At the Large Hadron Collider (LHC) at CERN, Geneva, Switzerland, the radiofrequency and transverse damper feedback systems digitize beam phase and position measurements for beam studies. The “observation box” (ObsBox) diagnostic system parasitically captures data streamed directly out of the feedback hardware into a Linux server through an optical fiber link managed by an FPGA. A custom Linux kernel driver retrieves the data from the hardware while a userspace data acquisition and controls software fetches it. This permits processing and buffering of full rate bunch-by-bunch data for around one minute. The system is connected to an LHC-wide trigger network for detection of beam instabilities, which allows efficient capture and processing of signals from the onset of beam instability events. The data is also made available for offline analysis by client applications through interfaces which are exposed as standard equipment devices within CERN’s controls framework (FESA).
Miguel Ojeda, CERN