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TY - UNPB AU - Li, R. AU - Tennant, C. ED - Schaa, Volker RW ED - Power, Maria ED - Shiltsev, Vladimir ED - White, Marion TI - A Discussion on Phase Space and Beam Emittance J2 - Proc. of NAPAC2016, Chicago, IL, USA, October 9-14, 2016 C1 - Chicago, IL, USA T2 - North American Particle Accelerator Conference T3 - 3 LA - english AB - The use of the term 'beam emittance' as a description of beam performance often has a contextual meaning, which may not be obvious to the reader. This tutorial presents a general discussion on the topic of beam emittance to differentiate between the various descriptions and definitions and where they are best applied. The tutorial begins with an overview of Hamiltonian dynamics and Liouville's Theorm to define the beam emittance based on canonical coordinates. The goal in accelerators is often to preserve the beam emittance. Discussion is therefore given to phenomena causing emittance non-conservation. We conclude with a statistical analysis of beam emittance, often calculated with beam tracking simulation codes, and how they are practically measured in particle accelerators. Examples demonstrate the subtleties of various definitions, particularly to reveal the many contributors to the emittance in a space-charge dominated and magnetized electron bunch. PB - JACoW CP - Geneva, Switzerland ER -