Characterization of beam optics considering fringe fields of quadrupole magnets in a LIPAc 5 MeV beamline

Abstract This paper investigates the effect of the fringe fields of quadrupole magnets (quads) on the beam optics of a 5 MeV beamline in the Linear IFMIF Prototype Accelerator (LIPAc). IFMIF stands for the International Fusion Materials Irradiation Facility. We optimized the beam optics using a hard-edge (HE) model for all quads to minimize particle losses. However, during beam commissioning, we observed particle losses and differences in the rms beam sizes between measurements and simulations. To address these issues, we incorporated quad field maps into the beam optics simulation and calibrated the conversion coefficients of each quad from magnetic gradients g to excitation currents I (GtoI) using a 5 MeV deuteron beam. This approach enabled us to achieve a matched beam, reducing particle losses and ensuring the successful transport of a 120 mA/5 MeV deuteron beam to the beam dump. We present the difference in the transfer matrices between the HE models and the field maps, along with the calibration method of each GtoI of the quads with the deuteron beam. We also compare the simulated and measured beam sizes.