Design and construction of the new BESIII endcap Time-of-Flight system with MRPC Technology

Abstract In order to improve the particle identification capability, the Beijing Spectrometer (BESIII) collaboration has upgraded the End-cap Time-Of-Flight detector (ETOF) based on Multi-gap Resistive Plate Chamber (MRPC) technology. In this paper, the design and engineering development of each part of the project are reported. There are 72 MRPC modules, forming 2 rings. Adjacent modules are staggered placed to avoid dead regions. Each MRPC module contains 12-layer thin gaps to get fast signals with high efficiency and 12 strips to readout the induced signals from two ends, effectively reducing the timing uncertainties from the scattering and positioning. Also, the analog-digital conversion is done near the MRPC and only the digital signals are transferred through thin coax cables, ensuring good signal-to-noise ratio. The complex electromagnetic noises in the BESIII colliding area are well shielded to protect the tiny signals from the MRPC. After careful correction and calibration, the total time resolution of upgraded ETOF system is 65ps.