Wong, C.Y. Cogan, S. Hao, Y. Lidia, S.M. Lund, S.M. Maruta, T. Omitto, D.O. Ostroumov, P.N. Pozdeyev, G. Ren, H.T. Shane, R. Yoshimoto, T. Zhao, Q. JACoW Geneva, Switzerland 978-3-95450-192-2 10.18429/JACoW-IBIC2017-MOPCC14 English 72-76 MOPCC14 ion dipole emittance simulation cyclotron Contribution to a conference proceedings 2018 2018-03 https://doi.org/10.18429/JACoW-IBIC2017-MOPCC14 http://jacow.org/ibic2017/papers/mopcc14.pdf We study Allison-type phase-space scanners by extending analytic models to include two important geometric features that are conventionally omitted, namely asymmetric slit-plate to dipole-plate gaps at the two ends and finite slit-plate thickness. Their effects can be significant for high-resolution Allison scanners and lead to two corrections in the measurement data relative to more idealized descriptions: 1) a change in the voltage-to-angle conversion relation, and 2) a data point weight compensation factor. These findings are corroborated by numerically integrated single-particle trajectories in a realistic 2D field map of the device. The improved model was applied to the Allison scanner used to measure a 12 keV/u heavy-ion beam in the front-end of the Facility for Rare Isotope Beams (FRIB) at Michigan State University. Preliminary measurements show that the improved model results in significant (>10%) modifications to beam moments, thus rendering the corrections important for accurate phase-space characterizations.