Development of a prototype TPC with CF4 & GEM readout for heavy ion collision

This article describes the R&D of Time Projection Chamber (TPC) for heavy ion collisions. A prototype TPC was developed for the R&D of CF₄ gas. It has a capability of using GEM readout. The characteristics of CF₄ is a small diffusion coefficient and large drift velocity. It is suitable for our purpose of heavy ion collisions. Characteristics of CF₄ gas, such as a diffusion coefficient and a drift velocity, were measured with the prototype TPC. In addition, a tracking resolution and sensitivities of double track separation and particle identification were measured using MWPC and pad readout. We achieved position resolution of 100 μm with 2.5 mm square pads. For future use of a TPC readout, we have produced Gas Electron Multiplier (GEM) using a plasma etching method. Gain of the GEM was measured as a function of an applied voltage with an X-ray source. A gain of 104 was obtained in argon mixture gases.