Ronchi test for characterization of X-ray nanofocusing optics and beamlines

Abstract

A Ronchi interferometer for hard X-rays is reported in order to characterize the performance of the nanofocusing optics as well as the beamline stability. Characteristic interference fringes yield qualitative data on present aberrations in the optics. Moreover, the visibility of the fringes on the detector gives information on the degree of spatial coherence in the beamline. This enables the possibility to detect sources of instabilities in the beamline like vibrations of components or temperature drift. Examples are shown for two different nanofocusing hard X-ray optics: a compound refractive lens and a zone plate.

Perfect X-ray focusing via fitting corrective glasses to aberrated optics

“…It was characterized in detail by ptychography with a test object placed slightly out of focus (Fig. 1a) and showed pronounced spherical aberration4 that was also confirmed by the Ronchi test2526 (Fig. 1b).…”

Quantitative characterization of X-ray lenses from two fabrication techniques with grating interferometry

“…The limit of 1.4 m is a factor of 4.3 smaller than in previous experiments [4]. More general approaches can be used to characterize lenses of arbitrary focal length, for example investigating the image of the grating produced in a microscopy setup [8], or a Ronchi type interferometer [9]. However, in these techniques it is not possible to obtain a flat field image to characterize the incident wavefront without lens, which makes the determination of absolute, quantitative values difficult.…”

Aberration correction for hard x-ray focusing at the nanoscale

“…Hence, the predominant type of aberrations in these optics is spherical aberration. 11,34 As many CRLs are typically stacked to form a lens with short focal length and high NA, shape errors add up and aberrations become severe for CRL optics with higher NA ≥ 0.5 × 10 −3 . For an individual lens surface of the CRLs used here (R = 50 µm) it was found that the shape only deviates by 0.5 µm from the ideal parabola over the whole lens aperture of D = 300 µm.…”