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TY - CONF AU - Jia, H. AU - Plum, M.A. ED - Schaa, Volker RW ED - Ji, Daheng ED - Li, Lu ED - Zhao, Ning TI - Fringe Field Overlap Model for Quadrupoles J2 - Proc. of SAP2017, Jishou, China, 28-30 August 2017 C1 - Jishou, China T2 - Symposium on Accelerator Physics T3 - 13 LA - english AB - In the large aperture-to-length ratio quadrupoles, there will be long fringe field. When putting three of this type quadrupoles next to each other, the field will overlap and change the beam dynamics of "hard-edge" model of Triplet quadrupoles. By numeric integration, we find that the transfer matrix difference is quite significant at the first part of MEBT of CADS Injector II. By re-exploring the 'hard-edge' model, the traditional definition of quadrupole's effective length and effective gradient are found to be just rough approximations and not right in this condition. The finding explains the good prediction of beam dyanamics model of MEBT by emittance measurements with different current settings of the triplet quadrupoles, and may be also helpful in explaining some discrepancies in beam lines around the world PB - JACoW CP - Geneva, Switzerland SP - 99 EP - 102 KW - ion KW - quadrupole KW - focusing KW - emittance KW - factory DA - 2018/02 PY - 2018 SN - 978-3-95450-199-1 DO - 10.18429/JACoW-SAP2017-MOPH31 UR - http://jacow.org/sap2017/papers/moph31.pdf ER -