Unified description of angular distributions of target particles in light and heavy ion induced interactions in nuclear emulsions at high energies

Some investigations show that in light ion （LI） induced reactions, such as He, O, Ne, and Ar in nuclear emulsions （Em） at high energies, the angular distributions of the target particles show a wide structure around the polar angle V ≈ 60°. With heavy ions （HI） such as Kr and Au such a wide structure has not been observed. The experimental results on Mg-Em and Si-Em interactions also do not show such a wide structure in the angular distribution of the target particles. Using a multisource ideal gas model we uniformly describe the angular distributions of the target particles produced in LI-Em and HI-Em interactions. The result is not only in agreement with the mean trend, but also with the fluctuations of the experimental data. We conclude that the wide structure observed in LI-Em interactions may be the result of statistical fluctuations.     

Restoration of rotational symmetry in deformed relativistic mean-field theory

We report on a very recently developed three-dimensional angular momentum projected relativistic mean-field theory with point-coupling interaction (3DAMP+RMF-PC). Using this approach the same effective nucleon-nucleon interaction is adopted to describe both the single-particle and collective motions in nuclei. Collective states with good quantum angular momentum are built projecting out the intrinsic deformed mean-field states. Results for ²⁴Mg are shown as an illustrative application.     

硬X射线光子筛波导效应研究

基于快速傅里叶变换光束传播法,研究了硬X射线光子筛中高高宽比金属结构的波导效应,确定了硬X射线光子筛的物理边界条件,采用角谱法计算了硬X射线光子筛的点扩展函数,并分析了吸收体厚度对聚焦性能的影响.研究结果表明波导效应一定程度上有利于抑制光子筛高级衍射的产生,提高聚焦性能.在同样的特征尺寸下,硬X射线光子筛的空间分辨率优于菲涅尔波带片,其缺点是衍射效率的下降.吸收体厚度的提高有利于提高光子筛的聚焦性能和衍射效率,但是相应的纳米加工工艺难度会增加. 关键词： 菲涅尔波带片 硬X射线光子筛 光束传播法 角谱法     

双波长敏感的非水溶性光致聚合物存储特性研究

研究了一种新型的对红光和蓝光敏感的非水溶性光致聚合物材料的全息存储特性。该聚合材料由复合单体、复合光敏剂、复合引发剂、链转移剂及成膜物等成分组成,它具有防潮、后处理简单、分辨率高及耐高温等特点,对红、蓝光2种衍射效率均不低于75%,灵敏度为(45～65)mJ/cm2。对该材料先后进行了双波长复用存储实验和角度复用存储实验,当用红光或蓝光再现时再现图像清晰可见,相邻2副图像之间无明显干扰,说明该材料具有良好的存储性能,适合作高密度数字全息存储的记录材料,可用作光通信中的波分复用器及其他光学元件。     

光纤陀螺在转台测试中的应用

光纤陀螺是一种速率陀螺,其适合用来对转台作低速测试.根据转台所用编码器的参数,分析了转台不同角速率下光纤陀螺所需的数据刷新率及陀螺零偏稳定性对测量结果的影响.用光纤陀螺测量了转台以1°/s角速率转动时的角速率波动,对陀螺输出数据作了功率谱分析,并与示波器直接测量的结果进行了对比,结果表明光纤陀螺的测量结果是正确的;应用光纤陀螺对转台以(0.05°/s,1°/s)范围内固定角速率转动时的角速率波动进行了测量,通过对测量结果的分析表明:光纤陀螺可以用于转台的测试,它能测量出转台低速转动时的角速率波动;最后给出了光纤陀螺对转台角速率测试的下限.     

大气信道中单光子轨道角动量纠缠特性的研究

本文讨论了大气信道中轨道角动量纠缠光子对的纠缠度, 并利用von Karman大气湍流谱来建立双光子纠缠度的模型, 分析了大气湍流对不同轨道角动量纠缠光子对纠缠度的影响. 研究表明: 在大气信道中, 由于大气湍流的存在, 纠缠光子对的纠缠度随着传输距离z的增加而减小; 大气湍流强度越大, 纠缠光子对的纠缠度下降的越快, 纠缠光子对传输的距离越小; 在湍流强度相同的大气信道轨道角动量指数越大的纠缠光子对, 纠缠度下降得越慢, 纠缠光子对传输的距离越远.     

