Automated positioning of transparent targets using defocusing method in a laser proton accelerator

• DOI: 10.1016/j.nima.2019.02.034
• Publication Date: 2019-02-25T05:22:40Z
• Authors: Yinren Shou; Dahui Wang; Pengjie Wang; Jianbo Liu; Zhengxuan Cao; Zhusong Mei; Yixing Geng; Jungao Zhu; Qing Liao; Yanying Zhao; Kun Zhu; Chen Lin; Haiyang Lu; Wenjun Ma; Xueqing Yan
• Keywords: Micrometer

Abstract We report an automated target positioning method with an accuracy of 2 μ m for a compact laser proton accelerator. This method is based on micrometer-scale dots on the images of transparent targets. In order to interpret the variation of these dots quantitatively, we developed a defocusing method making transparent targets visible as phase objects and applied it in target positioning. Automated positioning of transparent targets can be realized by means of minimizing the standard deviations σ of the pixel values of the images. Fast positioning based on the relationship between the radius of spherical aberration ring and defocusing distance is also discussed. Laser proton acceleration experiments have been carried out to demonstrate the performance of this positioning method.