K_α单光子计数CCD标定北大核心CSCD

对三台单光子计数CCD的能量响应特性和探测效率进行实验标定。采用标准放射源对CCD进行照射,将CCD图像进行统计处理后,得到CCD的能量响应曲线。响应曲线近似为线性,不同的CCD响应曲线斜率明显不同。编写了MATLAB程序对多像素事件进行处理,获得CCD的探测效率曲线。在不同的能点处,CCD的探测效率明显不同,在5.1keV附近探测效率达到最大值。标定结果与XOP软件计算得到的吸收效率理论结果比较一致。该标定结果可用于超强激光打靶产生的Kα荧光光子产额和能谱的定量精确处理。     

3×3锗酸铋晶体阵列探测器对于0.5—21MeV光子能量响应的研究

建造了由九块国产锗酸铋晶体组成的采用光电倍增管读出的阵列式探测器. 应用γ放射源、中子放射源、静电加速器(p,γ)反应以及核反应堆(n,γ)反应得到0.5—21MeV γ射线. 在这个能量范围内进行的测试显示了线性的能量响应. 能量分辨率在低能量下满足预期的E^1/2关系, 而能量在4.43MeV以上实际测得的数值较预期为大. 实验中还考察了光子在晶体阵列中沉积能量的横向分布情况, 结果与蒙特卡罗模拟一致. 本工作表明, 采用放射源及低能(p,γ)反应作为锗酸铋电磁量能器定标和监测的手段是实际可行的.     

利用磁谱仪测量90Sr-90Y放射源的β衰变能谱

利用近代物理实验中的磁谱仪测量了90Sr～90Y放射源的β衰变能谱．得到的能谱和普遍的口衰变能谱相似;得到的口射线最大能量与平均能量比值和文献中给出的一些放射源的比值接近,这些都说明了该实验测量数据的可靠性．运用库里厄（Kurie）图,研究了此放射源的β衰变能谱,得到的跃迁性质和能级自旋宇称与此放射源已有的数据相吻合,说明在近代物理实验中能够利用磁谱仪测量原子核的β衰变能谱、研究原子核的跃迁性质和能级自旋宇称．     

通过响应矩阵计算横向振荡的振幅函数和相位

 响应矩阵反映了束流位置监测器（BPM）位置处观察到的束流在校正铁磁场空间中的运行规律。根据电子储存环理论模型,采用迭代方法从实测响应矩阵计算束流横向振荡的振幅函数和相位。计算结果的精度主要受响应矩阵测量误差、BPM测量误差和校正铁电源刻度误差影响。计算响应矩阵的误差代表了迭代所采用的工作点的正确度,实际的工作点对应于计算响应矩阵的最小均方差,以此可推导实际的工作点。     

KAl(MoO4)2晶体中掺杂Cr3+的能谱和g因子的理论计算*

采用强场方案和三角基，通过对角化三角畸变的立方晶场下的d3 完全能量矩阵，计算出了KAl(MoO4)2:Cr3+ 的能谱和波函数。使用对角化完全能量矩阵所获得的波函数，进一步计算了KAl(MoO4)2:Cr3+ 的基态g 因子。计算结果与光谱，EPR谱实验数据很好地符合。研究表明,利用对角化完全能量矩阵获得的波函数对 g 因子所作的计算为整个理论计算及波函数的归属提供了重要判据,充分体现了将能谱和g 因子作统一计算的重要性和必要性.     

一种聚焦型X射线探测器在轨性能标定方法

X射线探测器是X射线天文观测及脉冲星导航的核心器件,受发射振动、高能粒子辐射损伤及元器件老化等影响,X射线探测器空间观测性能会逐渐变化,X射线探测器在轨标定有利于观测天体X射线辐射信息的准确获取及精确建模.研究利用了脉冲星辐射能谱标定X射线探测器性能的方法,能较好地消除探测器本底及空间环境噪声的影响,通过处理脉冲星导航试验卫星(XPNAV-1卫星)的Crab脉冲星观测数据,评估了我国首款聚焦型X射线探测器的在轨性能.计算结果表明,XPNAV-1卫星上聚焦型X射线探测器的有效面积在0.6-1.9 keV能段内优于2 cm~2,其中在0.7 keV能量处取得最大值3.06 cm~2,探测效率约10%;有效面积随着探测能量增大而减小,在2—3.5 keV能段内有效面积约为1 cm~2,而大于5 keV能段的有效面积约为0.1 cm~2,且此能段估计精度明显受光子统计误差影响.同时研究了考虑能量响应矩阵的探测器有效面积标定新方法,利用地面性能测试中五个特征能谱处的能量分辨率重构其能量响应矩阵,重新标定了聚焦型X射线探测器有效面积,发现该能量响应矩阵对结果影响较小.最后建议观测某些超新星遗迹监测能量分辨率及能量线性等指标的变化.     

