Gamma-ray Intensities Research Articles

Measuring the Mass of Missing Baryons in the Halo of Andromeda Galaxy with Gamma-Ray Observations

Abstract It has been suggested that a huge amount of baryon resides in the circumgalactic medium (CGM) extending out to the virial radii of galaxies. In this work we attempt to measure the baryon mass in the CGM with a novel method based on the gamma-ray observations of the extended halo of the Andromeda galaxy Messier 31 (M31). Since cosmic-ray particles generated inside the galaxy will eventually escape to the CGM, they will produce gamma-ray emission via the proton–proton collision with the CGM and produce gamma-rays. Different from some traditional measurements that are sensitive only to certain metallic ions in specific temperature range, the hadronic gamma-ray flux is sensitive to baryonic gases in all phases and does not rely on the metallicity in the halo, hence the measured gamma-ray flux from the galaxy’s halo can be used to constrain the mass of the CGM. By dealing with the cosmic-ray transport in the halo and calculating the hadronic gamma-ray intensity, we find that the total baryon mass contained within the virial radius is less than (1.4–5) × 1010 M ⊙ according to the gamma-ray intensity obtained with a model-dependent analysis. It implies that the CGM of Andromeda galaxy may not account for more than 30% of the missing baryons, but the result is subject to uncertainties from the gamma-ray intensity upper limit, diffusion coefficient of the cosmic-rays in the halo, as well as the stellar mass and dark matter halo mass of the galaxy. This method will become more constraining provided better understandings on these issues and more sensitive gamma-ray telescopes in the future.

Constraining millisecond pulsar geometry using time-aligned radio and gamma-ray pulse profile

Context. Since the launch of the Fermi Gamma-Ray Space Telescope, several hundred gamma-ray pulsars have been discovered, some being radio-loud and some radio-quiet with time-aligned radio and gamma-ray light curves. In the second Fermi Pulsar Catalogue, 117 new gamma-ray pulsars have been reported based on three years of data collected by the Large Area Telescope on the Fermi satellite, providing a wealth of information such as the peak separation Δ of the gamma-ray pulsations and the radio lag δ between the gamma-ray and radio pulses. Aim. We selected several radio-loud millisecond gamma-ray pulsars with period P in the range 2–6 ms and showing a double peak in their gamma-ray profiles. We attempted to constrain the geometry of their magnetosphere, namely the magnetic axis and line-of-sight inclination angles for each of these systems. Method. We applied a force-free dipole magnetosphere from the stellar surface up to the striped wind region – well outside the light cylinder – to fit the observed pulse profiles in gamma-rays, consistently with their phase alignment with the radio profile. In deciding whether a fitted curve is reasonable or not, we employed a least-square method to compare the observed gamma-ray intensity with that found from our model, emphasising the amplitude of the gamma-ray peaks, their separation, and the phase lag between radio and gamma-ray peaks. Results. We obtained the best fits and reasonable parameters in agreement with observations for ten millisecond pulsars. Eventually, we constrained the geometry of each pulsar described by the magnetic inclination α and the light-of-sight inclination ζ. We found that both angles are larger than approximately 45°.

A Fast Method for Modelling A Gamma-Ray Field over Inhomogeneous Ground Sources

Designing airborne gamma-ray surveys for geological purposes, mineral prospecting, environmental applications or radioactive contamination mapping requires the optimal choice of survey parameters such as the survey altitude, line spacing and survey speed with respect to the sensitivity of the instruments employed and the presumed size and intensity of the detected anomalies. The gamma-ray field attenuates significantly with the distance from the source; being able to model gamma-ray field intensity in various detector positions can be very useful. In recent years, the use of mini-airborne UAV radiometric measurement has developed rapidly. On the one hand, the low payload capacity of UAV results in low sensitivity of the employed detectors; the possibility of increasing gamma-ray signals from low altitude surveys and low speeds on the other hand raises the demand for simulating the gamma-ray field of local inhomogeneous radiometric anomalies. The gamma-ray field modelling method introduced in this paper is based on the monoenergetic approach and discretization of geological radioactive sources utilizing a three-dimensional net of point sources. The optimal density of point sources depends on the detection altitude and the degree of inhomogeneity of the radioactive source. The designed modelling method was verified by comparing the model data with experimental data from three localities where uranium anomalies occur. The degree of conformity of the model and experimental data is acceptable and confirms the applicability of the modelling method. The paper describes a relatively fast and simple gamma-ray field modelling method that is appropriate for ground planar radioactive anomalies. The method is useful for designing survey parameters and for interpretation of detected airborne gamma-ray anomalies.

