基于微波带状线结构纵向束团形状测量探针研制

Longitudinal bunch shape is one of the significant parameters to evaluate the beam quality. According to measuring longitudinal bunch shape, longitudinal emittance can be derived, beam lattice can be validated, the indirect measuring longitudinal bunch shape such as using beam position monitor can be checked in each other, and the assumption of a Gaussian shape for the longitudinal distribution can be confirmed. Therefore, accurately measuring longitudinal bunch shape can provide the guidance for debugging and operating an accelerator, giving the reliable data for matching in the different accelerator components, and making sure the validation of the physics simulation. This project will develop a novel longitudinal bunch shape monitor with 13GHz bandwidth and 76ps resolution for linear accelerator, especially for high current linear accelerator. It is based on the microwave stripline with High Temperature Ceramics structure to increase the working bandwidth and reduce the signal noise. The Tantalum copper composited material and the water cooling structure will be used to improve the high heat tolerance. The higher time resolution and the lower cost detector used for longitudinal bunch shape measurement will be expected in this project. These results will meet the requirements of the longitudinal parameters measurement for linear accelerator.

纵向束团形状是衡量束流品质的重要参数之一，通过纵向束团长度的测量，可以推算出束流的纵向发射度，验证束流的lattice，并为其他间接测量束团长度的方法(如BPM)提供验证手段（低能时BPM测不准束团长度），而且还可以验证通过模拟计算所假设的束流纵向高斯分布等。因此，准确测量纵向束团形状可以为机器的调试和运行提供指导，为各部分之间的匹配提供可靠依据，为物理模拟计算提供验证依据。本课题将研制一种工作带宽为13GHz，时间分辨为76ps纵向束团形状测量探针，用于直线加速器尤其是强流直线加速器中纵向束团形状准确测量。本课题拟采用基于高温陶瓷微波带状线结构以增加带宽和降低噪声，同时，采用钽铜复合材料并加入水冷结构以提高探针耐热性。本课题研究旨在提高探针时间分辨率，降低成本，并满足直线加速器纵向参数测量的迫切需求。

纵向束团形状是衡量束流品质的重要参数之一，准确测量纵向束团形状可以为机器的调试和运行提供指导，为各部分之间的匹配提供可靠依据，为物理模拟计算提供验证依据。本课题研究旨在提高探针时间分辨率，降低成本，并满足直线加速器纵向参数测量的迫切需求。课题组完成了预期研究内容和目标，取得主要研究成果如下：.本课题成功完成了纵向束团形状测量探针研制及在线束流测试。该纵向束团形状测量探针是一种由步进电机控制的拦截式的装置，其工作原理是基于AIN陶瓷带状线结构。纵向束团长度主要是通过1 mm的小孔采样到一部分束流再与带状线相互作用而得到的。探针的工作带宽高达15 GHz，时间分辨率好于67 ps。为了满足强流直线加速器的要求，纵向束团形状测量探针的探头大部分采用耐高温材料，并且该探针还采用了水冷的方法以提高探头的热转换以及防止过热损坏探头。利用热分析方法对纵向束团形状测量的探头进行了热分析。该探测器成功安装在CADS质子直线减速器II上进行了束流在线测试，而且精确地测量了纵向束团形状，实验和理论结果吻合良好。