[en] A heavy-ion storage ring, named the “Rare-RI Ring (R3)” has been constructed at the RIKEN RI Beam Factory. This ring has been designed to make high-precision mass measurements of extremely short-lived and rarely produced unstable nuclei (rare-RIs). We chose the method of isochronous mass spectrometry (IMS) to give a measurement time shorter than 1 ms. Since isochronism is established with a cyclotron-like magnetic structure in R3, rare-RIs with a large momentum spread, Δp/p = ±0.5%, are acceptable. An idea for the efficient use of rare-RIs produced at unpredictable times is to employ an individual injection scheme in which the rare-RI itself triggers the injection kicker. An ultra-fast response feature is imposed on the kicker system to establish the injection scheme. The technical challenges are the formation of a precision isochronous magnetic field and the development of a fast-response kicker system. We started test experiments to evaluate the R3's performance in the year 2014. (author)