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TY - CONF AU - van der Geer, S.B. AU - Muratori, B.D. AU - de Loos, M.J. ED - Henderson, Stuart ED - Akers, Evelyn ED - Satogata, Todd ED - Schaa, Volker R.W. TI - Tracking Through Analytic Quadrupole Fringe Fields With GPT J2 - Proc. of IPAC2015, Richmond, VA, USA, May 3-8, 2015 C1 - Richmond, VA, USA T2 - International Particle Accelerator Conference T3 - 6 LA - english AB - In the early design stages it is customary to work with a highly simplified analytic model to describe the beam line. Dipoles and quadrupoles are often based on hard-edged approximations. This is not only unrealistic, it also significantly slows down time-domain spacecharge tracking codes such as the General Particle Tracer (GPT) code. The underlying reason for the poor performance is that despite the fact that the simple hard-edged field equations are fast to evaluate, they force the integration process to use excessively small step sizes near the fields discontinuities in order to achieve the desired accuracy. In other worlds, the apparently simple equations turn out to be the most difficult ones to evaluate numerically. An obvious solution is to switch to field-maps, but this is not practical in the early design stages. In this contribution we show a new solution implemented in the GPT code based on analytical expressions for the fringes where the transverse size of the magnet is properly taken into account. In addition to producing more realistic results, the smooth fields increase tracking speed by over an order of magnitude for typical test cases. PB - JACoW CP - Geneva, Switzerland SP - 489 EP - 491 KW - quadrupole KW - simulation KW - space-charge KW - interface KW - multipole DA - 2015/06 PY - 2015 SN - 978-3-95450-168-7 DO - 10.18429/JACoW-IPAC2015-MOPJE075 UR - http://jacow.org/ipac2015/papers/mopje075.pdf ER -