New RF trip diagnostic system of BEPCII

The upgrade project of the Beijing Electron Positron Collider (BEPCII) is a high-current electron–positron collider with beam intensity close to 1A. The RF system plays an important role in providing energy for the beam, compressing the beam length and maintaining beam lifetime. Once the RF system shuts down the RF power for various reasons, the accelerator will stop working. In order to determine which reason causes the RF trip, a new RF trip diagnostic system was built based on the NI PXI system. The new RF trip diagnostic system is used to collect the data of the forward power, reflected power, cavity voltage, and beam current in a period of time before and after the RF trip event happens. The system uses LabVIEW as the control software, which conducts I/Q sampling of down-converted RF signals directly, then calculates the amplitude and phase of each RF signal, and plots the change curve. The data and figures are stored in the disk and MySQL database. The change curve can be replotted by the data browser which developed by the Python or PHP language. Through the analysis of the RF trip data and figures that produced by the new RF trip system, it can be clear whether the RF trip is caused by the RF system, so as to locate the reason of the RF trip more quickly and improve the reliability and stability of the machine operation.