Brightness Of Radiation Research Articles

ВЛАДИМИР АЛЕКСАНДРОВИЧ АРТЕМЬЕВ – БОЛЕЕ 60 МОРСКИХ ЭКСПЕДИЦИЙ ОТ АРКТИКИ ДО АНТАРКТИКИ

The article is dedicated to the 70th birthday of Vladimir Aleksandrovich Artemiev, senior researcher at the Ocean Optics Laboratory of the IO RAS. This is a unique electronics specialist who directly performs scientific research and provides this opportunity to others. V.A. Artemyev has been developing and improving optical equipment for marine expeditionary research for over 40 years; Among the devices he developed are an underwater irradiance meter (Alfamer device), three types of submersible transparent meters (PUM, PUM-A, PUM-200). Member of more than 60 sea expeditions from the Arctic to the Antarctic and about two dozen coastal marine. Conducted measurements of the underwater brightness of solar radiation at depths of up to 300 m in the Philippine Sea, diving on the Pysis underwater manned vehicle (PA), and in the Black Sea on the Argus PA. Vladimir Aleksandrovich is an irreplaceable expeditionary employee both in terms of his business and human qualities: contact, benevolent, always ready to help, creating a friendly atmosphere in the team. Coauthor of over 80 scientific publications and one invention patent. Has state awards.

A calculation model of infrared detection system with improved detection capability

AbstractIn order to constantly and accurately recognize and track flying targets, using the infrared photoelectric detection system, while scientifically analyze the detection capability of the system, in complex background environments. This paper analyzes the measurement principle of the infrared photoelectric detection system, establishes a radiation energy calculation model of the background and the optical system and the target on the photoelectric detector surface. It further analyzes the influence of the photoelectric detector wavelength, the slit diaphragm and of the target effective radiation area, on the radiation energy. It obtains the contrast ratio calculation model between the target and the background, on the photoelectric detector surface, while it also derives the detection distance model of the system, combining the modulation transfer function of the system, to set up an improved detection distance calculation model, in complex background environments. Simulation and experimental analysis show that as background radiation brightness increases, in certain background environments, the detection distance of the system gradually reduces, while changing the slit diaphragm and photoelectric detector wavelength can improve the detection performance of the system. In complex background environments, changing the contrast ratio of photoelectric detector surface should be considered, to improve the detection capability of the system.

Measurement of laser-induced dynamic structures on the surface of materials in a real time scale

The processes induced by laser radiation in the region of its interaction with matter are characterized by a high development rate and exclude direct contact of measuring detectors in the interaction region. The opportunity of structural adjustment of the irradiated surface of the material requires recording the temporal characteristics of these dynamic processes, which essentially determine the structural surface phase transitions in a heterogeneous medium. Therefore, for their diagnostics the highly sensitive, non-contact and inertialess registration methods are required. We used promising in this aspect optical recording methods based on the two channel scheme, i.e. the pump-probe techniques: the power pump laser and additional/probe laser radiation (brightness amplifies) to measure the development of nonlinear dynamic processes on the solid surface under laser radiation. The approach in frame of work of the such unified intelligent laser technological system results in control in time of processes of both laser thermal hardening with corresponding characteristics and generation of the spatial structures of different types on the surface of metallic units. We demonstrated some results for the laser technological processing with powerful laser radiation of a metal surface.

Progress Towards Laser Wakefield Acceleration and Applications at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA)

Laser wakefield accelerators (LWFAs) are promising sources of high brightness particle and radiation beams with many possible applications, ranging from scientific research to medicine, industry and border security. The Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) is a university-based facility employing the use of two high-power, ultrashort pulse lasers to advance research, development and application of laser-plasma accelerators. Here we report on recent advancements in LWFA research at SCAPA and upcoming research programmes to demonstrate proof-of-concept applications of the LWFA.

Bright x-ray radiation from plasma bubbles in an evolving laser wakefield accelerator

We show that the properties of the electron beam and bright x-rays produced by a laser wakefield accelerator can be predicted if the distance over which the laser self-focuses and compresses prior to self-injection is taken into account. A model based on oscillations of the beam inside a plasma bubble shows that performance is optimised when the plasma length is matched to the laser depletion length. With a 200~TW laser pulse this results in an x-ray beam with median photon energy of \unit[20]{keV}, $> 6\times 10^{8}$ photons above \unit[1]{keV} per shot and a peak brightness of $\unit[3 \times 10^{22}]{photons~s^{-1}mrad^{-2}mm^{-2} (0.1\% BW)^{-1}}$.

