The photograph shows the front opening of the 10′ Soller collimators of the detector bank of D1A taken before its rebuild in the late 1990's. The protective shielding has been removed so that thin vertical mylar sheets covered in a white gadolinium oxide paint are visible. The ones shown here were designed to collimate neutrons to 10 arc minutes (0.17°). (The little hole seen on the detector bank was a large "pin-hole" collimator, positioned in front of the normally unused 11th detector.)

The Soller collimators designed for use on neutron diffractometers have large dimensions as illustrated by the figure below for 5′ collimation. The figure shows just two foils, but in practice many parallel foils are required since the diameter of the detectors is 2 to 5 cm.

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