Abstract
We describe the rare-RI (radioactive isotope) ring at the RI Beam Factory (RIBF). The main purpose of the rare-RI ring is to measure the mass of very neutron-rich nuclei, the production rates of which are very small (hence ‘rare RI’) and the lifetimes of which are predicted to be very short. In the rare-RI ring, there are two innovative pieces of apparatus: individual injection, which can realize the injection of 200 A MeV rare RIs one by one, and a cyclotron-like storage ring, which allows high isochronous magnetic fields with large angular and momentum acceptances. With these devices, we will achieve a 10−6 mass resolution, and will be able to access rare RIs, the production rate of which is down to 1 event/day/pnA. Construction of the rare-RI ring started in fiscal year 2012.
Highlights
The r-process nucleosynthesis is considered to be the origin of about half of all elements heavier than iron observed in nature
This is why we propose to construct a new device: the “rare-RI ring”, which fulfills the requirements of a high mass resolution of 1026, a short measurement time of less than 50 ms, and a high detection efficiency of 100% for rare RI simultaneously
Since the rare RI, which is produced by projectile-fragmentation or projectile-fission reactions of a primary beam from the cyclotron, arrives at the ring almost randomly in time, an individual RI injection mechanism [22] is needed for efficient use of the ring
Summary
The r-process nucleosynthesis is considered to be the origin of about half of all elements heavier than iron observed in nature. The main purpose of the rare-RI ring is to measure the mass of very neutron-rich nuclei, the production rates of which are very small ( ‘rare RI’) and the lifetimes of which are predicted to be very short. An advantage of ion-trap-based techniques is that a high mass resolution of better than 1027 is achievable This high resolution is attractive, a long observation time of 1 s prevents one from applying this technique to the mass measurement of short-lived r-process nuclei. We definitely need a dedicated setup for IMS to extend the mass measurement to r-process nuclei This is why we propose to construct a new device: the “rare-RI ring”, which fulfills the requirements of a high mass resolution of 1026, a short measurement time of less than 50 ms, and a high detection efficiency of 100% for rare RI simultaneously.
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