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The achievable beam current and beam quality of a particle accelerator can belimited by the build-up of an electron cloud (EC) in the vacuum chamber.Secondary electron emission from the walls of the vacuum chamber can contributeto the growth of the electron cloud. An apparatus for in-situ measurements ofthe secondary electron yield (SEY) of samples in the vacuum chamber of theCornell Electron Storage Ring (CESR) has been developed in connection with ECstudies for the CESR Test Accelerator program (CesrTA). The CesrTA in-situsystem, in operation since 2010, allows for SEY measurements as a function ofincident electron energy and angle on samples that are exposed to theaccelerator environment, typically 5.3 GeV counter-rotating beams of electronsand positrons. The system was designed for periodic measurements to observebeam conditioning of the SEY with discrimination between exposure to directphotons from synchrotron radiation versus scattered photons and cloudelectrons. The SEY chambers can be isolated from the CESR beam pipe, allowingus to exchange samples without venting the CESR vacuum chamber. Measurements sofar have been on metal surfaces and EC-mitigation coatings. The goal of the SEYmeasurement program is to improve predictive models for EC build-up andEC-induced beam effects. This report describes the CesrTA in-situ SEYapparatus, the measurement tool and techniques, and iterative improvementstherein.

Report on Instrumentation and Methods for In-Situ Measurements of the Secondary Electron Yield in an Accelerator Environment