A data aquisition system for abnormal RF waveform at SACLA

At the X-ray Free Electron Laser (XFEL) facility, SACLA, we developed a data acquisition (DAQ) system to capture an abnormal radio frequency (RF) waveform for the diagnosis of suddenly occurring failures. The DAQ system consists of VME systems, a cache server, and a NoSQL database system, Apache Cassandra. When the VME system detects an abnormal RF waveform, it collects all the related waveforms of the same shot. The waveforms are stored in Cassandra through the cache server. Before the installation to SACLA, we ensured the performance with a prototype system. We installed the DAQ system into 34 LLRF VME systems at SACLA and six LLRF VME systems at a dedicated accelerator for the SACLA wide-band beam line. The DAQ system successfully acquired rare abnormal waveforms and contributed to the investigation of the failure analysis. (author)