Development of Sealed MRPC with extremely low gas flow for muon tomography

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 (C2F4H2, SF6 and i-C4H10.) 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 C2F4H2 has been designed and studied. The prototype has a sensitive area of 500mm . 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.