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

•We have developed Time-of-flight detectors for the Rare-RI Ring.•Measurements to evaluate a time resolution and a detection efficiency have been performed using alpha particle and heavy ion beams.•Preliminary time resolution is about 130ps and detection efficiency is about 56% for the heavy ion beams. 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 (100mm×50mm2 and 60μg/cm2) is used as a sensitive material. The time resolution of σ≈130ps, the detection efficiency about 56% and a position dependence of the TOF about 1ns 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.