Point Source Of Radiation Research Articles

P-wave propagation in attenuative elliptical VTI media

Elliptical anisotropy is convenient to use as the reference medium in perturbation methods designed to study P-wave propagation for transverse isotropy (TI). We make the elliptically anisotropic TI model attenuative and discuss the corresponding P-wave dispersion relation and the wave equation. Our analysis leads to two conditions in terms of the Thomsen-type parameters, which guarantee that the P-wave slowness surface and the dispersion relation satisfy elliptical equations. We also obtain the viscoacoustic wave equation for such elliptically anisotropic media and solve it for point-source radiation using the correspondence principle. For the constant- Q TI model, we use the weighting function method to derive the viscoacoustic wave equation in differential form. Numerical examples validate the proposed elliptical conditions and illustrate the behavior of the P wavefield in attenuative elliptical TI models.

Internal stress transfer characteristics of coal–rock medium under concentrated force based on particle flow method

To solve the problem that the macroscopic deformation and failure of coal–rock medium under external loads are easy to be observed while the internal stress transfer mode and path are unclear. Based on the discrete element idea, the numerical models for pure coal or rock samples and coal–rock combination samples with different lithologies and combination methods under concentrated force are established by PFC2D software. Then the influence of coal or rock strength and combination methods on the internal stress transfer law and distribution evolution characteristics of coal–rock medium are discussed from the perspectives of macroscopic stress and mesoscopic force chain, respectively. The results showed that under concentrated load, the macroscopic stress transfer paths within pure coal or rock samples and coal–rock combination samples are primarily in the form of ‘point source radiation’. However, when transferring between coal–rock interfaces, there is a certain interface effect. For pure coal or rock samples, differences in lithology does not change the transfer rules and macro distribution patterns of internal stress, but it can cause changes in internal unit transfer stress value and local area transfer direction. For coal–rock combination samples, the greater the difference in lithology between the two sides of the interface, the more likely the interface effect will occur. In addition, the internal stress transfer is also influenced by the relative stratigraphic relationships of coal and rock. When the stress is transferred from a higher-strength rock to a lower-strength coal mass, the interface effect will be more significant. However, regardless of the combination pattern, the locations where significant stress surges occur are always within the higher strength rock mass near the interface. The findings are helpful to understand the mechanical properties and failure mechanism of mining coal and rock mass, and provide a theoretical basis for the study of the mining-induced mechanical behavior of the floor under the action of the coal pillar.

Characterization of a Germanium Detector by Means of Experimental Measurements and GEANT4 Monte Carlo Simulations

A HPGe detector was modelled and characterized by means of experimental measurements and Monte Carlo simulations. The simulation based on Monte Carlo GEANT4 was used to characterize the potential dead layer/inactive materials and Full Energy Peak Efficiency (FEPE). The calibration of FEPE for the HPGe detector was conducted in the γ-ray energy range from 88 keV to 1332 keV, using eight standard point sources of gamma radiation: 137Cs, 133Ba, 109Cd, 65Zn, 60Co, 57Co, 54Mn, and 22Na. The efficiency dependence curves were obtained by changing the source to detector distance from 8 cm to 12 cm. a remarkable similarity in FEPE for low energy measurements ranging from 88 keV to 122 keV was obtained between the simulation results and the experimental measurements.

Application of spherical harmonic filtering to 4π gamma imaging

Abstract 4π gamma imaging with sensitivity in all directions is useful for determining the incident direction of the gamma-ray to the detector. In this study, a spatial filter with a spherical harmonic function was proposed for 4π gamma imaging to reduce statistical noise in lower-event data. The application of the filtered 4π imaging for finding a point radiation source was investigated. In the filtered 4π images, the linearity and root mean squared error of the image improved with a small number of events. Furthermore, the finding of a 137Cs point source based on the filtered gamma imaging was demonstrated, and the accuracy of the estimated source location and activity was improved using lower-event data.

Further development of the LNMRI/IRD's TNF2 thermal system for flexible dose rate irradiation.

