Study of gas properties for GEM-based TPC

TPC is widely used as a tracking detector in many colliding beam experiments. A GEM-based TPC is under construction and the working gases are 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.