij corresponds to the probability that a photon of incident energy equal to j was detected in channel i of the gamma-ray spectrum. A discrepancy between the simulated gamma-ray spectrum and the actual behavior of the detector will have a direct impact on the result of the reconstruction. On the left: nature and associated proportion of radionuclides present in the gamma-ray spectrum.

Figure 6. Example of  152 Eu experimental spectra using a HPGe semiconductor (on the left) or a NaI(Tl) scintillator (on  the right).
Figure 6. Example of 152 Eu experimental spectra using a HPGe semiconductor (on the left) or a NaI(Tl) scintillator (on the right).

Gamma Rays from Space

General features of GRBs

However, only the discovery of the first X-ray afterglows in 1998 by the BeppoSax satellite [9] allowed the exact positions and identification of the γ-ray afterglow with 'normal'. They are not small and large versions of the same phenomenon; the two types of outbreaks have completely different sources. The figure also includes a scatterplot (bottom panel), a correlation between the T90 duration of the GRB and the integrated time fluence.

Furthermore, the integrated time flux is the energy deposited on the detector per unit area during the duration of the T90 GRB. If the GRB origin distance is determined, this last quantity allows an estimate of the energy released during the explosion. Bottom panel: correlation between T90 GRB duration and integrated temporal fluence based on 1188 Swift GRBs detected from 2004 December 17 to 2016 May 25.

Figure 1. Location in the sky (equatorial coordinate system) of 1188 Swift GRBs, detected from 17 December 2004 to 25  May 2016.
Figure 1. Location in the sky (equatorial coordinate system) of 1188 Swift GRBs, detected from 17 December 2004 to 25 May 2016.

Emission mechanisms

Thus, the reconverted kinetic energy to random energy must occur via shocks after the flow becomes optically thin (mainly synchrotron radiation). In short, the fireball model can reproduce the main features of the observed eruptions, regardless of the detailed physics of the central engine. These jets collide with the photons inside the star through an inverse Compton scattering process and produce gamma rays.

The emission range of these gamma rays is related to the layers (shields) inside the star where these projectiles collide. As with the fireball model, the CB model can describe afterglows such as X-ray, UV, and radio bursts. The CB model also includes the description of other phenomena such as the acceleration of cosmic rays (CR) in a successful way [26].

Ground level observations

  • Milagrito
  • Milagro
  • ARGO
  • HAWC

Astrophysical Radiation with Ground-based Observatory in Yangbajing, China (Tibet-. 4300 m.a.s.l.), under the auspices of the ARGO-YBJ experiment, is through an air shower detector. The ARGO-YBJ detector has a large active surface of about 6700 m2 resistive plate chambers, a wide field of view ~2 sr and a high duty cycle (>86%). ARGO-YBJ performed a search for gamma-ray burst (GRB) emission in the energy range 1-100 GeV coincident with satellite detection.

The HAWC Gamma-ray Observatory is a wide-field, continuously operating TeV gamma-ray telescope that investigates the origin and solar modulation of cosmic rays and searches for new TeV physics. HAWC is located at a high altitude of 4100 m above sea level in Mexico (Sierra Negra) and is a collaboration of 15 American and 12 Mexican institutions. HAWC monitors the northern sky and conducts simultaneous observations with other wide-field observatories.

Ground level observation of gamma-ray bursts from space

  • Association with the MAXI gamma-ray burst
  • Association with the Swift gamma-ray bursts

The trigger coordinates of MAXI trigger were within the field of view of the vertical Tupi telescope. In the absence of a signal, the background fluctuation of the count rate follows a Gaussian distribution. We estimate the Poisson probability of the count rate exceedance observed in the vertical Tupi telescope, in association with the MAXI GRB events, as a background fluctuation, as P, i.e. an annual rate of 2.9.

Fluctuation count rate distribution for the Tupi telescope (in units of standard deviations) within a 30-min temporal window around the MAXI transient event (cause 580727270). Bottom panel: time profile of the 4 s link count rate, expressed as the number of standard deviations, observed at the Tupi Vertical Telescope as a function of the time elapsed since the activation time of Swift BAT GRB140512A. We also estimated the Poisson probability of the observed overshoot in the count rate at the Tupi vertical telescope, related to the Swift GRB event, being a background fluctuation, as P, i.e., an annual rate of 73.1.

