高压电缆源平移扫描CT高效重建算法EI北大核心CSCD

为提高在役高压电缆X射线扫描图像重建速度,结合传统的滤波反投影算法,提出基于数据平滑的局部扫描重建算法。分析了源直线扫描局部计算机断层成像方法存在的有限角和数据截断问题,提出数据平滑方式解决方法。主要途径是利用余弦函数沿探测器方向和射线源方向分别进行数据平滑插值,避免投影数据值在这两个方向上突然降为零,起到抑制截断伪影和有限角伪影的作用。实验证明,所提方法能有效抑制图像伪影,有利于电缆阻水缓冲层缺陷识别。相较于原有的联合迭代重建算法,该方法缩短了重建时间且图像重建质量相当;相较于传统滤波反投影算法,重建图像质量提高但重建耗时基本一致。     

光纤耦合GAGG＿Ce型X射线探测器高分辨成像

闪烁屏信号串扰是影响X射线探测器空间分辨率的主要因素,基于点扩散函数理论对光纤耦合GAGG_Ce单晶闪烁屏型CCD/CMOS探测器的空间分辨率进行了研究。利用蒙特卡罗程序EGSnrc和光学仿真软件Zemax分别对GAGG_Ce单晶闪烁屏射线串扰和荧光串扰进行了仿真。仿真结果表明,对于低能X射线辐射成像,荧光串扰是影响探测器空间分辨率的最主要因素。此外,研究了通过降低光纤面板数值孔径以抑制荧光串扰的方法,得到了光纤面板数值孔径与探测器空间分辨率和X射线转换因子间的关系,并通过自制CCD探测器测试验证了仿真结果的正确性。     

用20—1020 keV单能质子刻度CR-39固体核径迹探测器

用北京师范大学2×1.7MV串列加速器和400 kV高压倍加器产生的20—1020 keV单能质子束对CR-39固体核径迹探测器进行了刻度.为了保证质子的单能性和固体核径迹探测器上径迹密度不能超过10⁶/cm²的要求,对两台加速器分别采用了不同方法控制质子辐照数量.在串列加速器上采用了狭缝加转盘的方法,在高压倍加器上采用了100 ns单次高压脉冲扫描束流的方法,既保持了质子的单色性,又达到了质子注量小于10⁶/cm²的 关键词： 单能质子 固体核径迹探测器 CR-39     

Generation of fast protons in moderate-intensity laser－plasma interaction from rear sheath

Forward fast protons are generated by the moderate-intensity laser--foil interaction. Protons with maximum energy 190~keV are measured by using magnetic spectrometer and CR-39 solid state track detectors along the direction normal to the rear surface. The experimental results are also modeled by the particle-in-cell method, investigating the time-varying electron temperature and the rear sheath field. The temporal and spatial structure of the sheath electrical field, revealed in the simulation, suggests that these protons are accelerated by target normal sheath acceleration (TNSA) mechanism.     

Neutron Generation and Kinetic Energy of Expanding Laser Plasmas

We investigate the kinetic energy of expanding plasma of a solid target heated by a ultra-short and ultra-intense laser pulse and the efllciency of energy coupling between the ultra-intense laser pulse and the solid target, in order to increase the utilization ratio of laser energy and to raise the neutron generation farther. Some new ideas about improving the energy utilization by head-on collision~, between the expanding plasmas are proposed. The significance is the raise of generation of shorter duration neutron, of the order of picoseconds, which allows for an increase of energy resolution in time-of-flight experiments and also for the investigation of the dynamics of nuclear processes with high temporal resolution.     

Faithful quantum entanglement sharing based on linear optics with additional qubits

This paper presents a scheme for faithfully distributing a pure entanglement between two parties over an arbitrary collective-noise channel with linear optics. The transmission is assisted by an additional qubit against collective noise. The receiver can take advantage of the time discrimination and the measurement results of the assistant qubit to reconstruct a pure entanglement with the sender. Although the scheme succeeds probabilistically, the resource used to get a pure entanglement state is finite, and so is easier to establish entanglement in practice than quantum entanglement purification.