Maria Guglielmina Pelizzo

The BEAR Beamline at Elettra

The BEAR (Bending Magnet for Emission Absorption and Reflectivity) beamline is installed at the right exit of the 8.1 bending magnet at ELETTRA. The beamline — in operation since January 2003 — delivers linear and circularly polarized radiation in the 5 – 1600 eV energy range. The experimental station is composed of a UHV chamber for reflectivity, absorption, fluorescence and angle resolved photoemission measurements and a UHV chamber for in‐situ sample preparation.

METIS: a novel coronagraph design for the Solar Orbiter mission

METIS (Multi Element Telescope for Imaging and Spectroscopy) METIS, the “Multi Element Telescope for Imaging and Spectroscopy”, is a coronagraph selected by the European Space Agency to be part of the payload of the Solar Orbiter mission to be launched in 2017. The mission profile will bring the Solar Orbiter spacecraft as close to the Sun as 0.3 A.U., and up to 35° out-of-ecliptic providing a unique platform for helio-synchronous observations of the Sun and its polar regions. METIS coronagraph is designed for multi-wavelength imaging and spectroscopy of the solar corona. This presentation gives an overview of the innovative design elements of the METIS coronagraph. These elements include: i) multi-wavelength, reflecting Gregorian-telescope; ii) multilayer coating optimized for the extreme UV (30.4 nm, HeII Lyman-α) with a reflecting cap-layer for the UV (121.6 nm, HI Lyman-α) and visible-light (590-650); iii) inverse external-occulter scheme for reduced thermal load at spacecraft peri-helion; iv) EUV/UV spectrograph using the telescope primary mirror to feed a 1st and 4th-order spherical varied line-spaced (SVLS) grating placed on a section of the secondary mirror; v) liquid crystals electro-optic polarimeter for observations of the visible-light K-corona. The expected performances are also presented.

Realization and characterization of an XUV multilayer coating for attosecond pulses.

The experimental characterization of an aperiodic reflecting multilayer (ML) structure designed to reflect and compress attosecond pulses in the extreme ultraviolet spectral region is presented. The MLs are designed for the 75-105 eV spectral interval with suitable reflectance and phase behavior, in particular high total spectral reflectivity coupled with very wide bandwidth and spectral phase compensation. The experimental phase behavior of the multilayer has been obtained through electron photoemission signal using an innovative method that is presented and discussed in this paper. With this ML we have demonstrated pulse compression by reflection from 450 as to 130 as.

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.

Sunscreen tests: Correspondence between in vitro data and values reported by the manufacturers

BACKGROUNDnIn vitro sunscreen tests are diffusively used to test both the sun protection factor (SPF) and the photo-stability of filters. Spectrophotometric measurements of the absorbance of ultraviolet radiations through a sunscreen applied on a suitable substrate allow a rapid evaluation of its protection factor both at short and long wavelength ultraviolet radiation (UVB and UVA).nnnOBJECTIVESnThe objective of this study has been to demonstrate if Teflon can be adopted as substrate both for SPF evaluation and photo-stability tests. Moreover, we have investigated if there is a correspondence between in vitro SPF measurements and values reported by manufacturers on sunscreens.nnnMATERIAL AND METHODSnTeflon has been used to perform several photo-stability tests by irradiating the filters with different wavebands and analyzing the combined effect of UV and infrared (IR) light. Similar analyses have been carried out using PMMA Plates, which is the standard substrate for UVA in vitro test.nnnRESULTSnWe have demonstrated that it is possible to establish a good correspondence between in vitro SPF and values reported by manufacturers on sunscreens. We have also verified that the in vitro/label SPF correlation curve depends on the quantity of product applied while this does not seem to be true for other parameters like Critical Wavelength and UVA ratio. With regard to photo-stability studies, our results indicate for the first time that IR irradiation may have a role on photo-degradation.nnnCONCLUSIONSnThe results show that there is a good correlation between the in vitro SPF determined by the present method and the SPF reported by the manufacturer. The compatibility of the results obtained using Teflon and PMMA Plates demonstrates that Teflon can be utilized for both SPF determination and photo-stability tests.

High performance EUV multilayer structures insensitive to capping layer optical parameters

We have designed and tested a-periodic multilayer structures containing protective capping layers in order to obtain improved stability with respect to any possible changes of the capping layer optical properties (due to oxidation and contamination, for example)-while simultaneously maximizing the EUV reflection efficiency for specific applications, and in particular for EUV lithography. Such coatings may be particularly useful in EUV lithographic apparatus, because they provide both high integrated photon flux and higher stability to the harsh operating environment, which can affect seriously the performance of the multilayer-coated projector system optics. In this work, an evolutive algorithm has been developed in order to design these a-periodic structures, which have been proven to have also the property of stable performance with respect to random layer thickness errors that might occur during coating deposition. Prototypes have been fabricated, and tested with EUV and X-ray reflectometry, and secondary electron spectroscopy. The experimental results clearly show improved performance of our new a-periodic coatings design compared with standard periodic multilayer structures.

