A heavy-ion collision facility called the cooler storage ring (CSR) external-target experiment (CEE) is scheduled in Lanzhou, China. The time measurement of the charged particles at the forward angle will be conducted by the external time-of-flight (eTOF) subsystem, which is built with multigap resistive plate chambers (MRPC). This work describes the tasks, performance criteria, detector layout, and prototype test results while outlining the technical design and development status of the CEE-eTOF wall. The effectiveness of the wall design has been validated using a FairRoot-based simulation, which is an essential part of the verification. With a $$3.2 \times 1.6~\textrm{m}^2$$3.2 × 1.6 m 2 coverage, a 60 ps overall time resolution, and a 2.6 m distance from the collision point, the eTOF wall enables the particle identification, system triggering, and event selection in cooperation with other related detectors. A novel structure called sealed MRPC will be applied to the subsystem. The design considerations of this type, prototype test, and results are also described in this paper.

This work reports the latest observations on the behavior of two Multigap Resistive Plate Chambers (MRPC) under wide high-luminosity exposures, which motivate the development and in-beam test of the sealed MRPC prototype assembled with low-resistive glass. The operation currently being monitored, together with previous simulation results, shows the impact of gas pollution caused by avalanches in gas gaps, and the necessity to shrink the gas-streaming volume. With the lateral edge of the detector sealed by a 3D-printed frame, a reduced gas-streaming volume of ~170 mL has been achieved for a direct gas flow to the active area. A high-rate test of the sealed MRPC prototype shows that, ensuring a 97% efficiency and 70 ps time resolution, the sealed design results in a stable operation current behavior at a counting rate of 3–5 kHz/cm². The sealed MRPC will become a potential solution for future high luminosity applications.

The future fixed target high-rate compressed baryonic matter (CBM) experiment is one of the experimental pillars of the Facility for Antiproton and Ion Research (FAIR) located in Darmstadt/Germany. In order to provide an excellent particle identification (PID) of charged hadrons, the CBM-time-of-flight (TOF) group has developed a concept of a 120 m $$^2$$2 large TOF wall with a system time resolution below 80 ps based on multi-gap resistive plate chambers (MRPC). Currently, timing MRPC systems are operated with a gas mixture based on tetrafluoroethane (R134a, C $$_2$$2 H $$_2$$2 F $$_4$$4 ) with additions of few vol% quencher gases, e.g., sulfur hexafluoride (SF $$_6$$6 ) or/and isobutane (i-C $$_4$$4 H $$_10$$1 0 ). Unfortunately, these gas mixtures have a high global warming potential (GWP) in the order of 1500, and therefore, strategies to reduce the environmental impact have to be developed. The various possibilities, including studies on eco-friendly gases, and the considered strategy by the CBM-TOF group will be elaborated in this article.