Studies of Charge Sensor and Gas Properties of an Ion-TPC for N$$\nu$$DEx Experiment

Searching for the neutrinoless double beta decay ( $${0{\nu}{\beta}{\beta}}$$ ) is crucial for studying the properties of neutrinos. Time projection chamber (TPC), with good energy resolution and track information, is an available technique. In $$\textrm{N}\nu\textrm{DEx}$$ experiment, we proposed a TPC with high pressure $${}^{82}\textrm{SeF}_{6}$$ to search for $${0{\nu}{\beta}{\beta}}$$ of $${}^{82}\textrm{Se}$$ , which will be deployed in China Jinping Underground Laboratory. To achieve best energy resolution as possible, the readout plane consisting of about 10k custom-designed Topmetal-S chips are being developed for direct charge collection. The effective noise charge of the current generation Topmetal-S chip is presented, depending on the operational point and test condition. Understanding the gas properties is important for $$\textrm{N}\nu\textrm{DEx}$$ experiment. With laser beam and a small TPC, we observed the minority and majority charge carriers in structurally similar $$\textrm{SF}_{6}$$ gas with electric fields from 735 to 1351 V/cm and pressures from 377 to 750 Torr, which paves the way for future study of the $$\textrm{SeF}_{6}$$ gas.