Experimental evaluation of multiple Compton backscattering of gamma rays in copper

The gamma ray photons continue to soften in energy as the number of scatterings increases in thick target, and results in the generation of singly and multiply scattered events. The number of these multiply scattered events increases with an increase in target thickness and saturates beyond a particular target thickness known as saturation depth. The present experiment is undertaken to study the saturation depth for 279 and 320 keV incident gamma ray photons multiply backscattered from copper targets of varying thickness. The backscattered photons are detected by a Nal(Tl) gamma detector whose pulse-height distribution is converted into a photon spectrum with the help of an inverse matrix approach. To extract the contribution of multiply backscattered photons only, the spectrum of singly scattered photon is reconstructed analytically. We observe that the numbers of multiply scattered events increases with an increase in target thickness and then saturate. The saturation depth is found to be decreasing with increase in incident gamma energy.     

Verification of terahertz-wave spectrophotometry by Compton backscattering of coherent synchrotron radiation

We developed a continuous-spectrum light beam from Compton backscattering by using coherent synchrotron radiation in an L-band linac at the Kyoto University Research Reactor Institute. The ratio of Compton backscattered photons to background photons when coherent synchrotron radiation was used was three times larger than when coherent transition radiation was used. The transmission spectrum of a polystyrene film in the terahertz-wave region was evaluated by measuring the spectrum of the Compton backscattered photons and it roughly agreed with that measured by a Martin–Puplett-type interferometer. The spectrophotometry using Compton backscattering shows promise as a new tool for investigations in terahertz-wave science.     

Statistical characteristics of nonstationary backscattering in randomly irregular media

Using the method of invariant immersion, we perform numerical simulations of the statistical characteristics of a plane nonstationary wave reflected from a one-dimensional, randomly irregular medium due to multiple scattering. The statistical effects in the mean reflected field are considered, and the behavior of its higher moments is analyzed. The possibility of obtaining the solution of the statistical inverse wave problem is discussed. Pacific Oceanological Institute of the Far-East Branch of the Russian Academy of Sciences, Vladivostok, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 12, pp. 1153–1164, December, 1999.     

On multiple Compton scattering in plasma clouds

Inverse Compton scattering of low energy photons in a nonrelativistic electron gas is considered. The angle dependence in the Thomson cross section is neglected and spatial and energy transport are separated in a multiple scattering development of the emerging spectrum. The energy transport is determined by a Green function G which may be obtained from the single scattering spectrum for small optical depth or from the Kompaneets equation in the optically thick medium (τ ? 1). The electron cloud is assumed to be spherical and homogeneous with constant temperature $\text{?}{}_{\mathrm{e}}\text{=}\text{kT}{}_{\mathrm{e}}\text{m}{}_{\mathrm{e}}\text{c}{}^2$. Photon escape probabilities P_N from the cloud after N scatterings are calculated from a random flight problem with absorbing walls and alternative methods are mentioned and compared in the limit of large optical depth.     

Uncertainty of the beam energy measurement in the e~+e~- collision using Compton backscattering

The beam energy is measured in the e+e-collision by using Compton backscattering. The uncertainty of this measurement process is studied by virtue of analytical formulas, and the special effects of variant energy spread and energy drift on the systematic uncertainty estimation are also studied with the Monte Carlo sampling technique. These quantitative conclusions are especially important for understanding the uncertainty of the beam energy measurement system.     

Monte-Carlo simulation on Compton double scattering of polarized X-rays

A Monte-Carlo simulation of energy spectra of Compton double scattered X-rays has been made as functions of the incident energy of elliptically polarized X-rays and the atomic number of samples having different shapes and volumes. This simulation is based on the previous one made by one of the authors (N.S.), in which completely circularly polarized γ-rays were only assumed, and is improved to meet the multiple scattering correction on experimental Compton profiles measured with linearly or elliptically polarized synchrotron radiations. The results are compared with two experiments in reasonable agreement.     

Deep inelastic Compton process and large QCD corrections

The reactions \(\bar vD \to \mu ^ + n\pi ^ - (p_s )\) and \(\bar vD \to \mu ^ + p\pi (n_s )\) have been studied at antineutrino energies varying from 5 to 200 GeV. The cross sections for these reactions were determined from 545 and 300 selected events for each channel respectively. The first reaction was used for the study of the decay properties of the Δ resonance that dominates this channel. The experimental results have been compared with the theoretical predictions of Rein and Sehgal [9] and of Fogli and Nardulli [10]. Using the first model we obtained for the axial form factor parameterM _a =1.01±0.05 GeV/c². With this value the model is in agreement with the experimentaldσ/dQ ² distributions forQ ²>0.25 GeV² and with the distributions of the invariant hadronic massW. The isospin structure of the one-pion production has been investigated and compared with the results of other experiments.     

Lorentz violation and black-hole thermodynamics: Compton scattering process

A Lorentz-noninvariant modification of quantum electrodynamics (QED) is considered, which has photons described by the nonbirefringent sector of modified Maxwell theory and electrons described by the standard Dirac theory. These photons and electrons are taken to propagate and interact in a Schwarzschild spacetime background. For appropriate Lorentz-violating parameters, the photons have an effective horizon lying outside the Schwarzschild horizon. A particular type of Compton scattering event, taking place between these two horizons (in the photonic ergoregion) and ultimately decreasing the mass of the black hole, is found to have a nonzero probability. These events perhaps allow for a violation of the generalized second law of thermodynamics in the Lorentz-noninvariant theory considered.     

