Surface quality of x-ray mirrors evaluated at the Advanced Photon Source

X-ray mirrors are polished and often coated optical substrates used on many synchrotron x-ray beamlines to reflect, focus, steer, or filter x-ray beams. Because their performance depends strongly on their surface quality, they are usually evaluated after delivery, independently (from the vendor), for compliance before acceptance by the buyer. This paper summarizes results of surface roughness and slope error measurements of mirrors delivered to the Advanced Photon Source (APS) and evaluated in the metrology laboratory during the period 1996 - 2001, using non-contact surface profilometry. For all the mirrors evaluated, the measured root-mean square (rms) slope error values range from 0.5 to 4.7 murad rms, and the surface rms values range from 0.9 to 4.3 A rms. Most of the measured mirrors have met the user specifications.