  Ultrafast-optical-pump -- structural-probe measurements, including ultrafast
electron and x-ray scattering, provide direct experimental access to the
fundamental timescales of atomic motion, and are thus foundational techniques
for studying matter out of equilibrium. High-performance detectors are needed
in scattering experiments to obtain maximum scientific value from every probe
particle. We deploy a hybrid pixel array direct electron detector to perform
ultrafast electron diffraction experiments on a WSe$_2$/MoSe$_2$ 2D
heterobilayer, resolving the weak features of diffuse scattering and moir\'e
superlattice structure without saturating the zero order peak. Enabled by the
detector's high frame rate, we show that a chopping technique provides
diffraction difference images with signal-to-noise at the shot noise limit.
Finally, we demonstrate that a fast detector frame rate coupled with a high
repetition rate probe can provide continuous time resolution from femtoseconds
to seconds, enabling us to perform a scanning ultrafast electron diffraction
experiment that maps thermal transport in WSe$_2$/MoSe$_2$ and resolves
distinct diffusion mechanisms in space and time.