Figure 5. Statistical significance (i.e., number of standard deviations) of the 1, 3, and 5 s binning counting rates observed  by the vertical Tupi telescope, as a function of the time elapsed since the MAXI transient 580727270 trigger time.
Figure 5. Statistical significance (i.e., number of standard deviations) of the 1, 3, and 5 s binning counting rates observed by the vertical Tupi telescope, as a function of the time elapsed since the MAXI transient 580727270 trigger time.

Summary

Of course, that the Tupi detector has recorded a count rate violation correlated with the gamma-ray bursts. In addition, there is an alternative mechanism useful to explain high-energy electrons from terrestrial gamma-ray flashes [45] and observations of ground-level gamma-ray bursts under storm clouds [46]. The high-energy gamma-ray influence and energy spectrum of GRB 970417a from Milagrito observations.

Searching for GeV gamma-ray bursts with the ARGO-YBJ detector: a summary of eight years of observations. Using Cherenkov water detectors to detect gamma-ray bursts at the Large Aperture GRB Observatory (LAGO). Observation of a muon excess near the ground relative to gamma-ray bursts detected from space.

Extragalactic Gamma‐Ray Background

The gamma-ray luminosity function

In this approach, the GLF involving the evolution of redshift as well as the distribution of spectral indices for a given source class can be established for all known sources and the observed population can be extrapolated to lower fluxes. To constrain the model parameters for various models of the evolving GLF, a maximum likelihood method first introduced by Marshall et al is adopted. In the luminosity-dependent density evolution (LDDE) model, the GLF evolution is determined by a redshift cutoff that depends on the luminosity, and the GLF can be given by

With the increase in the number of detected sources, the evolutionary form of those sources becomes more complicated and the updated forms of those models can be found in Ref. 33], which allows the Gaussian mean μ of the photon index and the evolutionary factorsðz,LγÞ to change with luminosity. Left: The evolution of the light density of FSRQs compared to that of BL Lac objects.

Figure 2. Left: The evolution of the luminosity density of FSRQs compared to that of BL Lac objects
Figure 2. Left: The evolution of the luminosity density of FSRQs compared to that of BL Lac objects

The extragalactic gamma-ray background

This cascade emission is considered to be contributing to the EGRB if the cascade flux flux is less than the sensitivity of the detector. In case I, the cascaded emission can contribute to the EGRB if the flux of the cascaded emission is lower than that of the LAT sensitivity. Based on the effect of the EGMF on the cascading contribution of blazars, Yan [84] studied the effect of cascading radiation on the contribution to the EGRB using a simple semi-analytical model.

They suggested that if the strength of the EGMF is large enough (BEGMF > 10−12 G), the cascade contribution can significantly alter the spectrum of the EGRB at high energies. If the small strength of the EGMF is large enough (BEGMF<10−14G), then the cascading contribution is small, but it cannot be ignored. It should be noted that about 95% of the EGRB can be naturally explained by blazars, star-forming galaxies, and radio galaxies in the 0.1–820GeV range.

Figure 3. The cascade radiation processes in no or non-zero extragalactic magnetic field (EGMF)
Figure 3. The cascade radiation processes in no or non-zero extragalactic magnetic field (EGMF)

Conclusion and discussion

Spectrum of the isotropic diffuse gamma-ray emission derived from first-year Fermi large-area telescope data. Gamma-ray luminosity function of blazars and the cosmic gamma-ray background: evidence for the luminosity-dependent density evolution. The blazar sequence and the cosmic gamma-ray background radiation in the Fermi era.

Flux and photon spectral index distributions of Fermi-LAT blazars and contributions to the extragalactic gamma-ray background. A revisited gamma-ray luminosity function and contribution to the extragalactic diffuse gamma-ray background for Fermi FSRQs. Contribution of gamma-ray-high radio galaxy nuclear emissions to the cosmic MeV and GeV gamma-ray background radiation.

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Figure 2. (1) Wall tiles; (2) pitch‐blend source for radium drinking device (3); (4) watch, compass, glass pearls; (5) gas  mantle and static eliminator; (6) bowl with paintings.
Figure 3. Activity trends of radiocaesium in soil, vegetation and cow's milk on a farm in Basel‐Country
Figure 4. S oil profiles from a soil filtration site of the drinking water producer of Basel
Figure 5. Correlations of radiocaesium between moss, tree bark and the corresponding soil activity.
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