Early Optical Observations of GRB 150910A: Bright Jet Optical Afterglow and X-Ray Dipole Radiation from a Magnetar Central Engine

Abstract Gamma-ray burst (GRB) 150910A was detected by Swift/Burst Alert Telescope (BAT), and then rapidly observed by Swift/XRT, Swift/Ultraviolet-Optical Telescope, and ground-based telescopes. We report Lick Observatory spectroscopic and photometric observations of GRB 150910A, and we investigate the physical origins of both the optical and X-ray afterglows, incorporating data obtained with BAT and XRT. The light curves show that the jet-emission episode lasts ∼360 s with a sharp pulse from BAT to XRT (Episode I). In Episode II, the optical emission has a smooth onset bump followed by a normal decay (α R,2 ≈ −1.36), as predicted in the standard external shock model, while the X-ray emission exhibits a plateau (α X,1 ≈ −0.36) followed by a steep decay (α X,2 ≈ −2.12). The light curves show obvious chromatic behavior with an excess in the X-ray flux. Our results suggest that GRB 150910A is an unusual GRB driven by a newly born magnetar with its extremely energetic magnetic dipole (MD) wind in Episode II, which overwhelmingly dominates the observed early X-ray plateau. The radiative efficiency of the jet prompt emission is η γ ≈ 11%. The MD wind emission was detected in both the BAT and XRT bands, making it the brightest among the current sample of MD winds seen by XRT. We infer the initial spin period (P 0) and the surface polar cap magnetic field strength (B p ) of the magnetar as 1.02 × 1015 G ≤ B p ≤ 1.80 × 1015 G and 1 ms ≤ P 0 v ≤ 1.77 ms, and the radiative efficiency of the wind is η w ≥ 32%.

Attosecond Coherence Time Characterization in Hard X-Ray Free-Electron Laser

One of the key challenges in scientific researches based on free-electron lasers (FELs) is the characterization of the coherence time of the ultra-fast hard x-ray pulse, which fundamentally influences the interaction process between x-rays and materials. Conventional optical methods, based on autocorrelation, are very difficult to realize due to the lack of mirrors. Here, we experimentally demonstrate a novel method which yields a coherence time of 174.7 attoseconds for the 6.92 keV FEL pulses at the Linac Coherent Light Source. In our experiment, a phase shifter is adopted to control the cross-correlation between x-ray and microbunched electrons. This approach provides critical diagnostics for the temporal coherence of x-ray FELs and is universal for general machine parameters; applicable for wide range of photon energy, radiation brightness, repetition rate and FEL pulse duration.

Coherence time characterization method for hard X-ray free-electron lasers.

Coherence time is one of the fundamental characteristics of light sources. Methods based on autocorrelation have been widely applied from optical domain to soft X-rays to characterize the radiation coherence time. However, for the hard X-ray regime, due to the lack of proper mirrors, it is extremely difficult to implement such autocorrelation scheme. In this paper, a novel approach for characterizing the coherence time of a hard X-ray free-electron laser (FEL) is proposed and validated numerically. A phase shifter is adopted to control the correlation between X-ray and microbunched electrons. The coherence time of the FEL pulse can be extracted from the cross-correlation. Semi-analytical analysis and three-dimensional time-dependent numerical simulations are presented to elaborate the details. A coherence time of 218.2 attoseconds for 6.92 keV X-ray FEL pulses is obtained in our simulation based on the configuration of Linac Coherent Light Source. This approach provides critical temporal coherence diagnostics for X-ray FELs, and is decoupled from machine parameters, applicable for any photon energy, radiation brightness, repetition rate and FEL pulse duration.

