Measurement of Coherent Emission and Linear Polarization of Photons by Electrons in the Strong Fields of Aligned Crystals

TL;DR

This study investigates high-energy photon emission and polarization from electrons in aligned silicon crystals, revealing less than 20% linear polarization in high-energy photons, with implications for understanding coherent bremsstrahlung in strong crystal fields.

Contribution

It provides new experimental measurements of photon polarization and energy in a specific crystal alignment, advancing knowledge of coherent emission processes in strong fields.

Findings

High-energy photons exhibit less than 20% linear polarization.

Photon energy and polarization measured individually in a multi-photon environment.

Results enhance understanding of coherent bremsstrahlung in aligned crystals.

Abstract

We present new results regarding the features of high energy photon emission by an electron beam of 178 GeV penetrating a 1.5 cm thick single Si crystal aligned at the Strings-Of-Strings (SOS) orientation. This concerns a special case of coherent bremsstrahlung where the electron interacts with the strong fields of successive atomic strings in a plane and for which the largest enhancement of the highest energy photons is expected. The polarization of the resulting photon beam was measured by the asymmetry of electron-positron pair production in an aligned diamond crystal analyzer. By the selection of a single pair the energy and the polarization of individual photons could be measured in an the environment of multiple photons produced in the radiator crystal. Photons in the high energy region show less than 20% linear polarization at the 90% confidence level.