The Research Of MRPC Performance For Beijing Spectrometer ? Endcap Time-of-fight Detector Upgrade

Beijing Spectrometer is a huge experimental apparatus that running in ?-charm en-ergy range, and engaging in searching for the physics in r-charm (such as light hardron, charm physicsm, lepton physics, c measons,etc), which are crucial for us to understand the Standard Model theory and search for new physics. According these physical goals, BESIII should have a good capability to identify particles. The Time-Of-Fight (TOF) detector plays a crucial role in the BESIII experiment, due to its capability of identifica-tion to charge hadrons:tt meason, K meason and proton. The current TOF at BES? consists of scintillator(BC404) and PMT(Hamamatsu R5924), and for ? the resolution could be acheived 90 ps at barrel TOF, while 138 ps at endcap TOF and 2a level ?/K seperation can reach 1.1 GeV. There are many reasons that deteriorate the endcap TOF, such as only one layer design, single end readout, and multihits generated from the elec-tron hits on the cable of electronics of MDC, which worsen the time heavily. In order to improve the hadrons identification capability, it is necessary to upgrade BESIII ETOF.The Multigap Resisitive Plate Chamber is a new type of gaseous time-of-fight detector, with high detection efficiency, excellent time resolution, relatively low cost and insensitive to the photon and the magnet field, and as the new generation of time of fight detector, has been widely applied as the particles identification detector in the high energy physics experiments.2012 BESIII collaboration started to upgrade the ETOF with MRPC technology. For the MIPs intrinsic time resolution of MRPC is demanded better than 60 ps and the detection efficiency is> 98%, the time jitter of the electronics system is< 25 ps. The entire ETOF system resolution for 800 MeV momentum ? should be 80-100 ps which will extend the ?/K seperation (2a) to 1.4 GeV. And all of other sub-systems such as DAQ, gas, slow control system should guarantee the steady performance.The author, as a joint training graduate student, study and work together with oth-er ETOF stuffs who are participating the efforts on ETOF upgrade at BESIII in BEPC national laboratory, Chinese Academy of Science. The MRPC detector had been un-derwent the beam test experiment at BEPCII E3 line. There were two sections. One included three scans for 800MeV/c momentum proton:high voltage scan, threshold scan and pad scan. The results indicated that performance of MRPC arrived at the plat plain when the high voltage>7000 V with resolution-37 ps and efficiecny 98%, in thresold scan the efficiency fell a little and the resolution became worse with step 0.17 ps/mV. And in pad scan, efficiency> 98%, the resolution was from 34 ps to 47 ps. The other experiment section is the momentum scan from 0.6GeV-1.2GeV for both ? and proton, and the results indicated that the efficiency kept steady and res-olution was different, the proton's became good while ?'s almost stayed at same. We made some reasonable explanation for the difference between them.The author also participated some electronics tests, including the resolution anal-ysis under electronics system self-testing mode, the radioactivity resisting test and FEE temperature measurement test. The resolution under self-testing was 25 ps, and it kept bellow 30 ps in the radioactivity dose environment, the temperature of main circiut in FEE board was sensitive with the environment's changing. All results indicated that the entire ETOF electronics system worked steady with good performance.To verify the working performance of ETOF/MRPC at BES1II,2 MRPCs were installed at the west endcap to substitute 4 old TOF detector and operated with other detectors at BESIII with physics runnings. The author had spent plenty efforts on 2 MRPCs study, such as high voltage scan and threshold scan. The results indicated that voltage ±7000 V and threshold 110 mV are better, and the strips'performance:with average resolution 45-65 ps and average efficiency>96%, while performance at different position along strip:resolution was 50-55ps and efficiency 97.5%. At November 2015 the BES? ETOF upgrade had been successfully done and operated with new physics runnings. The preliminary data analysis indicated that after ETOF upgrading the resolution acheived at 60 ps and efficiency could reach 98%, and the uniformity and consistency of the ETOF performance can be satisfied and guaranteed. Comparing-90 ps resolution at ALICE TOF/MRPC and-80 ps at STAR TOF/MRPC, ETOF at BES??60 ps reached world advanced level.