Muon-spin-rotation study of muon polarization losses in plastic scintillators and quartz

Muon polarization losses in plastic scintillators of two types and in fused quartz have been studied by the μSR method. The muon and muonium spin precession spectra have been measured on the μSR setup placed at the output of the muon channel of the Gatchina synchrocyclotron. It has been shown that a significant fraction of stopped muons participate in the formation of the muonium. As a result, these muons lose their polarization completely. The magnitude of muon depolarization depends considerably on the type of plastic. It has been found that the muon spin precession frequency in fused quartz in an external magnetic field (F _{Q, μ} = 0.116 ± 0.002 MHz) is shifted with respect to that in plastic scintillators (F _{1, μ} = 0.101 ± 0.005 MHz and F _{2, μ} = 0.101 ± 0.002 MHz).     

An irradiation chamber for experimental studies on SSNTD response to alpha particles

An irradiation apparatus was designed in our laboratory to study the detection efficiency dependence of SSNTDs (CR-39, LR115, Makrofol) on alpha particles of different energy and incident angle. The system was designed to irradiate up to nine detectors in a short time, allowing to obtain reproducible conditions on many detectors and therefore to reduce random variations of the results. The system is composed of a pressure-controlled stainless-steel chamber containing a ²⁴¹Am source and a circular rotating table with 10 detector holders, one of which is devoted to an ion-implanted silicon detector for irradiation energy monitoring. The table rotation is controlled electronically via a photodiode-based system, so that the position of the detectors under the source is known with a maximum uncertainty of 0.5 mm. The detector holders allow to change the detector (both passive and active) to source inclination angle continuously and with an uncertainty better than 1. The source-to-detector distance is controlled electronically and can be varied from 5 to 30 cm with an uncertainty of about 0.1 mm. Some simulations, obtained using the transport code TRIM, to project the irradiation chamber and its main characteristics are reported and discussed.     

Light yield of plastic scintillators in relation to the energy of external electrons

It is shown that the specific light yield of plastic scintillators irradiated with external electrons is not a constant quantity, owing to the probability of quenching at the surface of the scintillator. The degree of proportionality of plastic scintillators can be influenced by the choice of primary additive and its concentration.     

An experimental study on cross-section ratio of coherent to incoherent scattering for 145 keV incident gamma photons

The coherent (Rayleigh) to incoherent (Compton) scattering cross-section ratio of elements, in the range 6 ≤ Z ≤ 82, are determined experimentally for 145 keV incident gamma photons. An HPGe (High purity germanium) semiconductor detector is employed, at scattering angle of 50°, 70° and 90°, to record the spectra originating from interactions of incident gamma photons with the target under investigation. The intensity ratio of Rayleigh to Compton scattered peaks observed in the recorded spectra, and corrected for photo-peak efficiency of gamma detector and absorption of photons in the target and air, along with the other required parameters provides the differential cross-section ratio. The measured values of cross-section ratio are found to agree with theoretical predictions (corresponding to 4.939, 6.704 and 8.264 Å⁻¹ photon momentum transfer) based upon non-relativistic form factor, relativistic form factor, modified form factor and S-matrix theory.     

An analytical and experimental study of the vibration response of a clamped ribbed plate

An analytical solution is presented in this paper for the vibration response of a ribbed plate clamped on all its boundary edges by employing a traveling wave solution. A clamped ribbed plate test rig is also assembled in this study for the experimental investigation of the ribbed plate response and to provide verification results to the analytical solution. The dynamic characteristics and mode shapes of the ribbed plate are measured and compared to those obtained from the analytical solution and from finite element analysis (FEA). General good agreements are found between the results. Discrepancies between the computational and experimental results at low and high frequencies are also discussed. Explanations are offered in the study to disclose the mechanism causing the discrepancies. The dependency of the dynamic response of the ribbed plate on the distance between the excitation force and the rib is also investigated experimentally. It confirms the findings disclosed in a previous analytical study [T.R. Lin, J. Pan, A closed form solution for the dynamic response of finite ribbed plates, Journal of the Acoustical Society of America 119 (2006) 917–925] that the vibration response of a clamped ribbed plate due to a point force excitation is controlled by the plate stiffness when the source is more than a quarter plate bending wavelength away from the rib and from the plate boundary. The response is largely affected by the rib stiffness when the source location is less than a quarter bending wavelength away from the rib.     

