Development of the NFTHz accelerator beam profile measurement system
-
摘要: 针对太赫兹直线加速器,开发了基于EPICS分布式系统的横向截面尺寸测量系统。该系统采用束斑检测器完成束斑到光斑的转换,并通过远心镜头将光斑成像到CCD相机,完成对光斑图像的采集,之后基于ADAravis将相机采集的图像数据汇入到EPICS数据库。由于暗电流以及环境辐射的影响,在采集到的图像中会存在椒盐噪声,因此使用卷积神经网络(CNN)对图像中的椒盐噪声进行抑制,最后对图像进行高斯拟合计算出束流截面尺寸。实验结果表明,CNN可以有效地消除椒盐噪声,并且系统的分辨率达到15.8 μm,满足系统设计要求。Abstract: The “Composite Light Source” project of the National Synchrotron Radiation Laboratory, Terahertz Near-Field High-Flux Material Property Testing System, consists of an approximately 3-meter electron linear accelerator. To characterize the performance of the accelerator and monitor the status of the beam, it is necessary to measure the beam size. Specifically designed for the terahertz linear accelerator, a beam size measurement system based on the EPICS distributed system has been developed. A beam spot detector is taken for the conversion of the beam spot into an optical spot and a remote mirror is taken to image the optical spot onto a CCD camera for image acquisition. Subsequently, the camera-captured image data is integrated into the EPICS database using ADAravis. Due to the dark current and radiation environment, salt-and-pepper noise is present in the acquired images. Therefore, a Convolutional Neural Network (CNN) is employed to suppress the salt-and-pepper noise in the images. Finally, Gaussian fitting is applied to calculate the beam cross-sectional dimensions from the images. The experimental results indicate that the CNN can effectively eliminate salt-and-pepper noise, and the resolution of this system is 15.8 μm, which satisfies the design requirement.
-
Key words:
- EPICS /
- ADAravis /
- beam profile measurement /
- machine learning /
- convolutional neural network
-
表 1 GE680与MV-CH089-10GM参数对比
Table 1. Comparison of parameters between GE680 and MV-CH089-10GM
model resolution minimum exposure time/μs onboard RAM/MB GE680 640×480 25 32 MV-CA-016-10GM 1440×1080 1 128 表 2 降噪性能对比
Table 2. Denoising performance comparison
noise addition rate noise image PSNR medianBlur PSNR FCN PSNR 0.1 17.79 40.22 52.14 0.2 14.59 28.36 51.95 0.3 12.77 22.39 50.99 0.4 11.22 18.20 49.52 0.5 10.14 15.26 39.59 0.6 9.18 13.41 47.31 0.7 8.36 11.81 41.75 0.8 7.06 9.38 41.83 -
[1] Tian Huiyan, Huang Guorong, Xie Fengxin, et al. THz biosensing applications for clinical laboratories: bottlenecks and strategies[J]. TrAC Trends in Analytical Chemistry, 2023, 163: 117057. doi: 10.1016/j.trac.2023.117057 [2] Lejeune C, Aubert J, Septier A. Emittance and brightness: definitions and measurements in applied charged particle optics part A[M]. New York: Academic Press, 1980: 159. [3] Lawson J D. The physics of charged-particle beams[M]. Oxford: Clarendon Press, 1988: 156. [4] Zhu Dechong, Yue Junhui, Sui Yanfeng, et al. Performance of beam size monitor based on Kirkpatrick–Baez mirror at SSRF[J]. Nuclear Science and Techniques, 2018, 29: 148. doi: 10.1007/s41365-018-0477-y [5] 唐兵. THz-FEL直线加速器在线控制与测量系统改进设计[D]. 武汉: 华中科技大学, 2018Tang Bing. Improved design of the online control and measurement system for THz-FEL LINAC[D]. Wuhan: Huazhong University of Science & Technology, 2018 [6] 乔显杰, 李刚. 基于EPICS的StreamDevice的应用研究[J]. 核电子学与探测技术, 2011, 31(10):1073-1076Qiao Xianjie, Li Gang. Research of StreamDevice applications based on EPICS[J]. Nuclear Electronics & Detection Technology, 2011, 31(10): 1073-1076 [7] Hu Zheng, Mi Qingru, Zheng Lifang, et al. EPICS data archiver at SSRF beamlines[J]. Nuclear Science and Techniques, 2014, 25: 020103. [8] Ma Tianji, Yang Yongliang, Sun Baogen, et al. Development and application of the new BPM system data processing program at Hefei Light Source[J]. Nuclear Science and Techniques, 2012, 23(5): 261-266. [9] Zhang Qian, Huang Chao, Yang Lihua, et al. Salt and pepper noise removal method based on graph signal reconstruction[J]. Digital Signal Processing, 2023, 135: 103941. doi: 10.1016/j.dsp.2023.103941 [10] Raja J, Moorthi K, Rajendran A. De-noising of salt and pepper noise using deep learning-based alpha-guided grey wolf optimization[J]. Applied Soft Computing, 2022, 130: 109649. doi: 10.1016/j.asoc.2022.109649 [11] Akkoul S, Ledee R, Leconge R, et al. A new adaptive switching median filter[J]. IEEE Signal Processing Letters, 2010, 17(6): 587-590. doi: 10.1109/LSP.2010.2048646 [12] Weiss B. Fast median and bilateral filtering[J]. ACM Transactions on Graphics, 2006, 25(3): 519-526. doi: 10.1145/1141911.1141918 [13] Sa P K, Majhi B. An improved adaptive impulsive noise suppression scheme for digital images[J]. AEU-International Journal of Electronics and Communications, 2010, 64(4): 322-328. [14] Fu Bo, Zhao Xiaoyang, Li Yi, et al. A convolutional neural networks denoising approach for salt and pepper noise[J]. Multimedia Tools and Applications, 2019, 78(21): 30707-30721. doi: 10.1007/s11042-018-6521-4 [15] Prasetyo H, Hsia C H, Yu Kunyi. TV-based impulsive noise reduction with Weber Law detector[J]. Journal of Imaging Science and Technology, 2019, 63: jist0605.