How it works
Simulated experiment
The white beam (polychromatic) from the thermal tube H11 arrives at the monochromator.
Monochromatic diffracted beams reache the sample – a single crystal - located at the centre of the Eulerian cradle.
The curved two-dimensional position-sensitive detector (PSD) records all diffracted beams within its angular range (120° × 30°). This dramatically speeds up data collection.
If desired, the three angles of the Eulerian cradle are rotated to set the sample to a specific orientation.
The sample is rotated step by step around the vertical axis while the detector records the intensity profils of the diffracted beams.
When the intensities of a large enough number – typically 1000 to 100000 - of Bragg reflections have been collected, they can be used to compute the crystal structure of the sample i.e. to determine the position and nature of its atoms.
The power of D19
The large PSD of D19 and its relatively short wavelength makes it possible to record up to 3500 Bragg reflections at a time. The movie shows a set of diffraction pattern from a small protein crystals with a cell dimension of about 106 Å3.