Undulator-Based Production of Polarized Positrons
Abstract
Full exploitation of the physics potential of a future International Linear Collider will require the use of polarized electron and positron beams. Experiment E166 at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme in which an electron beam passes through a helical undulator to generate photons (whose first-harmonic spectrum extended to 7.9MeV) with circular polarization, which are then converted in a thin target to generate longitudinally polarized positrons and electrons. The experiment was carried out with a one-meter-long, 400-period, pulsed helical undulator in the Final Focus Test Beam (FFTB) operated at 46.6GeV. Measurements of the positron polarization have been performed at five positron energies from 4.5 to 7.5MeV. In addition, the electron polarization has been determined at 6.7MeV, and the effect of operating the undulator with a ferrofluid was also investigated. To compare the measurements with expectations, detailed simulations were made with an upgraded version of Geant4 that includes the dominant polarization-dependent interactions of electrons, positrons, and photons with matter. The measurements agree with calculations, corresponding to 80% polarization for positrons near 6MeV and 90% for electrons near 7MeV.
Cite
@article{arxiv.0905.3066,
title = {Undulator-Based Production of Polarized Positrons},
author = {Gideon Alexander and John Barley and Yuri Batygin and Steven Berridge and Vinod Bharadwaj and Gary Bower and William Bugg and Franz-Josef Decker and Ralph Dollan and Yuri Efremenko and Klaus Floettmann and Vahagn Gharibyan and Carsten Hast and Richard Iverson and Hermann Kolanoski and Jan W. Kovermann and Karim Laihem and Thomas Lohse and Kirk T. McDonald and Alexander A. Mikhailichenko and Gudrid Moortgat-Pick and Philipp Pahl and Rainer Pitthan and Roman Poeschl and Erez Reinherz-Aronis and Sabine Riemann and Andreas Schaelicke and Klaus-Peter Schueler and Thomas Schweizer and Duncan Scott and John C. Sheppard and Achim Stahl and Zenon Szalata and Dieter R. Walz and Achim Weidemann},
journal= {arXiv preprint arXiv:0905.3066},
year = {2015}
}
Comments
64 pages, 63 figures