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

TL;DR

This paper reports on integrating a fiber-coupled CMOS camera into an ultrafast electron diffraction setup, achieving higher resolution, better dynamic range, and eliminating blooming effects, thus enhancing diffraction pattern analysis under UHV conditions.

Contribution

The study introduces a fiber-optically coupled CMOS camera with improved resolution and dynamic range for ultrafast electron diffraction, overcoming limitations of previous MCP-based detectors.

Findings

Higher spatial resolution than MCP detectors

30% improvement in reciprocal space resolution

Elimination of blooming effect enabling quantitative analysis

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 detector upon bake-out of the UHV chamber. The TemCam provides an one order of magnitude higher spatial resolution than the previously used microchannel plate (MCP) based detector (Burle Chevron 3040FM) which enables a 30% higher resolution in reciprocal space. The low background intensity and the 4$\times$ lager dynamic range enables 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 using photons with h{\nu} < 1.12 eV, i.e., the indirect band gap of silicon, or by shielding any stray light.