Precision Storage-Lifetime Measurements of Highly Charged Heavy Ions in the CSRe Storage Ring using a Schottky Resonator

摘要: 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 non-destructive 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 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.