二元体系胶体晶体性质的实验研究

利用Kossel衍射技术和反射光谱对由总体积分数为0.02的二元聚苯乙烯胶体体系(94nm+141nm)形成的胶体晶体的性质进行了研究,实验结果显示胶体晶体的形成时间,平均粒子间距,晶体结构都与二元胶体体系中两种粒子的数密度比相关,当94nm聚苯乙烯粒子相对于141nm聚苯乙烯粒子的数密度比趋向1∶1时,胶体晶体的形成时间延长,当94nm聚苯乙烯粒子相对于141nm聚苯乙烯粒子的数密度比由1∶0向0∶1变化时,胶体晶体的平均粒子间距变大,另外实验中发现在两种粒子的数密度比为5∶1时,胶体晶体出现了超晶格结 关键词： 胶体晶体 聚苯乙烯 Kossel衍射 反射光谱     

A brief quantitative approach to determine the wavelength of photons as ultrarelativistic quantum particles

Given that a photon has (although small enough) a non-zero rest-mass, we derive an approximate mathematical expression for the wavelength of a single photon as ultrarelativistic quantum particle. In this context, the photon energy is also considered.     

Time evolving theory of the mechanics of single particles and single photons

We introduce space-time ensemble methods to formulate definitions of single particles and single photons as local abstractions of constant processes. We find the general form of the corresponding Stueckelberg Lagrangian for Riemannian and Newtonian spacetimes and supply a physical interpretation for the worldline parameter. We develop the corresponding mechanical theories over the extended configuration space and the extended phase space. We suppose that the background can be represented by an external field and we study several general examples. Certain phenomenological forms do not describe particles, others do not seem to describe theories in which the representation of the background is process independent (Riemannian case). At the canonical level the elimination of second-class constraints associated with null processes generates restrictions on the domain of definition of photon coordinates which correspond to the absence of zero energies. The requirement that the canonical process-anti-process classification exist leads to a factorization condition on the extended phase space which is satisfied for all the cases studied in which the configuration formalisms entail no difficulties, except one, which is the minimally coupled external vector field case over Riemannian space-times. We discuss the observation theoretical significance of our results.     

Specific features of interference of photons and other quantum particles

Specific features of the behavior of quantum particles in different experimental situations are considered. The variants of two-beam interference of single photon and other quantum particles, as well as their ability to form “standing” and “progressive” waves with the interference minima, i.e., “dead” zones in the propagation path, are studied. We also consider some type of quantum particle teleportation in an unconventional understanding of this word, where elementary particles overcome regions of the space where they cannot be, or rather the borders where the probability of finding them is zero. At these boundaries there is no pulse impact of particles on anything, it is as if they are unobservable. When observing three-beam interference, it turns out that all three modes should be present simultaneously in the light field prior to photodetection. If each mode involves a photon, it contradicts the energy conservation law, it is indicative of the fact that the observed quantity (number of photons in the field) has no any particular value prior to the measurement (a priori) unless the quantum system is in the eigen state of a measured value (Fock state).     

Newtonian forms for the motion of particles and photons in dilaton spacetime

Using Newtonian forms for equations of motion, we consider the motion of particles and photons in the dilaton spacetime. Some classical gravitational effects, such as the bending of light rays, the perihelion advance of a planet, the delay of radar echo, and the gravitational redshifts, have been investigated. The results show that the gravitational effects arising from the dilaton can be observed provided that the dilaton is large enough.     

Luminescence properties and radiation response of sodium borate glasses scintillators

We examined basic luminescence properties and radiation response of sodium borate glass scintillators activated with Pb²⁺, Cu⁺, Ti⁴⁺, V⁵⁺, W⁶⁺ and Yb³⁺ ions, respectively. These glasses had more than 80% transparency for emission wavelength range, and strong absorption bands due to the charge transition of the ions were observed. In the photoluminescence spectra, all glasses demonstrated intense emission peak in visible region, which are corresponding to the ions with s² (Pb²⁺), d¹⁰ (Cu⁺) and d⁰ (Ti⁴⁺, V⁵⁺, W⁶⁺) configuration. Additionally charge transfer emission was observed in Yb³⁺-doped glass. When ²⁴¹Am 5.5 MeV alpha-ray excited the glasses, they showed weak emission intensity because of low energy transfer efficiency from host lattice to emission center. By ²⁴¹Am irradiated pulse height spectra, Cu⁺-doped glass demonstrated the highest scintillation output in the glasses.     

