Research Of Trigger Electronics For LAWCA Experiment

The Large Area Water Cherenkov Array (LAWCA) aims at the physical target of gamma astronomy at high energies. The LAWCA detector consists of900Photon Multiplier Tubes (PMTs) which are scattered in a150×150m2area. Every3×3PMTs form a group and their outputs are fed to one Front End Electronic (FEE) module for time and charge information measurement.The data generated by FEE consists of valid signals and background noises. To eject the noises, the trigger electronics is demanded.Due to the complicated phenomena of cosmic ray showers, the flexibility of the trigger electronics must be guaranteed. During this research, we have made an investigation of the trigger electronics in other Water Cherenkov experiments. We also studied the "triggerless" total data readout method in the collider experiments.Invoked by the idea of hardware triggerless architecture and based on our survey, a scheme of LAWCA trigger electronics is designed with all data transferred to a trigger module for processing. In the trigger module, one single FPGA device is employed to carry out the real-time trigger processing.Compared with traditional trigger electronics receiving only part of the data from front end, much more detailed information can be utilized to achieve a better trigger flexibility. It also eliminates the need of trigger signals fed back to front end; thus better system simplicity can be accomplished. Based on the abundant programmable inner connections and logic resources in the FPGA, reconfigurable trigger electronics can be realized; meanwhile, the trigger algorithms can be upgraded online with future modifications. Besides, because a large part of fake events can be rejected by the trigger electronics, the requirement on DAQ is significantly reduced.Based on this scheme, a prototype of LAWCA trigger electronics is implemented. It could verify the correctless of this scheme and it could also be recognized as a good technical foundation for future engineering. A high capacity Xilinx Virtex-6series FPGA XC6VLX365T is adopted as the kernel device for trigger and data selection.10fiber based serial transmission channels are built; each supports a data transmission rate at1.25Gbps to accommodate the5.4Gbps system average data rate.The Gigabit Ethernet interface, which is used for triggered data transmission, is implemented with virtex-5XC5VFX70T FPGA and corresponding PHY chip. The online reconfiguration of this prototype is realized base on the VME bus. With these techniques, the requirements of the trigger electronics are met.This trigger electronics prototype is designed and evaluated based on a basic trigger pattern. According to this basic trigger pattern, the trigger algorithm and FPGA logic is developed. And then some initial tests are also carried out. Simulation data generated by physicists is imported to verify the correctless of the trigger processing logic. The simulation data is processed by MATLAB and the prototype independently. The results from these two are fully matched, which indicates that the prototype functions well with the trigger logic strictly following the expected trigger pattern.In the final chapter, the scheme and prototype research on the LAWCA trigger electronics is concluded. Some discussions about the future detector array layout modification are given. Some improved schemes on the TCP based Ethernet data transmission are also presented.