  We describe the development, operation, and application of the 4D Camera -- a
576 by 576 pixel active pixel sensor for scanning/transmission electron
microscopy which operates at 87,000 Hz. The detector generates data at
approximately 480 Gbit/s which is captured by dedicated receiver computers with
a parallelized software infrastructure that has been implemented to process the
resulting 10 - 700 Gigabyte-sized raw datasets. The back illuminated detector
provides the ability to detect single electron events at accelerating voltages
from 30 - 300 keV. Through electron counting, the resulting sparse data sets
are reduced in size by 10 - 300x compared to the raw data, and open-source
sparsity-based processing algorithms offer rapid data analysis. The high frame
rate allows for large and complex 4D-STEM experiments to be accomplished with
typical STEM scanning parameters.
