Design of a MAPS readout electronics prototype for BESIII inner tracker

Abstract

The spatial resolution and the reconstruction efficiency of the main drift chamber of the Beijing Spectrometer III has degraded after more than nine years of operation. An improved new inner drift chamber has been constructed to replace the old chamber in case of the radiation damage. A monolithic active pixel sensor (MAPS) based detector prototype is selected as one of the prototype schemes for the inner chamber upgrade. Design a set of MAPS readout electronics system for the inner drift chamber upgrade. This system can verify the function and performance of the selected MAPS chip and discover the matters needing attention when designing large-scale detectors. The electronics system design is composed of three parts. The first part is flexible printed circuit boards (PCBs) assembled with the MAPS chips. The second part is digital readout boards, which are connected to the flexible PCBs via FPGA mezzanine card cables. The digital readout board realizes the configuration of the MAPS chip register, receives and processes the data output by the MAPS chip, and transfers the processed data to the DAQ device. The third part includes a readout control board and two fan-out boards that used to separately fan out the trigger signal and the start signal to all the digital readout boards. A MAPS readout electronics system consisting of five MAPS based detector prototypes is designed. The system can work stably under the electron beam experimental conditions with a frequency up to 2 kHz and energy ranging from 1 to 5 GeV. The system detection efficiency of the electron beam is $$\sim 95\%$$, and the spatial resolution is $$\sim 5.3\, \upmu \hbox {m}$$ at electron energies of 1 GeV. The design of the electronics system meets the requirements for verifying the performance of the MAPS chips and the technical feasibility of the detector structure.