High average brightness water window source for short-exposure cryomicroscopy.

Laboratory water window cryomicroscopy has recently demonstrated similar image quality as synchrotron-based microscopy but still with much longer exposure times, prohibiting the spread to a wider scientific community. Here we demonstrate high-resolution laboratory water window imaging of cryofrozen cells with 10 s range exposure times. The major improvement is the operation of a λ=2.48 nm, 2 kHz liquid nitrogen jet laser plasma source with high spatial and temporal stability at high average brightness >1.5×10(12) ph/(s×sr×µm(2)×line), i.e., close to that of early synchrotrons. Thus, this source enables not only biological x-ray microscopy in the home laboratory but potentially other applications previously only accessible at synchrotron facilities.

Compact x-ray microscope for the water window based on a high brightness laser plasma source.

We present a laser plasma based x-ray microscope for the water window employing a high-average power laser system for plasma generation. At 90 W laser power a brightness of 7.4 x 10(11) photons/(s x sr x µm(2)) was measured for the nitrogen Lyα line emission at 2.478 nm. Using a multilayer condenser mirror with 0.3 % reflectivity 10(6) photons/(µm(2) x s) were obtained in the object plane. Microscopy performed at a laser power of 60 W resolves 40 nm lines with an exposure time of 60 s. The exposure time can be further reduced to 20 s by the use of new multilayer condenser optics and operating the laser at its full power of 130 W.

Note: study of extreme ultraviolet and soft x-ray emission of metal targets produced by laser-plasma-interaction.

Different metal targets were investigated as possible source material for tailored laser-produced plasma-sources. In the wavelength range from 1 to 20 nm, x-ray spectra were collected with a calibrated spectrometer with a resolution of λ/Δλ = 150 at 1 nm up to λ/Δλ = 1100 at 15 nm. Intense line emission features of highly ionized species as well as continuum-like spectra from unresolved transitions are presented. With this knowledge, the optimal target material can be identified for the envisioned application of the source in x-ray spectrometry on the high energy side of the spectra at about 1 keV. This energy is aimed for because 1 keV-radiation is ideally suited for L-shell x-ray spectroscopy with nm-depth resolution.

High spectral resolution x-ray optics with highly oriented pyrolytic graphite.

Thin films of highly oriented pyrolytic graphite (HOPG) give the opportunity to realize crystal optics with arbitrary geometry by mounting it on a mould of any shape. A specific feature of HOPG is its mosaicity accompanied by a high integral reflectivity, which is by an order of magnitude higher than that of all other known crystals in an energy range between 2 keV up to several 10 keV. These characteristics make it possible to realize highly efficient collecting optics, which could be also relevant for compact x-ray diagnostic tools and spectrometers. For these applications the achievable spectral resolution of the crystal optics is of interest. In this article measurements with a spectral resolution of E/DeltaE=2900 in the second order reflection and E/DeltaE=1800 in the first order reflection obtained with HOPG crystals are presented. These are by far the highest spectral resolutions reported for HOPG crystals. The integral reflectivity of these very thin films is still comparable with that of ideal Ge crystals. The trade-off between energy resolution and high integral reflectivity for HOPG is demonstrated by determining these parameters for HOPG films of different thickness.