| From the year 1936 that Carl D.Anderson discovered the muon, it has been 80 years that people do the research on muon. As an elementary particle of standard model, the research on muon is quite important. The property of muon is similar as electron but with high penetrability. Many applications can be achieved by using this special properties, such as muon probe and muon imaging. F.Rasetti directly measured the mean decay lifetime of muon for the first time in 1937. To measure the lifetime of muon is an important method to determine the Fermi coupling constant GF which describe the weak interaction. Nowadays, the Mulan experiment in PSI(Paul Scherrer Institut) measures the accurate muon lifetime with muon beam, and determines the Fermi coupling constant. Except to make the muon beam, we can use the natural muon source in cosmic ray to do the experiment. Traditionally, we measure the muon lifetime with the coincidence circuit which needs the complex experimental facility.In 2010, the HEP laboratory in department of modern physics of our university developed a set of equipment especially to mearsue the muon lifetime in cosmic ray. They proved the feasibility to measure the muon lifetime in cosimic ray with single detector by simulating and analyzing it. The experimental facility has been used in teaching and won the praise of it. Howerver, the time resolution is 20ns limited by the technology at that time.In order to improve the accuracy of the experiment, we decide to design a new electronic system. Due to the specificity of the experiment, we specially design the TDC to measure the time. We have designed two electronics system solutions based on counting-type TDC and vernier-type TDC.The counting-type TDC realizes the resolution of Ins with a range to 16.7ms with the cascade of high speed LVPECL fine counter and a cascaded coarse counter in MCU CY7C68013A. The system test results show that the direct counting-type TDC’s time measurement accuracy is better than 2ns, and the rest of the system is also able to meet the design requirements. We also explore the way to achieve the vernier-type TDC in FPGA. We have designed a complete FPGA logic. The test results show that measurement precision at short time interval can reach 250ps, and the measurement precision at long time interval can reach 3ns after correction.This paper introduces the features of the muon, measurement principle of cosmic ray muon lifetime, the time measurement method and focuses on the design of methods of two electronic system solutions. The cascaded counting-type TDC and the implementation of vernier-type TDC in FPGA are discussed in detail. Finally, we analyze the test results and summary the further work in the future. |
