A: A muon tomography system named Tsinghua University cosmic ray Muon tomography (TUMUTY) facility based on Multi-Gap Resistive Plate Chamber (MRPC) has been built in Tsinghua University in 2012. Our research is focused on developing a muon non destructive testing system that will be used in homeland security operations such as custom inspections, airport security and so on. The gases normally used to operate MRPCs (C 2 F 4 H 2 , SF 6 and i-C 4 H 10 .) have a high global warming potential. Eco-gas is a choice to solve this problem, but it will greatly increase the overall cost of the system. On the other hand, we can also reduce the greenhouse pollution by lowering the airflow to the chamber. In this paper, a sealed MRPC prototype filled only with C 2 F 4 H 2 has been designed and studied. The prototype has a sensitive area of 500 mm • 500 mm, and it can work very well at an extremely low gas flow of 0.5 ml/min. Moreover, we also studied the performance of the detector under a mode without gas exchange. The result shows that the detector can work for more than 60 hours without gas exchange. Under this mode, the average gas flow of the detector reduces to 0.05 ml/min.

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A: Muon tomography system built by 2-D readout high spatial resolution Multi-gap Resistive Plate Chamber (MRPC) detector is a project in Tsinghua University. In 2013, we had developed a prototype of muon tomography system named TUMUTY, now we try to develop larger sensitive area and smarter structure MRPC detector to upgrade the system to a car detection system, which is used to detect high Z metal hidden in cars or other objects. For the system, 2 layers ×3 detectors are needed to get the incident particle's track, and the setting is the same for the outgoing track. Therefore, there will four layers containing twelve detectors in total, and its detection area will reach 1 × 3 m 2 . An encoding readout method is suggested to minimize the number of the readout electronics, which reduces the complexity and the cost of the system. In this paper, we measured the performance of 12 MRPCs used for the system.