微扰计算中表象的选择

本文证明了：在能量为定值的简并空间中，微扰Ｈ’在表象（Ｈ０，Ａ，Ｂ）中的矩阵对角的充要条件为时易式［Ｈ’，Ａ］和［Ｈ’，Ｂ］在该简并空间中的矩阵 为零。此充要条件可作为微扰计算中选择表象的依 据     

散射环境下钨的质量吸收系数测量

CsI：T1晶体在辐射成像系统中的作用是非常重要的，利用CCD作为图像记录的X光探测系统的响应性能与其有密切的关系。为了得到响应关系的大致形式，在30MeV的射频加速器上，曾经用厚度为5，10，20mm的CsI：T1晶体作过研究，对于每一种厚度的CsI：T1晶体，响应还是线性的，但是彼此之间响应度的相对关系还是存在较大差异；由于^60Co放射源的特点，又专门设计了用^60Co放射源作为高能γ光子源来对系统的响应特性作定量研究，并且得到了在几乎没有散射影响下的响应关系，实验结果严格符合理论推导结论，     

放射源辐射场Monte Carlo模拟计算

选取Pu-238为放射源，采用简化的级联衰变链对其进行源项分析，得到放射源各衰变子体原子数及放射性活度的变化曲线，在此基础上，采用MCNP程序，对放射源进行了精确建模，对放射源辐射场及其有效屏蔽问题进行了模拟计算，得到放射源周围中子、能谱及辐射场分布，辐射场计算值与参考实验剂量吻合较好，屏蔽体的采用可有效降低放射源的辐射剂量，其中，剂量降低为裸源的0.1%左右，中子剂量降低为裸源的13%～17%。     

BC501A液体闪烁体对γ射线的光输出响应

研究了对BC501A液体闪烁体对γ射线的光输出响应特性。实验上利用γ放射源(60Co,137Cs)测量了不同光电倍增管高压下,尺寸为Φ5.08 cm×5.08 cm的BC501A液体闪烁体探测器的脉冲幅度谱。利用Geant4软件进行模拟,计算结果与实验数据很好地符合,得到了能量分辨函数及能量刻度曲线。利用Geant4研究了BC501A的脉冲幅度谱的康普顿边缘Ec、康普顿峰Emax及康普顿半高点E1/2与能量分辨率的关系。同时模拟结果显示,随γ射线能量(0.2～3 Me V)的增加,康普顿边缘位置Nc/Nmax从0.8至0.7线性减少。     

Wavefront response matrix for closed-loop adaptive optics system based on non-modulation pyramid wavefront sensor

Pyramid wavefront sensor (PWFS) is a kind of wavefront sensor with high spatial resolution and high energy utilization. In this paper an adaptive optics system with PWFS as wavefront sensor and liquid-crystal spatial light modulator (LC-SLM) as wavefront corrector is built in the laboratory. The wavefront response matrix is a key element in the close-loop operation. It can be obtained by measuring the real response to given aberrations, which is easily contaminated by noise and influenced by the inherent aberration in the optical system. A kind of analytic solution of response matrix is proposed, with which numerical simulation and experiment are also implemented to verify the performance of closed-loop correction of static aberration based on linear reconstruction theory. Results show that this AO system with the proposed matrix can work steadily in closed-loop operation.     

Wavepacket dynamics, quantum reversibility, and random matrix theory

We introduce and analyze the physics of “driving reversal” experiments. These are prototype wavepacket dynamics scenarios probing quantum irreversibility. Unlike the mostly hypothetical “time reversal” concept, a “driving reversal” scenario can be realized in a laboratory experiment, and is relevant to the theory of quantum dissipation. We study both the energy spreading and the survival probability in such experiments. We also introduce and study the “compensation time” (time of maximum return) in such a scenario. Extensive effort is devoted to figuring out the capability of either linear response theory or random matrix theory (RMT) to describe specific features of the time evolution. We explain that RMT modeling leads to a strong non-perturbative response effect that differs from the semiclassical behavior.     

基于蒙特卡罗方法的NaI探测器效率刻度及其测量轫致辐射实验

为了将NaI探测器更好地应用到轫致辐射谱测量工作中,对一套NaI探测器做了研究:利用~(137)Cs,~(60)Co等同位素γ源,结合蒙特卡罗方法,得到全能峰效率的模拟值与实验测量值符合得较好;利用蒙特卡罗N粒子编码模拟NaI对不同能量光子的响应,得到了该探测器对光子的能量响应,并将获得的能量响应用于轫致辐射的解谱工作,解谱结果与原始谱符合得很好;将该探测器应用到强流电子束打靶轫致辐射测量实验中,对轫致辐射在NaI探测器中的响应做了初步测量.     

