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A software package to be used in high-speed oscilloscope-based three-dimensional bunch-by-bunch charge and position measurement is presented. The software package takes the pick-up electrode signal waveform recorded by the high-speed oscilloscope as input, and it calculates and outputs the bunch-by-bunch charge and position. In addition to enabling a three-dimensional observation of the motion of each passing bunch on all beam position monitor pick-up electrodes, it offers many additional features such as injection analysis, bunch response function reconstruction, and turn-by-turn beam analysis. The software package has an easy-to-understand graphical user interface and convenient interactive operation, which has been verified on the Windows 10 system.

In order to improve machine performance, the optics parameters of the storage ring need to be measured accurately. The commonly used accelerator optics parameters, including momentum compaction factor and dispersion function, are key parameters that reflect the state of the machine. It is difficult to measure them with traditional methods during the user operation run. Based on a high-resolution bunch-by-bunch three-dimensional measurement system, a noninvasive measurement of momentum compaction factor and the dispersion function was performed at the Shanghai synchrotron radiation facility (SSRF). The dispersion function can be obtained purely from the direct observation results of the bunch-by bunch 3D position, based on the definition of the dispersion function during normal user operation run without perturbing the beam. The theoretical background and experimental results of the method are discussed in this paper. The measurement results are in good agreement with the design values.

Bunch-by-bunch beam parameters monitor is a very useful tool for accelerator operation and optimization. An in situ bunch-by-bunch three-dimensional position and charge measurement system has been developed at the Shanghai Synchrotron Radiation Facility. Signals from beam position monitors carry almost full beam information, a broadband digital receiver can retain most information. Therefore, a four-channel wideband oscilloscope is employed to capture the signals from all electrodes of the beam position monitor. Correlation coefficient-based methods are used to extract these bunch-by-bunch parameters synchronously. We evaluated the performance of this bunch-by-bunch information extraction method, the measurement uncertainty of longitudinal phase is less than 0.2 ps, the uncertainty of transverse position is less than $10\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ and the charge uncertainty is 0.3% under the condition that the bunch charge is 600 pC. Thanks to the great performance of the new system, it is accurate enough to study the transient state during injection. In addition, an in situ wakefield measurement system is planned to be established based on this system.

We report on the application of machine learning (ML) methods to extract longitudinal phase information such as parameters of the synchrotron damping oscillation. Parameters of the synchrotron damping oscillation are important for the evaluation of machine status and bunch stability. It is of concern to extract these parameters with high-speed and high-precision. The previous methods, such as multiparameter nonlinear fitting and table look-up, are slower and easily fall into local optimal solutions. Our approach based on ML-image processing consists of training a virtual diagnostic to predict parameters using the beam position monitor (BPM) electrical signal data as inputs. We find that when the noise of data is large, our ML-model can still get better results than other methods, an important step toward on-line multiparameter extraction from multidimensional raw data.

Lifetime is a key performance parameter of storage rings. DC current transformers (DCCT) are common employed to measure beam lifetime, which can only be applied to measure average lifetime. However, the physical lifetime formula is only strictly established for a single bunch. In order to provides a toolkit for complete and accurate representation of the behavior of all electron bunches, a bunch-by-bunch beam lifetime measurement system has been developed at the Shanghai Synchrotron Radiation Facility. A beam-position-monitor was used as the detector of beam-charge-monitor. Several effective techniques have been introduced to improve the resolution and data refresh rate of the single bunch charge measurement. Resolution of the new bunch-by-bunch charge monitor is better than 0.02% and data refresh rate is 140 Hz. A dedicated algorithm has been developed to extract lifetime of single bunch. Resolution of bunch-by-bunch vacuum lifetime measurement is 1 h. System setup, experiments and data analysis are presented in this paper.

Cavity Beam Position Monitor (CBPM) adopting a resonant cavity structure and using the characteristic modes excited by the electron beam to measure the beam parameters, has the advantage of high position resolution and is widely used in Free-electron Laser (FEL) facilities. The wake field of different modes carries different bunch information, the amplitude and phase of the signals of different modes can be extracted through the signal processing method to obtain the characteristic parameters of the source bunch. In the application of bunch charge and position measurement, the accurate amplitude extraction method for cavity BPM signal is the primary issue to be considered when designing the data acquisition and processing system. In this paper, through theoretical analysis and numerical simulation, it is proved that the optimal algorithm of amplitude extraction for CBPM exists, and the dependence between the data processing window size and the decay time of the cavity BPM under the optimal design is given. In addition, the relationship between the optimized amplitude extraction uncertainty and the noise-to-signal ratio, sampling rate of data acquisition and processing system, and the decay time of the cavity BPM is also proposed, which can provide clear guidance for the design and optimization of the CBPM system. Accordingly, the CBPM system in Shanghai Soft X-ray FEL (SXFEL) facility is optimized, and the resolution improved from 273 nm to 177 nm at the bunch charge of 500 pC.

Continuous tracking of bunch charges is the key to maintain stable operations in a storage ring in top-up mode. Recently, a precise bunch-by-bunch beam-current measurement (BCM) system has been developed at the Shanghai Synchrotron Radiation Facility. To avoid the influence of longitudinal oscillation on the amplitudes of the sampling points, a method called two-point equilibrium sampling is introduced. The results, obtained during routine operation time, show that the relative resolution of the measurement of the bunch charges is better than 0.02%. With this high resolution, the new BCM system is able to monitor the bunch-by-bunch beam lifetime. By using the filling pattern information, the Touschek lifetime and the vacuum lifetime can also be calculated. In this paper, the principle of the new method and the experiments is presented in detail.

A high-resolution bunch-by-bunch longitudinal phase measurement system has been developed at the Shanghai Synchrotron Radiation Facility. The system has a high-speed digital signal analyzer to capture the signals from a beam-position-monitor. Then the bunch phases can be collected by using a zero-crossing detection method and a longitudinal delta-over-sum lookup table method consecutively. The phase of the refilled charge is calculated by separating it from the stored bunch. In order to fully explore the evolution of the refilled charge damping oscillation, the transient state during injection was further studied. The arrival time of the refilled charge, the energy mismatch between the injector and the storage ring, and the synchrotron damping time can be obtained in the injection transient process. This system is capable of measuring the bunch-by-bunch phases online, which provides an additional way to monitor the machine status or to optimize the injector.

Beam signals captured from a button-type pickup contain multidimensional information including the bunch charge, transverse position, bunch length, and longitudinal phase. A bunch phase monitor, which retrieves longitudinal phase information from a pickup signal at a bunch-by-bunch rate, has been developed at the Shanghai Synchrotron Radiation Facility. This paper introduces the basic principles, system setup, data processing method, and preliminary experimental results of this system. The systematic measurement error introduced by the limited system bandwidth, bunch length, and bunch charge variation was studied using simulation data. The random measurement uncertainty was evaluated using experimental beam data. The experimental result shows that the longitudinal phase resolution of this system is better than 1.0 ps. The first application, measuring the relationship between the longitudinal phase and bunch charge to determine the energy loss factor, was implemented, and the preliminary result is also discussed.