高亮度电子束相空间重建技术的实验研究  

Experimental study on phase space reconstruction of high-brightness electron beam

作　　者：于清林 张猛[1] 谷端[1] 赵明华[1] 

机构地区：[1]中国科学院上海应用物理研究所嘉定园区,上海201800 [2]中国科学院大学,北京100049

出　　处：《核技术》2018年第3期13-19,共7页Nuclear Techniques

摘　　要：束团相空间是描述加速器中束流运行状态的重要参数,了解相空间的真实分布对于加速器设计、束团操纵具有非常重要的意义,利用相空间重建技术能够直观地得到束团二维相空间分布。本文结合计算机断层扫描技术(Computer Tomography,CT)与归一化相空间理论,在理论推导和模拟验证的基础上,分别利用MENT(Maximum Entropy)算法和FBP(Filtered Back Projection)算法在上海X射线自由电子激光装置(Shanghai Soft X-ray Free Electron Laser facility,SXFEL)专用束测段(BI1)对电子束团的横向归一化相空间进行重建。通过重建算法变换得到电子束团的真实相空间分布,并对重建结果进行对比和误差分析。实验结果表明,MENT算法能够精确测量电子束团横向相空间分布。[Background] Variance reduction is a common method to resolve the problems in deep penetration application such as radiation shielding, medical physics and well-logging. Currently, the study of the variance reduction techniques is based on simple theoretical geometric model, lacking the discussion on complex practical applications. [Purpose] This paper aims to find an optimized combined variance reduction technique in deep penetration application on the practical complex model. [Methods] With an electron irradiation accelerator as the model, this paper studied the effects of combined variance reduction techniques on MCNP5（Monte Carlo N Particle Transport Code） platform, including geometry splitting, biasing the source, exponential transform, step-step transform, DXTRAN and weight window. [Result] The results showed that the irradiation products had a great influence on the angular distribution of spectrum of the new source, and the geometric model should not be overly simplified. Compared with other variance-reducing techniques, the step-step transform and biasing the source efficiency reduced the relative error and could get a better calculation efficiency combined with geometric splitting, exponential transform and DXTRAN. Weight window had better computation efficiency and more objectivity. [Conclusion] The step-step transform and biasing the source, combined with other variance reduction techniques can resolve deep penetration problem in complex practical application based on weight window.

关 键 词：归一化相空间 相空间重建 MENT算法 上海X射线自由电子激光装置 

分 类 号：TL271[核科学技术—核燃料循环与材料]