Commissioning Simulations Of Diffraction Limited Storage Ring Light Source

Storage ring(SR)based synchrotron radiation light sources have come to the fourth generation after decades of development.The new generation facility is called diffraction limited storage ring(DLSR)light source,which is favored by synchrotron radiation experimenters because of its excellent features of high photon brightness and transverse coherence.Around 2010,the research and construction of DLSR light source was initiated by many large scientific centers worldwide.In order to achieve the high performance of lower beam emittance,higher photon brightness and higher transverse coherence,the multi-bends achromats(MBA)structure will be adopted by DLSR,as well as quadrupole magnets and sextupole magnets with higher magnetic field strength,and bending magnets with longitudinal gradient and quadrupole gradient.Due to the manufacturing errors and installation misalignments of the magnets,combined with the extremely complicated lattice structure and the very high magnetic field strength,the parameters of the electron beam will be affected unprecedented.Beam commissioning of the new generation of light sources will face great challenges.In this paper,simulation commissioning of diffraction limit storage ring is studied with the aim of successful beam commissioning and stable operation of storage ring light sources.In the first part of this paper,error analysis and beam first-turn trajectory correction are carried out from the error effects in DLSR.Firstly,the transverse motion of electrons in the storage ring is studied by derivation of theoretical formula,and the concept in theory is transformed into important parameters such as beam orbit which will be faced in real machine commissioning.Secondly,the beam orbit distortion caused by the misalignment errors in the diffraction limited storage ring is analyzed and the acceptance of the misalignment errors is evaluated.Then,the simulation study of beam orbit correction based on the Shanghai synchrotron radiation facility upgrade(SSRF-U)is launched,in which the beam first-turn trajectory correction method that can reduce the requirement of misalignment error is the focus of the study.Finally,the new beam first-turn trajectory correction method is used in simulation.Based on the simulation results of trajectory correction under different levels of errors,the requirements of alignment errors that can meet the successful commissioning of SSRF-U are proposed.The simulation of linear optics correction of DLSR is another important research in this paper.In this study,the theoretical formulas of the linear optical function,the stability analysis of the transverse motion and the linear optical distortion analysis of DLSR are carried out first.Then,the linear optics correction method is analyzed,and the feasibility of the linear optics correction strategy based on LOCO is analyzed in view of the possibility of missing correction elements and linear optical elements of lattice in the commissioning process of DLSR.Next,the linear optics correction simulation on SSRF-U is performed.Finally,the linear optics correction of SSRF storage ring under similar conditions based on LOCO method is carried out,and the results show that LOCO method can be used to complete linear optics correction of missing correction elements or lattice optical elements.The stability of betatron tunes and linear optics is an important guarantee for DLSR light source to play its design performance.On the one hand,the beam stability mainly depends on the betatron tunes and the linear optical functions,and the deviation of these two parameters can cause serious transverse oscillation,which may increase the beam loss rate or even directly lead to the beam loss.On the other hand,some DLSRs plan to realize round beam by means of linear coupling differential resonance,which requires high stability of the betatron tunes.Therefore,another important content of this paper is the study of betatron tune stability of DLSR.The study and simulation of tune feedback based on the SSRF-U storage ring lattice is performed.At the same time,in view of the great similarity between the DLSR light source and the third-generation storage ring light source,the tune feedback system is tested and operated on the SSRF storage ring in turn.The results show that the feedback not only stabilizes the tunes within ±0.001,but also improves the stability of several beam parameters.In summary,the simulation commissioning is carried out based on the main difficulties in the commissioning and operation of DLSR light sources.The simulations of orbit correction,linear optics correction and tune feedback are carried out in order to provide valuable references for beam commissioning of diffraction limit storage ring light sources which are being widely constructed.