SRF2015 - List of Authors (Douglas, D.)

Paper	Title	Page
MOPB061	Suppression of Upstream Field Emission in RF Accelerators	246
	F. Marhauser, S.V. Benson, D. Douglas JLab, Newport News, Virginia, USA L.J.P. Ament ASML US Inc., Wilton, CT, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 So-called electron loading is the primary cause for cavity performance limitations in modern RF accelerating cavities. In superconducting RF cavities in particular, the onset of parasitic electron effects may start at field levels as low as a few MV/m. Electron loading can be attributed to mainly three phenomena: field emission, multiple impact electron amplification, and RF electrical breakdown. Field emission has been a persistent issue despite advances in SRF technology, whereas RF electrical breakdown and multipacting can be controlled by appropriate cavity design choices. Field emission becomes a major concern when the electrons emitted are captured by the accelerating RF field and directed along the beam axis through a series of cavities or even entire cryomodules. Consequently, electrons can accumulate energy comparable to that of the main beam over similar distances. This can represent a considerable dark current, which can travel downstream or upstream depending on the field-emitting site of origin. In this paper, a method is presented that can significantly suppress the upstream field emission by design.
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Paper

Title

Page

Suppression of Upstream Field Emission in RF Accelerators

246

F. Marhauser, S.V. Benson, D. Douglas
JLab, Newport News, Virginia, USA
L.J.P. Ament
ASML US Inc., Wilton, CT, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
So-called electron loading is the primary cause for cavity performance limitations in modern RF accelerating cavities. In superconducting RF cavities in particular, the onset of parasitic electron effects may start at field levels as low as a few MV/m. Electron loading can be attributed to mainly three phenomena: field emission, multiple impact electron amplification, and RF electrical breakdown. Field emission has been a persistent issue despite advances in SRF technology, whereas RF electrical breakdown and multipacting can be controlled by appropriate cavity design choices. Field emission becomes a major concern when the electrons emitted are captured by the accelerating RF field and directed along the beam axis through a series of cavities or even entire cryomodules. Consequently, electrons can accumulate energy comparable to that of the main beam over similar distances. This can represent a considerable dark current, which can travel downstream or upstream depending on the field-emitting site of origin. In this paper, a method is presented that can significantly suppress the upstream field emission by design.

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