Efficient Propagation of Polarization from Laser Photons to Positrons through Compton Scattering and Electron-Positron Pair Creation

Abstract

We have demonstrated for the first time the production of highly polarized short-pulse positrons with a finite energy spread in accordance with a new scheme that consists of two-quantum processes, such as inverse Compton scattering and electron-positron pair creation. Using a circularly polarized laser beam of 532 nm scattered off a high-quality, 1.28 GeV electron beam, we have obtained polarized positrons with an intensity of $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ ${e}^{+}/\mathrm{\text{bunch}}$. The magnitude of positron polarization has been determined to be $73\ifmmode\pm\else\textpm\fi{}15(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}19(\mathrm{syst})%$ by means of a newly designed positron polarimeter.