The development of perturbation model for fringe field in Open XAL and its application in beam commissioning of CSNS

Background The China Spallation Neutron Source (CSNS) accelerator employs Open XAL as the control software in beam commissioning. The main magnets of CSNS/RCS have serious fringe field effect; however, there is not corresponding model for fringe field in Open XAL. Purpose The purpose is to develop a suitable model for fringe field and append to the online model of Open XAL. Methods On the basis of the requirements of beam commissioning and model features of Open XAL, a perturbation model was developed to correct the effect of fringe field. Results The comparison of the parameters calculated by slice model with the values obtained from Open XAL with perturbation model showed the validity of the model. Furthermore, with the response matrix method, the values obtained from Open XAL with perturbation model were very close to the measured response matrices, which showed the accuracy of the model. Conclusion The perturbation model is effective for correcting the fringe field effect in Open XAL.