用于重离子治癌回旋引出的实时流强测量系统北大核心CSCD

为满足重离子治癌加速器装置(HIMM)回旋加速器引出段束流流强的测量需求,设计了新的束流流强测量系统,该系统利用积分电流变换器(ICT)及锁相放大器等配套电子学,能够实现束流流强的非拦截实时测量。文中首先分析了中能束线(MEBT)束流流强的测量需求,并对设计方案进行了实验室系统分析和在线束流强测量。实验室结果表明,锁相放大器的幅度和相位响应一致性满足测量需求。由于ICT对束流流强的测量是相对测量,先使用法拉第筒对ICT进行在线标定;标定前先对法拉第筒(FC)(20μA档位)和ICT系统的流强分辨在线测量,分别为6.45 nA和5.163 nA。由于束流抖动的影响,测量的束流的稳定性约90 nA,其对应的相对测量误差约8%,ICT系统响应时间小于1 ms。测量结果表明,该系统满足物理测量需求。回旋加速器高频系统参数变化引起ICT标定系数变化的工作将在进一步工作中展开。

Real-time beam intensity measurement system for extraction section of cyclotron in Heavy Ion Medical Machine

To meet the beam intensity measurement requirements at the extraction section of the cyclotron in Heavy Ion Medical Machine (HIMM), the integral current transformer (ICT) and lock-in amplifier scheme was adopted to implement non-destructive and real-time beam intensity measurement on the medium energy beam transport line (MEBT). ICT acquires the relative beam intensity which can’t be monitored directly, as a result, the Faraday cup which is a kind of destructive detector was used to achieve calibration of ICT with beam. In this paper, the requirements and design scheme of beam intensity measurement at MEBT are firstly analyzed, and based on the design scheme, tests with this beam intensity measurement system are carried out in the laboratory and with beam. According to the test results, the beam intensity stability is about 90 nA, while the corresponding relative error is about 8%. Furthermore, the response time of ICT and Faraday cup system is less than 1 ms and 100 ms respectively, which meet the physical measurement requirements. Further study on the relationship between frequency-variation of cyclotron radio-frequency system and beam current measured by ICT will be carried on in the next step.