Transnational Access

Beam-splitter polarisers for polarimetry at key spectral lines for solar physics

The obtained beam time has been used to characterize the polarizing properties of a polariser tuned to operate at 10.2 eV (121.6 nm, hydrogen Lyman α spectral line), as a candidate for a future polarimeter for solar corona research. Characterization consisted in measuring its polarizing properties both by reflectance and by transmittance. Measurements were performed by selecting a small fraction of the beam in the beam central plane in order to obtain mostly linearly polarized light. Measurements were performed in a narrow photon-energy range containing 10.2 eV and at three incidence angles, in order to select the optimum one.  Polariser reflectance and transmittance performance was measured along the two polarizations and in all three incidence angles.  Some of the results obtained are summarized in the paper “Multilayer beamsplitter polarizers for key UV-FUV spectral lines of solar polarimetry” by  Gutiérrez-Luna, Nuria et al. Optics Express 2022, vol 30, N. 16, page 29735.

Vibration tests of composite materials thin filter samples investigated for the Athena space mission

Vibration tests have been performed to investigate the mechanical resistance of filter breadboards manufactured within the development program of the Athena/X-IFU instrument and to increase its TRL. The main results obtained are: a) The new large filter design with large diameter and novel mesh materials made out of beryllium copper alloy seems a mature technology capable of sustaining the Arianne 6 qualification vibration load levels. b) Particular attention must be given to the external frame of the small filter since the aluminum frame adopted (instead of the stainless steel ones) caused some deflections on the membrane during the tightening of the filter over the interface (I/F) that could add stress to the film leading to premature failure (TBC). c) During the vibration tests performed in atmospheric pressure care must be given to the design and study of the I/F and its natural resonances that could produce unexpected acoustic waves that could over-stress the sample. Results will be presented in a paper that is in preparation.

XPS and XAS analysis of the aluminium oxide on aluminium-coated membranes investigated for the Athena filters

An ample experimental campaign has been carried out for a total of 10 working days at BABE. The main results achieved are: a) with the XPS campaign  the full test plan characterizing a large number of samples (9 samples of aluminium coated CNT membranes with different CNT densities, different aluminium thicknesses and presence of passivation layers, and 2 samples of polyimide/aluminium filters) was completed. The large amount of  high quality data promises useful information on the ageing processes of aluminium on PI and CNT filters. b) The XAS campaign has also been quite successful with a large part of the test plan completed. From a quick data analysis of XAS measurements of two PI/Al samples, the amount of total aluminium oxide has not undergone measurable increase compared to the Feb. 2021 test campaign indicating that the oxidation process after six years from production has likely reached a saturation. This initial claim needs a more detailed ongoing analysis for a final assessment. Results will be presented in a paper that is in preparation.

NYUAD Spacecraft & Moondust Photoemission

The spectral photoelectric yields of materials covering the surface of the lunar rover Rashid have been obtained. The materials investigated are magnesium alloy, indium-tin-oxide, titanium, the commercial off-the-shelf FTO-coated solar panel cover-glass, and the graphite coatings on the Langmuir probes, namely AerodagâG and Graphit 33. The yields of gold and silver plates have been also measured for reference and calibration purposes. The BABE facility beam line was used to scan the 5–1500 eV (1–248 nm) energy region, covering most of the solar spectrum that leads to photoelectron emission on the Moon. The total photoelectron current density was calculated by combining the measured yield curves with solar spectral irradiance data. The results of this study will be used in numerical models of an electron sheath forming around Rashid, the lunar rover built by the Mohammed Bin Rashid Space Centre in Dubai. These models will help estimate the background signal for its upcoming in-situ measurements of the density of the electron sheath forming above the Moon’s surface. Results will be presented in a paper that will be submitted shortly.