Bonn 2020 – scientific programme
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T: Fachverband Teilchenphysik
T 60: Various topics in elementary particle physics
T 60.9: Talk
Wednesday, April 1, 2020, 18:30–18:45, L-2.017
Polarization of Photon Beam Generated in Helical Undulator at ILC-250GeV — •Khaled Alharbi1, 3, 4, Sabine Riemann3, Gudrid Moortgat-Pick1, 2, and Andriy Ushakov1 — 1University of Hamburg — 2Desy, Hamburg — 3Desy, Zeuthen — 4KACST, Saudi Arabia
The positron source of the ILC is based on a superconducting undulator passed by the high-energy electron beam to generate polarized photons which hit a target to create electron-positron pairs. These pairs will inherit the photon polarization so that a polarized positron beam is generated. The degree of polarization depends on the photon energy and emission angle. Considering an ideal undulator, the collimation of the photon beam increases the polarization. In a real undulator, the parameters as K value and period vary within margin defined be the fabrication process. The resulting effective polarization differs from that expected by an ideal helical undulator. The photon spectra from non-ideal undulator can be simulated by the HUSR code by introducing errors in the helical undulator magnetic field map. This study presents a comparison of the ideal and realistic polarization distribution of the photon beam expected for ILC250. Further, 23 masks are inserted to protect the undulator wall along the 320m undulator line from power deposition by the photon beam. These masks collimate slightly the photon beam and modify the polarization. Also this effect is evaluated in the study.