电子储存环中高灵敏度工作点测量系统的关键技术及应用研究

Tune is one of the most important parameters in electron storage ring. For conventional measurement method, tune is detected effectively by applying a certain resonant excitation to the stored beam. Disturbance to beam with these methods makes application of tune measurement greatly limited. In order to reduce disturbance to stored beam in electron storage ring, an improved tune measurement technique based on direct diode detection method is proposed. This technology can greatly improve detection sensitivity and dynamic range for beam beta oscillation. The detection sensitivity for beam beta oscillation amplitude can be achieved to sub-nanometer, so tune could be measured with only a small excitation or even without external excitation, which makes application range of tune measurement system greatly extended. Based on this high sensitivity tune measurement technology, some experimental studies of beam instability analysis, injection system parameters optimization, beam motion state detection with sub-nanometer resolution and beam closed orbit position measurement with sub-micron resolution will be carried out in the HLS-II electron storage ring. Through the implementation of the project, new key technologies for high sensitivity beam diagnosis technology can be accumulated and the research results have a very important significance in construction and stable operation of electron storage ring.

工作点是电子储存环最重要的参数之一，常规的测量方法中，通常必须对储存束流施加一定的共振激励才能有效检测到工作点，对束流的扰动使得工作点测量在应用中受到了很大的限制。为了降低工作点测量对储存束流的扰动，提出了一种改进型的基于二极管检波的工作点测量技术。该技术能大幅提高束流Beta振荡信号检测灵敏度和动态范围，使得可检测的束流Beta 振荡幅度灵敏度达到亚纳米量级，仅极小激励甚至无需外部激励就能精确测量工作点，能有效扩展工作点测量的应用范围。利用该技术在合肥光源电子储存环上开展束流不稳定性分析、注入系统参数优化、亚纳米量级束流运动状态检测技术和亚微米分辨率束流闭轨位置测量技术的研究。该项目研究成果为电子储存环高灵敏度束流诊断技术的研究积累新的关键技术，对于电子储存环的建设和稳定运行有着非常重要的意义。

在电子储存环中，工作点的测量方法一般有扫频激励法、锁相环法和束流频谱分析法。扫频激励法和锁相环法都需要对束流进行激励，对束流产生扰动。束流频谱分析法又简称FFT法，只能在注入阶段测量机器的工作点。基于直接二极管检波的基带工作点检测(Direct Diode Detection-Base Band Tune，简称为3D-BBQ)技术，将束流Betatron振荡的大部分频谱搬移到了基带，有力提高了工作点测量的灵敏度。研制了一套3D-BBQ电子学模块，利用该模块，在合肥光源电子储存环中开展了一些实验研究。研究结果表明，使用基于3D-BBQ技术的工作点测量系统得到的工作点大小与扫频激励法、FFT法得到的工作点大小是一致的，证明了基于3D-BBQ技术的工作点测量系统测量的工作点是正确的。比较了基于3D-BBQ技术的工作点测量系统与其他的工作点测量系统，结果表明基于3D-BBQ技术的工作点测量系统在测量机器工作点时对束流的激励信号最小。深度优化了3D-BBQ电子学模块之后，利用优化后的3D-BBQ电子学模块，在合肥光源电子储存环上对束流无激励情况下成功测量到了工作点，而且测量到的水平和垂直方向工作点信号相对于噪声的信噪比分别好于20dB和12dB，证明了基于3D-BBQ技术的工作点测量系统具有很高的灵敏度。