Development Of VME-based RPC Electronics For Daya Bay Reactor Neutrino Experiment

The Daya Bay Reactor Neutrino Experiment aims to measure the neutrino mixing angle θ13to a precision of0.01with90%confidence. Because the major part of the background comes from cosmic ray, the anti-coincidence detectors, which are composed of the water Cherenkov detector and the Resistive Plate Chamber (RPC) detector, are designed to identify neutron background generated by the cosmic ray. This thesis introduces the design and implementation of the VME-based RPC electronics, and gives the test results analysis. The first chapter presents the background of the neutrino experiment and the overview of the Daya Bay reactor neutrino experiment. The second chapter introduces the design requirements and the architecture of the VME-based RPC electronics. The third chapter is about the design and development of the trigger sub-system of the RPC electronics, and the hardware and firmware designs of the RPC Trigger Module (RTM) are especially introduced. And the fourth chapter is about the design and development of the readout sub-system of the RPC electronics, and the design and upgrade of the Readout Module (ROM) are especially introduced. The test results of the RPC electronics are given in the fifth chapter. The sixth chapter summaries work in this thesis and looks forward to the future work.According to the design requirements of the RPC electronics, we designed the VME-based RPC electronics that are composed of trigger sub-system and readout sub-system after summing up the Muon readout systems of other high energy physics experiments. The trigger sub-system consists of Front-End Card (FEC), Readout Transceiver (ROT) and the RTM. The FEC collects the RPC strip output signals and generates coincidence signals based on the strip output signals. ROT is responsible for the conversion of the data transmission between the RTM and the FEC. The RTM generates local triggers based on the coincidence signals from the FECs and sends these local triggers back to the related FECs. Using the Field Programmable Gate Array (FPGA), the RTM forms a trigger map corresponds to all the RPC modules in the experiment hall to fulfill the adjacent trigger mechanism. The adjacent trigger mechanism is that when there is a coincidence signal from one FEC, the trigger sub-system should generate a local trigger for this FEC, and also for each of the adjacent FECs. In order to evaluate the trigger performance and assess the background, the RPC trigger system must also be capable of accepting a cross trigger from the master trigger system. The readout sub-system consists of Front-End Card (FEC), Readout Transceiver (ROT) and the ROM. The readout sub-system uses FPGA to achieve the real-time data readout. Both ROM and RTM are9U size VME modules. The RPC electronics transfer the event data and trigger data to the DAQ system via the VME bus by using the Chain Block Transfer (CBLT) mode.The anti-interference performance has been fully considered during the design of the system architecture. Following measures are adopted:●The connection between FEC and ROT adopts the star connection.●Between ROT and RTM (or ROM), the optical fiber transmission is used.●The shield cable is used between FEC and ROT.●The ROT and FEC are shielded by using chassis and shield box.●Adopting the anti-interference transmission design for the critical signals such as the local trigger.In order to verify the functionality and performance of the RPC electronics system, a series of test have been completed. Test results indicate that the RPC electronics fully meet the design requirements. The joint test with the RPC modules in Daya Bay near hall indicates that the RPC electronics have stable operation in the experimental field and meet the demand of detector data readout.The installation of the RPC electronics in the three experimental halls in Daya Bay has been completed. The first result from Daya Bay:Discovery of a new kind of neutrino transformation is announced on March8,2012by Yifang Wang, the spokesman for the international cooperation group in Daya Bay neutrino experiment.The work of this thesis has the following characteristics:●The front-end of the RPC electronics adopts the star connection.●The combination of system trigger and local trigger is adopted in RPC electronics.●Both event data and trigger data contain the timestamps that are synchronized with other detector systems and Global Positioning System (GPS).●The UNIX second and nanosecond in the timestamp are added separately to the event data. The UNIX second is added to the event data on FEC and the nanosecond is added to the event data on ROM. The UNIX second error caused by the data transmission is solved by second parity check.●A polling readout method is adopted to achieve the real-time data readout of multiple channels.●FPGA are widely used in the RPC electronics to buffering data and achieve the local trigger function.