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Title: Direct Measurement of the Transverse Wakefields of Tapered Collimators

Abstract

We report on a recent set of measurements of the transverse wakefields from longitudinally-tapered collimators. The measurements were performed with a low-emittance 1.19 GeV beam in the SLAC linac by inserting a collimator aperture into the beam path and reconstructing the vertical deflection of the beam as a function of the vertical position of the aperture. Each collimator in the experiment was designed to present a relatively large transverse impedance and to minimize the impedance from other contributions such as resistivity. In addition, the collimator parameters were chosen to provide some insight into the scaling of the transverse geometric wakefield as a function of the collimator's geometry. Description of the experimental apparatus and the aperture design, method of data collection and analysis, and comparison to theoretical and numerical predictions are presented.

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
897443
Report Number(s):
SLAC-PUB-12086
TRN: US0701510
DOE Contract Number:
AC02-76SF00515
Resource Type:
Journal Article
Resource Relation:
Journal Name: Submitted to Physical Review Special Topics -- Accelerators and Beams
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; APERTURES; COLLIMATORS; DESIGN; GEOMETRY; IMPEDANCE; LINEAR ACCELERATORS; STANFORD LINEAR ACCELERATOR CENTER; Accelerators,ACCPHY

Citation Formats

Tenenbaum, P., Bane, K.L.F., Eriksson, L., Irwin, J., Jobe, R.K., McCormick, D., Ng, C.K., Raubenheimer, T.O., Ross, M.C., Stupakov, G., Walz, D., and /SLAC. Direct Measurement of the Transverse Wakefields of Tapered Collimators. United States: N. p., 2007. Web. doi:10.1103/PhysRevSTAB.10.034401.
Tenenbaum, P., Bane, K.L.F., Eriksson, L., Irwin, J., Jobe, R.K., McCormick, D., Ng, C.K., Raubenheimer, T.O., Ross, M.C., Stupakov, G., Walz, D., & /SLAC. Direct Measurement of the Transverse Wakefields of Tapered Collimators. United States. doi:10.1103/PhysRevSTAB.10.034401.
Tenenbaum, P., Bane, K.L.F., Eriksson, L., Irwin, J., Jobe, R.K., McCormick, D., Ng, C.K., Raubenheimer, T.O., Ross, M.C., Stupakov, G., Walz, D., and /SLAC. Tue . "Direct Measurement of the Transverse Wakefields of Tapered Collimators". United States. doi:10.1103/PhysRevSTAB.10.034401. https://www.osti.gov/servlets/purl/897443.
@article{osti_897443,
title = {Direct Measurement of the Transverse Wakefields of Tapered Collimators},
author = {Tenenbaum, P. and Bane, K.L.F. and Eriksson, L. and Irwin, J. and Jobe, R.K. and McCormick, D. and Ng, C.K. and Raubenheimer, T.O. and Ross, M.C. and Stupakov, G. and Walz, D. and /SLAC},
abstractNote = {We report on a recent set of measurements of the transverse wakefields from longitudinally-tapered collimators. The measurements were performed with a low-emittance 1.19 GeV beam in the SLAC linac by inserting a collimator aperture into the beam path and reconstructing the vertical deflection of the beam as a function of the vertical position of the aperture. Each collimator in the experiment was designed to present a relatively large transverse impedance and to minimize the impedance from other contributions such as resistivity. In addition, the collimator parameters were chosen to provide some insight into the scaling of the transverse geometric wakefield as a function of the collimator's geometry. Description of the experimental apparatus and the aperture design, method of data collection and analysis, and comparison to theoretical and numerical predictions are presented.},
doi = {10.1103/PhysRevSTAB.10.034401},
journal = {Submitted to Physical Review Special Topics -- Accelerators and Beams},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 09 00:00:00 EST 2007},
month = {Tue Jan 09 00:00:00 EST 2007}
}
  • The authors present a direct measurement of the short-range wakefield of a series of tapered collimators. The wakefields were measured by inserting a fixed aperture in the path of the electron beam at the 1.19 GeV point of the SLAC linac. As the vertical position of the collimator is varied, the vertical deflection of the beam is measured on 29 downstream beam position monitors. A series of apertures with different geometries were studied to permit confirmation of the scaling laws and magnitude of deflection predicted by theory. Description of the apparatus and collimator aperture specifications, predicted centroid deflections, and measuredmore » deflections are discussed.« less
  • Direct measurement of the short-range wakefield due to a series of tapered collimators is presented. The wakefields were measured by inserting a fixed aperture in the path of the electron beam at the 1.19 GeV point of the SLAC linac. As the vertical position of the collimator is varied, the vertical deflection of the beam is measured on 29 downstream beam position monitors. A series of apertures with different geometries were studied to permit confirmation of the scaling laws and magnitude of deflection predicted by theory. Description of the apparatus and collimator aperture specifications, predicted centroid deflections, and measured deflectionsmore » are discussed.« less
  • Precise collimation of the beam halo is required in the International Linear Collider (ILC) to prevent beam losses near the interaction region that could cause unacceptable backgrounds for the physics detector. The necessarily small apertures of the collimators lead to transverse wakefields that may result in beam deflections and increased emittance. A set of collimator wakefield measurements has previously been performed in the ASSET region of the SLAC Linac. We report on the next phase of this program, which is carried out at the recently commissioned End Station A (ESA) test facility at SLAC. Measurements of resistive and geometric wakefieldsmore » using tapered collimators are compared with model predictions from MAFIA and GdfidL and with analytic calculations.« less
  • We report on a series of measurements of the transverse wakefield from tapered collimators. The collimators were designed to principally present a geometric impedance to the beam, and to minimize impedances from resistivity or surface features; in addition, the geometries of the collimators were selected to permit examination of the scaling behavior of the wakefield due to collimator taper angle and minimum gap size. We present the measured near-center wakefields of the collimators, as well as the effect of bunch-length variation. The measurements are compared to analytic models and MAFIA simulations.