Tsing Hua Univ, Dept Engn Phys, Beijing 100084, Peoples R China
; Inst Chem Def, Beijing 102205, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
TPC is widely used as a tracking detector in many colliding beam experiments. A GEM-based TPC is under construction and the working gases axe to be considered. The paper summarizes the transport properties of ionization electrons generated in gas mixtures that are suitable to work in TPC with GEM as its endcap detector. The lifetime of electrons, the drift velocity and diffusion are simulated and investigated, with the help of Garfield. With a theoretical analysis, a gas mixture of Argon, CH4 and CF4 is proposed. The performance of GEM with the proposed gas is excellent with regard to the gas gain and energy resolution, which makes it a promising candidate for the future GEM-based TPC.