Development Of Secondary Electron Time Detector For Ion Beams

A time detector is under development for the mass measurement with the Rare-RI (radioactive iso- tope) Ring at the RI beam factory (RIBF) in RIKEN. To perform successful mass measurement, a time detector requires a small energy loss of the ion beams, a good time resolution, and a suf- ficient detection efficiency. To satisfy these requirements, our time detector utilizes isochronous transport of the secondary electrons emitted from a thin foil. The isochronous transport of the electrons from the foil to the micro-channel plate (MCP) detector is provided by the crossed electromagnetic field. To improve the detection efficiency, the transport time of the electrons is reduced by a factor of two using a strong magnetic field. An experiment to test the performance of the time detector was carried out with heavy ion beams. The time resolution was σ < 100 ps with a maximum detection efficiency of 99% for heavy ion beams. The details of the detector are presented in this contribution.