Impact of Seismic Activities on the Optical Synchronization System of the European X-ray Free-Electron Laser

TL;DR

This paper examines how seismic activities, including earthquakes and ocean microseisms, affect the stability of the optical synchronization system at the European XFEL, revealing high sensitivity to environmental vibrations.

Contribution

It provides a detailed analysis of seismic impacts on phase-locked loops in the XFEL's synchronization system, highlighting the system's sensitivity and disturbance mitigation capabilities.

Findings

Seismic events cause significant fluctuations in control signals.

Ocean microseisms have a substantial impact on system stability.

The system can detect vibrations from civilization noise.

Abstract

This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser. We analyze the controller I/O data of phase-locked-loops in length-stabilized links, focusing on the response to earthquakes, ocean-generated microseism and civilization noise. By comparing the controller data with external data, we were able to identify disturbances and their effects on the control signals. Our results show that seismic events influence the stability of the phase-locked loops. Even earthquakes that are approximately \qty{5000}{\km} away cause remarkable fluctuations in the in-loop control signals. Ocean-generated microseism in particular has an enormous influence on the in-loop control signals due to its constant presence. The optical synchronization system is so highly sensitive that it can even identify vibrations caused by civilization, such as road traffic or major events like concerts or sport events. The phase-locked loops manages to eliminate more than 99% of the existing interference.