The trigger and DAQ systems of the Na59 experiment

The Na59 experiment on the CERN SPS-H2 beamline took data during the summers of 1999 and 2000 to perform intercalibration studies of polarization measurement and to test the use of an aligned crystal as a quarter-wave plate. The analysis revealed a proof of concept for the birefringence property of aligned crystals for photons in the 30-170 GeV energy range. The 90-m-long detector for this fixed target experiment had two independent readout schemes: one for more than 120 time-to-digital and analog-to-digital converter channels to obtain tracking and energy information; and another for the readout of the silicon strip detectors to improve vertex resolution. The readout electronics of the Na59 experiment was based on VMEbus and CAMAC systems. Novel data acquisition and online monitoring software were written to work on the commodity hardware (PCs) running mainly the Linux operating system.