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SLAC Publication: SLAC-PUB-17401
SLAC Release Date: February 12, 2019
THE EFFECT OF WAKE FIELDS ON THE FEL PERFORMANCE
Novokhatski, Alexander.
When a beam travels near collimator jaws, it gets an energy loss and a transverse kick due to the back reaction of the beam field diffracted on the collimators jaws. The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. In the Linac Coherent Light Source (LCLS) at SLAC a collimation system is used to protect the undulators from radiation due to particles in the beam halo. The collimators in the LCLS must remove the halo par... Show Full Abstract
When a beam travels near collimator jaws, it gets an energy loss and a transverse kick due to the back reaction of the beam field diffracted on the collimators jaws. The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. In the Linac Coherent Light Source (LCLS) at SLAC a collimation system is used to protect the undulators from radiation due to particles in the beam halo. The collimators in the LCLS must remove the halo particles before they affect and eventually degrade the very precise fields of the permanent magnet undulators [1]. The wake field effect from the collimators not only brings an additional energy jitter and change of the trajectory of the beam, but also rotates the beam on the phase plane that consequently leads to a degradation of the performance of the Free Electron Laser (FEL) at LCLS. In this paper, we describe a model of the wake field radiation in the SLAC linac collimators. We also present results of experimental measurements, which clearly confirm our model. Show Partial Abstract
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  • Interest Categories: Accelerator Physics, X-Ray Free Electron Laser