Beam-loss driven injection optimization for CSNS/RCS

This paper summarizes the painting injection optimization for the Chinese Spallation Neutron Source （CSNS） ring. This optimization focuses on two main design goals： the lower beam loss and a spacecharge tune shift low enough to avoid strong resonances. Finally, the 3-D particle tracking is performed and we get some important results about the beam properties and beam loss.     

人椅系统肢体气动特性数值模拟

为了研究弹射过程中人体肢体气动特性和高速气流防护装置的有效性,采用有限体积方法数值求解Navier-Stokes方程,空间和时间离散分别采用中心格式和五步龙格库塔格式,并应用基于SA紊流模型DES方法,数值模拟了人椅系统马赫数在0.6、雷诺数在12.3×106、迎角在-90°～90°范围内的气动特性,计算结果与风洞试验结果较为吻合.在此基础上对比模拟了马赫数在0.8～2.0、雷诺数在(6.75～13.85)×106、迎角在5°～30°范围内,有、无防护下人体肢体的气动特性.结果表明限臂板、抬腿机构和导流挡板等高速气流防护装置在保护肢体的同时,也产生一些不利干扰.因此,在实际应用中,应优化设计,最大程度发挥高速气流防护装置的作用.     

豆科植物种子的选择性败育及其影响因素的研究现状

果实与种子的形成是相关又不相同的两个过程,在不确定的传粉和母本环境中,常出现果实或种子的"过量分化".败育的花或胚珠具潜在的生殖功能.在那些生殖资源受限的植物上或者以提高后代适合度为选择力时,果实和种子败育是选择性败育,此现象在被子植物中比较普遍,尤其在豆科植物中开展了较多的研究.本文在介绍国际上有关植物选择性败育研究的基础上,重点介绍了豆科植物种子的选择性败育类型及其影响因素,并讨论了植物选择性败育的生态学意义.这为豆科牧草或农作物种子产量研究,以及种子植物选择性败育的生态学研究提供了理论依据.     

基于螺线管扫描法进行电磁叠加场中热发射度测量的仿真分析

在一种猝发高重频的X射线自由电子激光（XFEL）装置中,由于受到光阴极注入器内补偿螺线管与电子枪之间特殊结构的限制,阴极附近电场与磁场为叠加状态。实验中需要对阴极热发射度进行测量,而测量热发射度常用的螺线管扫描法基于几何发射度不变的前提,无法直接应用于电磁场叠加的结构。针对这一问题,考虑到归一化过程可以剔除电场对发射度的影响,基于此,研究归一化相空间中应用的螺线管扫描法,并通过仿真计算与分析,最终证明该方法适用于电磁叠加场中阴极热发射度的测量。     

正电子发射成像回旋加速器磁铁设计与测试

中国工程物理研究院流体物理研究所目前正在建造一台医用11 MeV回旋加速器,该加速器磁铁采用小气隙、深谷结构以提供更高的平均磁场和更强的聚焦能力。为实现510-4的测量精度,自行研发了一套磁场点测装置,该装置可实现二维极坐标下的精确测量。经过多次磁场垫补,束流的相位偏移控制在9,一次谐波幅值控制在0.001 T以内,满足了磁铁的设计需求。在束流调试过程中,成功实现了质子束的引出,表明回旋加速器磁铁建造成功。此外,还对磁铁研制过程中出现的磁场缺陷及磁测误差进行了讨论。     

Longitudinal RF capture and acceleration simulation in CSNS RCS

China Spallation Neutron Source (CSNS) is a high power proton accelerator-based facility. Uncontrolled beam loss is a major concern in designing the CSNS to control the radioactivation level. For the Rapid Cycling Synchrotron (RCS) of the CSNS, the repetition frequency is too high for the longitudinal motion to be fully adiabatic. Significant beam loss happens during the RF capture and initial acceleration of the injection period. To reduce the longitudinal beam loss, beam chopping and momentum offset painting methods are used in the RCS injection. This paper presents detailed studies on the longitudinal motion in the RCS by using the ORBIT simulations, which include different beam chopping factors, momentum offsets and RF voltage optimization. With a trade-off between the longitudinal beam loss and transverse incoherent tune shift that will also result in beam losses, optimized longitudinal painting schemes are obtained.     

Longitudinal RF capture and acceleration simulation in CSNS RCS

China Spallation Neutron Source (CSNS) is a high power proton accelerator-based facility. Uncontrolled beam loss is a major concern in designing the CSNS to control the radioactivation level. For the Rapid Cycling Synchrotron (RCS) of the CSNS, the repetition frequency is too high for the longitudinal motion to be fully adiabatic. Significant beam loss happens during the RF capture and initial acceleration of the injection period. To reduce the longitudinal beam loss, beam chopping and momentum offset painting methods are used in the RCS injection. This paper presents detailed studies on the longitudinal motion in the RCS by using the ORBIT simulations, which include different beam chopping factors, momentum offsets and RF voltage optimization. With a trade-off between the longitudinal beam loss and transverse incoherent tune shift that will also result in beam losses, optimized longitudinal painting schemes are obtained.     

RF trapping and acceleration in CSNS/RCS

In this paper, two injection scenarios with different chopping rate are discussed. The waveforms of the RF voltage are studied and optimized, respectively. Some suggestions are made, concerning chopping and momentum painting of the injected beam. Furthermore, the momentum spread and transverse tune shift are calculated so that the beam aperture and the beam loss can be estimated. Finally, the beam loss with magnet field error is analyzed.     

水泥密度和套管尺寸对油井套管波的影响

通过数值模拟结合实验测量,研究了第一、第二界面胶结良好情况下套管井内的声场,考察了水泥密度、套管直径及其壁厚对套管波幅度的影响,并将部分数值模拟结果与实验结果进行了对比.结果表明,套管波幅度随固井水泥密度增大而减小,低密度水泥和常规密度水泥固井时所得到的套管波幅度相差较大;因此,进行固井质量评价时对不同密度的水泥应采用不同的评价标准.当套管直径不变而壁厚增大时,套管波到时不变而幅度增大;当套管壁厚不变而直径增大时,套管波到时延后而其绝对幅度减小.对油田中常用的三种套管,在大型号套管中所得到的套管波的相对幅度也较大.另外,数值结果中套管波相对幅度随水泥密度的变化规律与实验测量结果基本一致.     

基于CCD电极直接驱动控制的双脉冲发光图像高速曝光技术原理研究

电荷耦合器件(CCD)是一类高性能的光电成像器件,具有成像阵列大、图像质量好的特点。但由于正常工作驱动时序复杂,工作帧频一般较低,无法满足较高成像帧频的要求。针对一种双脉冲发光图像的高速高分辨高质量成像要求,根据CCD信号电荷收集及转移的电极驱动特性,选择合适的CCD类型,以电荷转移时序为时间分隔界限,设计了一种电极直接进行控制的时序,实现了两个光脉冲图像的分离积分及信号转移、读出等,完成了双脉冲发光图像的等效高帧频曝光的原理验证,在保持CCD原有高成像质量的情况下获得了μs级间隔的两幅图像可分辨的能力,并实现了一种二分幅相机系统。