一种用于波荡器磁中心高精度标定的磁靶标

波荡器磁中心轴的标定是保证自由电子激光装置波荡器安装准直精度的重要前提。介绍了一种利用磁靶标实现波荡器磁中心高精度标定的方法。设计制造了由若干块永磁块组合构成的磁靶标,其能产生一正一斜两个高梯度四极场。测出了两四极场垂直分量的零点位置分布并依此给出了磁靶标的具体使用方法。结果表明：标定后的波荡器磁中心在磁靶标坐标系中水平方向测量精度好于±20 μm,垂直方向测量精度好于±2 μm。     

上海光源首批波荡器永磁块研制

介绍了上海光源2台混合型真空室内波荡器IVU25用636件Sm2Co17sub>永磁块(规格为65 mm×25 mm×8.965 mm)和1台APPLE-Ⅱ型椭圆极化波荡器EPU100用668件NdFeB永磁块(规格为35 mm×35 mm×25 mm)的研制情况。指出了影响剩磁离散性、磁化偏角、机械尺寸精度等技术要求的基本因素,并对其原理进行了分析。研制的Sm2Co17sub>和NdFeB永磁块的磁性能、磁场品质、机械尺寸精度等满足了上海光源首批波荡器插入件技术要求。     

纯永磁波荡器基波与谐波磁场的三维计算与测试

对标淮的纯永磁波荡器进行了三维磁场的有限元计算,给出了纯永磁波荡器的基波与谐波磁场的幅值与相位,并与测试结果进行对比,结果表明,标准的纯永磁波荡器谐波磁场幅值比基波幅值低两个数量级。     

In situ characterization of undulator magnetic fields

A new in situ method is proposed to characterize the peak magnetic fields of undulator sources. The X‐ray beam emitted by the HU52 Apple‐2 undulator of the DEIMOS beamline of the SOLEIL synchrotron is analyzed using the Bragg diffraction of a Si(111) crystal. Measurements over the undulator gap range in linear horizontal polarization are compared with simulations in order to rebuild the Halbach function linking the undulator gaps to their peak magnetic fields. The method presented also allows information about the electron beam to be obtained.     

有轴向磁场的平面摆动器自由电子激光的自发辐射

研究了电子在有轴向磁场的平面摆动器中的辐射，得到了一个较普遍的自发辐射谱表达式，谱线的形状也是由函数ｓｉｎｃ（ｕ）决定，当电子的能量较高或者没摆动器轴线观察时，辐射是满圆极化的，数值分析表明，在平面摆动器中附加适当的轴向磁场，可以提高各次谐波辐射的强度，对于基波和较低次谐波，提高更明显。     

Refurbishment of a used in‐vacuum undulator from the National Synchrotron Light Source for the National Synchrotron Light Source‐II ring

The National Synchrotron Light Source (NSLS) ceased operation in September 2014 and was succeeded by NSLS‐II. There were four in‐vacuum undulators (IVUs) in operation at NSLS. The most recently constructed IVU for NSLS was the mini‐gap undulator (MGU‐X25, to be renamed IVU18 for NSLS‐II), which was constructed in 2006. This device was selected to be reused for the New York Structural Biology Consortium Microdiffraction beamline at NSLS‐II. At the time of construction, IVU18 was a state‐of‐the‐art undulator designed to be operated as a cryogenic permanent‐magnet undulator. Due to the more stringent field quality and impedance requirements of the NSLS‐II ring, the transition region was redesigned. The control system was also updated to NSLS‐II specifications. This paper reports the details of the IVU18 refurbishment activities including additional magnetic measurement and tuning.     

横向聚焦波荡器磁场的计算与分析

横向聚焦波荡器可用于电子束能量较低、函数较小的情况。在现有横向聚焦波荡器设计方案的基础上,通过倾斜磁块端面和磁极面提出了几种不同结构的横向聚焦波荡器方案。利用三维磁场模拟程序Radia,对这些波荡器的聚焦场特性进行了模拟计算,对其聚焦特性与主要参数的关系进行了研究,并与现有其他横向聚焦波荡器的聚焦特性进行了对比。对弱聚焦和强聚焦两种情况,分别给出较好的结构方案。对于弱聚焦,平均聚焦梯度随中心场强的增大而略有增大,变化不明显;对于强聚焦,平均聚焦梯度随中心场强的增大而明显增大,呈高次曲线关系。     

A simple optical system delivering a tunable micrometer pink beam that can compensate for heat‐induced deformations

The radiation from an undulator reflected from one or more optical elements (usually termed `pink‐beam') is used in photon‐hungry experiments. The optical elements serve as a high‐energy cutoff and for focusing purposes. One of the issues with this configuration is maintaining the focal spot dimension as the energy of the undulator is varied, since this changes the heat load absorbed by the first optical element. Finite‐element analyses of the power absorbed by a side water‐cooled mirror exposed to the radiation emitted by an undulator at the Advanced Photon Source (APS) and at the APS after the proposed upgrade (APSU) reveals that the mirror deformation is very close to a convex cylinder creating a virtual source closer to the mirror than the undulator source. Here a simple optical system is described based on a Kirkpatrick–Baez pair which keeps the focus size to less than 2 µm (in the APSU case) with a working distance of 350 mm despite the heat‐load‐induced change in source distance. Detailed ray tracings at several photon energies for both the APS and APSU show that slightly decreasing the angle of incidence on the mirrors corrects the change in the `virtual' position of the source. The system delivers more than 70% of the first undulator harmonic with very low higher‐orders contamination for energies between 5 and 10 keV.     

参数激励与晶体摆动场辐射的稳定性

寻找新光源, 特别是短波长相干光源备受关注. 本文讨论了晶体摆动场辐射作为短波长激光的可能性和必须满足的基本条件; 指出了至今尚未获得可利用的短波长激光可能不只是技术原因, 而且还有物理原因. 利用参数激励方法对这个问题进行了分析. 在经典力学框架内和偶极近似下, 引入正弦平方势, 把粒子运动方程化为具有阻尼项和参数激励项的摆方程. 利用Melnikov方法讨论了系统的稳定性, 并对系统的临界条件进行了分析. 结果表明: 系统的稳定性与其参数有关, 只需适当调节这些参数, 系统的稳定性就可以原则上得到保证.关键词：晶体摆动场辐射沟道辐射参数激励稳定性     

用于THz源的混合型波荡器数值模拟

波荡器是基于自由电子激光的小型THz源关键器件, 其可调节的周期性磁场结构与两端的光腔配合, 使得穿越的电子束产生带增益的相干辐射, 最终达到THz源所需要的功率. 同纯永磁结构相比, 混合型波荡器通过软铁材料调节由永磁块磁化方向性差异导致的磁场分布误差, 同时可提供更高的场强. 本文针对小型THz源需求, 对混合型波荡器进行了相关物理设计. 在解析方法分析的基础上, 采用OPERA3D/TOSCA有限元分析软件, 对波荡器进行了三维磁场数值模拟和积分场优化. 通过对波荡器端部结构的调整, 优化后模型的一次场积分(导向误差)小于0.01Gs﹒m, 电子轨迹偏移小于0.02mm.