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Transmission hard X-ray microscope using planar crossed SU-8 parabolic objective and condenser
Figure 1: (a) SEM view of the element of used condenser lens and (b) ist photograph. (c) SEM photo of elements of objective lens.

A transmission hard X-ray microscope (THXM) using refractive planar crossed parabolic condenser and objective lenses made of SU-8 polymer by deep X-ray lithography was set up at the ANKA FLUO station at 12.5 keV. Different test nanostructures with sizes down to 200 nm were imaged with this THXM using in-line phase-contrast, with an X-ray magnification factor of 65, a spatial resolution of about 100 nm and an exposure times in the order of 5 s. The illuminated area for the observation of objects corresponded to the 50 μm aperture of the objective lens used.
Sets of planar SU-8 crossed lenses are fabricated in IMT/FZK within the institutes’ flagship project. The lenses focusing in two directions are made by direct tilted deep X-ray lithography using an X-ray mask with tilted gold absorber structures. Deep X-ray lithographic exposures are performed at the ANKA LITHO stations.
The profile of the absorber structures on the mask takes into account the lithographic peculiarities of SU-8 resist to reproduce the designed profile of the lens elements exactly. The lens profiles are measured by means of a special optical microscope method using step-by-step polishing of the lens structures in a polymer matrix.
Nanostructures with sizes down to 200 nm have been imaged in the in-line phase contrast geometry of the THXM setup. 3-dimentional translations and 2-axial rotations are applied for the adjustment of the objective lens and condenser. The tower for an object allows 3D translations also.
The distance between the synchrotron radiation source and the condenser position was 12 m.
The source size is equal to 0.12×0.8 mm2 for its vertical and horizontal full widths at half maximum of intensity. The corresponding coherence field is ~0.5 x 2 μm2.
X-ray images of test microstructures with the minimal lateral size of about 200 nm were taken with 65-fold X-ray magnification for a photon energy of 12.5 keV. Phase contrast images of test micro structures were recorded with a resolution of 93 ±19nm with exposure times on the order of 5 sec.
SU-8 polymer refractive lenses are promising as they allow constructing a THXM in air surrounding within a total length of about 2 m for an X-ray energy up to 40 keV.
For a THXM based on SU-8 refractive optics, the large coherence field and long distance from a synchrotron radiation source are not required.
We tend to create a THXM for observation of biological living cells with their natural movements in water solutions; condensers with large apertures are designed to provide X-ray exposure time of ~0.1 sec for the THXM magnification in the range of 50 – 100 and the view field up to 100×100 μm2.