Publication
Article Metrics
Citations
Online attention
Bimorph mirrors: The good, the bad, and the ugly
DOI:
10.1016/j.nima.2012.10.135
Authors:
Simon G.
Alcock
(Diamond Light Source)
,
John
Sutter
(Diamond Light Source)
,
Kawal
Sawhney
(Diamond Light Source)
,
Dave
Hall
(Diamond Light Source)
,
Katherine
Mcauley
(Diamond Light Source)
,
Thomas
Sorensen
(Diamond Light Source)
Co-authored by industrial partner:
No
Type:
Conference Paper
Conference:
The 4th international workshop on Metrology for X-ray Optics, Mirror Design, and Fabrication
Peer Reviewed:
No
State:
Published (Approved)
Published:
November 2012
Abstract: Bimorph mirrors are widely used by the X-ray, Laser, Space, and Astronomy communities to focus or collimate photon beams. Applying voltages to the embedded piezo ceramics enables the user to globally bend the optical substrate to a range of figures (including cylindrical, parabolic, and elliptical), and finely correct low spatial frequency errors, thus improving optical performance. Bimorph mirrors are employed on numerous synchrotron X-ray beamlines, including several at Diamond Light Source. However, many such beamlines were not achieving the desired size and shape of the reflected X-ray beam. Metrology data from ex-situ, slope measuring profilometry (using the Diamond-NOM) and in-situ, synchrotron X-ray “pencil-beam” scans, revealed sharp defects on the optical substrate directly above the locations at which the piezo ceramics are bonded together. This so-called “junction effect” has been observed on a variety of bimorph mirrors with different numbers of piezos, substrate length, and thickness. To repair this damage, three pairs of bimorph mirrors were re-polished at Thales-SESO. We review the re-polishing process, and show that it successfully removed the junction effect, and significantly improved beamline performance. Since the internal structure of the bimorph mirrors was not modified during re-polishing, it is hoped that the mirrors will retain their surface quality, and remain operational for many years. We also highlight the combination of super-polishing techniques with bimorph technology to create the “Ultimate” mirror, and discuss a next generation, bimorph mirror which is predicted not to suffer from the junction effect.
Journal Keywords: Piezo bimorph mirrors; Junction effect; Active optics; Synchrotron mirrors; Diamond-NOM; Nano-metrology
Subject Areas:
Physics
Technical Areas:
Metrology
,
Optics
Added On:
02/12/2012 11:51