Análise da exposição ao ofuscamento e à insolação em ambiente de uso prolongado

Ocupantes expostos à radiação solar indesejada e a brilhos e contrastes excessivos, quando em ambiente de uso prolongado, vivenciam desconforto térmico ou visual e consequentemente reagem alterando as características de sua ocupação ou do sistema de iluminação natural mais comum: a janela. Neste contexto, essa pesquisa se objetivou em identificar e relacionar os níveis de probabilidade de ofuscamento e de radiação solar incidente para um ocupante em uma sala de permanência prolongada. A partir da modelagem e simulação computacional da irradiação solar, os valores horários dos indicadores de ofuscamento e insolação foram transformados em frequências e perfis anuais. Dentre as frequências anuais de ofuscamento, se atingiram diferenças de até 74%, advindas da mudança de 90º na direção de visão. As frequências de radiação solar direta maior que 50 W/m² apontaram vulnerabilidade, em cerca de 1/5 do tempo de uso, para ocupantes a 1,5 m da abertura, nas orientações Norte, Leste e Oeste. Os perfis anuais de probabilidade de ofuscamento e de radiação solar incidente permitiram identificar as horas do dia e os meses do ano em que há necessidade de controle solar. Correlações lineares realizadas entre valores horários de DGP (Daylight Glare Probability) e de radiação solar resultaram em grau (R²) abaixo do significativo, porém permitiram demonstrar a influência de cada componente no desconforto visual apurado. As 60 combinações investigadas de posições (03), direções de visão (05) e orientações solares (04) foram discriminadas com relação à exposição excessiva e assim agregaram recomendações de projeto que previnem os ocupantes do ofuscamento e da insolação.

Fast Radio Bursts from Interacting Binary Neutron Star Systems

Abstract Recent observations of repeating fast radio bursts (FRBs) suggest that some FRBs reside in an environment consistent with that of binary neutron star (BNS) mergers. The bursting rate for repeaters could be very high and the emission site is likely from a magnetosphere. We discuss a hypothesis of producing abundant repeating FRBs in BNS systems. Decades to centuries before a BNS system coalesces, the magnetospheres of the two neutron stars start to interact relentlessly. Abrupt magnetic reconnection accelerates particles, which emit coherent radio waves in bunches via curvature radiation. FRBs are detected as these bright radiation beams point toward Earth. This model predicts quasi-periodicity of the bursts at the rotation periods of the two merging neutron stars (tens of milliseconds and seconds, respectively) as well as the period of orbital motion (of the order of 100 s). The bursting activities are expected to elevate with time as the two neutron stars get closer. The repeating FRB sources should be gravitational-wave (GW) sources for space-borne detectors such as Laser Interferometer Space Antenna (LISA), and eventually could be detected by ground-based detectors when the two neutron stars coalesce.

Bright magnetic dipole radiation from two-dimensional lead-halide perovskites.

Light-matter interactions in semiconductors are uniformly treated within the electric dipole approximation; multipolar interactions are considered "forbidden." We experimentally demonstrate that this approximation inadequately describes light emission in two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs), solution processable semiconductors with promising optoelectronic properties. By exploiting the highly oriented crystal structure, we use energy-momentum spectroscopies to demonstrate that an exciton-like sideband in 2D HOIPs exhibits a multipolar radiation pattern with highly directed emission. Electromagnetic and quantum-mechanical analyses indicate that this emission originates from an out-of-plane magnetic dipole transition arising from the 2D character of electronic states. Symmetry arguments and temperature-dependent measurements suggest a dynamic symmetry-breaking mechanism that is active over a broad temperature range. These results challenge the paradigm of electric dipole-dominated light-matter interactions in optoelectronic materials, provide new perspectives on the origins of unexpected sideband emission in HOIPs, and tease the possibility of metamaterial-like scattering phenomena at the quantum-mechanical level.

Electron Beam Brightness and Undulator Radiation Brilliance for a Laser Plasma Acceleration Based Free Electron Laser

We report here on spontaneous undulator radiation and free electron laser calculations after a 10-m long transport line (COXINEL) using a Laser Plasma acceleration (LPA) source. The line enables the manipulation of the properties of the produced electron beams (energy spread, divergence, dispersion) in view of light source applications. The electron beam brightness and undulator radiation brilliance are addressed by an analytical approach enabling us to point out the influence of chromatic effects in the COXINEL case.

