Detection of turn-by-turn beam loss in electron storage rings
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摘要: 调束初期,电子储存环的逐圈束流损失信号可以直观展示出束流的注入、储存和积累状态。介绍了束流损失的种类和机制,列举了几种常见的束流损失探测器及其关键参数。基于北京正负电子对撞机(BEPCII)重大改造工程机器参数,用Geant4模拟了BEPCII束流条件下束流丢失引起的二次粒子分布情况,分析了真空室外簇射电子和光子的分布,根据分析结果,最终选用闪烁体加光电倍增管(PMT)型探测器探测逐圈束损信号,并在BEPCII进行了束流测试。针对闪烁体型束损探测器性能不一致问题,对探测器进行了灵敏度校准并在BEPCII上完成了束流验证,最后介绍了信号采集与处理电子学并计算分析了其测量精度。上述实验为闪烁体束损探测器在高能同步辐射光源储存环上的应用奠定了基础。Abstract: At the initial stage of beam commissioning, the turn-by-turn beam loss signals from the electron storage ring directly display the injection and accumulation of the beam. This paper introduces the types of beam loss mechanisms and enumerates several common types of beam loss monitors and their parameters. Based on the parameters of the upgrade project of the Beijing Electron Positron Collider (BEPCII) , beam loss was simulated using Geant4. The distribution of shower electrons and photons outside the vacuum chamber was analyzed. A scintillator coupled with a photomultiplier tube (PMT) monitor was chosen to detect the turn-by-turn beam loss signals. Beam tests were conducted at BEPCII, and the self-developed electronic system was used for signal acquisition and processing. To address the issue of inconsistent performance among scintillator beam loss monitors, sensitivity calibration was performed, followed by beam verification at BEPCII. This paper also introduces the signal acquisition and processing in electronics, along with the calculation and analysis of the measurement accuracy. These experiments has laid the foundation for the application of scintillation beam loss monitors in high energy photon source.
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Key words:
- beam loss monitor /
- Geant4 /
- photomultiplier tube /
- beam diagnostics /
- high energy photon source
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表 1 几种常见的束流损失探测器及其参数
Table 1. Several common beam loss monitors and their parameters
response time/ns sensitivity/(nC·rad−1) dynamic range short ionization chamber 8.9×104 638 108 long ionization chamber 270 200 104 PIN diode 5 100 108 CVD diamond 3.6 44 106 Cherenkov fiber 20 270Mg 106 scintillation detector 10 1.8×104Mg 106 Note: Mg is the multiplication factor of PMT. 表 2 H10721-110及N2013型光电倍增管性能参数
Table 2. Performance parameters of H10721-110 and N2013 photomultiplier tubes
rise time/ns spectral range/nm typical gain H10721-110 0.57 230~700 2.2×105 N2013 1.50 270~650 8×106 -
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