# Implementation and performance of a fiber-coupled CMOS camera in an ultrafast reflective high-energy electron diffraction experiment

## TL;DR

A new CMOS camera was integrated into an ultrafast electron diffraction setup, offering improved resolution and performance in vacuum conditions.

## Contribution

The paper introduces a fiber-coupled CMOS camera with enhanced spatial resolution and reduced blooming effects for ultrafast electron diffraction.

## Key findings

- The TemCam-XF416 provides 30% higher resolution in reciprocal space compared to previous detectors.
- The camera's low background and larger dynamic range allow analysis of Kikuchi lines and bands.
- The absence of blooming enables quantitative spot profile analysis in diffraction patterns.

## Abstract

The implementation of a monolithic fiber-optically coupled CMOS-based TemCam-XF416 camera into our ultra-high vacuum (UHV) ultrafast reflection high-energy electron diffraction setup is reported. A combination of a pumpable gate valve and a self-built cooling collar allows UHV conditions to be reached without the need to remove the heat-sensitive device. The water-cooled collar is mounted to the camera housing and prevents heating of the camera upon bakeout of the UHV chamber. The TemCam possesses an one order of magnitude higher spatial resolution, which provides 30% higher resolution in reciprocal space than the previously used microchannel plate detector. The low background intensity and the four times larger dynamic range enable analysis of the diffuse intensity of the diffraction pattern like Kikuchi lines and bands. A key advantage over the previous MCP detector is the complete absence of the blooming effect, which enables the quantitative spot profile analysis of the diffraction spots. The inherent light sensitivity in an optical pump experiment can be overcome by subtracting a pump image without a probe, using photons with
hν<1.12 eV (indirect bandgap of silicon), or shielding any stray light.