Recently, a stability of Data Acquisition System (DAQ) has become a vital precondition for a successful data taking in high energy physics experiments. The intelligent, FPGA-based Data Acquisition System (iFDAQ) of the
COMPASS experiment at CERN is designed to be able to readout data at the maximum rate of the experiment and runsin a mode without any stops. DAQ systems fulfilling such requirements reach the efficiency up to 99%. The newly
introduced continuously running mode enables to collect data without a necessity of any other user intervention.Such mode affects all processes of the iFDAQ with high emphasis on timing and precise synchronization. However,
every undesirable interruption of data taking can potentially result in a possible loss of physics data. Running24/7 puts stress on reliability and robustness of the system. Therefore, the improvement of the iFDAQ stability had to come first. The continuously running mode and the improved iFDAQ stability helped to collect more physicsdata in the Run 2017. In the paper, we present the continuously running mode in more detail and discuss the overall iFDAQ stability.
An on-line data acquisition system for particle physics experiments using PDP-11 computers