High-intensity, fully coherent X-ray radiation with a tunable polarization over a wide spectral range is of great importance to many experiments. In this paper, we propose a tapered crossed-polarized undulator configuration for X-ray free electron laser oscillator (XFELO) to produce arbitrarily polarized X-ray pulses in hard X-ray region. A numerical example utilizing the parameters of the Shanghai High-Repetition-Rate XFEL and Extreme Light Facility (SHINE) is presented to demonstrate the generation of polarization controllable, fully coherent Hard X-ray pulses with 99.9% polarization degree and 20 KHz polarization switching rate. This scheme also holds the possibility to be used in cavity tunable XFELO.
@article{arxiv.1911.10660,
title = {Polarization control of an X-ray free electron laser oscillator},
author = {Nanshun Huang and Kai Li and Haixiao Deng},
journal= {arXiv preprint arXiv:1911.10660},
year = {2020}
}