Static, refractive and monolithic Fourier transform spectrometer: development and prototyping.

Static Fourier transform spectrometers are devices that can be realized as monolithic and compact assemblies. In the "grating-based" monolithic version, they are usually realized gluing together a beam-splitter with two reflective diffraction gratings using spacers as connecting elements. In this work we present the development and test of an alternative form of this kind of instrument in which the dispersive elements are Littrow's prisms and are glued to the splitting element, forming in this way a robust and filled structure with no air gaps. The device can work in the visible/near infrared spectral region with a resolution power that varies across the spectral range due to the dispersion of the used glasses. The absence of hollow regions inside the monolithic block makes the device extremely robust and protects the optical surfaces inside the interferometer from possible contaminations. The device can be easily miniaturized, as it does not require spacers or structural elements other than just the optical parts. The tested instrument works in the 470-850 nm wavelength range with a variable resolution between 3000 and 300.

High sensitivity static Fourier transform spectrometer.

Static Fourier transform spectrometers (S-FTSs) are well-consolidated instruments providing high throughput and high spectral resolution in a narrow spectral band. They use two reflective gratings as dispersive elements in a Michelson interferometer. Gratings allow high spectral dispersion and consequently high resolution, but, due to the light diffused from their grooves, they are one of the main noise sources in the reconstructed spectrum. In this work, we compare the signal-to-noise ratio performance of a prism-based S-FTS with that of a grating-based S-FTS. As a primary advantage, prisms give intrinsically lower diffused light than gratings. Furthermore, they do not have multiple diffracted orders, reducing thereafter the optical constraints on the instrumental baffling.

Palladium on plastic substrates for plasmonic devices.

Innovative chips based on palladium thin films deposited on plastic substrates have been tested in the Kretschmann surface plasmon resonance (SPR) configuration. The new chips combine the advantages of a plastic support that is interesting and commercially appealing and the physical properties of palladium, showing inverted surface plasmon resonance (ISPR). The detection of DNA chains has been selected as the target of the experiment, since it can be applied to several medical early diagnostic tools, such as different biomarkers of cancers or cystic fibrosis. The results are encouraging for the use of palladium in SPR-based sensors of interest for both the advancement of biodevices and the development of hydrogen sensors.

Stability of EUV multilayer coatings to low energy alpha particles bombardment.

Future solar missions will investigate the Sun from very close distances and optical components are constantly exposed to low energy ions irradiation. In this work we present the results of a new experiment related to low energy alpha particles bombardments on Mo/Si multilayer optical coatings. Different multilayer samples, with and without a protecting capping layer, have been exposed to low energy alpha particles (4keV), fixing the ions fluency and varying the time of exposure in order to change the total dose accumulated. The experimental parameters have been selected considering the potential application of the coatings to future solar missions. Results show that the physical processes occurred at the uppermost interfaces can strongly damage the structure.

Extreme ultraviolet multilayer for the FERMI@Elettra free electron laser beam transport system.

In this work we present the design of a Pd/B4C multilayer structure optimized for high reflectance at 6.67 nm. The structure has been deposited and also characterized along one year in order to investigate its temporal stability. This coating has been developed for the beam transport system of FERMI@Elettra Free Electron Laser: the use of an additional aperiodic capping layer on top of the structure combines the high reflectance with filter properties useful in rejecting the fundamental harmonic when the goal is to select the third FEL harmonic.

Capped Mo/Si multilayers with improved performance at 30.4 nm for future solar missions.

Novel capping layer structures have been deposited on periodic Mo/Si multilayers to optimize reflectance at 30.4 nm. Design, deposition and characterization of such coatings are presented. Most of the structures proposed show improved performance with respect to standard Mo/Si multilayers and are stable over time. Reflectance at 121.6 nm and in the visible spectral range have been also tested to explore the applicability of such coatings to the Multi Element Telescope for Imaging and Spectroscopy (METIS) instrument, a coronagraph being developed for the ESA Solar Orbiter platform.

Stability of extreme ultraviolet multilayer coatings to low energy proton bombardment.

In this work we present results of an new experiment related to low energy protons bombardments on nano-structured optical coatings. Multilayer structures protected by different capping layers have been fabricated and exposed to low energy protons (1 keV). The experimental parameters have been selected considering the potential application of the coatings to solar mission instrumentation. Future solar missions will investigate the Sun from very close distances and optical components are constantly exposed to low energy ion particles irradiation. The experiment was repeated fixing the proton flux while varying the total dose accumulated. Results show that physical processes occurred at the uppermost interfaces can strongly damage the structure.

Iridium/silicon multilayers for extreme ultraviolet applications in the 20-35 nm wavelength range.

We have developed an Ir/Si multilayer for extreme ultraviolet (EUV) applications. Normal incidence reflectance measurements of a prototype film tuned to 30 nm wavelength show superior performance relative to a conventional Mo/Si multilayer structure; we also find good stability over time. Transmission electron microscopy and electron dispersive x-ray spectroscopy have been used to examine the microstructure and interface properties of this system: we find amorphous Si layers and polycrystalline Ir layers, with asymmetric interlayer regions of mixed composition. Potential applications of Ir/Si multilayers include instrumentation for solar physics and laboratory EUV beam manipulation.

Detection of lead in Zea mays by dual-energy X-ray microtomography at the SYRMEP beamline of the ELETTRA synchrotron and by atomic absorption spectroscopy.

This study is related to the application of the X-ray dual-energy microradiography technique together with the atomic absorption spectroscopy (AAS) for the detection of lead on Zea mays stem, ear, root, and leaf samples. To highlight the places with lead intake, the planar radiographs taken with monochromatic X-ray radiation in absorption regime with photon energy below and above the absorption edge of a given chemical element, respectively, are analyzed and processed. To recognize the biological structures involved in the intake, the dual-energy images with the lead signal have been compared with the optical images of the same Z. mays stem. The ear, stem, root, and leaf samples have also been analyzed with the AAS technique to measure the exact amount of the hyperaccumulated lead. The AAS measurement revealed that the highest intake occurred in the roots while the lowest in the maize ears and in the leaf. It seems there is a particular mechanism that protects the seeds and the leaves in the intake process.

Qualitative detection of Mg content in a leaf of Hedera helix by using X-ray radiation from a laser plasma source.

In this article, a method to reveal the presence of Mg content inside the different parts of leaves of Hedera helix is presented. In fact a sample of a Hedera helix's leaf, commonly characterized by a green and a white side, is analyzed under X-ray radiation. The presence of two zones with different colors in the Hedera helix's leaf has not been explained. In this connection, there are presently three hypotheses to explain the characteristic double-color appearance of the leaf. The first hypothesis suggests a different cytoplasmic inheritance of chloroplasts at the cell division, the second a different allelic composition, homozygote and heterozygote, between the two zones, and finally the third the action of a virus which changes the color properties in the Hedera's leaves. The resulting effect is a different content of "something" between the green and the white side. We utilized X-ray radiation, obtained from a plasma source with a Mg target, to image Hedera helix leaves and we found that the green side of the leaf is highlighted. We may suppose that the reason why the X-rays from a Mg plasma source, allow us to pick up the green side is probably due to the greater presence of the amount of Mg (from chlorophyll or other complexes and/or salts) in the two sides, green and white, of the leaf.