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Effect of the non-linear magnetic fields on the emittance growth in the ATF extraction line

Abstract : Since several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, has been significantly larger than that measured in the damping ring (DR) itself. The EXT line that transports the beam to the ATF2 Final Focus beam line has been rebuilt, but the extraction itself remains in most part unchanged, with the extracted beam transported off- axis horizontally in two of the quadrupoles, beyond the linear region for one of them. A few other nearby magnets have also modelled or measured non-linearity. In case of a residual vertical beam displacement, this can result in increased vertical emittance through coupling between the two transverse planes. Tracking studies as well as measurements have been carried out to study this effect and the induced sensitivity of beam optical parameters to the trajectory at injection, in view of deriving tolerances for reproducible and stable operation.
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Submitted on : Thursday, January 14, 2010 - 4:35:18 PM
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  • HAL Id : in2p3-00424414, version 1




M. Alabau Pons, A. Faus-Golfe, P. Bambade, G. Le Meur, F. Touze, et al.. Effect of the non-linear magnetic fields on the emittance growth in the ATF extraction line. 23rd Particle Accelerator Conference "PAC09", May 2009, Vancouver, Canada. pp.WE6PFP075. ⟨in2p3-00424414⟩



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