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TY - UNPB AU - Jia, H.Y. AU - Huang, S. ED - Schaa, Volker RW ED - Huang, Wenhui ED - Yan, Xueqing ED - Tang, Chuanxiang ED - Li, Lu TI - Correction of Electron Beam Aberration Due to Multipole Fields in a Continuous-Wave Photocathode Gun J2 - presented at SAP2023, Xichang, China, 10-12 July 2023 CY - Xichang, China T2 - Symposium on Accelerator Physics T3 - 14 LA - english AB - Continuous-wave photocathode guns can deliver electron beams with high repetition rates and high average currents, but their achievable accelerating gradients and cathode fields are relatively low. This leads to a large beam size at the gun exit due to space charge effects, which makes the beam more sensitive to optical aberrations and poses challenges for low-emittance electron beam transmission. This work focuses on the aberration caused by multipole fields. It analyzes the effects of quadrupole, sextupole, octupole and higher order fields on beam shape and transverse emittance, and proposes a beam-based method for rapid characterization and correction of multipole fields. Additionally, an experimental study is being conducted on the DC-SRF-II photocathode gun at Peking University, with corresponding correctors designed for the quadrupole and sextupole fields in the beamline. The experimental results show that the electron beam aberration due to multipole fields can be effectively corrected through appropriate corrector settings, resulting in improved beam symmetry and reduced emittance. ER -