| The accurate knowledge of nuclear masses plays an important role in many scientific research fields such as mass model testing of atomic nuclei,evolution of nuclear structure and astronomical physics.Today,the challenge is to obtain precise masses of nuclei located far away from the stability valley.Since such nuclei are characterized by low production cross-section and short half-lives,highly efficient and fast mass measurement techniques are required.The isochronous mass spectrometer HIRFL-CSRe and the HIAF-SRing are high-precision experimental facilities for such nuclei.The thesis mainly introduces the isochronous optical design,isochronous theoretical calculation of the HIRFL-CSRe and the HIAF-SRing,and isochronous experimental investigation on the HIRFL-CSRe,including the influence of magnet setting on the?t curve and higher order isochronous correction.The optical design of the isochronous mass spectrometer focuses on improving the mass resolution.For large emittance and large momentum dispersed ions,the mass resolution will be poor.The nonlinear magnetic field errors,including the higher order magnetic field and the magnetic fringe fields,will have a serious impact on the mass resolution of the nucleus.Therefore,these effects and higher order isochronous must be corrected.In the thesis,the GICOSY program is used to theoretically calculate the isochronous mode of the HIRFL-CSRe and the HIAF-SRing.The influence of emittance and nonlinear magnetic field on the?t curve and the??T?/T of the isochronous mode of the storage ring are investigated.On this basis,the higher order isochronous condition and chromaticity are corrected,respectively.For the isochronous setting?t=1.36 of the HIRFL-CSRe,with 3 families of sextupole magnets and 1 family of octupole magnets corrections,the relative variation of revolution time reaches 0.48·10-5 with the momentum spread of?0.2%,which corresponds to the mass resolution of m/?m=1.10·105.For the isochronous setting?t=1.43 of the HIAF-SRing,??T?/T=9.00·10-7 with the momentum spread of?0.3%,which corresponds to the mass resolution of m/?m=5.43·105.In the thesis,the effects of HIRFL-CSRe magnets on the?t curve and higher order isochronal correction experiments were studied using the double TOF method.Under the optical setting of?t=1.36,the theoretical curve of?t and the experimental results are in good agreement.According to the experimental results,it can be seen that the?t curve was horizontally,vertically shifted as well as rotated,by varying dipole magnetic fields,quadrupole magnetic fields and sextupole magnetic fields,respectively.Correspondingly,these adjustments changed the optimal region for the experiment by different ratios.These results could be seen as a reference to control the?t curve.With the quadrupole magnets and sextupole magnets corrections,a mass resolution of 171332?FWHM?and??T?/T=1.34·10-6 were reached,which shall be compared with 31319?FWHM?and??T?/T=7.35·10-6 obtained without correction.The mass resolution is improved by about 5 times.The thesis makes theoretical calculations and experimental studies on the isochronous mode of the HIRFL-CSRe and the HIAF-SRing.It has certain guiding significance for isochronous mass measurement experiments of the HIRFL-CSRe and optical design of the HIAF-SRing isochronous mode. |
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