Precision storage lifetime measurements of highly charged heavy ions in the CSRe storage ring using a Schottky resonator

Schottky mass spectrometry utilizing heavy-ion storage rings is a powerful technique for the precise mass and decay half-life measurements of highly charged ions. Owing to the nondestructive ion detection features of Schottky noise detectors, the number of stored ions in the ring is determined by the peak area in the measured revolution frequency spectrum. Because of their intrinsic amplitude-frequency characteristic（AFC）, Schottky detector systems exhibit varying sensitivities at different frequencies. Using low-energy electron-cooled stored ions, a new method is developed to calibrate the AFC curve of the Schottky detector system of the Experimental Cooler Storage Ring（CSRe） storage ring located in Lanzhou, China. Using the amplitude-calibrated frequency spectrum, a notable refinement was observed in the precision of both the peak position and peak area. As a result, the storage lifetimes of the electron-cooled fully ionized 56Fe26+ ions were determined with high precision at beam energies of 13.7 and 116.4 MeV/u, despite of frequency drifts during the experiment. When electron cooling was turned off, the effective vacuum condition experienced by the 116.4 MeV/u 56Fe26+ ions was determined using amplitude-calibrated spectra, revealing a value of 2 × 10-10 mbar, which is consistent with vacuum gauge readings along the CSRe ring. The method reported herein will be adapted for the next-generation storage ring of the HIAF facility under construction in Huizhou, China. It can also be adapted to other storage ring facilities worldwide to improve precision and enhance lifetime measurements using many ions in the ring.