A Common Readout Driver for the COMPASS Experiment

The main goal of the COMPASS experiment is the determination of the gluon polarization DeltaG/G. To achieve this goal, particles produced in the muon-nucleon scattering process have to be detected. For this measurements particle identification has to be provided as well as track reconstruction over a wide acceptance range. This requires a multitude of different detectors resulting in a large number of detector channels to be read out. The COMPASS DAQ is designed as a tree-structured, fully pipelined system. A central part of this readout system is the CATCH module developed and integrated into the system within the scope of this thesis. The system has been in use for the beam time 2001 with 73 CATCH modules. Performance measurements of the central components have been carried out as part of this thesis. Data of up to 6912 channels were processed by a single CATCH and trigger rates of 115kHz, far above the expected maximum, were successfully attained. Depending on the event size the data rate within the CATCH module was determined, reaching values up to 155MByte/s close to the theoretical maximum. From the CATCH these data were transmitted via optical fibers to the subsequent components of the COMPASS DAQ. In total, 15TByte of data were written to tape. The results of detailed studies concerning the capability of the CATCH module and the whole DAQ show the functionality and quality of the COMPASS readout system. In summary, a high speed data acquisition system which fulfills all current requirements of the COMPASS experiment could successfully be provided. The setup for 2002 comprises a total of 129 CATCH modules. With this configuration the physics goals of the COMPASS experiment can be realized. The proven capability of handling high data rates and trigger rates above 100kHz shows that the CATCH module is prepared for the forthcoming tasks even far beyond the year 2002.