The 'Inverse Square Law' (ISL)( 1) requires the existence of a point radiation source to be validated, but in some cases where there is more than one source, its use is possible as long as a point is determined where a virtual source can be positioned and from this point the points correspond to the ISL. Ambient dose equivalent rate values were obtained by simulation and measurements at various points along the LNMRI Thermal Neutron Flux 2 (TNF2) central axis front face, determining a function corresponding to the inverse square of the distance and the font position at the virtual point 'y0', so that the ISL is respected. This function will help in the neutron monitors calibration, previously estimating the ambient dose equivalent at a certain distance from the face.

Method of correlation reception of radio light with spatial resolution and its implementation

A method for receiving ultra-wideband noise-like microwave radiation -- radio light is considered, based on the correlation reception of signals coming from spaced apart space of receiving antennas, for the purpose of further effective image formation radio-illuminated environment. A mathematical model has been developed to study the formation possible response of the receiving system and assessing the influence of signal accumulation time on its dynamicrange. One-dimensional responses of the correlation receiving system to point sources of radiation were obtained, for which radio light sources were used. An experimental model of a correlation radio light receiver was developed and physical experiments were carried out with it, confirming the results obtained during modeling, as well as the overall performance of the proposed approach.

Gas Discharge Point Source of UV Radiation Based on Argon–Copper Gas–Vapor Mixture

Gas Discharge Point Source of UV Radiation Based on Argon–Copper Gas–Vapor Mixture

On a paradox" in the scattering theory

The solution of the "paradox" in scattering theory is considered, according to which the extinction cross section is expressed in terms of the forward scattering amplitude (the so-called "optical theorem"), whereas for a point source, and as a consequence, for any emitter located at a finite distance from the scatterer, a similar ratio is often written through a scattered field near the emitter, i.e. determined by "backscattering". A clear picture of the formation of radiation losses during the transition of energy from the source to the scatterer is presented. It is shown that although the field backscattered to the source determines the change in its radiation characteristics (the Purcell effect), the optical theorem includes an extinction factor which is generally related to the work of the incident wave on the currents induced in the scatterer. This factor passes into the forward scattering amplitude in the limiting case of a plane incident wave. Keywords: optical theorem, energy conservation, radiation losses, Purcell effect, point source of radiation.

МОДЕЛИРОВАНИЕ ВОЗБУЖДЕНИЯ ПОВЕРХНОСТНЫХ ПЛАЗМОН-ПОЛЯРИТОНОВ В ПРЯМОУГОЛЬНОМ НАНОРЕЗОНАТОРЕ НА ОСНОВЕ ЗОЛОТА

This paper considers the modeling of surface plasmon polaritons excitation in a limited nanostructure on the basis of a two-dimensional area discrete model, the area interacts with the oscillator. The nanostructure is a rectangle defined on the metal surface at the interface of the gold–silicon oxide, the surface plasmon–polaritons are excited by an electromagnetic radiation point source located above the metal surface. The dynamics of radiation point source is described by a discrete version of the Van der Pol equation with a small nonlinearity of the source parameters. The parameters of the goldsilicon oxide structure (the wave phase speed, the radiation source frequency, the characteristic time in the system, etc.) will be received from the dispersion relation for surface plasmon–polaritons at a single metal–dielectric interface. The distributions of the wave field in the structure will be analyzed at different positions of the point oscillator and different coupling coefficients of the wave field with the oscillators. The resonant wave field mode composition at different positions of the point oscillator and different coupling coefficients will be found using the two-dimensional Fourier transform of the wave field, the time evolution of excited modes of the wave field amplitudes will be also analyzed. In conclusion, the paper gives applicability limits of the considered model for studying the surface plasmon polaritons excitation in a limited nanostructure.