A calibration data curve fitting method based on matrix orthogonal triangulation

This paper proposes a calibration data curve fitting method based on matrix orthogonal triangulation, which is applied in the field of ground calibration technology to solve the problem of low curve fitting precision and poor stability of the existing calibration data processing method. Firstly, the sampling data outputted by the infrared measuring system at different black body temperatures is decoded to obtain image data of a plurality of sampling points; the image gray mean value of each sampling point is calculated according to the image data of each sampling point, and the black body of each sampling point is obtained. The temperature value is converted into the black body radiation brightness value to obtain a plurality of original sampling point data; according to the linear original least squares principle, the matrix orthogonal triangulationmethod is used to solve the fit curve of the black body temperature-image gray value and black body radiance - the image gray value. The above method can fit straight lines and multiple curves, and has high fitting precision and good stability.

Simulation of solar radiation brightness fields in the presence of optically anisotropic crystal clouds: algorithm and test results

Simulation of solar radiation brightness fields in the presence of optically anisotropic crystal clouds: algorithm and test results

A Precipitation Detection Method for MWTS-II Radiance Assimilation in Typhoon Simulation

FY-3C Microwave Temperature Sounder Ⅱ (MWTS-Ⅱ) lacks observations at 23.8 GHz, 31 GHz and 89 GHz, making it difficult to remove the data contaminated by precipitation in assimilation. In this paper, a fast forward operator based on the Community Radiative Transfer Model (CRTM) was used to analyze the relationship between the observation minus background simulation (O-B) and the cloud fractions in different MWTS-Ⅱ channels. In addition, based on the community Gridpoint Statistical Interpolation (GSI) system, the radiation brightness temperature of the MWTS-Ⅱ was assimilated in the regional Numerical Weather Prediction (NWP) model. In the process of assimilation, Visible and Infrared Radiometer (VIRR) cloud detection products were matched to MWTS-Ⅱ pixels for precipitation detection. For typhoon No. 18 in 2014, impact tests of MWTS-Ⅱ data assimilation was carried out. The results show that, though the bias observation minus analysis (O-A) of assimilated data can be reduced by quality control only with | O-B | < 3K; however, the O-A becomes much smaller while the precipitation detection is performed with Fvirr < 0.9 (VIRR cloud fraction threshold of 0.9). Besides, the change of the environmental field around the typhoon is more conducive to make the simulated track closer to the observation. The 72-hour typhoon track simulation error also shows that, after the precipitation detection, the error of simulated typhoon track is significantly reduced, which reflects the validity of a precipitation detection method based on a double criterion of | O-B | < 3K and Fvirr < 0.9.

Effects of atmospheric moisture on the radiation intensity of objects in millimeter-wave band

The complex weather system in Taiwan often brings precipitation that decreases the accuracy of electromagnetic-wave guided weapons. In order to solve this problem, this paper aims at assisting the weapons to distinguish the difference between targets and background environment at a relatively accurate level. Given the characteristics of thermal radiation (brightness temperature), which is a type of electromagnetic-wave, are able to distinguish the differences between target areas and background atmosphere, the thermal radiation has been detected by using a dual-polarization radiometer in the millimeter-wave band (36.5 GHz) during the period of 98 days from 3rd May to 8th August in 2014.Two remarkable results are found to assist us to improve the accuracy of the weapons. First, the difference of brightness temperatures between the background atmosphere and the targets including tanks, grass and a forest is 100 K. Second, a difference of 15 K caused by diurnal changing is also identified. It is not surprising for us to learn that the brightness temperatures of the targets are gradually approaching to be comparable with the background when the rainfall is increasing. Identifying the targets by the weapons becomes much more difficult given the difference of the brightness temperatures between the targets and the background becomes minor. We also identify that the quantities of rain rate constrain the function of the radiometer. When the rain rate is lower than 20 mm per hour, the radiometer is capable to accurately detect the difference between the targets and the background. However, the higher the rain rate, the lower the accuracy of the radiometer. The radiometer is totally disable to detect any difference when the rain rate is above 58.2 mm per hour.

Investigation of the diffusion of alloying elements in multicomponent alloy using the photometric analysis of the radiation brightness spectrum

In this paper we consider the results of studying the diffusion of molubdenum and boron in the alloy G 35 (USA), in the chemical composition of which there were 12 elements, with the help of the method of photometric analysis of structural images (PHASI), developed in IMET RAS. PHASI method is based on comparison according to the differential scheme of the spectra of the brightness of the reflection of visible light from the fragments of the surface of the object under study and their images before, during and after heating. The study was performed in situ in a high temperature metallographic microscope. The digital camera allowed in a periodic mode to register the image of the investigated fragment of the sample surface. Analysis of the data obtained by the PHASI method made it possible to establish the time and radial dependencies of the partial derivatives of the concentrations of the first and second order alloying elements that appear in the diffusion equation. A complete analysis of the obtained experimental data made it possible to obtain temperature dependencies of the diffusion coefficients of chromium and boron.

