Beams Document 7968-v1

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E-cloud study at Fermilab

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Rob Ainsworth
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Rob Ainsworth
Document Created:
28 Jan 2020, 13:37
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28 Jan 2020, 13:37
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28 Jan 2020, 13:37
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The electron cloud (E-cloud) can potentially cause operational problems in accelerators all around the world. There are planned beam intensity increases due to upgrades of the Fermilab accelerator complex, so E-cloud could become a problem. This research took several approaches toward understanding the risk of E-cloud at Fermilab. The evolution of the SEY of the SS316L (stainless steel), TiN coated SS316L, and amorphous carbon coated SS316L were measured in-situ using a Secondary Electron Yield coefficient (SEY) measurement test stand in the MI tunnel. Direct measurements of the electron cloud were done as well, and compared to simulation. The electron cloud bombardment rate was measured at different beam intensities and bunch lengths. The Retarding Field Analyzer (RFA) measuring the electron cloud bombardment rate was near the instrument that is used to measure the SEY of the beam pipe material. This proximity provided an accurate SEY value for simulations, so that the simulated electron cloud bombardment rate could be better compared to measurement. The POSINST simulations of electron cloud were a good match to direct measurements. This gave confidence that predictions could be made concerning the E-cloud densities at upgrade intensities. These densities were compared against corresponding proton densities to predict the SEY required to avoid instabilities. That prediction and the information provided by the SEY measurements provide helpful information regarding the risks of electron cloud effects at future beam intensities at Fermilab.
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