Dynamic motion trajectory control with nanoradian accuracy for multi-element X-ray optical systems via laser interferometry

TL;DR

This paper presents a laser interferometry-based motion control system achieving nanoradian accuracy for X-ray optical systems, significantly improving stability and coherence in next-generation high-brightness X-ray sources.

Contribution

It introduces an optical metrology approach integrated with motion control to achieve nanoradian precision in X-ray optics, enabling advancements in high-coherence X-ray applications.

Findings

Achieved sub-microradian motion control accuracy

Demonstrated real-time compensation of optical element errors

Validated system performance on a prototype X-ray cavity

Abstract

The past decades have witnessed the development of new X-ray beam sources with brightness growing at a rate surpassing Moore's law. Current and upcoming diffraction limited and fully coherent X-ray beam sources, including multi-bend achromat based synchrotron sources and high repetition rate X-ray free electron lasers, puts increasingly stringent requirements on stability and accuracy of X-ray optics systems. Parasitic motion errors at sub-micro radian scale in beam transport and beam conditioning optics can lead to significant loss of coherence and brightness delivered from source to experiment. To address this challenge, we incorporated optical metrology based on interferometry and differential wavefront sensing as part of the X-ray optics motion control system. A prototype X-ray optics system was constructed following the optical layout of a tunable X-ray cavity. On-line interferometric metrology enabled dynamical feedback to a motion control system to track and compensate for motion errors. The system achieved sub-microradian scale performance, as multiple optical elements are synchronously and continuously adjusted. This first proof of principle measurement demonstrated both the potential and necessity of incorporating optical metrology as part of the motion control architecture for large scale X-ray optical systems such as monochromators, delay lines, and in particular, X-ray cavity systems to enable the next generation cavity-based X-ray free electron lasers.