Time-of-flight detector applied to mass measurements in Rare-RI Ring

A large time-of-flight (TOF) detector has been developed for the Rare-RI Ring. This detector consists of a Multi Channel Plate (MCP) and a carbon foil. Secondary electrons from the carbon foil are transported to the MCP by crossed electric and magnetic fields. In order to cover the beam size of the ring, a large and thin carbon foil (100 mm × 50 mm2 and 60 μg/cm2) is used as a sensitive material. The time resolution of σ≈130 ps, the detection efficiency about 56% and a position dependence of the TOF about 1 ns are obtained. A calculated position dependence of TOF adopting experimental (inhomogeneous) electric field and a homogeneous magnetic field is in agreement with the experimental one. These results suggest that the homogeneity of electric field is important to improve the time resolution in the large size detector.