The construction of China Accelerator Facility for Superheavy Elements(CAFe2) is advancing based on Chinese ADS Front-end Demo Linac(CAFe). However, the original Beam Position Monitor(BPM) read-out electronics of CAFe could not meet the requirements of the CAFe2 BPM probes in terms of quantity and the measurement demands of low-intensity heavy ion beams. In response to this challenge, a high-speed RF switch array supporting multi-channel multiplexing, adjustable gain and filtering was developed. This array served as the RF signal conditioning front-end, together with the RF front-end and digital signal processing platform, to constitute a complete BPM read-out electronics. Laboratory testing validated the feasibility of the high-speed RF switch array and the entire read-out electronics. Compared with traditional read-out electronics, the read-out electronics equipped with the high-speed RF switch array enables the measurement of 32 signals from 8 BPM probes. This approach significantly improves the system's integration and reusability, while offers an efficient solution for implementing multi-channel time-division multiplexing measurement under different beam intensities and operating frequencies. Additionally, by simultaneously accessing signals from multiple BPM probes, this system better supports differential measurement. Overall, the high-speed RF switch array not only meets the requirements of CAFe2 but is also applicable for other accelerators with multiple BPM probes.

The on-line calibration of beam synchronous phase (SP) is crucial for enhancing the operational efficiency of accelerators. Recently, we developed an artificial intelligence (AI)-based beam information measure model that uses transient beam loading information as input while simultaneously predicting beam current and SP. This method employs Long Short-Term Memory (LSTM) to extract multi-dimensional radio frequency (RF) time-series features and incorporates an attention mechanism to evaluate the weights of RF waveforms at different times. The method can work in complex operating conditions such as open-loop, closed-loop, and with or without cavity detuning, and has higher precision and stronger generalization capabilities compared to other online calibration method of SP (such as those based on cavity differential equations or RF beam vector). We validated the consistency of the algorithm results with BPM and BCM measurements on the Buncher of European Spallation Source. Our method achieves an mean absolute error of 0.28° for predicting SP and 0.47 mA for predicting beam current, showing very promising results.

Accurate calibration of beam synchronous phase is essential for the optimal operation of accelerators. Traditional methods, such as the "phase scan method," not only consume significant machine runtime but are also susceptible to environmental disturbances. DESY has introduced a novel method based on "transient beam loading effects" for calibrating synchronous phase. However, this method requires the RF system to operate in an open-loop mode, limiting its applicability in proton linear accelerators. In this paper, leveraging the classical cavity differential equations, we propose a new method based on the steady-state "vector diagram of beam-induced voltage "for calibrating beam phase. This method enables on line calibration of beam phase and beam current under closed-loop operation of the radio-frequency cavities. We validated our approach on the CAFe (the Chinese ADS Front-end proton facility) at the Institute of Modern Physics, China, and the European Spallation Source. The measurement errors for beam current and phase using our method and the beam diagnostic system were 2% and within ±1 degree, respectively. Experimental results confirm the effectiveness of our method as a new solution for on line calibration of beam synchronous phase.

Online beam monitoring is crucial for enhancing the efficiency and availability of high-power accelerator operations. While real-time monitoring of transverse beam parameters is commonly employed in modern accelerators, there is a scarcity of online measurement techniques for longitudinal beam characteristics. We are currently developing an online tool for measuring fundamental longitudinal beam parameters: synchronous phase and energy gain. This endeavor is founded upon a comprehensive understanding of beam-RF cavity interactions, facilitated by advanced hardware platforms, flexible software applications, and computationally intensive algorithms. Validation of our measurement methods has been conducted using beam and RF data acquired during the latest beam commissioning at the European Spallation Source (ESS). This validation encompassed both single-cell and multi-cell cavities, affirming the reliability and feasibility of our techniques. Furthermore, comprehensive comparative analyses were performed, aligning results from various measurement methodologies with theoretical calculations, enhancing our understanding of measurement accuracy. Our ongoing research aims to provide accelerators with robust and real-time monitoring tools for longitudinal dynamics aspects based on beam and RF cavity interaction, thereby ensuring optimal efficiency and performance in high power accelerator operation.