Nanoradian angular stabilization of x-ray optical components

TL;DR

This paper demonstrates nanoradian-level angular stabilization of x-ray optical components using a feedback loop, significantly improving stability for x-ray monochromators and supporting the development of x-ray free electron laser oscillators.

Contribution

The authors developed a feedback stabilization method achieving nanoradian angular stability for x-ray optical components, advancing precision control in x-ray optics.

Findings

Achieved approximately 13 nrad angular stability in x-ray monochromators.

Demonstrated the effectiveness of a null-detection based feedback loop.

Supported the stability requirements for x-ray free electron laser oscillators.

Abstract

An x-ray free electron laser oscillator (XFELO) has been recently proposed [K. Kim, Y. Shvyd'ko, and S. Reiche, Phys. Rev. Lett. 100, 244802 (2008)]. Angular orientation and position in space of Bragg mirrors of the XFELO optical cavity must be continuously adjusted to compensate instabilities and maximize the output intensity. An angular stability of about 10 nrad (rms) is required [K. Kim and Y. Shvyd'ko Phys. Rev. STAB 12, 030703 (2009)]. To approach this goal, a feedback loop based on a null-detection principle was designed and used for stabilization of a high energy resolution x-ray monochromator ($\Delta E/E \simeq 4 \times 10^{-8}$, $E$ = 23.7 keV) and a high heat load monochromator. Angular stability of about 13 nrad (rms) has been demonstrated for x-ray optical elements of the monochromators.