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Photoproduction experiments of hadrons using the γ ray from 1.5 to 2.9 GeV have been performed at the SPring-8/LEPS2 facility. We are now taking data with a large acceptance calorimeter (BGOegg) and a forward TOF array consisting of RPCs[1]. After the BGOegg experiment, we will start a new experiment using LEPS2 solenoid spectrometer. The detector system inside of the LEPS2 solenoid msagnet is now under construction and development. The long RPCs with 2-m lengths will be used as barrel TOF counters. The LEPS2 solenoid magnet has a large cylindrical bore whose size is approximately two meters both in diameter and length. Each RPC covers a polar angular region from 30 to 120 degrees in the laboratory system, where the momentum of produced particles are almost less than 1 GeV/c. The particle identification in this momentum region is done by time-of-flight measurement with the RPC. The distance from the target to the RPC is from 1 m for 90 degrees to 2 m for 30 degrees. Since the flight distance is rather short, we need a RPC-TOF system with a high time-resolution around 50ps. In order to reduce the number of readout channels, we are developing an RPC with a 2-m length, based on the 1-m RPC which have been used in the BGOegg experiment[1]. Since the commercially available size of glass and PCB foundation on which the readout strips are printed is only 1 m, we have to connect two glasses and PCB foundations to make the RPC with a 2-m length. In order to construct such RPCs, we need to study the following items: 1. The stability against discharges at the seam of glasses. 2. The time resolution of a readout strip which has a joint. From these viewpoints, we produced two small prototype RPCs which have different joint structures and performed test experiments using the LEPS2 beamline in February 2015. We are now making a 2-m RPC based on the result of the test experiment and will make evaluation of its various performances. we will report the results of these development of the RPCs. [1] N. Tomida, et al., JINST 9 (2014) C10008.