Gas-Discharge Point Source of UV Radiation Based on a Gas-Vapor Mixture of Argon and Copper

The characteristics of a pulse periodic source of a long-range UV radiation with overvoltage pumping by a bipolar discharge of nanosecond duration between copper electrodes in argon at atmospheric pressure are investigated. Copper vapors were introduced into the discharge due to the ectonic mechanism, in which a sufficient amount of the electrode material vapors is introduced into the discharge gap due to microexplosions of inhomogeneities of the surface of metal electrodes in a strong electric field of an overvoltage high-current nanosecond discharge. The characteristics of an overvoltage nanosecond discharge at a distance between the electrodes of 2 mm are studied. The emission spectra of the discharge were analysed, and the intensity of the UV radiation of a point emitter was optimized depending on the supply voltage of the high-voltage modulator and the repeti-tion rate of discharge pulses. The identification of the emission spectra of plasma made it possible to establish the main excited plasma products that form the spectrum of the UV radiation of the plas-ma. The study of the spectral characteristics of plasma based on gas-vapor mixtures "copper – ar-gon" showed that the most intense were the spectral resonance spectral lines of the copper atom and ion. It was found that a space-uniform overvoltage nanosecond discharge was ignited between copper electrodes at an inter-electrode distance of 2 mm. It was found that the maximum value of the average UV power at p(Ar) = 101 kPa was observed for the UV-A range.

Corrigendum: Particle Filter Based Range Search Approach for Localization of Radioactive Materials

In the original article, there was an error. In equation (1) small "i" is typed instead of capital I, subscript of symbols and italic, use of ";" instead of "," missing of B(x, y), reference (Chin et al., 2008) instead of (Rao et al., 2008).The localization of a point radiation source of unknown strength Au expressed in a unit of micro-Curie (Ci) called the source rate will be considered. The source is located at an unknown location (xu, yu). The source gives a radiation intensity of ( ) = ( , ) = × ×2.22×10 6 ( − ) 2 +( − ) 2(1) Last Name author1 et al.Pc 2 (Expressed in counts per minute or CPM) when measured by a sensor at point p = (x, y), where E is an efficiency constant unique to the sensor. The radiation count induced by the source and observed at the sensor per unit time is a Poisson random variable with parameter λ = I(xi, yi), not accounting for the background radiation B(x, y) (Rao et al., 2008) denote the background radiation strength at (x, y) expressed in CPM, called the background rate. The radiation count measurement (due to the background radiation) at a sensor i located at (xi, yi) is given by the Poisson random variable with parameter B (xi, yi). For comparison purposes, the radiation model, actual measurements, and calibration process (Rao et al., 2008) are followed.

Метод розрахунку функції розсіювання точки оптичної системи

The article presents a mathematical apparatus for precise calculation of the three-dimensional point spread function (PSF) of a high-aperture optical system. The proposed method is based on the Huygens-Fresnel principle: a spherical wave on the three-dimensional surface of the exit pupil is considered as result of the superposition of elementary secondary point radiation sources. These point sources emit coherent electromagnetic waves with a spherical wave front. They form a certain distribution of generalized complex amplitudes in three-dimensional space near the focus point. This distribution is used to calculate the intensity distribution in the focus area of ​​the optical system, which is the PSF. The article presents the results of PSFcalculations and their comparative.

Propagation of Cosmic Rays in Plasmoids of AGN Jets-Implications for Multimessenger Predictions

After the successful detection of cosmic high-energy neutrinos, the field of multiwavelength photon studies of active galactic nuclei (AGN) is entering an exciting new phase. The first hint of a possible neutrino signal from the blazar TXS 0506+056 leads to the anticipation that AGN could soon be identified as point sources of high-energy neutrino radiation, representing another messenger signature besides the established photon signature. To understand the complex flaring behavior at multiwavelengths, a genuine theoretical understanding needs to be developed. These observations of the electromagnetic spectrum and neutrinos can only be interpreted fully when the charged, relativistic particles responsible for the different emissions are modeled properly. The description of the propagation of cosmic rays in a magnetized plasma is a complex question that can only be answered when analyzing the transport regimes of cosmic rays in a quantitative way. In this paper, therefore, a quantitative analysis of the propagation regimes of cosmic rays is presented in the approach that is most commonly used to model non-thermal emission signatures from blazars, i.e., the existence of a high-energy cosmic-ray population in a relativistic plasmoid traveling along the jet axis. It is shown that in the considered energy range of high-energy photon and neutrino emission, the transition between diffusive and ballistic propagation takes place, significantly influencing not only the spectral energy distribution, but also the lightcurve of blazar flares.