CEA-JSI Experimental Benchmark for validation of the modeling of neutron and gamma-ray detection instrumentation used in the JSI TRIGA reactor

Constant improvements of the computational power and methods as well as demands of accurate and reliable measurements for reactor operation and safety require a continuous upgrade of the instrumentation. In particular, nuclear sensors used in nuclear fission reactors (research or power reactors) or in nuclear fusion facilities are operated under intense mixed neutron and gamma-ray fields, and need to be calibrated and modeled to provide selective and accurate neutron and gamma-ray measurements. The French Atomic Energy and Alternative Energies Commission (CEA) and the Jožef Stefan Institute (JSI) have started an experimental program dedicated to a detailed experimental benchmark with analysis using Monte Carlo particle transport calculations and a series of neutron and gamma-ray sensor types used in the JSI TRIGA Mark II reactor. CEA has setup a simplified TRIPOLI-4® modeling scheme of the JSI TRIGA reactor based on the information available in the IRPhEP benchmark in order to facilitate analysis of future neutron and gamma-ray measurements. These allow the CEA to perform a TRIPOLI-4 instrumentation calculation scheme benchmarked with the JSI MCNP model. This paper presents the main results of this CEA calculation scheme application and the analysis of their comparison to the JSI results obtained in 2012 with the MCNP5 & ENDF/B-VII.0 calculation scheme. This paper will conclude with some information about the new experimental program to be carried out in 2022 in the TRIGA reactor core.

Development of a Mutant Population of Micro-Tom Tomato Using Gamma-Irradiation

Knowledge of genetic resources is essential for breeders to create new crop varieties with improved characteristics. In this respect, mutant populations may conveniently provide a powerful tool for identifying new functional genes. Therefore, we used the Micro-Tom tomato variety, which has a reduced size and a relatively short life-cycle compared to other commercial tomato cultivars, to construct a mutant population using gamma-ray radiation as a mutagen. To determine the optimal mutagenic intensity of gamma rays for tomato, dry seeds of Micro-Tom were irradiated with gamma-ray intensities from 0 to 1000 gray (Gy) with increments of 100 Gy. The germination rate of mutagenized seeds (M1 seeds) on MS media was not affected by the tested gamma-ray intensity range. However, seedling growth was severely reduced with increasing irradiation. Seedling growth rate at eight days after germination showed that the median gamma-ray doses for hypocotyl and root elongation were 600 and 300-400 Gy, respectively. The survival test for 300, 400, and 500 Gy-treated M1 seeds showed that survival rates significantly decreased with increasing irradiation. The survival rate of 400 Gy-radiated seeds was 48%, while that of 500 Gy-radiated seeds was only 25%, compared with the control treatment. Therefore, we concluded that gamma-ray irradiation at 300-400 Gy is best for tomato mutagenesis. To find new mutants, M2 seeds produced by M1 plants were grown. We found several mutants, including plants with varying cotyledon number, variegated or red leaves, and green hypocotyls.

Sunflower seed oil effect on some physiological cases of adult chickens. Running Title: Gamma ray effects as oxidant stress on several physiological cases

This study aims to evaluate the effects of gamma-ray oxidation stress (ionization of biological cell as sperm) on the adult chicken reproductive system. In this research, we used cocks chicken at 36-54 weeks of age and find the importance of semen volume in (ml / brid / ejac). Concentration in (Million cells / ml.) and total sperm (Million cells / ejaculation). The value of semen volume, semen concentration and total sperm significantly increased with increased age of cock chicken but not at all ages, only at limited ages considered as control group. These values were found at irradiation with low dose rate (low intensity) of gamma ray (33, 42, and 75 mGy/h) which is a chronic dose rate (long time of irradiation) at 8 h/day for 40 days, which was significant decrease with increase low dose rate gradually. The semen volume decrease ratio with irradiation doses of approximately 5-14% and with semen concentration of approximately 5-12% for three chronic low doses relative to the control group for each cock generation. The average value of both groups showed a substantial decrease in all parameters with increased gamma radiation dose levels. The current study also aimed to identify the problems that may arise from exposure to a slow and equal dose of radiation on certain sperm parameters for a relatively long period of time and to compare them with the findings of previous work on the same mechanism and Use of sunflower seed oil as a protective and protective material against oxidative stresses resulting from radiation exposure and work Reducing its percentage, especially on certain sperm parameters in male chickens.

