Trigger system prototype for BaF2 detector array at CSNS-WNS

Abstract

A segmented 4π detector array composed of 92 BaF2 crystals is under development for neutron capture cross-section measurements at CSNS-WNS (White Neutron Source at China Spallation Neutron Source). Each of the detector channels will be recorded by a high performance digitizer, which will produce huge amount of raw data and bring challenges to data acquisition. To decrease the data rate, a trigger system based on the PXI Express (PXIe) platform that helps to filter desired signal out of the backgrounds is proposed in this paper. The trigger system is used to obtain the relevant hit information from all the detector signals, including the total energy (ESum) and the channel hit status (NHit). The trigger system is located in 4 PXIe chassis, together with the readout electronics. Between different chassis, the trigger signal is encoded and distributed using the high speed serial link. While within the same chassis, trigger signal is fanned out via PXIe backplane star trigger bus. Exploiting these methods, the number of distributing cables decreases drastically and the trigger system is much more compact. Test results exhibit the feasibility of this proposed method.