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Description
To measure the resonance energies of $^{5,7}$H, an experiment using the $^{6,8}\mathrm{He}(p,2p)$ reaction in inverse kinematics has been planned at the RIBF SAMURAI facility.
In this experiment, it is necessary to detect Z = 1 $^{3}$H particles in an environment with a Z = 2 beam intensity exceeding 1 MHz.
To satisfy this requirement, we introduced the scintillating fiber detector.
The detector consists of three layers, X, Y, and U, each composed of 320, 224, and 320 square plastic scintillating fibers (0.75 mm × 0.75 mm), respectively.
The U layer is tilted by 45°, which enables two-particle measurements.
The optical signals from these fibers are read out by MPPCs and acquired by the newly introduced TOFPET2 ASIC from PETsys Electronics S.A.
In May and June 2025, test experiments were conducted at SAMURAI.
Using 250 MeV/u $d$ and $^{3,4}$He beams, we measured the detection efficiency relative to plastic scintillators installed upstream and downstream of the detector.
In December, the rate tolerance of the detector was investigated at the RARiS Aobayama facility of Tohoku University under high-rate beam conditions ranging up to $\sim$2 MHz.
In this experiment, gate settings were optimized to suppress background, while enabling integration with the RIBF DAQ trigger system.
Furthermore, event building with other detectors was successfully achieved using timestamp-based data merging during analysis.