Development status of efficiency improvement at the Rare-RI Ring facility

Abstract：

The rare radioactive-isotope (RI) ring is an isochronous storage ring for deriving the masses of extremely short-lived rare RIs. Since the successful commissioning experiment in 2015, the time of flight mass measurement technique has been established through test experiments using unstable nuclei with well-known masses. The experiments for unknown masses were started in 2018. While conducting experiments, we continue to develop equipment to further improve the efficiency and precision of mass measurements. The upgraded kicker system can generate a magnetic field with an extractable duration equivalent to the revolution time of the ring. This is essential for extracting extremely rare events as well as shortening the measurement time compared with that in the initial experiments. New steering magnets make it possible to eliminate an uncertain vertical beam deviation that occurs upstream. As a result, we confirm that the extraction yield is increased. A new resonant Schottky pick-up is able to detect single particles in timeframes on the order of milliseconds. It will be useful not only for beam diagnostics but also for lifetime measurement experiments of extremely short-lived rare RIs planned as a future application.