X-ray Zernike full field microscope

Figure 2: Bright field image (top) and positive Zernike phase contrast image (bottom) of Ni Siemens Star recorded at 6.2 keV.

For investigation of cells and tissue a Zernike phase contrast X-ray microscope is installed at beamline P11. The microscope is built in a collaboration with I. Vartiainen and C. David from Paul-Scherrer-Institut in Switzerland. The microscope is operated at wavelengths of 4.2 and 6 keV. The current version of the microscope provides a field of view of 50 x 50 µm2 with a resolution of down to 50 nm. The combination of relatively low X-ray energies (tender X-rays) with Zernike phase contrast allows achieving high contrast from weakly absorbing samples, such as biological materials, mainly consisting of carbon, oxygen and nitrogen. The advantage of our setup compared to classical soft X-ray microscopy in the water window is the much larger depth of field of the setup.

Figure 1: Schematic drawing of the Zernike full field setup and experimental implementation at beamline P11.

A schematic drawing of the experimental setup and an image of the current installation at beamline P11 is shown in figure 1. The incoming X-rays are focused using a diffraction grating based condenser generating an uniform illumination over an area of 50 x 50 µm2. Behind the sample an objective zone plate generates a magnified image of the sample on a CCD detector equipped with a YAG fluorescence screen. For Zernike phase contrast applications a phase plate can be inserted into the beam path. Figures 2 and 3 show several X-ray micrographs of different objects recorded with the setup.

Figure 3: Zernike phase contrast image of heavy metal stained HUH7 liver cells (E = 6.2 keV). A: untreated sample, B: sample treated with oleic acid. The formation of lipid droplets (LD) is associated with Hepatitis C Virus infection and supposed to be involved in virus replication. Cellular features observed include the cell nucleus (N), nucleolus (NE), nuclear membrane (NM), cellular membrane (CM), lipid droplets (LD), and internal membranes (IM). This work was done in collaboration with Dr. R. Reimer and Dr. E. Herker from the Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology in Hamburg.

The current setup is limited to 2D microscopy. First tomography experiments are scheduled for summer 2013. After the PETRA III extension shutdown a newly developed microscope will be installed at beamline P11. This combined full field / scanning transmission microscope will be operated in vacuum and thus allow operation at X-ray energies down to 2.4 keV with full tomographic capability. It will further allow for cryogenic sample cooling for radiation sensitive samples.

For further information please contact:

Warmer
Martin Warmer
E-Mail: Martin Warmer
Phone: +49 (0)40 8998 4472