A data collection system for protein crystallography with area‐sensitive proportional counters

To take full advantage of the capabilities of an area‐sensitive electronic detector for x‐ray crystallography, data analysis and reduction has to be performed in parallel to the data collection. A data collection system is described that makes extensive use of computer modules for the VME bus. The data acquisition electronics is embedded in the computer system that analyzes the diffraction pictures so as to keep data transfer time short. It is based on an intelligent computer module allowing us to add the electronic hardware necessary for our specific application. Using a fast FIFO buffer we can collect 24‐bit‐wide data words at an average rate of almost 300 kHz with a dead time τ_D of 100 ns between successive events.