Estimation of the contribution of scattered ionising radiation to the dosimeter readings during measurements inside a low-background chamber

The article evaluates the contribution of ionising gamma radiation scattered by structural materials when measuring the dose rate in a low-background chamber. The contribution of scattered radiation to the total dose rate was estimated using Monte Carlo simulations. A model of a low-background camera and a BDKG-05K dosimeter was created in the computer program Fluka. In addition, a model of a point source of 137Cs gamma radiation was placed in the low-background chamber. The fraction of scattered radiation was calculated by comparing the dosimeter readings when measuring the dose rate inside the low-background chamber with the reference model (the dosimeter model is placed together with the source in a vacuum, as a result, scattered radiation is completely absent). The calculation was carried out for two positions of the dosimeter relative to the source (30 and 100 cm). It was found that the contribution of scattered radiation to the dose rate reaches 38 % (distance from the source to the detector is 100 cm). To minimise the contribution of scattered radiation to the readings of the dosimeter, a design in the form of a collimator, inside which the source is located, was considered. Additionally, the work investigated the dependence of the dose rate formed by the scattered radiation on the design features of the collimator. It was found that the use of a collimator makes it possible to reduce the contribution of scattered radiation to 3 %. The aim of the work was to calculate the optimal design of the collimator, in which the contribution of scattered radiation to the total dose rate will be minimal. The results of the work will be used to create a prototype of a low-background camera and an optimised collimator.

Silicon cuboid nanoantenna with simultaneous large Purcell factor for electric dipole, magnetic dipole and electric quadrupole emission

The Purcell effect is commonly used to increase the spontaneous emission rate by modifying the local environment of a light emitter. Here, we propose a silicon dielectric cuboid nanoantenna for simultaneously enhancing electric dipole (ED), magnetic dipole (MD) and electric quadrupole (EQ) emission. We study the scattering cross section, polarization charge distribution, and electromagnetic field distribution for electromagnetic plane wave illuminating the silicon dielectric cuboid nanoantenna, from which we have identified simultaneous existence of ED, MD and EQ resonance modes in this nanoantenna. We have calculated the Purcell factor of ED, MD and EQ emitters with different moment orientations as a function of radiation wavelength by placing these point radiation source within the nanoantenna, respectively. We find that the resonances wavelengths of the Purcell factor spectrum are matching with the resonance modes in the nanoantenna. Moreover, the maximum Purcell factor of these ED, MD and EQ emitters is 18, 150 and 118 respectively, occurring at the resonance wavelength of 475, 750, and 562 nm, respectively, all within the visible range. The polarization charge distribution features allow us to clarify the excitation and radiation of these resonance modes as the physical origin of large Purcell factor simultaneously occurring in this silicon cuboid nanoantenna. Our theoretical results might help to deeply explore and design the dielectric nanoantenna as an ideal candidate to enhance ED, MD and EQ emission simultaneously with very small loss in the visible range, which is superior than the more popular scheme of plasmonic nanoantenna.

