Experimental investigation of the transition energy [formula omitted] in the isochronous mode of the HIRFL-CSRe.

Abstract The Isochronous Mass Spectrometry (IMS) based on storage rings is a powerful technique for mass measurement of short-lived exotic nuclei. The transition energy γ t of the storage ring is a vital parameter of the IMS technique. It is difficult to measure the γ t and its relation to momentum spread or circulating length, especially to monitor the variation of γ t during experiments. An experimental investigation on the γ t has been performed for the IMS experiment at the Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSRe). With the velocity measured by two time-of-flight (TOF) detectors, the γ t as a function of orbital length can be determined. The influences of higher order magnetic field components on the γ t function were inferred for isochronous correction. This paper introduces and investigates the influence of dipole magnetic fields, quadrupole magnetic fields and sextupole magnetic fields on the γ t function. With the quadrupole magnets and sextupole magnets corrections, a mass resolution of 171332 (FWHM) and σ (T) ∕ T = 1. 34 × 1 0 − 6 were reached, which shall be compared with 31319 (FWHM) and σ (T) ∕ T = 7. 35 × 1 0 − 6 obtained without correction. [ABSTRACT FROM AUTHOR]