Bp-defined isochronous mass spectrometry and mass measurements of 58Ni fragments

A novel isochronous mass spectrometry, termed as Bp-defined IMS, has been established at the experimental cooler-storage ring CSRe in Lanzhou. Its potential has been studied through high precision mass measurements of 58Ni projectile fragments. Two time-of-flight detectors were installed in one of the straight sections of CSRe, thus enabling simultaneous measurements of the velocity and the revolution time of each stored short-lived ion. This allows for calculating the magnetic rigidity Bp and the orbit length C of each ion. The accurate Bp(C) function has been constructed, which is a universal calibration curve used to deduce the masses of the stored nuclides. The sensitivity to single stored ions, fast measurement time, and background-free characteristics of the method are ideally suited to address nuclides with very short lifetimes and smallest production yields. In the limiting case of just a single particle, the achieved mass resolving power allows one to determine its mass-over-charge ratio m/q with a remarkable precision of merely similar to 5 keV. Masses of Tz = -3/2 fp-shell nuclides are re-determined with high accuracy, and the validity of the isospin multiplet mass equation is tested up to the heaviest isospin quartet with A = 55. The new masses are also used to investigate the mirror symmetry of empirical residual proton-neutron interactions.

Automated summary

A novel isochronous mass spectrometry called Bp-defined IMS has been established at CSRe in Lanzhou, China. By measuring the velocity and revolution time of stored short-lived ions simultaneously, the method allows for calculating the magnetic rigidity Bp and orbit length C of each ion, enabling accurate mass determination. This method is ideal for studying nuclides with short lifetimes and low production yields. The new masses obtained were used to investigate isospin multiplet mass equation and mirror symmetry of proton-neutron interactions.