Isochronous mass spectrometry has been applied to 112Sn projectile fragments at the HIRFL-CSR facility in Lanzhou. To produce short-lived nuclei of interest, we used projectile fragmentation of 112Sn35+ primary beams in a ～10 mm thick 9Be production target. The fragments were selected and analyzed by RIBLL2 and injected into the experimental storage ring(CSRe) every 25 s. To measure revolution times of stored ions,we used a Time-Of-Flight detector installed in CSRe. A new particle identification method was developed to distinguish ions on the measured revolution time spectrum for each injection. Based on this method, the shifts of the revolution time due to instable dipole magnet fields can be corrected and the ground and isomeric states of 101In have been well-resolved. The measured excitation energy is consistent with the theoretical value in the error range of 112 keV. The lifetime of the isomeric states of 101In is more than 200 μs.

The decay of the fully stripped ion 94mRu44+ in the order of one hundred microseconds has been studied for the first time by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou.94mRu44+ waS produced via projectile fragmentation of a 112Sn primary beam bombarding on a 9Be production target.After the in-flight separation with RIBLL2,the ions were injected into the experimental ring (CSRe) and then stored there.The revolution times of the stored ions were measured by a Time-of-Flight (TOF) detector.Due to the mass change of a 94mRu44+ ion caused by its de-excitation to the ground state,hence the revolution time change,the decay process of 94mRu44+ could be directly observed in the CSRe.The sensitive window for detection of the decay events and the measurement precision of the decay time have been determined in this work.At the same time,we measured the mass of short-lived 94mRu44+ with the half-life about one hundred microseconds,which is the shortest among nuclides that have been studied by using storage-ring mass-spectrometry.

Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.