TXM SRL
  null   Full-field Transmission X-ray Microscopy

Capabilities
The transmission X-ray microscope (TXM) on beam line 6-2c at SSRL is capable of 2D imaging and tomography of many materials including biological and environmental samples, and complex hierarchical systems such as fuel cells and battery electrodes, with chemical information, at 30 nm resolution. The field of view (FOV) is 30 microns, but samples can be raster scanned to increase the FOV while maintaining the same resolution. Because the microscope is equipped with optics that can be used from ~5 to 14 keV, it is useful for characterizing metal distribution and chemical states by imaging at X-ray absorption edges for many metals involved in energy materials. 3D elemental mapping is accomplished via acquisition of tomography above and below the X-ray absorption edge. 2D mapping of chemical states is accomplished with XANES (X-ray absorption near edge structure) imaging, in which many images are acquired along the X-ray absorption edge of a metal, and constructed spectra can be compared to those for model compounds of known structure. It is also possible to acquire 3D XANES tomography, in which chemical states can be mapped in 3D.

Current Energy Applications
Fuel cells and batteries both involve nanoscale electrochemical surface phenomena, which can be characterized using TXM. For effective catalysis, fuel cells require transport of electrons and ions and therefore studies of porosity, and chemical states and particle size of particular elements as a function of reaction conditions can be very valuable. For optimization of charging and discharging of battery electrodes it is important to be able to determine oxidation states, and correlate these with morphological changes. This can be accomplished with 2D and 3D XANES imaging to determine nanoscale chemistry, as well as single-energy tomography to determine porosity and tortuosity. For future work we plan imaging of in situ battery electrodes and fuel cells.

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Normal mouse tibia trabecular region in microCT at 10 µm resolution (left), followed by 20X objective differential interference contrast picture of a single thin trabecula, at ~ 0.75 µm resolution (center), followed by TXM mosaic composite with phase contrast at 8 keV, with 40 nm resolution (right). Each frame is 13.9 µm square. Background removal was improved using Adobe Photoshop

 
Downloads & Links

PDF iconIf you would like to read the full research paper please click on the PDF icon to download the research paper that explores the new TXM imaging technology at SSRL.
  null   Advance the Understanding of Biological Systems

   
Absorption   Tomography   Phase contrast

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Examples of work involving the TXM
We have developed imaging capabilities for Zernike phase contrast and absorption contrast over a wide energy range, and built up a strong user community in a variety of fields. In addition to imaging of yeast cells (Chen et al. 2010, Andrews et al. AIP 2010, Liu et al. 2010) we have observed microorganisms thought to be involved in mercury methylation (Patty et al. 2009) and imaged patterns of arsenic accumulation in rice (Seyfferth et al. 2010). We were able to quantify mineral content in bone and other mineralized tissue using tomography and calibration with an apatite standard (Andrews et al. Microsc. Microanal. 2010). Over this time we began to use the energy-tuning capability of the beam line to add chemistry to distinguish elements (Moore 2009) and to quantify attenuation coefficients to identify chemical elements present (Andrews et al. Microsc. Res. Tech. 2010, Liu et al. 2010). We have also begun to distinguish chemical speciation in 2D (Liu et al. 2010), and to perform initial work on 3D XANES imaging (Meirer et al. 2011).

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