基于多路复用体全息光栅的角度放大器设计

为设计基于多路复用体全息光栅的角度放大器, 建立了多路复用角度放大器(MAM)模型, 从效率均衡性和角度分布均匀性两个方面归纳了其设计规则; 研究了光刻过程中的误差对MAM性能的影响; 分析了实际发散光束对MAM性能的影响. 研究表明:控制光栅空间频率和光栅倾斜角可以实现需要的MAM角度分布, 控制光栅厚度和折射率调制深度可以实现MAM最佳衍射效率; MAM最大复用路数不超过10路; 增大光栅倾角或者记录光与工作光波长之比有利于抑制参考光角度误差带来的MAM出射角分布误差, 减小光栅厚度有利于抑制厚度误差与折射率调制深度误差对衍射效率的影响; 当远场发散角大于光栅角半宽时, 最佳衍射效率下降到50%以下且角度选择曲线失去局部最小值; 增大空间频率或者光栅厚度可以减小所需的折射率调制深度, 增多MAM可复用路数, 但是不利于效率均衡性设计和抑制发散光束的影响.     

基于叠栅条纹的光刻对准理论分析及标定方法

在线光栅用于纳米光刻对准理论的基础上,为实现光栅方向的标定和掩模硅片对准,提出一种利用相位斜率消除角位移的新方法,并给出线光栅标记及其对准原理。在对准前,掩模对准标记和硅片对准标记存在角位移,重点讨论了此种情况下叠栅条纹的特性以及与光栅物理参数的关系,并给出了相应的计算公式。基于傅里叶频域分析法,对叠栅条纹频率成分与条纹的关系做了简要分析。利用提取叠栅条纹行列方向的一维相位,通过数据拟合,得出了相位斜率与角位移的内在关系,实现了条纹方向的标定。模拟实验结果表明,该方法简单可靠,可分辨的最小角位移低于0.02°。     

Novel multisection design of anisotropic diffusion phantoms

Diffusion-weighted magnetic resonance imaging provides access to fiber pathways and structural integrity in fibrous tissues such as white matter in the brain. In order to enable better access to the sensitivity of the diffusion indices to the underlying microstructure, it is important to develop artificial model systems that exhibit a well-known structure, on the one hand, but benefit from a reduced complexity on the other hand. In this work, we developed a novel multisection diffusion phantom made of polyethylene fibers tightly wound on an acrylic support. The phantom exhibits three regions with different geometrical configuration of fibers: a region with fibers crossing at right angles, a region with parallel fibers and homogeneous density, and, finally, a region with parallel fibers but with a gradient of fiber density along the axis of symmetry. This gives rise to a gradual change of the degree of anisotropy within the same phantom. In this way, the need to construct several phantoms with different fiber densities is avoided, and one can access different fractional anisotropies in the same experiment under the same physical conditions. The properties of the developed phantom are demonstrated by means of diffusion tensor imaging and diffusion kurtosis imaging. The measurements were performed using a diffusion-weighted spin-echo and a diffusion-weighted stimulated-echo pulse sequence programmed in-house. The influence of the fiber density packing on the diffusion parameters was analyzed. We also demonstrate how the novel phantom can be used for the validation of high angular resolution diffusion imaging data analysis.     

The Wigner distribution functions of coherent and partially coherent Bessel-Gaussian beams

Based on the integral representation of the Bessel functions and the generating function of the Tricomi function, an analytical expression of the Wigner distribution function (WDF) for a coherent or partially coherent Bessel-Gaussian beam is presented. The reduced two-dimensional WDFs are also demonstrated graphically, which reveals the dependence of the reduced WDFs on the beam parameters.