Portable x-ray fluorescence spectrometer for coating thickness measurement

peer reviewedA handheld x-ray spectrometer has been realized and tested. The purpose of the device is to measure the thickness of coated samples in the range of 1-1500 nm in an industrial environment. Accuracy of similar to 3% has been achieved in this range with a measurement time of 1 min. Automated software has been implemented to allow utilization by a nonspecialist operator. An automated calibration procedure, based on measurements of reference samples, is used. (C) 2007 American Institute of Physics

Assessment of atomic layer deposited TiO2 photocatalytic self-cleaning by quartz crystal microbalance

The self-cleaning properties emerging from photocatalytic effects consist in the elimination of an organic contamination layer by light-induced redox reactions. Quartz crystal microbalances (QCMs), monitoring the contaminant mass loss under UV illumination, were used to investigate this effect and its efficiency. A new setup dedicated to such purpose is introduced along with the results of a self-cleaning experiment performed with a 20-nm TiO2 thin film coated on a QCM by atomic layer deposition. In particular, a 10-nm paraffin oil thin film deposited under vacuum is shown to be degraded down to its complete removal according to a zeroth order photocatalytic reaction. Finally, the experimental opportunities offered by the new setup, such as a controlled environment composition, are presented.Peer reviewe

Design status of ASPIICS, an externally occulted coronagraph for PROBA-3

The "sonic region" of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona, as well as phenomena that lead to coronal mass ejections (CMEs), which influence space weather. Improvement on this front requires eclipse-like conditions over long observation times. The space-borne coronagraphs flown so far provided a continuous coverage of the external parts of the corona but their over-occulting system did not permit to analyse the part of the white-light corona where the main coronal mass is concentrated. The proposed PROBA-3 Coronagraph System, also known as ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with its novel design, will be the first space coronagraph to cover the range of radial distances between ~1.08 and 3 solar radii where the magnetic field plays a crucial role in the coronal dynamics, thus providing continuous observational conditions very close to those during a total solar eclipse. PROBA-3 is first a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future European missions, which will fly ASPIICS as primary payload. The instrument is distributed over two satellites flying in formation (approx. 150m apart) to form a giant coronagraph capable of producing a nearly perfect eclipse allowing observing the sun corona closer to the rim than ever before. The coronagraph instrument is developed by a large European consortium including about 20 partners from 7 countries under the auspices of the European Space Agency. This paper is reviewing the recent improvements and design updates of the ASPIICS instrument as it is stepping into the detailed design phase

Characterization of Vacuum Deposited Thin Organic Layers by Phase Shifting Interferometry and FTIR Spectroscopy for Space Contamination Study

Although satellites and spacecrafts are exposed to very small amounts of organic contamination (typically 10-9 to 10-5 g.cm-2 cumulated over their lifetime) from the outgassing of some of their own structural components, fixation and photo-degradation of organic compounds can significantly alter the thermo-optical properties of critical surfaces involved in their passive thermal regulation. The study of surface molecular contamination under conditions representative of space environment is therefore of prime interest in order to define mitigation strategies. The Centre Spatial de Liège has recently initiated research work on this topic and first experimental results are presented here. Organic thin films have been deposited using vacuum thermal evaporation / sublimation and their topology and equivalent surface concentration have been characterized using phase shifting interferometry. Furthermore, FT-IR spectroscopy in reflection configuration have been tested in different conditions in order to monitor the IR signature of contaminated surface samples this in the perspective of implementing an in situ monitoring system on a deposition chamber with UV exposure capability

Nanoparticles in solar sail materials

Solar sailing is a spacecraft propulsion mean exploiting the radiation pressure of sunlight. This concept is undergoing a regain of interest from the space agencies around the world partly driven by the development of manufacturing technologies. Typically, tens of thousands of square meters of sail materials are required to propel a spacecraft. In its most common proposed embodiment, the sail material is constituted of a thin polymer foil coated with a reflective layer on the front side and eventually an emissive layer on the back side. The photons momentum is transferred to the sail upon reflection and its thermal balance is governed by radiative processes (absorption over the solar spectrum and reemission of thermal infrared radiation). The impact of nanoparticles inclusion in the polymer foil on the sail performance will be evaluated for operation in the inner solar system. The aspects of passive thermal regulation and resistance of the polymer to UV radiation will be addressed within the framework of optical calculations based on effective media approximations. Copyright ©2010 by the International Astronautical Federation. All rights reserved

Roughness evolution of sol-gel optical coatings by ion beam sputtering

The surface roughness evolution of two silica-based sol-gel materials under 650 eV argon ion beam sputtering has been investigated. The liquid sol-gel solutions had been applied on silicon substrates using the dip coating technique and then thermally cured to obtain solid thin films. Their thickness had then been controlled over the samples surface using spectroscopic ellipsometry. The surface roughness of the sol-gel films has been measured using both interferometric profilometry and atomic force microscopy at different sputtering depths. Roughness increases significantly faster with sputtering depth in sol-gel layers than on bulk fused silica. Interestingly, the sputtering rates of the sol-gel layers are also observed to be much higher that of bulk fused silica. The development of micron scale holes with relatively stable interstices rules the surface roughness evolution. AFM measurements revealed a regular submicron scale lateral structure which nanometric amplitude is amplified under sputtering

Experimental astrochemistry: from ground-based to space-borne laboratories (Foreword)

peer reviewedThe investigation of the origin and evolution of molecules in space environments, either in interstellar or interplanetary conditions, constitutes a topic of high importance in modern space sciences. The presence of diversified and complex molecules motivates astrochemists to explore their formation mechanisms along with the physical conditions ruling these physico-chemical processes. Beside theoretical approaches aiming at simulating these processes, experimental techniques are nowadays frequently applied. Both laboratory and space experiment projects allow to reproduce to some extent the adequate conditions to understand some of these processes. The most recent results based on these techniques, and the prospects for future investigations, including the use of space platforms, were the scientific motivation of this workshop. These proceedings summarize a part of the content of this workshop, including abundant references to the relevant bibliography