  We report the design and performance of a time-resolved electron diffraction
apparatus capable of producing intense bunches with simultaneously single digit
micron probe size, long coherence length, and $200$ fs rms time resolution. We
measure the 5d (peak) beam brightness at the sample location in
micro-diffraction mode to be $7 \times 10^{13} \
\mathrm{A}/\text{m}^2\text{-rad}^2$. To generate high brightness electron
bunches, the system employs high efficiency, low emittance semiconductor
photocathodes driven with a wavelength near the photoemission threshold at a
repetition rate up to 250 kHz. We characterize spatial, temporal, and
reciprocal space resolution of the apparatus. We perform proof-of-principle
measurements of ultrafast heating in single crystal Au samples and compare
experimental results with simulations that account for the effects of
multiple-scattering.