An experimental study on the effects of relative rotation direction on the wake interferences among tandem wind turbines

An experimental study was conducted to investigate the effects of relative rotation direction on the wake interferences among two tandemwind turbines models.While the oncoming flow conditions were kept in constant during the experiments,turbine power outputs,wind loads acting on the turbines,and wake characteristics behind the turbines were compared quantitatively with turbine models in either co-rotating or counter-rotating configuration.The measurement results reveal that the turbines in counter-rotating would harvest more wind energy from the same oncoming wind,compared with the co-rotating case.While the recovery of the streamwise velocity deficits in the wake flows was found to be almost identical with the turbines operated in either co-rotating or counter-rotating,the significant azimuthal velocity generated in the wake flow behind the upstream turbine is believed to be the reason why the counter-rotating turbines would have a better power production performance.Since the azimuthal flow velocity in the wake flow was found to decrease monotonically with the increasing downstream distance,the benefits of the counter-rotating configuration were found to decrease gradually as the spacing between the tandem turbines increases.While the counter-rotating downstream turbine was found to produce up to 20%more power compared with that of co-rotating configuration with the turbine spacing being about 0.7D,the advantage was found to become almost negligible when the turbine spacing becomes greater than 6.5D.It suggests that the counter-rotating configuration design would be more beneficial to turbines in onshore wind farms due to the smaller turbine spacing(i.e.,~3 rotor diameters for onshore wind farms vs.~7 rotor diameters for offshore wind farms in the prevailing wind direction),especially for those turbines sited over complex terrains with the turbine spacing only about 1–2 rotor diameters.     

传输线变压器匹配和响应特性的实验研究

针对传统变压器的局限,提出采用柔韧性好的同轴电缆和高导磁率的铁基非晶磁性材料绕制的1∶4阻抗变换的传输线变压器（TLTs）作为输出变换装置,并进行相关的实验研究。根据传输线理论及波的折反射分析了实际工程中的最佳匹配条件以及实际情况中阻抗失配引起的波形畸变;给出了磁芯材料对脉冲的响应分析。实验结果表明:TLTs对输出脉冲的响应良好,改善了波形前沿,减小了能量损耗,且与理论值具有较好的一致性。     

传输线变压器匹配和响应特性的实验研究

针对传统变压器的局限,提出采用柔韧性好的同轴电缆和高导磁率的铁基非晶磁性材料绕制的1∶4阻抗变换的传输线变压器（TLTs）作为输出变换装置,并进行相关的实验研究。根据传输线理论及波的折反射分析了实际工程中的最佳匹配条件以及实际情况中阻抗失配引起的波形畸变;给出了磁芯材料对脉冲的响应分析。实验结果表明：TLTs对输出脉冲的响应良好,改善了波形前沿,减小了能量损耗,且与理论值具有较好的一致性。     

带电胶体粒子结晶过程的实验研究

利用带电单分散聚苯乙烯胶体粒子，通过自组装机理，制备了体积百分比为4.8%的具有多晶结构的胶体晶体，并用Kossel衍射技术和紫外可见分光光度计分别对晶体的生长过程进行了监测.通过对Kossel的图像分析检测不同阶段相应的晶格结构，发现胶体结晶过程晶体结构演变顺序为由液态—随机层结构—堆无序结构—面心立方孪晶结构到面心立方结构.定量地确定了结晶过程中晶体不同晶面的晶面间距和晶体的晶格常数，通过紫外可见分光光度计测量的晶体透射谱图，计算得到111晶面的晶面间距和晶体的晶格常数，与用Kossel衍射技术得到的结果相一致，还发现随样品放置时间的延长，衰减峰变窄和加深，并向短波方向移动，对应着晶体的晶格常数减小的现象. 关键词： 胶体晶体 自组织 Kossel环 聚苯乙烯粒子     

Coherence of radiation as studied by multiple coincidences of photons and particles

Coincidences of photons and particles are measured by counting the number of events occurring simultaneously in two or more detectors. Coherent and incoherent radiation may have different behavior when the number of coincidence counts is studied with different arrangements of the coincidence detectors: the coincidence rate for the coherent radiation field, such as that obtained from a single-mode laser, is independent on the transverse separation between the detectors as long as the intensity of the radiation stays constant. On the other hand, with incoherent thermal radiation, using suitable monochromatization, the coincidence rate can show a significant bunching effect at detector separations smaller than the transverse coherence length. As a third alternative, photon antibunching may be observed if the radiation field is prepared in a number state, such as that available from resonance fluorescence of atoms, ions or molecules. If the time resolution of the detectors is not sufficient to resolve separate counts, corresponding effects can be observed in experiments, where the analog outputs of the detectors are multiplied to produce an intensity correlation signal. Intensity correlation and coincidence studies of photons and particles are reviewed in this report starting from the early experiments in the 1950’s and including recent work on X-ray coincidences and three-pion correlations. New results are presented for three- and four-photon coincidences at the X-ray wavelengths.