Crystal-based intensive gamma-ray light sources

We discuss design and practical realization of novel gamma-ray Crystal-based Light Sources (CLS) that can be constructed through exposure of oriented crystals (linear, bent, periodically bent) to beams of ultrarelativistic charged particles. In an exemplary case study, we estimate brilliance of radiation emitted in a Crystalline Undulator (CU) LS by available positron beams. Intensity of CU radiation in the photon energy range $10^0-10^1$ MeV, which is inaccessible to conventional synchrotrons, undulators and XFELs, greatly exceeds that of laser-Compton scattering LSs and can be higher than predicted in the Gamma Factory proposal to CERN. Brilliance of CU-LSs can be boosted by up to 8 orders of magnitude through the process of superradiance by a pre-bunched beam. Construction of novel CLSs is a challenging task which constitutes a highly interdisciplinary field entangling a broad range of correlated activities. CLSs provide a low-cost alternative to conventional LSs and have enormous number of applications.

The prolonged gamma ray enhancement and the short radiation burst events observed in thunderstorms at Tien Shan

We report the observation results of the hard radiation flashes which accompanied the lightning discharges above the mountains of Northern Tien Shan. Time series of the counting rate intensity, numerical estimations of absolute flux, and energy distribution of accelerated electrons and of (20−2000) keV gamma rays were obtained at the height of 3700 m a. s. l., immediately within thunderclouds, and in closest vicinity (≲100 m) to discharge region. Two different kinds of radiation emission events are presented here: a relatively prolonged rise of gamma ray intensity with minute-scale duration (the thunderstorm ground enhancement, TGE) which has preceded a negative field variation, and a short sub-millisecond radiation burst, which accompanied a close lightning discharge in thundercloud. It was revealed also an indication to positron generation in thunderclouds at the time of gamma ray emission, as well as modulation of the neutron counting rate in Tien Shan neutron monitor which was operating at a (1.5–2) km order distance from the region of lightning development.

Measurement of the radiation dose distribution in EAST hall based on thermoluminescence dosimeter

The spatial distribution of relative intensity of neutron dose and gamma-ray dose in the Experimental Advanced Superconducting Tokamak (EAST) machine hall were measured by multiple thermoluminescence dosimeters (TLDs) during second experimental campaign of 2019. This activity has been performed twice, the first measurement lasted 5 days and adopted 64 pieces of dosimeters, the second time lasted 10 days and employed 100 pieces of dosimeters. These dosimeters were arranged on the ground plane outside the tokamak device with different positions to obtain the radiation dose distribution of the deuterium plasma and activated radionuclide. Generally speaking, the radiation dose decreased with the increase of radial distance. However, the measurement results of TLDs showed that the variation trends of normalized neutron dose and normalized gamma-ray dose with the increase of radial distance were unsymmetrical and not always under the attenuation law in the radial distribution of EAST ports. Some large scale of equipment and the thick concrete shielding wall had significant effect on the dose distribution. Both radiation intensity of neutron and gamma-ray raised slightly near the equipment and shielding wall in generally. Furthermore, statistics of measurements from multiple dosimeters showed that there was a certain correlation between the normalized gamma-ray dose and normalized neutron dose.

A simple test for power-law behavior

In this article, I propose a new test for power-law behavior. The statistical test, pwlaw, is locally optimal if the possible alternative distributions are contained in the Pareto type (IV) family. After deriving the test, I examine four classical datasets: the frequency of unique words in an English text ( Moby Dick); the human populations of U.S. cities; the frequency of U.S. family names; and the peak gamma-ray intensity of solar flares. I show that in the first case there is no indication of any power-law behavior and that in the second and fourth cases there is evidence in that regard.