Calculation of the Effective Energy Release Centerʼs Position of Inorganic Scintillation Detectors for Calibration at Small “Source–Detector” Distances

Inorganic scintillation detectors are widely used to measure of dose rate in the environment due to their high sensitivity to photon radiation. A distinctive feature when using such detectors is the need to take into account of the position of the effective energy release center. This peculiarity is actual when using measuring instruments with inorganic scintillation detectors as working standards during calibration at short “source–detector” distances in conditions of low-background shield or using a facility with protection from external gamma radiation background in the dose rate range from 0.03 to 0.3 μSv/h (μGy/h). The purpose of this work was to calculate the position of the effective energy release center of NaI(Tl) scintillation detectors and to take it into account when working at short “source–detector” distances.An original method of determining the position of the effective energy release center when irradiating the side and end surfaces of inorganic scintillation detector with parallel gamma radiation flux and point gamma radiation sources at small “source–detector” distances using Monte Carlo methods is proposed. The results of calculations of the position of the effective energy release center of NaI(Tl) based detectors of “popular” sizes for the cases of parallel gamma radiation flux and point sources of gamma radiation at small “source–detector” distances are presented. The functional dependences of the position of the effective energy release center of NaI(Tl) based detectors on the distance to the point gamma radiation sources and the energy of gamma radiation sources are presented.As a result of the study it was found that for scintillation NaI(Tl) detectors of medium size (for example, Ø25×40 mm or Ø40×40 mm) the point gamma radiation source located at a distance of 1 m or more, creates a radiation field which does not differ in characteristics from the radiation field created by a parallel flux of gamma radiation. It is shown that approaching the point gamma radiation source to the surface of scintillation detector leads to displacement of the position of the effective energy release center to the surface of the detector.

Equivalent Analysis of Thermo-Dynamic Blow-Off Impulse under X-ray Irradiation

X-ray thermodynamic effect is an important damage mode for spacecraft. Blow-off impulse as the main thermodynamic damage parameter has been widely studied by combining laboratory and numerical simulations. In this paper, most calculations and analyses have been carried out by using the self-developed software RAMA, including the equivalent calculation of blow-off impulse of monoenergetic and blackbody X-ray, and soft/hard blackbody X-ray irradiated at different incidence angles of LY-12 aluminium target. The results show that the characteristic mono-energetic X-ray can be exploited to simulate the blow-off impulse of the blackbody X-ray under certain conditions as a feasible equivalent method for the equal-flux and equal-impulse relations between mono-energetic and intense pulse blackbody of blow-off impulse. Moreover, the equivalent thermodynamic effect can be achieved between the point source radiation and parallel X-ray of X-ray. Furthermore, the cosine distribution of blow-off impulse is conducive to designing and calculating X-ray radiation load of hard aluminium corresponding to 1–5 keV blackbody spectrum. The mentioned results can be referenced for pulse X-ray simulation source and enhance the fidelity of the thermal-mechanical effect by electron beam. It is noteworthy that the study on the thermodynamic effects of intense pulsed X-ray is of high significance.

A Medium-Range-Energy X-Ray Source Based on an Image Converter Tube

A point source of X-ray radiation with an energy range of up to 40 keV has been developed on the basis of a specially designed image converter tube. The source is capable of operating in pulsed and continuous modes. The main purpose of this is to use the source for testing X-ray streak cameras. The device can also be used in X-ray microscopy and spectroscopy as a reference radiation source, in biomedical research, and in other fields.

A simple method of demonstrating Huygens’ principle in the classroom

Huygens’ principle in which every point on a propagating wave acts like a point source of radiation is a foundation principle of physics. Normally, Huygens’ principle is demonstrated by passing a wave, for example a water or light wave through an aperture comparable in size to the wavelength. In this paper, an experiment is described in which a 0.1 mm diameter copper wire is placed in front of a laser pointer to demonstrate Huygens’ principle in empty space. The diffraction pattern was photographed using a phone camera, and the bandwidth measured using a free image analysis program, ImageJ. The diffraction diameter of the wire was The experiment can easily be performed in a classroom.

Тензор Герца как основа релятивистской субэлектродинамики

The classical theory of radiation of charged particles is currently a complete theory. It has wide applications in the creation of various sources of radiation: synchrotron, undulator, etc. At the same time, the issues of radiation of the intrinsic magnetic moment of particles have not been fully investigated. In this paper, we describe a way to construct radiation fields of a point source within the framework of the Hertz tensor formalism. The derivation of the potentials and field strengths of a point radiation source is given.