SRF2015 - List of Authors (Trofimova, O.)

Paper	Title	Page
MOPB035	Nature and Implication of Found Actual Particulates on the Inner Surface of Cavities in a Full-Scale Cryomodule Previously Operated With Beams	164
	R.L. Geng, J.F. Fischer, E.A. McEwen, O. Trofimova JLab, Newport News, Virginia, USA
	Field emission in an SRF cavity is often the result of small foreign particulates lodging on the cavity inner surface. To avoid these particulate field emitters, careful cleaning and handling of individual cavities and clean room assembly of cavity strings are common practice. Despite these elaborate processes, some particulates persist to stay on the final surface of a beam-ready cavity. Moreover, as will be shown in this contribution, new particulates accumulate after a cryomodule is placed in the accelerator tunnel. The nature of these accumulated particulates on the inner surface of a beam-accelerating cavity is largely unknown for two reasons: (1) lack of access to such surfaces; (2) lack of a workable procedure for investigation without destroying the cavity. In this contribution, we report the first study on found actual particulates on the inner surface of 5-cell CEBAF cavities in a full-scale cryomodule previously operated with beam. The nature of the studied particulates is presented. The implication of the findings will be discussed in view of reliable and efficient operation of CEBAF and future large-scale SRF accelerators.
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Paper

Title

Page

Nature and Implication of Found Actual Particulates on the Inner Surface of Cavities in a Full-Scale Cryomodule Previously Operated With Beams

164

R.L. Geng, J.F. Fischer, E.A. McEwen, O. Trofimova
JLab, Newport News, Virginia, USA

Field emission in an SRF cavity is often the result of small foreign particulates lodging on the cavity inner surface. To avoid these particulate field emitters, careful cleaning and handling of individual cavities and clean room assembly of cavity strings are common practice. Despite these elaborate processes, some particulates persist to stay on the final surface of a beam-ready cavity. Moreover, as will be shown in this contribution, new particulates accumulate after a cryomodule is placed in the accelerator tunnel. The nature of these accumulated particulates on the inner surface of a beam-accelerating cavity is largely unknown for two reasons: (1) lack of access to such surfaces; (2) lack of a workable procedure for investigation without destroying the cavity. In this contribution, we report the first study on found actual particulates on the inner surface of 5-cell CEBAF cavities in a full-scale cryomodule previously operated with beam. The nature of the studied particulates is presented. The implication of the findings will be discussed in view of reliable and efficient operation of CEBAF and future large-scale SRF accelerators.

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