| Neutrino and dark matter physics have been the focus of science in recent years. The experiments featuring low background and high sensitivity needs VETO to reduce background. RPC with good performance, low cost and suitable for large area production, has been proposed to as the VETO for JUNO.Resistive Plate Chamber (RPC) is gaseous parallel plate detecotrs that implement eletrodes made from a material with a high volume resistivity. For their good resolution in both timing and positioin measurements over large areas at relatively low cost, RPCs have been widely used in many High Energy and Nulcear Physics experiments, such as at accelerator and in cosmic ray detection. The early RPC electrodes are made of bakelite.Although baklite is available at low resistivity, its resitivity increases during the RPC operation. In addition, bakelite RPCs can be damaged at relatively high temperatrue because the electrode surface facing the gas gap is treated with linseed olil. Compared with bakilite, glass has following advantages:better surface finish, higher surface flatnes, which made glass RPC works stably. But float glass RPC is susceptible to chemical etching by Hydro Fluoride(HF) formed because that Freon(R134a) gas contaminated with moister, which affects the performance stability and lifetime.Four RPCs made of different glasses are tested with cosmic ray here. Fisrt, We study the properties of glasses and that of high-strength, corrosion-resistant, high bulk resistivity were got. Then, complete the RPCs. Next, establish the test platform. Finally, the variation of detection efficiency, single counting rate and dark current curves are given. The results show that RPCs have good performance, but high bulk resistivity lead RPC to require a higher voltage to reach plateau operation, and work in a very low rate experiment. Accoring to the test results and the experiment of JUNO, the RPC module’s efficiency, noise accidental coincidence rate and purity are caculated by theory and simulation, and then design the VETO, which also provides reference to other designs of underground experiments’VETO. |
