中子垂直聚焦单色器的调试

中子聚焦单色器可有效提高中子散射谱仪样品处的中子注量率。对安装在中国工程物理研究院核物理与化学研究所的中子衍射谱仪中子垂直聚焦单色器进行调节，在样品处利用中子照相确定了束斑的中心位置和大小，通过在水平和垂直方向上的扫描得到了可利用的中子束的面积，测量了该处的最大中子注量率。在样品处得到略大于1倍的增益。这一结果表明，调试是成功的。     

中子应力谱仪常用聚焦单色器的模拟与比较

用蒙特卡罗中子射线追踪程序McStas对中子衍射应力谱仪单色器部件进行模拟优化:以Cu(220)比较了单色器起飞角和准直系统对样品处中子注量率、分辨率的影响;计算得到给定条件下单色器最佳单晶条数和镶嵌度;单晶条倾角精度建议好于0.1°;计算了Cu(222)、(220)和(002)在不同起飞角情况下获得的中子注量率;相同条件下,Cu和Ge常用晶体单色器中以Cu(220)获得的中子注量率最大,而Cu(222)获得的波长分辨率最佳。     

应力测量中子衍射谱仪聚焦单色器的模拟

为提高样品处入射中子束强度,满足高分辨和小体积标样测量的需要,应用MCSTAS软件对中国先进研究堆上应力测量中子衍射谱仪的核心部件垂直聚焦单色器进行模拟和优化设计,得到了单色器在不同起飞角下的最佳聚焦条件,即所需的曲率半径和相邻单晶条之间的最佳倾角。在此条件下,可获得相对于平板单色器6~7倍的强度增益,样品处中子注量率达10⁷cm^-2•s^-1以上。在使用聚焦单色器的情形下,对标准的α-Fe多晶样品在无应变、拉应变和压应变下的(211)衍射峰进行了模拟。结果表明:该谱仪的分辨水平至少能测量500με以上的应变,且应变测量最高精度约为20με。     

中子粉末衍射谱仪垂直聚焦单色器的调试方法

介绍了中子散射谱仪用的中子垂直聚焦单色器的基本原理,描述了安装在中国工程物理研究院核物理与化学研究所的中子衍射谱仪的中子垂直聚焦单色器的调节方法.在样品处利用中子照相确定了束斑的中心位置和大小,通过在水平和垂直方向上的扫描得到了可利用的中子束的面积,测量了该处的最大中子注量率,结果表明在样品处得到略大于一倍的增益.     

中子单色器模拟分析研究

为研究单色器对中子能谱的选择规律,本文利用MCSTAS程序模拟分析了机械速度选择器与晶体单色器几个特征参数对中子能量选择影响。分析结果显示经机械速度选择器单色选择中子注量率要下降1~2个量级,而晶体单色器要下降2~3个量级。因此,对于单色化要求比较高选用晶体单色器,对于实验时间要求较高的选用机械速度选择器。     

中子应力谱仪双聚焦Si单色器设计、模拟与测试

本文对中国先进研究堆中子应力谱仪使用的双聚焦Si单色器进行了设计、模拟和测试。采用SIMRES模拟程序确定了单色器垂直曲率及Si片厚度的最优值,并得到品质因数与散射角、单色器水平曲率和波长的依赖关系。实际测试结果表明,与平板Cu单色器相比,使用双聚焦Si单色器样品处中子强度提高了15倍。     

双晶单色器水冷晶体的设计加工

简要介绍了弧矢聚焦双晶单色器的作用及结构原理,根据设计指标确定了水冷晶体衍射面及外形尺寸,分析了高热负载下水冷晶体的热变形,根据国外经验采用直接水冷却法进行高热负载的热缓释,设计了用于直接水冷却的刻槽晶体及冷却结构,根据设计完成了晶体的材料选择、定向切割、冷却水槽的刻制等加工工艺,最终完成了适用于弧矢聚焦双晶单色器的直接水冷分光晶体的加工,该晶体能承受大于0．5W/mm^2的热负载。     

高能劳厄单色器晶体压弯性能的研究

上海光源二期工程拟建的超硬多功能线站将采用一台弧矢聚焦高能劳厄单色器,晶体压弯机构是单色器的核心部件,晶体弧矢半径与子午半径的优化对单色器的光通量和分辨率有很大影响。本文利用有限元软件分析了影响劳厄晶体压弯性能的主要因素——斜切晶体的各向异性以及晶体的长宽比。通过分析,确定了硅晶体切割边为[011]方向和[0-11]方向,晶体的优化尺寸为90 mm×40 mm×1 mm。硅晶体表面的弧矢和子午面形误差(均方根)分别为3.02μrad和1.25μrad,满足设计要求。     

中子单色器姿态调整台

中子单色器姿态调整台是大多单色中子散射谱仪所必需的机械部件之一,主要用来安放晶体单色器,并可通过远程控制对单色器进行姿态调整以保证得到所需的单色中子。该装置体积小、自由度多、运动精度高,是一集光机电和计算机控制技术为一体的五自由度运动设备。该装置研制成功后将首先应用于中国先进研究堆中子残余应力谱仪上。     

