Author: Greenwald, S.
Paper Title Page
THPFI087 Measurements of Secondary Electron Yield of Metal Surfaces and Films with Exposure to a Realistic Accelerator Environment 3493
  • W. Hartung, J.V. Conway, C.A. Dennett, S. Greenwald, J.-S. Kim, Y. Li, T.P. Moore, V. Omanovic
    CLASSE, Ithaca, New York, USA
  One of the central goals of the CESR Test Accelerator program is to understand electron cloud (EC) effects in lepton rings and how to mitigate them. To this end, measurements of the secondary electron yield (SEY) of technical surfaces are being done in CESR. The CESR in-situ system, in operation since 2010, allows for measurements of SEY as a function of incident electron energy and angle on samples that are exposed to a realistic accelerator environment, typically 5.3 GeV electrons and positrons. The system was designed for periodic measurements to observe beam conditioning of the SEY and discrimination between exposure to direct photons from synchrotron radiation versus scattered photons and cloud electrons. Measurements so far have been done on bare metal surfaces (aluminum, copper, stainless steel) and EC-mitigatory coatings (titanium nitride, amorphous carbon, diamond-like carbon). A significant decrease in SEY with exposure to beam was observed for all cases other than the amorphous C samples; for the latter, the SEY remained near 1, independent of beam exposure. The SEY results are being used to improve predictive models for EC build-up and EC-induced beam effects.