Prospects for Direct Electron Detectors in Ultrafast Electron Diffraction and Scattering Experiments

Abstract

Ultrafast electron diffraction and phonon-diffuse scattering [UED(S)] experiments make use of photo-induced changes to electron scattering intensity across 2D detectors to report on a very wide range of dynamic structural phenomena in molecules and materials. Hybrid pixel counting detectors (HPCDs) are a promising technology for improved sensitivity and signal-to-noise in UED(S) experiments, as they offer near-zero readout noise and dark counts with the possibility of new acquisition modalities (e.g., shot-to-shot normalization) due to their high frame rates. However, it is well known that HPCDs suffer from count losses at high electron fluxes even in CW beam applications. How this translates to ultrashort electron pulse exposures has yet to be determined and is critical to understanding the application of this technology to ultrafast electron scattering experiments. Here we show that count losses are significantly exacerbated in ultrafast (pulsed) experiments and that HPCDs require unconventional data handling and saturate above $\approx 2$ electrons per pixel per pulse. This count-rate limitation presents a severe constraint on electron bunch charge when interrogating single crystal samples. Normalization strategies to optimize signal-to-noise in UED(S) and a complete model for measurement uncertainties using HPCDs are developed and tested using a large dataset. Finally, we suggest ways HPCDs could be better adapted to ultrashort pulsed beam experiments.

15 pages, 6 figures

References in corpus (17)

• High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy
• Light-Induced Charge Density Wave in LaTe${}_3$
• The Ultrafast Einstein-De Haas Effect
• Polarized phonons carry the missing angular momentum in femtosecond demagnetization
• Probing photo-induced melting of antiferromagnetic order in La0.5Sr1.5MnO4 by ultrafast resonant soft X-ray diffraction
• Tracking the Ultrafast Non-Equilibrium Energy Flow between Electronic and Lattice Degrees of Freedom in Crystalline Nickel
• Solving the Jitter Problem in Microwave Compressed Ultrafast Electron Diffraction Instruments: Robust Sub-50 fs Cavity-Laser Phase Stabilization
• Time- and momentum-resolved phonon population dynamics with ultrafast electron diffuse scattering
• A compression scheme for radio data in high performance computing
• Light-induced dimension crossover in 1T-TiSe${}_2$ dictated by excitonic correlations
• Direct view of phonon dynamics in atomically thin MoS${}_2$
• Ultrafast formation of topological defects in a 2D charge density wave
• Using Electron Energy-Loss Spectroscopy to Measure Nanoscale Electronic and Vibrational Dynamics in a TEM
• Excimer Formation in Zinc-phthalocyanine Revealed using Ultrafast Electron Diffraction
• Ultrafast Electron Diffuse Scattering as a Tool for Studying Phonon Transport: Phonon Hydrodynamics and Second Sound Oscillations
• Megahertz cycling of ultrafast structural dynamics enabled by nanosecond thermal dissipation
• Shot-to-shot acquisition ultrafast electron diffraction