Designing a High-Performance Quarter Waveplate for Improved Signal Quality in X-ray Magnetic Circular Dichroism Studies at EMA Beamline

Abstract X-ray Magnetic Circular Dichroism (XMCD) is a key technique for probing the magnetic properties of intricate materials, utilizing differences in absorption spectra of circularly polarized X-rays with opposite helicities from a magnetized sample. At the EMA beamline in Sirius, polarization control is achieved through quarter-wave plates, enabling changes in X-ray helicity at a rate of 10 Hz. This work proposes an instrumentation redesign to increase the frequency of X-ray polarization switching, optimizing the use of EMA’s high photon flux and improving XMCD signal quality. The new design aims to oscillate crystals up to 200 Hz, operate between 3 and 22 keV, follow the high dynamic double crystal monochromator fly-scan at 1 keV / s, accommodate six different crystal configurations, and maintain a vacuum level better than 10 −8 mbar. This advance is expected to significantly enhance XMCD studies, particularly for samples with very low magnetization, and advance research within the synchrotron community by providing a versatile and high-performance tool for investigating magnetic properties.