Precise Mass Measurement Of Fp-shell Proton-rich Nuclei Using Storage Ring

The mass is one of the fundamental properties of a nucleus.It reflects the interactions among the nucleons inside the nucleus,and plays an essential role in understanding the nuclear structure and the origin of elements.Most of nuclear masses near the?-stability line have been accurately measured experimentally,whereas the precise mass measurement of the nuclide far away is more difficult to perform due to their short life times and lower production yields.Heavy Ion Research Facility in Lanzhou provides one of the few large facilities in the world that can be used to measure the mass of exotic nuclei.In this thesis,the mass measurement conducted at the experimental cooler storage ring of HIRFL is introduced.In the experiment,a ⁵⁸Ni¹⁹⁺primary beam was focused onto the 15 mm thick beryllium target placed in front of the fragment separator RIBLL2.Secondary ions were produced by the projectile fragmentation.The fragment selected by RIBLL2 were injected into the CSRe for periodic motion.The revolution times of stored ions were measured using the TOF detector.The revolution time spectrum was calibrated using the nuclei with well-known masses,and the masses of nuclei of interest were determined according to the calibration.Comparing with previous experiments,we set a metal slit of 60 mm width in the beam line to reduce the momentum spread of stored ions.With the help of the slit,high-precision mass values have been achieved in this experiment.The installation of the slit restricts the deviations ion's magnetic rigidity,thus the ions that stored in the ring for more the 100?s have been used in the data analysis.Finally,the statistic of each nuclide was greatly increased,and some of nuclide could be increased twice.The masses of ⁵²Co,⁴⁴V and ⁵⁶Cu measured for the first time,and the mass precision of other nuclide have been improved.Based on our new mass values,some issues in the studies of nuclear structure have been discussed.The masses of the ⁵²Co ground state and its isomeric state have been accurate mea-sured for the first time in this experiment.Using our mass values together with the previous information of beta-delayed proton and gamma emission of ⁵²Ni,the decay scheme of ⁵²Ni has been re-constructed in which the isobaric analog state?IAS?of ⁵²Ni in⁵²Co has been newly suggested.The newly determined excitation energy of the IAS fits well into the famous Isospin Multiplet Mass Equation?IMME?.We conclude that IAS decay predominantly by?transition rather than by proton emission.By using the experimental results,the mass dependence of vector and tensor coulomb energies has been studied.In addition,the new mass can be used to study the fundamental interaction.We are trying to test the Conserved Vector Current hypothesis of weak interaction by using the precise masses.Finally,the uncertainties of ft values for corresponding transitions were greatly improved.We point out that the uncertainties of branching ratios become dominant factors for precise calculations of ft values.