Isochronicity corrections for isochronous mass measurements at the HIRFL-CSRe

Isochronous Mass Spectrometry (IMS) is a unique experimental method for mass measurement experiments on short-lived nuclei. Mass measurements of Kr-78 projectile fragments were performed in HIRFL-CSRe at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. The short-lived secondary beams were produced by bombarding a 15 mm thick beryllium target in the Radioactive Ion Beam Line (RIBLL2) and were then injected into the CSRe storage ring. The masses of stored ions were measured by employing the IMS technique, which is based on the determination of the ion revolution Limes. A dedicated time-of-flight. (TOP) defector is used for the latter purpose. However, the isochronicity, and thus the mass resolving power, depends on the momentum spread and the transverse ernittance of the injected beams. Here, we present. the first order isochronicity optimization, the chromaticity and second order isochronicity corrections through the modification of the quadrupole and sextupole field strengths. With the help of these corrections, the mass resolution of Delta m/m = 10(-6) can be achieved. (C) 2014 Elsevier B.V. All rights reserved.