Elemental Characterisation and Speciation using
Nuclear Analytical Techniques
Nuclear analytical techniques (NATs) in general and ion beam based NATs in particular, have in essence the potencial to providing much more information out of the analysed samples, than what is usually achieved using the established methods in conservative approaches. The aim of this main activity of ETN, is thus to extend NATs capacity beyond the present state-of-the-art. Exploiting usually unused approaches, developing new specialised software and new analytical methodologies are thus the major components of the work in this context. In a recent past, a beyond the state-of-the-art instrumentation was installed and two breakthrough PhD thesis were finished. At present, operationalization, validation and fine tunning of new capabilities are underway, joins exploitation for fundamental and applied research, without losing view of the original motivation that remains an important ultimate societal challenge.
The HRHE-PIXE facility
The High Resolution High Energy Particle Induced X-ray Emission (HRHE-PIXE) facility installed in 2008, is one of the few, if not still the single PIXE setup in the world, able to provide PIXE X-ray spectra covering an almost 120 keV window energy (from just below 1 keV up to above the 110 keV of the 19F(p,p'γ)19F nuclear reaction γ ray), while presenting a state-of-the-art relative resolution reaching 0.25% and always better than 1.5%.
The full 120 keV range is achieved using two detectors. A CdTe detector, operational for energies above 3.3 keV, complements a first generation transition edge sensor, TES, X ray Microcalorimeter Spectrometer (XMS), capable of providing better than 1% relative resolution from below 1.0 keV up to 20 keV, while reaching 0.25% relative resolution at 10.550 keV Pb Kα
Fundamental research
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The specific characteristics of the HRHE-PIXE system open the possibility to carry out fundamental research on the improvement of atomic parameters database, a very important subject presently in discussion in the frame of the X-ray Spectrometry comunity.
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Software and capacity building
Frontier research on NATs implies developing new software, which requires among others additional developments on:
Cross-section routines:
quantifying K, L and M shell transitions must be carried out efficiently, therefore new and fast algorithms were established and included in the specific software under development, as well as integrated in the Geant4 Colaboration code.
CdTe detector response functions:
while Si(Li) detectors response function is fenomenologically well established, CdTe and other detectors, are not. Proper response functions were modelled and implemented in the dedicated DT2 code under development.
Applied research
In the frame of applied research, fields of intervention cover a wide scope that includes:
Mineral resources:
mappings of nearly pristine mineral samples are obtainable and the resolution allows Rare Earth Elements (REE) determination in iron (Fe) containing matrix samples.
Thin films:
the high sensitivity of ion beam NATs allows the measurement of low mass samples, while the high resolution allows the quantification of nearby elements, like Co in a TbFe film.
Nanoparticles and airborne particles:
while the picogram absolute detection limits of PIXE allow the characterisation of nanoparticle samples even when very small sample volume is available, the high throughput of the technique can be used in aerosol studies.
Societal challenges
Nanotoxicology and environmental health:
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a decade ago, the quest for elemental speciation using NATs was a response to the need to identify chemical species of airborne elements. The LCEA laboratory installation in 2008 and the identification, in 2009, of a relation between airborne chlorine in PM2.5 and diabetes incidence, were two important marks in this quest. The ultimate goal was not yet achieved, but possible ways there are being pointed out.