SummaryWe demonstrate compact full-field soft X-ray transmission microscopy with sub 60-nm resolution operating at λ = 2.48 nm. The microscope is based on a 100-Hz regenerative liquid-nitrogen-jet laser-plasma source in combination with a condenser zone plate and a micro-zone plate objective for highresolution imaging onto a 2048 × 2048 pixel CCD detector. The sample holder is mounted in a helium atmosphere and allows imaging of both dry and wet specimens. The microscope design enables fast sample switching and the sample can be prealigned using a visible-light microscope. High-quality images can be acquired with exposure times of less than 5 min. We demonstrate the performance of the microscope using both dry and wet samples.

The condenser is a critical component in compact water-window x-ray microscopes as it influences the exposure time via its efficiency and the resolution via its numerical aperture. Normal-incidence multilayer mirrors can reach large geometrical collection efficiencies and match the numerical aperture of the zone plate but require advanced processing for high total reflectivity. In the present article we demonstrate large-diameter normal-incidence spherical Cr∕Sc multilayer condensers with high and uniform reflectivity. Dc-magnetron sputtering was used to deposit 300 bilayers of Cr∕Sc with a predetermined d-spacing matching the λ=3.374nm operating wavelength on spherical substrates. The mirrors show a uniform reflectivity of ∼3% over the full 58mm diameter condenser area. With these mirrors an improvement in exposure time by a factor of 10 was achieved, thereby improving the performance of the compact x-ray microscope significantly.

No abstract

No abstract

Key words. colloidal gold, image analysis, soft X-ray microscopy. SummaryColloidal gold is a useful marker for functional-imaging experiments in transmission X-ray microscopy. Due to the low contrast of gold particles with small diameters it is necessary to develop a powerful algorithm to localize the single gold particles. The presented image-analysis algorithm for identifying colloidal gold particles is based on the combination of a threshold with respect to the local absorption and shape discrimination, realized by fitting a Gaussian profile to the identified regions of interest. The shape discrimination provides the possibility of size-selective identification and localization of single colloidal gold particles down to a diameter of 50 nm. The image-analysis algorithm, therefore, has potential for localization studies of several proteins simultaneously and for localization of fiducial markers in X-ray tomography.