# Detector Damage at X-Ray Free-Electron Laser Sources

## TL;DR

This paper reviews seven years of detector damage at LCLS FELs, identifying 19 damage mechanisms and proposing mitigation strategies to ensure detector longevity and experimental success in a high-intensity, high-pressure environment.

## Contribution

It provides a comprehensive analysis of damage mechanisms in FEL detectors and introduces effective mitigation strategies based on extensive operational experience.

## Key findings

- 19 damage mechanisms identified in FEL detectors
- Damage mitigation strategies improve detector longevity
- Operational procedures reduce damage risk

## Abstract

Free-electron lasers (FELs) opened a new window on imaging the motion of atoms and molecules. At SLAC, FEL experiments are performed at LCLS using 120 Hz pulses with 10^12 to 10^13 photons in 10 fs (billions of times brighter than at the most powerful synchrotrons). Concurrently, users and staff operate under high pressure due to flexible and often rapidly changing setups and low tolerance for system malfunction. This extreme detection environment raises unique challenges, from obvious to surprising, and leads to treating detectors as consumables. We discuss in detail the detector damage mechanisms observed in 7 years of operation at LCLS, together with the corresponding damage mitigation strategies and their effectiveness. Main types of damage mechanisms already identified include: (1) x-ray radiation damage (from "catastrophic" to "classical"), (2) direct and indirect damage caused by optical lasers, (3) sample induced damage, (4) vacuum related damage, (5) high-pressure environment. In total, 19 damage mechanisms have been identified. We also present general strategies for reducing damage risk or minimizing the impact of detector damage on the science program. These include availability of replacement parts and skilled operators and also careful planning, incident investigation resulting in updated designs, procedures and operator training.