Measurement of the absolute gamma emission intensities from the decay of Th-229 in equilibrium with progeny

There are few long-lived radionuclides yielding high intensity gamma-rays emission with energies ranging from 100 keV to 500 keV that can be applied as radioactive gamma standard to calibrate HPGe detectors. Furthermore, this energy range represents the main emitted energies of the majority of radionuclides used in nuclear medicine. The Brazilian National Laboratory for Ionizing Radiation Metrology (LNMRI/IRD/CNEN) has attempted to identify radionuclides that have the potential to be used as a calibration source due to their long half-life as well as their emission spectrum. Hence, LNMRI promotes standardization studies of gamma-emitting radionuclides that meet these criteria on order to disseminate them. Thorium-229, with its well-defined energies and relatively high intensities, is one such candidate radionuclide for the energy and full-energy peak efficiency calibration of high-purity gamma spectrometers. Thorium-229 was standardized by the method of 4παβ(LS)-γ(NaI(Tl)) live timed anticoincidence counting. The emission intensities of gamma-rays associated with the decay of 229Th have been determined by HPGe gamma ray spectrometry with accuracy and precision. The results are in agreement with current literature data.

Improved plutonium and americium photon branching ratios from microcalorimeter gamma spectroscopy

Photon branching ratios are critical input data for activities such as nuclear materials protection and accounting because they allow material compositions to be extracted from measurements of gamma-ray intensities. Uncertainties in these branching ratios are often a limiting source of uncertainty in composition determination. Here, we use high statistics, high resolution (̃60–70 eV full-width-at-half-maximum at 100 keV) gamma-ray spectra acquired using microcalorimeter sensors to substantially reduce the uncertainties for 11 plutonium (238Pu, 239Pu, 241Pu) and 241Am branching ratios important for material control and accountability and nuclear forensics in the energy range of 125 keV to 208 keV. We show a reduction in uncertainty of over a factor of three for one branching ratio and a factor of 2–3 for four branching ratios.

Early Cretaceous Terrestrial Milankovitch Cycles in the Luanping Basin, North China and Time Constraints on Early Stage Jehol Biota Evolution

This research analyzes the cyclostratigraphy of the lacustrine Dabeigou Formation (DBG) of early Jehol Biota age (~130-135 Ma) in the Luanping Basin, northern China. A high-resolution (2 cm interval), 117.82-meter-long magnetic susceptibility (MS) stratigraphic series was measured along the Yushuxia section. MS is positively correlated with thorium, potassium and uranium concentrations associated with gamma ray intensity, and represents a proxy for detrital influx to the Luanping Basin. Power spectral analysis identifies a hierarchy of sedimentary cycles with wavelengths of 16.38 m, 5.85-3.28 m, 1.88-1.33 m and 0.98-0.7 m, which are interpreted to represent Earth’s orbital eccentricity, obliquity and precession index cycles. Objective testing of the MS series supports the interpretation of Milankovitch cycles, indicating an average sedimentation rate of 4.642 cm/kyr to 4.723 cm/kyr. A floating astronomical time scale with a duration of 2478 kyr is established from interpreted 405 kyr long orbital eccentricity cycles along the MS series. The 405-kyr tuned DBG MS time series closely matches the predicted orbital eccentricity of the La2004 astronomical solution from 130.787 Ma to 133.265 Ma, providing independent temporal constraints on early stage Jehol Biota evolution. Finally, this estimated time interval for the DBG MS time series indicates that it occurred entirely within the Weissert Event.

New Directions for Axion Searches via Scattering at Reactor Neutrino Experiments.

Searches for pseudoscalar axionlike-particles (ALPs) typically rely on their decay in beam dumps or their conversion into photons in haloscopes and helioscopes. We point out a new experimental direction for ALP probes via their production by the intense gamma ray flux available from megawatt-scale nuclear reactors at neutrino experiments through Primakoff-like or Compton-like channels. Low-threshold detectors in close proximity to the core will have visibility to ALP decays and inverse Primakoff and Compton scattering, providing sensitivity to the ALP-photon and ALP-electron couplings. We find that the sensitivity to these couplings at the ongoing MINER and various other reactor based neutrino experiments, e.g., CONNIE, CONUS, ν-cleus, etc., exceeds existing limits set by laboratory experiments and, for the ALP-electron coupling, we forecast the world's best laboratory-based constraints over a large portion of the sub-MeV ALP mass range.

