Hall, C.C. Bruhwiler, D.L. Murokh, A.Y. Musumeci, P. Park, Y. Sun, Y. Webb, S.D. Zholents, A. JACoW Geneva, Switzerland 978-3-95450-179-3 10.18429/JACoW-FEL2017-TUP022 English 284-287 TUP022 ion linac gun electron simulation Contribution to a conference proceedings 2018 2018-02 https://doi.org/10.18429/JACoW-FEL2017-TUP022 http://jacow.org/fel2017/papers/tup022.pdf The Linac Extension Area (LEA) is a new beamline planned as an extension of Argonne's APS linac. An S-band 1.6-cell copper photo-cathode (PC) RF gun has been installed and commissioned at the APS linac front end. The PC gun will provide a beam to the LEA for accelerator technology development and beam physics experiments, in interleaving with a thermionic RF gun which provides a beam for APS storage ring operations. Recently an experiment was proposed to demonstrate the TESSA high-efficiency concept at LEA. In support of this experiment, we have begun simulating the photo-injector using the code OPAL (Object-oriented Particle Accelerator Library). In this paper, we first benchmark OPAL simulations with the established APS photo-injector optimization using ASTRA and ELEGANT. Key beam parameters required for a successful high-efficiency TESSA demonstration are discussed.