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.     

The characteristics simulation of FMCW laser backscattering signals

Optical Review - A Monte Carlo simulation model of FMCW laser transmission in a smoke interference environment was established in this paper. The aerosol extinction coefficient and scattering...     

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.     

Transmutation of nuclear wastes using photonuclear reactions triggered by Compton backscattering photons at the Shanghai laser electrongamma source

Based on the facility of the Shanghai Laser Electron Gamma Source (SLEGS),the transmutation for nuclear wastes such as 137Cs and 129I is investigated.It is found that nuclear waste can be transmuted efficiently via photonuclear reaction triggered by gamma photons generated from Compton backscattering between CO2 laser photons and 3.5 GeV electrons.The nuclear activities of 137Cs and 129I are evaluated and compared with the results of transmutation triggered by bremsstrahlung gamma photons driven by ultra intense laser.Due to the better character of gamma photon spectrum as well as the high brightness of gamma photons,the transmutation rate of Compton backscattering method is much higher than that of the bremsstrahlung method.     

降雨融化层后向散射的蒙特卡罗仿真

云层上端冰雪粒子的融化形成了降雨融化层，随着粒子的下落融化过程开始，因此融化层的微观特性在垂直方向上是连续变化的.建立了降雨融化层的仿真模型，应用更为切合实际的三层球形粒子代替了融化层中的粒子.根据降雨过程中雨滴的尺寸分布推导了融化层中融化粒子的尺寸分布.根据Mie理论，计算了降雨率小于12.5 mm/h时，降雨融化层对5，10，35，94 GHz电磁波的雷达反射率和特征衰减因子的垂直廓线.计算结果表明，当电磁波频率高于20 GHz时，将无法观测到“雷达亮带”，这与实验结果相符.根据辐射传输理论，应用蒙特卡罗方法计算了垂直方向微观特性连续变化的降雨融化层对不同频率电磁波的反射率，比较了两种不同尺寸分布(Gamma分布和Marshall-Palmer分布)融化层反射率的差别，这为利用高频电磁波对降雨融化层进行遥感提供了理论和数值依据. 关键词： 降雨融化层 蒙特卡罗方法 后向散射 电磁波     

近距云雾回波蒙特卡罗模拟与实验测量

在激光引信中,云雾后向散射会产生引发虚警的回波信号。基于蒙特卡罗法对云雾回波信号进行了模拟仿真,并在云雾室内开展了测量实验,利用测量结果对理论模型进行了验证。研究结果表明：当发射脉冲宽度小于10 ns时,云雾散射回波展宽效应显著,且展宽效应主要是由多次散射产生的;激光回波的实验测量结果与理论计算结果吻合得较好,都近似为高斯波形,且其回波宽度的差别小于6%,回波功率差别小于30%。     

Transmutation of nuclear wastes using photonuclear reactions triggered by Compton backscattering photons at the Shanghai laser electron gamma source

Based on the facility of the Shanghai Laser Electron Gamma Source (SLEGS), the transmutation for nuclear wastes such as ¹³⁷Cs and ¹²⁹I is investigated. It is found that nuclear waste can be transmuted efficiently via photonuclear reaction triggered by gamma photons generated from Compton backscattering between CO₂ laser photons and 3.5 GeV electrons. The nuclear activities of ¹³⁷Cs and ¹²⁹I are evaluated and compared with the results of transmutation triggered by bremsstrahlung gamma photons driven by ultra intense laser. Due to the better character of gamma photon spectrum as well as the high brightness of gamma photons, the transmutation rate of Compton backscattering method is much higher than that of the bremsstrahlung method.     

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)].