Prototype of time digitizing system for BESIII endcap TOF upgrade

TL;DR

This paper presents a prototype time digitizing system for the BESIII endcap TOF upgrade, demonstrating high time resolution and data throughput suitable for particle physics experiments.

Contribution

The paper introduces a novel distributed architecture for the ETOF digitizing system that improves performance without modifying existing barrel TOF structures.

Findings

Time resolution less than 20ps in lab tests

Complete system time resolution under 45ps in beam tests

Data throughput reaching 92Mbps to DAQ

Abstract

The prototype of time digitizing system for the upgrade of BESIII endcap TOF (ETOF) is introduced in this paper. The ETOF readout electronics has a formation of distributed architecture that hit signal from multi-gap resistive plate chamber (MRPC) is signaled as LVDS by front-end electronics (FEE) and sent to the back-end time digitizing system via long shield differential twisted pair cables. The ETOF digitizing system consists of 2 VME crates each of which contains modules of time digitizing, clock, trigger and fast control etc. The time digitizing module (TDIG) of this prototype can support up to 72 electrical channels of hit information measurement. The fast control (FCTL) module can operate at barrel or endcap mode. The barrel FCTL fans fast control signals from the trigger system out to endcap FCTLs, merges data from endcaps and transfers to the trigger system. Without modifying the barrel TOF structure, this time digitizing architecture benefits for improving ETOF performance without degrading barrel TOF measuring. Lab experiments show that the time resolution of this digitizing system can be less than 20ps, and the data throughput to DAQ can be about 92Mbps. Beam experiments show that the complete time resolution can be less than 45ps.