Synchrotron-based X-ray Tomographic Microscopy (SRXTM) is nowadays a powerful technique for non-destructive, high-resolution investigations of a broad kind of materials. High-brilliance and high-coherence third generation synchrotron radiation facilities allow micrometer and sub-micrometer, quantitative, three-dimensional imaging within very short time and extend the traditional absorption imaging technique to edge-enhanced and phase-sensitive measurements. At the Swiss Light Source TOMCAT, a new beamline for TOmographic Microscopy and Coherent rAdiology experimenTs, has been recently built and started regular user operation in June 2006. The new beamline get photons from a 2.9 T superbend with a critical energy of 11.1 keV. This makes energies above 20 keV easily accessible. To guarantee the best beam quality (stability and homogeneity), the number of optical elements has been kept to a minimum. A Double Crystal Multilayer Monochromator (DCMM) covers an energy range between 8 and 45 keV with a bandwidth of a few percent down to 10 −4 . The beamline can also be operated in white-beam mode, providing the ideal conditions for real-time coherent radiology. This article presents the beamline design, its optical components and the endstation. It further illustrates two recently developed phase contrast techniques and finally gives an overview of recent research topics which make intense use of SRXTM.

Zinc production by solar carbothermic reduction of ZnO offers a CO2 emission reduction by a factor of 5 vis-a`-vis the conventional fossil-fuel-based electrolytic or Imperial Smelting processes. Zinc can serve as a fuel in Zn-air fuel cells or can be further reacted with H2O to form high-purity H2. In either case, the product ZnO is solar-recycled to Zn. We report on experimental results obtained with a 5 kW solar chemical reactor prototype that features two cavities in series, with the inner one functioning as the solar absorber and the outer one as the reaction chamber. The inner cavity is made of graphite and contains a windowed aperture to let in concentrated solar radiation. The outer cavity is well insulated and contains the ZnO-C mixture that is subjected to irradiation from the inner graphite cavity. With this arrangement, the inner cavity protects the window against particles and condensable gases and further serves as a thermal shock absorber. Tests were conducted at PSI’s Solar Furnace and ETH’s High-Flux Solar Simulator to investigate the effect of process temperature (range 1350-1600 K), reducing agent type (beech charcoal, activated charcoal, petcoke), and C:ZnO stoichiometric molar ratio (range 0.7–0.9) on the reactor’s performance and chemical conversion. In a typical 40-min solar experiment at 1500 K, 500 g of a ZnO-C mixture were processed into Zn(g), CO, and CO2. Thermal efficiencies of up to 20% were achieved.

The mechanical design and performance of a device to suppress higher orders of a spherical grating monochromator at a constant deviation angle is described. The higher order suppressor (HOS) is used for a scanning transmission x-ray microspectroscope beamline (PolLux) at a bending magnet of the Swiss Light Source (SLS). The instruments allow microspectroscopy in polymer science, of biological samples in the water window as well as the study of magnetic materials with circular or linear polarized light in a photon energy range of 200 eV to 1400 eV. The HOS uses three mirrors acting as a low pass filter for soft x-rays to improve the absorption spectroscopy of carbon, oxygen and nitrogen 1s core levels. The successful installation and operation of the HOS located after the monochromator is reported. First results obtained using samples from materials research and environmental sciences exemplify the improved spectroscopy capabilities of the instrument.

Solar energy can be stored chemically by using concentrated solar irradiation as an energy source for carbothermic ZnO reduction. The produced Zn might be used for the production of electricity in Zn-air fuel cells or of H2 by splitting water. In either case the product is again ZnO which can be reprocessed in the solar process step. This innovative concept will be scaled up to 300kW solar input power within the so-called SOLZINC-project. In this paper we report on experimental results obtained with a two cavity reactor operated at solar power inputs of 3-8kW in a solar furnace. The objective was to generate input data which are necessary for designing the scaled up reactor, such as the effect of process temperature (1100-1300°C) and carrier gas (N2 and CO) on the overall reaction rate. Furthermore, construction materials were tested and a variety of carbonaceous materials were screened for their use as reducing agents by means of thermogravimetric measurements. As a result, beech charcoal was chosen as the standard reducing agent.

In the framework of the EU-project SOLZINC, a 300-kW solar chemical pilot plant for the production of zinc by carbothermic reduction of ZnO was experimentally demonstrated in a beam-down solar tower concentrating facility of Cassegrain optical configuration. The solar chemical reactor, featuring two cavities, of which the upper one is functioning as the solar absorber and the lower one as the reaction chamber containing a ZnO/C packed bed, was batch-operated in the 1300–1500 K range and yielded 50 kg/h of 95%-purity Zn. The measured energy conversion efficiency, i.e., the ratio of the reaction enthalpy change to the solar power input, was 30%. Zinc finds application as a fuel for Zn/air batteries and fuel cells, and can also react with water to form high-purity hydrogen. In either case, the chemical product is ZnO, which in turn is solar-recycled to Zn. The SOLZINC process provides an efficient thermochemical route for the storage and transportation of solar energy in the form of solar fuels.