X-ray microscopy in the water-window region (ë=2.3-4.4 nm) based on diffractive zone plate optics is an attractive technique for high-resolution imaging. Conventional x-ray microscopes are based on synchrotron radiation sources. However, many scientists would benefit from having an x-ray microscope as one imaging tool among others in their own laboratory. For this purpose we developed and demonstrated the first compact x-ray microscope with sub-µm resolution [1].
In this presentation we describe the improved second-generation compact full-field x-ray transmission microscope. It is based on a compact liquid-jet-target laser-plasma source, featuring operation at ë=3.37 nm [2] or ë=2.48 nm [3]. The mechanical and optical design is user-friendly and allows stable operation [4]. Thin ~3 µm carbon-containing samples can be imaged with good contrast using the ë=3.37 nm wavelength, whereas thicker ~10 µm biological objects require operation at ë=2.48 nm where the x-ray transmission is higher. When operating at ë=3.37 nm, x-rays are focused onto the sample using a normal-incidence multilayer mirror condenser [5]. Due to poor performance of such mirrors at ë=2.48 nm, a large ~4.5 mm diameter condenser zone plate [6] is employed. The sample holder is mounted in a helium atmosphere and allows imaging of both dry and wet specimens. Future systems will include cryo-fixation of the sample. The imaging of the sample onto a CCD detector is performed by in-house fabricated state-of-the-art nickel micro zone plates with outer zone widths down to 25 nm [7]. We show that this microscope is capable of resolving 60 nm period gratings with good contrast [4] and demonstrate the performance of the instrument by presenting images from both dry and wet samples.
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2. U. Vogt et.al., Appl. Phys. B 78, 53-58 (2004)
3. P. A. C. Jansson et.al., Rev. Sci. Instrum. 76, 43503-1 (2005)
4. P. A. C. Takman et.al., accepted by J. Microsc. (2007)
5. H. Stollberg et.al., Rev. Sci. Instrum. 77, 123101-1 (2006)
6. S. Rehbein et.al., J. Vac. Sci. Technol. B 22, 1118-1122 (2004)
7. A. Holmberg et.al., IPAP Conference Series 7: X-ray microscopy, 124-126 (2006)
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