小型活性靶时间投影室性能研究

Performance Study of Small Active Target Time Projection Chamber

本文设计了使用64路一维读出条的小型活性靶时间投影室,并对其性能进行了测试,其气体室的灵敏体积为10cm×10cm×14cm,通过连接2层厚气体电子倍增器进行电子放大.为改善场笼边缘的电场不均匀性,引入场笼环的设计结构.当场笼环加高压为-950 V时,测得α粒子沿漂移电场方向的径迹位置分辨小于0.2 mm,径迹角度分辨小于0.6°,时间分辨小于20 ns.活性靶时间投影室的工作气体为96%He+4%CO2.实验中也观察到了清晰的α粒子在He气上的弹性散射事件.

An active target time projection chamber(AT-TPC) was designed and its performance was tested. The chamber has an active tracking volume of 10 cm×10 cm×14 cm, which is equipped with two layers of thick gas electron multiplier(THGEM) and connected to 64 readout strips. A guard ring was also integrated above the GEM foils in order to adjust the electric field in the gas vessel, which allowed to improve the overall performance of the system. At a guard ring HV of-950 V, the AT-TPC achieved a tracking position resolution better than 0.2 mm, an angular resolution below 0.6° and a time resolution better than 20 ns, obtained from α particles test. By using the gas mixture 96%He+4%CO2 as the sensitive working gas as well as the target material, the α+α elastic scattering events can be clearly imaged.