Cooperative stimulated Brillouin and Rayleigh backscattering process in optical fiber

We observed an unusually narrow spectrum of Stokes field and Gaussian statistics of Stokes power for the stimulated Brillouin scattering (SBS) process in 300-m single-mode optical fiber with high Rayleigh losses. The measured characteristics of the Stokes radiation indicate that SBS lasing took place in the fiber. The effect is explained as the result of dynamic distributed feedback that is due to double Rayleigh scattering (RS) of the Stokes field. The results of numerical simulation of the cooperative SBS-RS process in fiber are in good agreement with experimental results.     

湍流大气中激光聚焦光束后向散射的数值模拟

 对基于聚焦光束后向散射到达角起伏的湍流测量进行了数值模拟。通过近轴标量波动方程和分形相屏算法,提出了聚焦光束二次传输的数值模型,分别就固定点信标光源和聚焦光束后向散射的到达角起伏方差的统计特征进行了分析,并取得了很好的相关性,得出了可以从聚焦光束的回波图像信号里提取大气湍流信息的结论。讨论了聚焦距离对固定点光源和回波光束的到达角起伏方差相似度的影响。     

Analytic simulation of the backscattering of hundreds eV positrons from elemental solids

Backscattering (Bcs) coefficients for low-energy positrons (∼100 eV) from elemental solids have been simulated using an analytic approach. The model is based on the use of the transport cross-sections (TCSs) and the stopping power calculated from partial wave methods and the best-fit stopping power data of Ashley, respectively. The new result is an extension of recent calculations in the medium energy range. Comparisons, when possible, with experimental and Monte-Carlo (MC) simulation data have been made.     

气泡幕后向散射光信号特性的蒙特卡罗方法研究

利用蒙特卡罗方法对水介质中的气泡幕的后向光散射回波信号进行了系统仿真。通过对计算结果与实验结果的比较,证明了蒙特卡罗方法的有效性。根据仿真结果,结合理论分析的方法,对气泡幕位置、厚度和接收器视场角等参数对回波信号的影响进行了分析,结果表明:回波信号出现时间与气泡幕位置存在一一对应的关系;在气泡幕的衰减系数ρσt不变的情况下,存在一个有效气泡幕厚度,当大于该厚度时,气泡幕的后向光散射回波信号基本不变;在系统各项参数不变的情况下,适当增加接收器的视场角,可有效地提高回波信号的信噪比。     

Cosmic Gamma-ray from inverse Compton process in unstable dark matter scenario

Motivated by the PAMELA anomaly in the fluxes of cosmic-ray e⁺$e^{+}$ and e⁻$e^{-}$, we study the cosmic γ  -ray induced by the inverse Compton (IC) scattering process in unstable dark matter scenario assuming that the anomaly is due to the e^±$e^{\pm }$ emission by the decay of dark matter. We calculate the fluxes of IC-induced γ-ray produced in our Galaxy and that from cosmological distance, and show that both of them are significant. If the γ-ray flux is precisely determined by Fermi Gamma-ray Space Telescope for various line-of-sight directions, it will provide an important test of the decaying dark matter scenario.     

Monte Carlo simulation of the coherent backscattering of electrons in a ballistic system

We study weak localization effects in the ballistic regime as induced by man-made scatterers. Specular reflection of the electrons off these scatterers causes backscattered trajectories to occur, which interfere with their time-reversed path resulting in weak localization corrections to the resistance. Using a semi-classical theory, we calculate the change in resistance due to these backscattered trajectories. We found that the inclusion of the exact shape of the scatterers is very important in order to explain the experimental results of Katine et al.[Superlattices and Microstructures 20 , 337 (1996)].     

A two-way paraxial system for simulation of wave backscattering by a random medium

This paper presents a probabilistic analysis of an iterative two-way paraxial scheme for the simulation of wave propagation in anisotropic random media. This scheme has the computational cost of the standard one-way paraxial wave equation but has the accuracy of the full wave equation in a regime beyond the classical paraxial regime. More precisely, it accurately predicts the statistics of the reflected wave field. The accuracy depends on two parameters: the order of the iterative scheme and the ratio of the random backscattering intensity over the random forward-scattering intensity.     

Statistical simulation of the process of acoustic radiation propagation through the moving turbulent atmosphere with allowance for refraction

The Monte–Carlo method is used to solve the problem of sound propagation through the lower plane-stratified 500-meter layer of the moving turbulent atmosphere. Quantitative estimates of the intensity of transmitted and multiply scattered radiation are obtained with allowance for the influence of the refraction effects.     

Statistical simulation of the structure of amorphous alloys

Summary The total and partial distribution functions of a metalloid/transition-metal amorphous alloy (Fe₈B₁₅) have been calculated by means of a ?nonstandard? hard-sphere dense-random-packing model. Based on these results, a comparison with the ?canonical? dense-random-packing model is discussed.

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Riassunto Si presenta un calcolo delle funzioni di distribuzione radiale parziali e totali di una lega metallo-metalloide amorfa (lega Fe-B) generate mediante simulazione numerica. La struttura viene realizzata tramite un modello ad impaccamento di sfere rigide basato su criteri di crescita probabilistici. I risultati sono confrontati con il modello ad impaccamento denso e casuale (dense random packing) ?canonico? di Bennet.

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Резюме Вьічисляются полньіе и парциональньіе функции распределения для аморфного сплава ?металлоид-переходной металл? (Fe₈B₁₅), используя ?нестандартную⎴ модель плотной случайной упаковки твердых сфер. Полученные результаты сравниваются с результатами ?канонической? модели плотной случайной упаковки.

     

求扩展不确定度的模拟统计方法

不使用方和根公式,采用计算机模拟统计方法,求得扩展不确定度.