Numerical study of transitional brittle-to-ductile debonding of a capsule embedded in a matrix

This work presents a numerical study that addresses the role of the interfacial fracture energy on the debonding process of a capsule embedded in an elastic matrix, which undergoes a uniaxial far-field stress. The motivation of this work is to analyze and to understand the effects of this energy in the framework of the so-called encapsulation-based self-healing cementitious materials, where glass capsules filled with a fluid healing agent are embedded in a cement-based matrix. A two-dimensional plane strain model based on a combination of the classical finite element method and cohesive surface techniques implemented in the commercial code Abaqus^® has been used. It has been found that there exist three types of debonding regimes, ranging from a perfect brittle response up to a ductile-limited response, and whose range of validity is governed by a straightforward dimensionless number able to predict the type of debonding as a function of flexural properties of the capsule and the interface strength.     

A direct measurement of the energy spectrum of cosmic ray muons in the Mont Blanc underground laboratory

Using a transition radiation detector we have neasured the energy of cosmicray muons in the Mont Blanc laboratory, where the NUSEX experiment is located. With this technique we have been able to cover linearly the energy range from 0.1 TeV to about 0.5 TeV, where the detector response begins to saturate. The measurements are consistent with a muon energy spectrum deduced from a E^−3.71 distribution folded with 5000 hg/cm² standard rock absorption.     

A nucleon-nucleon soft core central potential

We have calculated a central nucleon-nucleon potential with a soft core for the singleteven and the triplet-even state. The radial dependence of these potentials is given by a sum of one repulsive and two attractive Gaussians; therefore matrix elements with shell-model and cluster-model like functions may be calculated quite easily. The potentials are fitted to reproduce the phase shifts up to 300 MeV laboratory energy and the binding energy of the deuteron.     

Potential reduction interior point algorithm unfolding of neutron energy spectrum measured by recoil proton method

A reconstruction algorithm for unfolding neutron energy spectra has been developed, based for the first time on the potential reduction interior point algorithm. This algorithm can be easily applied to neutron energy spectrum reconstruction in the recoil proton method. We transform the neutron energy spectrum unfolding problem into a typical nonnegative linear complementarity problem. The recoil proton energy spectrum and response matrix at angles of 0^o and 30^o are generated by the Geant4 simulation toolkit. Several different neutron energy test spectra are also employed. It is found that this unfolding algorithm is stable and provides efficient, accurate results.     

X-ray tube spectra measurement and correction using a CdTe detector and an analytic response matrix for photon energies up to 160 keV

The aims of our work were: i) to measure selected normalized X-ray beam spectra with the commercially available cadmium telluride detector based spectrometry system; ii) to construct the approximate response matrix of the detector using a simple algebraic model approach; iii) to reconstruct the physical energy spectra from the measured instrumental spectra using the detector response matrix; iv) to compare the obtained spectra parameters with the published and reference data in order to verify the model and to optimize the measurement setup if necessary. In particular, the spectra of five “narrow-spectrum series” beams, namely N60 to N150, were measured with a spectrometry system consisting of the Amptek XR-100T X-ray semiconductor detector and the PX5 multichannel analyser. Two different measuring geometries were used. The response matrix R(E, E′) of the detector was constructed which quantifies the energy dependence of the relative detection efficiency of the detector, the probabilities of the escape effects, and the probability of the Compton effect. A single matrix operation was applied to recover the physical energy spectra from the measured instrumental ones. The parameters of the corrected spectra were compared with the published and reference data. Despite the fact that the effect of incomplete charge collection was not implemented in the detector model, a fully satisfying quantitative correspondence was observed between the measured corrected spectra and the available reference data.     

Global Analysis of Response in the Piezomagnetoelastic Energy Harvester System under Harmonic and Poisson White Noise Excitations

The piezomagnetoelastic energy harvester system subjected to harmonic and Poisson white noise excitations is studied by using the generalized cell mapping method. The transient and stationary probability density functions (PDFs) of response based on the global viewpoint are obtained by the matrix analysis method. Monte Carlo simulation results verify the accuracy of this method. It can be observed that evolutionary direction of transient and stationary PDFs is in accordance with the unstable manifold for this system, and a stochastic P-bifurcation occurs as the intensity of Poisson white noise increases. This study presents an efficient numerical tool to solve the stochastic response of a three-dimensional dynamical system and provides a new idea to analyze the energy harvester system.     

Global Analysis of Response in the Piezomagnetoelastic Energy Harvester System under Harmonic and Poisson White Noise Excitations

The piezomagnetoelastic energy harvester system subjected to harmonic and Poisson white noise excitations is studied by using the generalized cell mapping method. The transient and stationary probability density functions(PDFs) of response based on the global viewpoint are obtained by the matrix analysis method. Monte Carlo simulation results verify the accuracy of this method. It can be observed that evolutionary direction of transient and stationary PDFs is in accordance with the unstable manifold for this system, and a stochastic P-bifurcation occurs as the intensity of Poisson white noise increases. This study presents an efficient numerical tool to solve the stochastic response of a three-dimensional dynamical system and provides a new idea to analyze the energy harvester system.