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该自动测量装置是根据原子能科学研究院自由电子激光(FEL)装置对电子束发射度测量的特殊要求而设计的,该装置采用单孔取样,用微机、步进电机和光栅尺组成闭环控制,监控采样步长,使取样孔从束剖面径向走过并在预定处取样,避免了普通孔像法在荧光靶上产生的像斑迭加现象,即便束径小到φ2.5mm也能进行分析处理;通过设计专门的电路,实现了图像数据的抓取与脉冲电子束团的同步,减小了随机抓图带来的测量误差。在结构设计上,采用带滑键的外部轴向定位,避免了传动部分在运行过程中出现卡死的隐患;金属靶板上还带有水冷结构,使得该系统可承受较大的功率。在实验中还对取样孔基板厚度引起使得电子散射的“管道效应”进行了研究,证明了该装置对于4MeV的电子束发射度测量的有效性。该测量系统在当前配置(L=630mm,采样孔与荧光靶间距)下相图测量的范围是:(0.006～0.1)cm·rad,可分析的最小束径为:φ2.5mm,金属靶板上取样孔的定位误差为:±0.02mm,系统的角分辩率为:1.6mrad。
The automatic measuring device is designed according to the special requirements of e-beam emissivity measurement by the free electron laser (FEL) device of the Institute of Atomic Energy. The device uses the single-hole sampling and the closed-loop control is composed of a microcomputer, a stepper motor and a grating ruler, Sampling steps are monitored so that the sampling hole passes radially from the beam profile and is sampled at a predetermined location, eliminating the superimposition of speckle on the fluorescent target by the conventional hole-borne method, even if the beam diameter is as small as φ2.5 mm Through the design of a special circuit, the capture of image data and the synchronization of pulsed electron bunch are realized, which reduces the measurement error caused by random capture. In the structural design, the use of external axial positioning with a sliding key, to avoid the transmission part of the stuck in the operation of the hidden dangers; metal target also has a water-cooled structure, making the system can withstand greater power. The “tube effect” that causes electron scattering caused by the thickness of the sampling hole substrate was also investigated in the experiment, demonstrating the effectiveness of the device for electron beam emissivity measurements at 4 MeV. The measurement system in the current configuration (L = 630mm, sampling hole and the distance between the target and the fluorescent target) phase measurement range is: (0.006 ~ 0.1) cm · rad, the smallest beam diameter can be analyzed: φ2.5mm, metal target Positioning hole on the sampling error: ± 0.02mm, the system’s angular resolution: 1.6mrad.