In the context of ESA’s Cosmic Vision 2015-2025 scientific program, Solar Orbiter (SolO) represents the first M-class mission, currently under implementation for a launch planned in October 2018.
One of the SolO solar remote-sensing instruments is the Multi Element Telescope for Imaging and Spectroscopy (METIS), under development by an Italian consortium ATI composed by CGS and TAS-I. METIS is a coronagraph that will perform simultaneously broad-band imaging in visible light and narrow-band imaging in UV of the Sun corona with unprecedented spatial resolution.
The surfaces of several Ti-6Al-4V components of the METIS Optical Unit must have a very low reflectance in order to minimize straylight and therefore ACKTAR Magic BlackTM coating was specified. An example is represented by the internal surface of the Inverted External Occulter (IEO) - the front part of the instrument - which is exposed to the direct solar flux and experiences challenging environmental conditions. Qualification for 450°C was required whereas Acktar's Magic BlackTM qualified maximum temperature was 380°C.
A dedicated thermal-vacuum cycling test (100 total cycles, −120°C − 450°C) was conducted to qualify Magic BlackTM to quantify any performance degradation under these conditions:
• optical (reflectance)
• thermal (∝ and ε values) to allow calculation of the radiative heat transfer of the METIS parts during mission
• mechanical performances
The following success criteria were established:
• total reflectance at wavelengths of 400−1000nm <;5%
• degradation of absorptance ∝ and emissivity ε to be <10%
• surface resistivity <5 kΩ/square
This paper proposes the X-Ray CT imaging as appropriate tool for investigating the capillary water absorption in
sedimentary rocks. This technique, in fact, provides information useful for deeping the knowledge about of the porosity
and the kinetics of the water capillary absorption in porous materials. The possibility to improve in non invasive manner,
the understanding of this phenomenon, constitutes a fundamental aspect to take actions in the restoration and
conservation of lapideous artifact and monuments from cultural heritages. The investigated sedimentary rocks come
from different Sicilian quarries and were used for the building of the Greek temples in the archaeological areas of
Agrigento, Selinunte and in the baroque monuments of the Val di Noto area. The image acquisition was carried out at
different times after contact with water. The wetting front progression along the height of the sample was evaluated on
the basis of the estimated CT attenuation value maps. An average of the CT attenuation values measured by the ROI
(Region of Interest) was used to evaluate the mean height of the wetting front, with different CT scans at fixed time
intervals after sample wetting, in order to describe the dynamic behaviour of the imbibition process. CT imaging results
have shown that the water absorption is highly subject to the sample porous morphology.
The laser-induced breakdown spectroscopy (LIBS) is an applied physical technique that has shown, in recent years, its
great potential for rapid qualitative analysis of materials. The possibility to implement a portable instrument that perform
LIBS analysis makes this technique particularly useful for in situ analysis in the field of cultural heritages.
The aim of this work is to compare the results, obtained by LIBS measurements with X-Ray Fluorescence (XRF) ones,
on calcareous and refractory materials coming from the Greek-Roman theater of Taormina. Calibration curves for LIBS
and XRF were obtained by measuring certified reference materials and using them as standards. LIBS measurements
were performed with a new mobile instrument Modì (Mobile Double pulse Instrument for LIBS Analysis) that use an
innovative experimental set-up, based on the use of two suitably retarded laser pulses that greatly improves the potential
of this technique for accurate quantitative analysis. XRF analyses were performed with a portable instrument ArtTAX
that use a collimated X-Ray beam equipped with a fluxing system of helium gas on the detection path to the aim to detect
the lighter elements with a good accuracy. LIBS results have shown that this technique is highly subjected to the sample
chemical and physical characteristics.
We report preliminary measurements of the air UV fluorescence light yield as a function of pressure using as a stimulus hard x-rays. For comparison measurements in pure nitrogen are also reported. Knowledge of the air UV fluorescence light yield induced by hard x-rays is needed in order to evaluate the capability to detect, in an AIRWATCH FROM SPACE experiment, Gamma Ray Burst (GRB) events. The experiment was carried out a the LAX x-ray facility in Palermo, by using an high flux collimated x-ray photon beam. The experimental result indicate that the fluorescence yield is inversely proportional to the filling pressure. At pressures below 30 mbar, corresponding to the value for the upper atmospheric layers in which the X and gamma ray photons of the GRBs are absorbed, about 0.1 percent of the total energy of a GRB is transformed in UV photons. This makes possible the observation of the GRBs with the technique proposed in the AIRWATCH FROM SPACE experiment.
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