Research On Multi-channel Data Acquisition System For DIRC-Like Detector

DIRC-Like detector is an important type of Cherenkov detector.Compared with the traditional Detection of Internally Reflected Cherenkov light(DIRC)detector,the DIRC-Like detector can obtain the arrival time of Cherenkov light while maintaining the detection of the internal total reflection Cherenkov light.Utilize the detected arrival time of Cherenkov light,we can rebuild the propagation track of the Cherenkov light in the radiator to obtain higher particle discrimination capabilities than traditional DIRC detectors or Time of Flight(TOF)detectors.As the main application of this thesis,the DIRC Time-of-Flight(DTOF)detector is one kind of DIRC-Like detector,which is part of the Particle Identification Detector(PID)on the pre-research-stage Super Tau-Charm Facility(STCF).In order to fulfill the target of particle discrimination ability of the PID system,the DTOF detector needs to achieve 3σ separation of π/K within the range of 2 GeV/c momentum.Correspondingly,the timing precision per track of the DTOF detector needs to be better than 50 ps,and the timing performance of the readout electronics of the DTOF detector needs to achieve a timing precision of 15 ps,which makes the design of the DTOF electronics system very challenging.The DTOF detector uses a Micro-Channel-Plate Photomultiplier Tube(MCP-PMT)as the photoelectric conversion device,and its output signal has a fast leading edge and narrow signal pulse width.In addition,the DTOF detector contains a total of 6912 detector channels.Therefore,It is a quite challenging design to realize the high-performance timing readout of the multi-channel DTOF detector where the high-bandwidth front-end readout capability,the high-precision timing measurement capability and the high-speed data transmission structure are to be achieved.This thesis focuses on in-depth research on these highperformance requirements.After fully investigating various implementation methods,this thesis selected the"leading edge discriminating(LED)+FPGA TDC" timing method based on the characteristics of the DTOF detector itself(FPGA:Field Programmable Gate Array;TDC:Time to Digital Converter).In view of the fast rising time and the narrow signal pulse width of the MCP-PMT selected by the DTOF detector,a multi-edge TDC coding scheme with anti-bubble capability is proposed in this thesis to encoded the threshold time with high-precision.Furthermore,this thesis proposes an implementation scheme of FPGA TDC with high timing measurement precision.Using this scheme,the key timing-measurement module in the timing-measurement system can achieve a 3-ps precision.In addition,to lower the threshold for using high-performance FPGA TDC,this thesis completed the packaging of two high-performance FPGA TDC IP(Intelligent Property)with the help of a new method of implementing TDC constraints.Utilizing the new constraint method,not only the stability and reliability of the TDC crucial tapped-delay-line structure are retained,but also the flexibility,versatility and ease-ofuse of the TDC IP are increased.The performance of the packaged TDC IP is equivalent to that of the original TDC module.Considering that the DTOF electronic system has requirement of realizing the clock synchronization and data transmission at the same time,so the clock synchronization scheme is chosen to use the same data link as the data and clock transmission in the paper.Furthermore,this thesis also designs a hardware trigger selection system,a data grading concentrating scheme and the data transmission protocol,which is based on the structure of the front-end readout circuit,for the data transmission of the multi-channel detector.The protocolized hierarchical data transmission structure finally realizes the data concentrating of all detector channels.It is worth noting that the designed electronic system is not satisfied with only meet the requirements of the current DTOF detector,it is actually a set of scalable general-purpose DIRC-Like detector data acquisition system that can be used in particle physics experiments.After completing the overall scheme design of the DIRC-Like detector electronics,this thesis constructs a 128-channel DTOF prototype detector according to the overall scheme design.The prototype detector contains all the technologies that need to be realized in the overall scheme design.This lays a solid foundation for the realization of the overall scheme design of the system.At the end of this paper,some performance verification tests of the key functional modules in the prototype detector and the cosmic ray test of the prototype detector are carried out.The verification test result shows that the Root Mean Square(RMS)value of the timing measurement precision of the front-end readout board itself is about 10 ps,and the peak-to-peak value of the clock synchronization accuracy between different boards is better than 15 ps.In addition,the data transmission rate between the front-end board and the first-stage data concentrator is evaluated to be 3.5 Gbps and can be further improved,while the average data transmission rate from the first-stage data concentrator to the second-stage data concentrator is 5.8 GB/s.The results of the verification test show that the design performance of the electronic system has reached the expected goal.The cosmic ray test of the prototype detector has finished the channel detection efficiency test and the fired channel ratio test,and the actual measurement results are basically consistent with the Geant4 simulation results,which indicates that the DTOF detector and the electronic system in the joint test is basically functioning well.In next test phase,the DTOF detector system needs to be calibrated thoroughly from the detector to the electronics to correct the various mismatches between the detector channels and between the electronics channels.Additionly,the research team of detector also needs to study the TOP reconstruction algorithms to reconstructed the trajectory of Cherenkov light to help obtain better timing measurement precision.