Unusual High Exposure to Ultraviolet‐C Radiation

Abstract UV radiation is known to cause acute and chronic eye and skin damage. The present case report describes a 90 min accidental exposure to UV-C radiation of 26 medical school students. Germicidal lamps were lit due to a malfunctioning of the timer system. Several hours after irradiation exposure, all subjects reported the onset of ocular symptoms, subsequently diagnosed as photokeratitis, and skin damage to the face, scalp and neck. While the ocular symptoms lasted 2–4 days, the sunburn-like condition produced significant erythema followed by deep skin exfoliation. The irradiation was calculated to be approximately 700 mJ cm−2 absorbed energy, whereas the actual radiation emitted by the lamps was 0.14 mW cm−2 (the radiometric measurements confirmed these calculi, because the effective irradiance measured from the height of the autopsy table to about 1 m under the UV-C lamp varied from 0.05 to 0.25 mW cm−2) but, more likely, the effective irradiance, according to skin phototype and symptoms, was between 50 and 100 mJ cm−2. The ocular and skin effects produced by such a high irradiation (largely higher than that accepted by the American Conference of Governmental Industrial Hygienists [ACGIH] threshold limit values [TLVs]) appeared reversible in a relatively short time.

Effectiveness of different substrate materials for in vitro sunscreen tests.

BACKGROUNDnIn vitro measurements of sunscreen products are used to assess their reliability in terms of photoprotection and photo-stability.nnnOBJECTIVEnIn this study, several substrates have been fully characterized for in vitro sunscreen testing.nnnMETHODSnThe following different substrates have been utilised in the study: roughened PMMA plates, Transpore, Vitro-Skin, roughened quartz plate and a laboratory prepared roughened PTFE plate. The suitability of these substrates for SPF evaluation has been investigated by performing total absorbance measurements of seven sunscreen products with different SPF values produced by the same manufacturer.nnnRESULTS AND CONCLUSIONSnApplication of sunscreen products on Transpore, roughened quartz plate, PMMA, PTFE and Vitro-Skin was performed efficiently. With regard to photo-stability of the substrate materials, only PMMA plate, PTFE and roughened quartz plate showed to be photo-stable after UV irradiation. With regard to SPF tests, our results indicate that Transpore, roughened quartz plate and Vitro-Skin are preferable to assess SPF values because of a better correlation between in vitro and in vivo measurements. Our study also confirms that an initial calibration must be performed for sunscreen products labelled with different SPF values. Finally, the results of our measurements demonstrate that, although a correlation between in vitro and in vivo SPF results can be established, it is never exactly 1:1.

Design of aperiodic multilayer structures for attosecond pulses in the extreme ultraviolet

The design of aperiodic reflecting multilayer (ML) structures for attosecond physics in the extreme ultraviolet spectral region is presented. An optimization procedure based on evolutive strategy has been developed in order to get coating structures reflecting high photon fluxes in ultrashort duration pulses. The MLs are designed for a specific (75-105 eV) spectral interval with suitable reflectance and phase characteristics, in particular high total spectral reflectivity coupled with very wide bandwidth, spectral phase compensation, and amplitude reshaping. Furthermore, to take into account manufacturing tolerances, solutions stable with respect to random layer thickness variations are selected. To test the reliability of the proposed design procedure, examples of Mo/Si ML structures designed to reflect ultrashort pulses with different amplitude profiles and phase behavior are considered. The performances of the various structures are analyzed.

Effects of ion bombardment and gas incorporation on the properties of Mo/a-Si:H multilayers for EUV applications

Abstract A study of Mo/a-Si:H multilayer for EUV mirrors produced by rf-magnetron sputtering in pure Ar, Xe and Ar/H 2 gas mixtures is presented. The high reflectance mirrors are designed for solar space experiments at 17, 19 and 30.4 nm and for the lithography applications at 13 nm. The multilayers are grown in different ion bombardment conditions determined by different bias levels of the substrate. Plasma diagnostics are performed to correctly evaluate flux and energy of plasma ions bombardment. The a-Si:H layers have been obtained by introducing H 2 gas in the sputtering chamber at different partial pressures during silicon deposition. The deposition rates as well as the composition of Mo and Si layers have been investigated by Ion Beam Analysis (RBS and ERDA). The coating microstructure has been characterised primarily by X-ray micro-diffraction (micro-XRD). X-Ray Reflection analysis (XRR) has been carried out to investigate the layer density and the multilayer structure. RBS analyses show that noble gas (Ar, Xe) incorporation is limited to the Si layers and depends on the sample bias. Noble gas concentration is correlated to the different ion bombardment growth conditions that influence also the (110) orientation of Mo nano-crystals. ERD analyses of Si layers show hydrogen incorporation up to 30 at.% as a function of the H 2 partial pressure. Hydrogen incorporation leads to a decrease of the a-Si layer density. Hydrogen content in Mo layers is less than 0.5 at.% even at the highest H 2 partial pressure. The optical properties of these mirrors have been characterised by EUV reflection measurements.