Estimate of the impedance due to wall surface roughness

In the Next Linear Collider (NLC) after being accelerated the beam is collimated to remove tail particles. Wakefields generated in the collimator section, however, can significantly degrade the beam emittance. The collimators are, therefore, carefully designed to balance and minimize the effects of...

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Bibliographic Details
Main Authors: Bane, K.L.F., Ng, C.K., Chao, A.W.
Format: Conference Proceeding
Language:English
Subjects:
Acceleration
Colliding beam accelerators
Colliding beam devices
Collimators
Degradation
Particle beams
Rough surfaces
Surface impedance
Surface roughness
Tail
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Summary:In the Next Linear Collider (NLC) after being accelerated the beam is collimated to remove tail particles. Wakefields generated in the collimator section, however, can significantly degrade the beam emittance. The collimators are, therefore, carefully designed to balance and minimize the effects of the geometric and the resistive wall wakefields. Recent measurements of collimator wakefields in the Stanford Linear Collider (SLC) linac seem to confirm the geometric wakefield calculations but yield results for the resistive wall wakefield that are 3-4 times as large as expected. One possibility is that this discrepancy is due to the roughness of the collimator surface. In this report we estimate this effect.
DOI:10.1109/PAC.1997.750991