Design and beam dynamic simulation of the thermionic RF electron gun with external resonant cavity for transverse emittance reduction

Abstract The accelerator components and radiation production systems at the PBP-CMU Electron Linac Laboratory of the Plasma and Beam Physics Research Facility are currently being developed and upgraded to make it possible for generation of the mid-infrared free-electron laser (MIR FEL) and the coherent intense terahertz (THz) radiation via transition radiation and superradiant undulator radiation. To generate a high brightness radiation, a high quality electron beam is crucially required. One of the important keys for this issue is the good performance and reliable electron source . Development of a new thermionic radio-frequency (RF) electron gun is foreseen at our facility. The design of the new RF gun was conducted with the aim to reduce transverse emittance while keeping the longitudinal phase space distribution that is suitable for the bunch compression with the alpha magnet. The present design of the PBP-CMU RF electron gun, which has 1-1/2 cell TM 010 reentrant cylindrical standing-wave resonant cavities and a side-coupling cavity, was used as the starting model for this work. The shape and dimensions of the new RF gun were optimized and the electromagnetic field distribution was simulated by using the program CST Microwave Studio 2016. Electron beam dynamic simulations were done with program ASTRA. The initial particle distribution from thermionic emission process was created by using the self-developed MATLAB script that provides the thermal emittance values corresponding well to the theoretical values. The results of this work suggest that by adding an external resonant cavity with a rounded pill-box shape to the present RF gun model can reduce the transverse emittance. This additional cavity has an optimal length of 25 mm and is connected to the present RF gun at the position 13 mm downstream the second cavity exit. The RF wave is coupled from the second cavity to the external cavity via the second side-coupling cavity. The entire structure finally has a resonant frequency of 2856.03 MHz, an unloaded quality factor of 15623 and a shunt impedance of 1.18 M Ω . The maximum electric field values in the first, the second and the external cavity are 32.8, 65.0 and 29.8 MV/m, respectively. The results from beam dynamic simulations show that this new design RF gun should be able to produce electron bunches with a charge of 170 pC per bunch, a maximum kinetic energy of 2.72 MeV and an energy spread of 540 keV. The simulated horizontal and vertical normalized emittances of 90% beam were respectively reduced by 11.6% and 4.5% compared to the values obtained from the original PBP-CMU RF gun. Furthermore, it was found that the transverse emittance is conserved at the distance longer than 60 cm downstream the external cavity exit.

All-optical generation of petawatt gamma radiation via inverse Compton scattering from laser interaction with tube target

A scheme for generating gamma photons from laser interaction with a hollow-tube target filled with near-critical-density plasma is investigated using quantum electrodynamics particle-in-cell simulation. The solid-density tube wall stabilizes the laser propagation in the tube, guides the laser-accelerated relativistic electrons, and its endplate reflects the laser light. As the electrons collide head-on with the reflected laser, a large number of MeV gamma photons are generated through inverse Compton scattering. It is found that bright gamma radiation with power up to 1.4 PW and 37% laser-to-gamma ray energy conversion efficiency can be obtained with 5 × 1022 W cm–2 laser pulse.

Undulator radiation brightness and coherence near the diffraction limit

The brightness and transverse coherence of undulator radiation in synchrotron light sources is investigated using the Wigner formulation in a full 4D treatment. New results are presented on the impact of energy spread on the brightness and coherence as a function of the emittance. In contrast to other work on this topic, it is found that as emittance decreases, the effect of energy spread increases, but as the diffraction limit is approached, the behavior of brightness and coherence diverge. The accuracy of the commonly used Gaussian approximation for brightness and coherence is also explored in detail, resulting in a new conclusion that the commonly used projected source sizes and divergences are not the appropriate quantities to use in the Gaussian approximation to obtain the most accurate results. New expressions are derived for the rms source size and divergence as a function of the energy spread for use in the Gaussian approximation.