Improved isochronous mass spectrometry with tune measurement

In conventional isochronous mass spectrometry (IMS) performed on a storage ring, the precision of mass measurements for short-lived nuclei depends on the accurate determination of the revolution times (T) of stored ions. However, the resolution of T inevitably deteriorates due to the magnetic rigidity spread of the ions, limiting the mass-resolving power. In this study, we used the betatron tunes Q (the number of betatron oscillations per revolution) of the ions and established a correlation between T and Q. From this correlation, T was transformed to correspond to a fixed Q with higher resolution. Using these transformed T values, the masses of ⁶³Ge, ⁶⁵As, ⁶⁷Se, and ⁷¹Kr agreed well with the mass values measured using the newly developed IMS ( \(B\rho\) $B\rho$ -IMS). We also studied the systematics of Coulomb displacement energies (CDEs) and found that anomalous staggering in CDEs was eliminated using new mass values. This method of T transformation is highly effective for conventional IMS equipped with a single time-of-flight detector.