Measurement of the transition energy γ_t and isochronicity correction in the CSRe storage ring

In this paper we introduce a method to measure the γ_t online during IMS experiments by using the acquired experimental data. Furthermore, since the storage ring has (in our context) a relatively large momentum acceptance, the variation of the γ_t across the ring acceptance is a source of systematic uncertainty of measured masses. With the installation of two time-of-flight (TOF) detectors, the velocity of each stored ion and its revolution time are simultaneously available for the analysis. These quantities enabled us to determine the γ_t as a function of orbital length in the ring. The developed method has been used to correct isochronous condition of the CSRe in a recent IMS experiment with two TOF detectors. (author)