Estimation of absorbed gamma dose rate from granite by Monte Carlo simulation approach

Apart from the continuous exposure of humans to background ionising radiation, an increased level of radiation may also originate from the use of building materials with an enhanced level of radioactivity. Thus, it is necessary to examine the content of radionuclides present in building materials, as well as the corresponding dose which may be received by residents from these materials. In this paper, particular attention was dedicated to finding the absorbed dose rate and annual effective dose caused by the presence of naturally occurring radioisotopes 226Ra, 232Th, and 40K in granite, a widely used building material, by means of Monte Carlo simulations. In addition, the obtained dose rate simulation results were compared with values estimated from commonly used simple equations, relating to the dose rate emitted by granite plates, covering the interior of a standard room. In the simulation, a room was constructed with standard dimensions (4 m × 5 m × 2.8 m), and with floor and walls covered with 3 cm thick granite. A water cylinder (approximate mass 65 kg) was positioned in the center of the room, representing a human body. The emission of the most intense gamma rays from 226Ra and 232Th progenies, as well as from 40K, emanating from the granite matrix, was simulated. The number of generated photons in each simulation (typically it was an order of magnitude of ~106) precisely represented actual activity concentrations of 226Ra, 232Th, and 40K in granite samples. All processes playing a role in the interactions of gamma photons with the granite matrix itself, the outer concrete shell, the air within the room, and the water cylinder, were taken into account by GEANT4 simulation software, after which the spectra of deposited energy inside of the water cylinder were obtained. Based on the deposited energy, the absorbed dose rate and annual effective dose were calculated for 6 analysed granite samples, each with different 226Ra, 232Th, and 40K contents. Furthermore, the effect of the position of the water cylinder in the simulated room on the absorbed dose rate was considered, as well as the distribution of the deposited energy within the water cylinder. The absorbed dose rates, and consequently annual effective dose, obtained in the simulations were found to be 30%–40% higher than the values obtained from using a standard formula.

Petrophysical and mechanical properties of the lower Silurian perspective oil/gas shales of Lithuania

Lithuania is situated in the central and eastern parts of the Baltic Sedimentary Basin. Several prospective Lower Palaeozoic gas shale formations are identified in the basin. Most of the published studies concern the organic chemistry and evaluation of gas potential, whereas only scarce data are provided on the petrophysical and mechanical properties of oil/gas shales. It is typical also for other basins, essentially concerning parameters like cation exchange capacity, swelling index, erodibility etc. Mineralogical, petrophysical and mechanical properties of the Lower Silurian organic rich shales of west Lithuania (within petroleum window area), considered as a most prospective body for unconventional oil/gas exploitation, are discussed in the present study. The most distinct feature due to anomalous organic matter (OM) content is the Middle Llandovery black shales that are compatible to the Llandovery “hot” shales defined in sedimentary basins of Africa and Arabian Peninsula. Brittleness index (BI) of shales was calculated from mineral composition, shales are classified as moderately brittle (predominate) to moderately ductile. It was stated that clay content and quartz content directly correlate with the BI, despite that they have a reverse effect on shale brittleness. The unconfined compressive strength and tensile strength also indicate low brittleness of shales that is accounted to high natural fracturing of the Lower Silurian shales. Low porosity, varying from 12 to 16% to less than 3%, have no discernible effect on shale strength properties. Cation exchange capacity measurements show low values that is related to high illite and detrital minerals content in shales. Organic matter (OM) content have noticeable statistically positive correlation with gamma ray intensity in organic most rich “hot” shales. Roller oven technique was applied to measure the shale erodibility. Experiments show that application of the tap water leads to high erodibility of shales, they are classified as the moderate to high erodibility rocks. Reversely, diesel considerably reduces erodibility index causing low erodibility of shales. As regards the acid solutions, the best effect in decreasing shale erodibility is measured when K2Cl (7%) solution is applied (moderate erodibility). Generally low erosion susceptibility is explained in terms of high content of detrital silt and predominance of illite and chlorite in the clay fraction. Cation suction time (CST) characterises the shale swelling capacity. It was noticed that CST negatively correlates with the GR intensity logs as they mainly reflect the OM content in shales. The most organic rich black Middle Llandovery “hot” shales show the lowest swelling capacity compared to other less OM enriched shales. The measured parameters are therefore evaluated as positive for oil/gas exploitation (low swelling, low erodibility, and low stiffness) or of moderate quality (brittleness), some parameters decrease the quality of shales (e.g. low CEC, low porosity).

