  The Cooling Storage Ring (CSR) External-target Experiment(CEE) is the first
multi-purpose nuclear physics experimental device to operate in the GeV energy
range at the Heavy-Ion Research Facility(HIRFL-CSR) in Lanzhou, China. The
primary goals of the CEE are to study the bulk properties of dense matter and
to understand the quantum chromo-dynamic (QCD) phase diagram by measuring the
charged particles produced in heavy-ion collisions at the target region with a
large acceptance. An inner time of flight (iTOF) system has been proposed to
measure the multiplicity, angular distribution, and time information of the
charged particles. Herein, we introduce the performance requirements of iTOF
according to calculations and GEANT4 simulations. The proposed system is
characterized by high granularity and time performance, hence, the conceptual
design of the iTOF wall adopts high granularity Multi-gap Resistive Plate
Chambers (MRPC) with a time resolution of around 30 ps. To evaluate the MRPC
design, the cosmic ray test was performed. A timing resolution better than 28
ps and an efficiency better than 98% has been achieved for MIPs, as interpreted
by the cosmic ray GEANT4 simulation of time jitter components.
