Characterization of a next-generation piezo bimorph X-ray mirror for synchrotron beamlines

Abstract

Piezo bimorph mirrors are versatile active optics used on many synchrotron beamlines. However, many bimorphs suffer from the 'junction effect': a periodic deformation of the optical surface which causes major aberrations to the reflected X-ray beam. This effect is linked to the construction of such mirrors, where piezo ceramics are glued directly below the thin optical substrate. In order to address this problem, a next-generation bimorph with piezos bonded to the side faces of a monolithic substrate was developed at Thales-SESO and optimized at Diamond Light Source. Using metrology feedback from the Diamond-NOM, the optical slope error was reduced to $ 0.5 mrad r.m.s. for a range of ellipses. To maximize usability, a novel holder was built to accommodate the substrate in any orientation. When replacing a firstgeneration bimorph on a synchrotron beamline, the new mirror significantly improved the size and shape of the reflected X-ray beam. Most importantly, there was no evidence of the junction effect even after eight months of continuous beamline usage. It is hoped that this new design will reinvigorate the use of active bimorph optics at synchrotron and free-electron laser facilities to manipulate and correct X-ray wavefronts.

X-ray beam expansion by the application of re-entrant surface profiles to deformable bimorph mirrors

“…However, it should be mentioned that the test mirror of this article and the mirror used at I02 both belong to the first generation of bimorphs, in which the piezoelectric elements are sandwiched between an upper and a lower substrate 2 . On the other hand, the mirror installed at I24 is one of the first examples of the second generation of bimorphs, in which the piezoelectric elements are attached to the sides of the substrate 20 . The dependence of the PRFs on the construction of a bimorph will be an important topic for future studies.…”

Long, elliptically bent, active X-ray mirrors with slope errors <200 nrad

“…This can be achieved either by using active optics or a transfocator containing a user-selectable number of compound refractive X-ray lenses. Active optics with deformable reflective surfaces, such as piezo bimorph deformable mirrors (Alcock et al, 2015) or mechanically bent mirrors, enable focusing parameters of the beamline to be easily and quickly adjusted. The simplest form of mechanical bender employs a single actuator to apply equal forces to the ends of a cuboid-shaped substrate, thereby inducing a cylindrical bend in the optical surface.…”

Variable-spot ion beam figuring

“…As a deterministic method, it has proven effective and applicable in processing both large optics [3,4] and small optical components [5]. For years, it has seen a growing demand of the high-quality ultra-precision optics finished by IBF technologies in many fields such as astronomy telescopes [3,4], synchrotron beamlines [6,7,8], and the extreme ultraviolet lithography [9].…”