Determination of spent nuclear fuel parameters using modelled signatures from non-destructive assay and Random Forest regression

Verification of fuel parameters is a central undertaking for nuclear inspectors aiming at verifying the completeness and correctness of operator declarations. Traditionally, such verification is done analysing data from one instrument at a time. Here we present a study based on simulated data from various non-destructive assay measurement techniques applied on modelled PWR nuclear fuel assemblies. The data comprised multiple signatures and were analysed using machine learning algorithms. These signatures included activities from gamma-ray emitting fission product radionuclides, the parametrised early die-away time τ from the prototype Differential Die-away Self-Interrogation (DDSI) instrument, as well as the total Cherenkov light intensity which is directly measurable.The objective of the work is to systematically explore the capability to predict values of the fuel parameters initial enrichment (IE), burnup (BU) and cooling time (CT) independently of operator declarations, using Random Forest regression and modelled pressurised water reactor (PWR) fuel.The results show that passive gamma-ray activities alone can be used to predict IE, BU and CT for CT<20 years, and that by adding a feature proportional to the total gamma-ray activity, the errors in the predictions are significantly reduced. In this work, two measures proportional to total gamma activity have been studied: the sum of all considered gamma-ray intensities, and the total Cherenkov light intensity. From this work it was concluded that for fuels with CTs between 20 and 70 years, CT can be well determined by a multivariate analysis of the activities of 134Cs, 137Cs, 154Eu. For a BU determination, an additional feature corresponding to total gamma activity is required. This is, however, not sufficient to determine IE, which requires inclusion of the neutron signature τ as well.

Review of nuclear techniques for planetary science

Spaceflight instruments that measure the energy and intensity of gamma rays and neutrons emitted by the surfaces of planetary bodies have been included in planetary science missions since 1966. These instruments use nuclear techniques to determine the elemental composition and related information about planetary surface and near-surface materials from the analysis of these gamma ray and neutron data. This paper provides a short review of these nuclear techniques as they have been used in current and past orbital and landed missions. A description of the nuclear instrumentation on many such missions is provided. Finally, descriptions of future missions that will employ gamma ray and neutron instruments will be presented.

Гамма-активационный анализ селена на ускорителе электронов “Микротрон-сТ”

In this work, an activation analysis of selenium under its irradiation with bremsstrahlung gamma radiation on a cyclic electron accelerator “Microtron-sT” with an energy of 21 MeV is carried out irradiation was performed at room temperature for 1 h, the gamma-ray intensity was ~ 5·1013 γ/s. Irradiation was carried out on two types of state of the samples (Se) in the form of granules of the (osch), weight 5-10 mg, and microparticles (powder) obtained by mechanical dispersion. Samples in the state of microparticles were suspended in distilled water, in separate polyethylene capsule. On each sample, after irradiation with bremsstrahlung gamma radiation, the spectra of quantum radiation of radionuclides were measured. The measurements were carried out repeatedly in order to observe a decrease in the activity of the samples and their energy gamma spectrum. From the results obtained, it can be seen that all radionuclides are formed on selenium nuclei with different mass numbers by reactions: (γ, n), (γ, p), (γ, 2n), (γ, p + n). The half-life of (T1/2) in identified radionuclides is within 3.9 minutes — 119.8 days. The energy of emitted quanta by radionuclides is equal to from 121.1 to 657 keV. The radiation intensity of radionuclide gamma rays is in the range: 0.25-99.0%.

Research of Dynamic Azimuth Gamma Instrument while Drilling for Mine

In view of the problems that the existing gamma logging instruments in coal mines can only carry out static fixed-point measurement and are not suitable for rotary drilling, this paper, based on the analysis of the characteristics of measurement while drilling in coal mines and the principle of gamma logging, designs and realizes the dynamic gamma azimuth instruments for mines by means of power line carrier, rotation positioning and gamma measurement technology, which can measure the intensity of natural gamma ray in two directions around the borehole in real time, effectively reflect the changes of different radioactive strata, and guide the geosteering while drilling in coal mine.