Design optimization of isochronous mode in the HIAF-SRing

【摘要】 The measurement of mass,or equivalently the binding energy,of exotic nuclei has reached the limits of nuclear existence,which are characterized by tiny production cross-sections and short half-lives.The isochronous mode of the Spectrometer Ring at the High Intensity heavy-ion Accelerator Facility project in China（HIAF-SRing）offers the capacity for such measurements.However,many factors limit the revolution time resolution of the isochronous mode of the large acceptance HIAF-SRing.Nonlinear field errors as well as fringe fields of the wide aperture dipoles and quadrupoles strongly excite the higher-order aberrations,which negatively affect the revolution time resolution.Moreover,the transverse emittance of the beam is inversely proportional to the revolution time resolution.Their influence is investigated here,and a possible correction scheme with sextupoles and octupoles is shown.With higher-order corrections,a mass resolution of R（FWHM）=1 × 10⁶,corresponding to a relative revolution time of σ（T）/T～4.9 × 10^-7,is with the isochronous setting γ_t=1.43 within the momentum acceptance of±0.2%.更多还原

【Abstract】 The measurement of mass,or equivalently the binding energy,of exotic nuclei has reached the limits of nuclear existence,which are characterized by tiny production cross-sections and short half-lives.The isochronous mode of the Spectrometer Ring at the High Intensity heavy-ion Accelerator Facility project in China（HIAF-SRing）offers the capacity for such measurements.However,many factors limit the revolution time resolution of the isochronous mode of the large acceptance HIAF-SRing.Nonlinear field errors as well as fringe fields of the wide aperture dipoles and quadrupoles strongly excite the higher-order aberrations,which negatively affect the revolution time resolution.Moreover,the transverse emittance of the beam is inversely proportional to the revolution time resolution.Their influence is investigated here,and a possible correction scheme with sextupoles and octupoles is shown.With higher-order corrections,a mass resolution of R（FWHM）=1 × 10⁶,corresponding to a relative revolution time of σ（T）/T～4.9 × 10^-7,is with the isochronous setting γ_t=1.43 within the momentum acceptance of±0.2%.更多还原