Gibbs, M.L. Colocho, W.S. Osman, A. Shtalenkova, J. JACoW Publishing Geneva, Switzerland 2226-0358 978-3-95450-209-7 10.18429/JACoW-ICALEPCS2019-TUCPL04 English 773-775 TUCPL04 EPICS software undulator electron operation Contribution to a conference proceedings 2020 2020-08 https://doi.org/10.18429/JACoW-ICALEPCS2019-TUCPL04 https://jacow.org/icalepcs2019/papers/tucpl04.pdf The Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory is currently undergoing a major upgrade. In order to facilitate the development of new software that will be needed to operate the upgraded machine, a simulator has been developed to simulate the LCLS electron beam and the accelerator devices that measure and manipulate it. The simulator is comprised of several small "services" that simulate different types of devices, and provide an EPICS interface identical to the real control system. All of the services communicate with a central beam line model to change accelerator parameters and retrieve information about the simulated beam.