High efficiency and low absorption Fresnel compound zone plates for hard X-ray focusing

Circular and linear zone plates have been fabricated on the surface of silicon crystals for the energy of 8 keV by electron beam lithography and deep ion plasma etching methods. Various variants of compound zone plates with first, second, third diffraction orders have been made. The zone relief height is about 10 mkm, the outermost zone width of the zone plate is 0.4 mkm. The experimental testing of the zone plates has been conducted on SPring-8 and ESRF synchrotron radiation sources. A focused spot size and diffraction efficiency measured by knife-edge scanning are accordingly 0.5 mkm and 39% for the first order circular zone plate.Comment: 5 pages, 7 figure

Ion beam lithography for Fresnel zone plates in X-ray microscopy

Fresnel Zone Plates (FZP) are to date very successful focusing optics for X-rays. Established methods of fabrication are rather complex and based on electron beam lithography (EBL). Here, we show that ion beam lithography (IBL) may advantageously simplify their preparation. A FZP operable from the extreme UV to the limit of the hard X-ray was prepared and tested from 450 eV to 1500 eV. The trapezoidal profile of the FZP favorably activates its 2nd order focus. The FZP with an outermost zone width of 100 nm allows the visualization of features down to 61, 31 and 21 nm in the 1st, 2nd and 3rd order focus respectively. Measured efficiencies in the 1st and 2nd order of diffraction reach the theoretical predictions

X-ray diffraction microscopy based on refractive optics

We describe a diffraction microscopy technique based on refractive optics to study structural variations in crystals. The X-ray beam diffracted by a crystal was magnified by beryllium parabolic refractive lenses on a 2D X-ray camera. The microscopy setup was integrated into the 6-circle Huber diffractometer at the ESRF beamline ID06. Our setup allowed us to visualize structural imperfections with a resolution of approximately 1 micrometer. The configuration, however, can easily be adapted for sub-micrometer resolution.Comment: 9 pages, 4 figures. Submitted to Journal of Synchrotron Radiation on April 4th 2012. Rejecte

Design and imaging performance of achromatic diffractive/refractive X-ray and Gamma-ray Fresnel lenses

Achromatic combinations of a diffractive Phase Fresnel Lens and a refractive correcting element have been proposed for X-ray and gamma-ray astronomy and for microlithography, but considerations of absorption often dictate that the refractive component be given a stepped profile, resulting in a double Fresnel lens. The imaging performance of corrected Fresnel lenses, with and without `stepping' is investigated and the trade-off between resolution and useful bandwidth in different circumstances is discussed. Provided the focal ratio is large, correction lenses made of low atomic number materials can be used with X-rays in the range approximately 10--100 keV without stepping. The use of stepping extends the possibility of correction to higher aperture systems, to energies as low as a few kilo electron volts and to gamma-rays of $\sim$ mega electron volt energy.Comment: To be published in 'Applied Optics

Multi-Lens Array Full-Field X-ray Microscopy

X-ray full-field microscopy at laboratory sources for photon energies above 10 keV suffers from either long exposure times or low resolution. The photon flux is mainly limited by the objectives used, having a limited numerical aperture NA. We show that this can be overcome by making use of the cone-beam illumination of laboratory sources by imaging the same field of view (FoV) several times under slightly different angles using an array of X-ray lenses. Using this technique, the exposure time can be reduced drastically without any loss in terms of resolution. A proof-of-principle is given using an existing laboratory metal-jet source at the 9.25 keV Ga Kα-line and compared to a ray-tracing simulation of the setup

Refractive X-ray beam shaping

This work introduces new refractive illumination optics in the hard X-ray region and describes a method for overcoming fabrication limitations of X-ray depth lithography. In particular, the problem of high aspect ratio in X-ray prism lenses was addressed. The refractive X-ray optics are developed for the photon energy range 8-100 keV. In the following, we report the development of a principal new focusing optics with large aperture, an illumination condenser for full-field X-ray microscopy and a so-called beam shaping optics to overcome the limitation of the field of view at 3rd and 4th generation synchrotron sources. To reduce the absorption of X-rays in the material of the optical systems, the approach of X-ray prism lenses was pursued. Here, the optics consist of rows of micro prisms with an edge length of about 20 µm, which deflect the incident rays. This improves the ratio of the refractive power of the optics to the volume of the absorbing lens material. The mechanical stability of the fragile, very tall micro prisms is achieved by exposing thin, stabilizing support planes. In order to achieve focal sizes smaller than the prism edge lengths, double parabolic biconcave micro-lenses were added to the prism rows. A similar arrangement with biconvex micro-lenses was used to achieve beam expansion while simultaneously homogenizing the illumination of the image field of a full-field X-ray microscope. Beam shaping optics consisting of kinoform Fresnel lens elements were developed for vertical beam expansion at high brilliance synchrotron sources. In all cases, the theory is based on geometrical optics and ray tracing simulations. The optics were produced via deep X-ray lithography using the synchrotron radiation source at KIT at the LIGA I and II beamlines. The lens material is the negative resist mr-X, an epoxy resin-based polymer of type SU-8. The lenses were characterized at PETRA III, DESY in Hamburg and at ESRF in Grenoble