垂直聚焦单色器的蒙特卡罗模拟计算

利用蒙特卡罗方法对引进的1台粉末衍射仪上的垂直聚焦单色器进行了模拟检验，以得到起实际作用的单色器尺寸，聚焦曲率半径和倾角等参数。计算和对比了使用聚焦单色器和平板单色器的强度增益和样品位置中子强度分布，结果表明：由于前面孔道尺寸的限制，使用垂直聚焦单色器相对于使用平板单色器在样品量多的情况下没有明显的强度增益，只有在所能得到的样品量少的时候使用垂直聚焦单色器才能得到比较显著的强度增益。     

Sagittal聚焦晶体柔性铰链压弯机构研究

分析了弧矢聚焦晶体弯曲原理及柔性链运动方程,阐述了弧矢聚焦晶体柔性铰链压弯机的原理,同时提出了抑制子午形变的有效方法。该压弯机构在5－20keV能量扫描范围内,弧矢聚焦比为3：1,聚焦曲率相对误差＜0.75%,聚焦光斑弥散为25%,在10keV时聚焦面形误差＜2″。     

基于柔性铰链的压弯模型研究

将柔性铰链技术应用于弧矢聚焦晶体单色器中的聚焦研究,在对柔性铰链结构参数研究的基础上,建立起了基于柔性铰链的压弯驱动装置行程与压弯动态半径之间的数学模型,分析了影响压弯半径分辨率的主要因素,并且将这种压弯模型成功应用在上海同步辐射装置(Shanghai Synchrotron Radiation Facilty,SSRF)弧矢聚焦晶体单色器研制项目中.检测结果表明,依据这种压弯模型能够实现弧矢聚焦功能,并达到聚焦光斑性能指标.     

Alternating-gradient focusing in linear accelerators

A linear theory for alternating-gradient (strong) focusing in linear ion accelerators is presented.Presented at the All-Union Conference on the Physics of High Energy Particles, May 18, 1956.     

Ion beam propagation and focusing

Inertial confinement fusion with ion beams requires the efficient delivery of high energy (1 MJ), high power (100 TW) ion beams to a small fusion target. The propagation and focusing of such beams is the subject of this paper. Fundamental constraints on ion beam propagation and focusing are discussed, and ion beam propagation modes are categorized. For light ion fusion (LIF), large currents (2–33 MA) of moderate energy (3–50 MeV) ions of low atomic number (1A12) must be directed to a target of radius 1 cm. The development of pulsed power ion diodes for LIF is discussed, and the necessity for virtually complete charge neutralization during transport and focusing is emphasized. Fornear-term LIF experiments, the goal is to produce pellet ignition without the standoff needed for the ultimate reactor application. Ion diodes for use on Sandia National Laboratories Particle Beam Fusion Accelerators PBFA-I (2–4 MV, 1 MJ, 30 TW, operational) and PBFA-II (2–16 MV, 3.5 MJ, 100 TW, scheduled for operation in 1985) are discussed. Ion beam transport from these diodes to the pellet is examined in reference to the power brightness . While values of =2–5 TW/cm²/sr have been achieved to date, a value of 100 TW/cm²/sr is needed for breakeven. Research is now directed toward increasing , and means already exist (e.g., scaling to higher voltages, enhanced ion diode current densities, and bunching), which indicate that the required goal should be attainable. Forfar-term LIF applications, the goal is to produce net energy gain with standoff suitable for a reactor. This may be achieved by ion beam transport in preformed, current-carrying plasma channels. Channel transport research is discussed, including experiments with wire-initiated, wall-initiated, and laser-initiated discharge channels, all of which have demonstrated transport with high efficiency (50–100%). Alternate approaches to LIF are also discussed, including comoving electron beam schemes and a neutralized beam scheme. For heavy ion fusion (HIF), moderate currents (10 kA) of high energy (10 GeV) ions of high atomic number (A200) must be directed to a target of radius 0.3 cm. Conventional accelerator drivers for HIF are noted. For a baseline HIF reactor system, the optimum transport mode for low charge state beams is ballistic transport in near vacuum (10^–4–10^–3 Torr lithium), although a host of other possibilities exists. Development of transport modes suitable for higher charge state HIF beams may ultimately result in more economical HIF accelerator schemes. Alternate approaches to HIF are also discussed which involve collective effects accelerators. The status of the various ion beam transport and focusing modes for LIF and HIF are summarized, and the directions of future research are indicated.     

Optimal electrostatic axisymmetric microprobe focusing system

This paper investigates the possibility of utilising an electrostatic multiple cylinder lens to focus the beam in microprobes. Multiple cylinders reduce the lens potentials which are required. We use a new analytical model of the axial potential distribution varying the parameters of this distribution and the size of the object and aperture diaphragms to obtain the minimum spot size at the specimen for a given beam emittance and finding by this way the optimal parameters of the axial potential distribution. For synthesising the optimal physical model we applied an accurate version of the Integral Equation Method to solve Laplace's equation in order to obtain the parameters of the physical model which has the same axial potential distribution as the optimal analytical model.     

Strong focusing in a linear accelerator

In this paper we consider the use of strong focusing in linear proton accelerators and carry out a detailed quantitative analysis of the motion of protons in the system. Design calculations for quadrupole lenses are given together with the experimental results obtained with the use of strong focusing in a 5.5 Mev linear proton accelerator.In conclusion the authors wish to take this opportunity to thank Acid. AN SSSR K. D. Sinel'nikov and Cand. Phys.-Math. Sci. Ya. B. fainberg for their continued interest in this work and for valuable discussions.