Secondary slits define size and position of the monchromatic beam after the monochromator. But they also reduce background X-ray scatter from the white beam. The four blades are made of Tungsten carbide and motorised vertically (SSD and SSU) and horizontally (SSB and SSF).

 

secondaryslits.gif

 

It is also possible to change the gap and offset of the blades by moving 2 motors at the same time:

 

secondaryslits_gap_offset.gif