Assembling of a low energy ion bean analysis facility and use of Nuclear Microprobe technique in geological studies

Abstract

In about four decades, ion beam analysis ( IBA) techniques have evolved to became well established analytical techniques for routine analysis in archaeological. Bio-medical, geological and environmental sciences. The basically make use of the differente interactions of a high energy ion bean ( of few me V/amu) with the specimem matter so they presuppost the use of a participle accelarator. In laboratories where an accelarator is available, setting up an IBA facility can be for many reasons , a good choice. In conditions when neither enough analytical facilities nor skilled personnel are available, the possibility of creating a reseach facility which is accessible to multidisciplinary users allowing at the same time a manpower build up cam be regarded as a worthwhile investment. At the present work, special emphasis was put in these two issues in development a low energy IBA facility at the Eduardo Mondlane University in Maputo, Mozambique. By using an ion beam focussed down to micrometer scale and some scanning machanism with syncchonised detection of the spectra of each pixel, digital elemental maps of the analysed specimen can generated. This feature conferer microscopic ability ti the IBA techniques which are then known as Nuclear Microprobe ( NMP) technique. In this work both participle induced X- ray emission ( PIXE) and ion bean induced luminescence, or just ionoluminescence (IL) were uses for geochemical studies. The possibility of rapid absolute quantification of elements in the ppm level by PIXE combined with the yet higher sensitivity of il. Method to transition metals and REE activators, in the absence of quenchin phenomena, allow for a synergic use of the two methods in geological applications with enhanced sensitivity. IL and PIXE were combined for studying Rare Elements ( REE) distribition in apatite minerals and ion bear induced damage in inorganic material in general with emphasis with to synthetically grown zircon crystals doped with REE due to the sensitivity of IL to changes in chemical bonding in the material , bean damade effects cam be studied even at low integrated doses, through wavelength shift or fading of the induced light. Micro Pixe technique was used for studying line profile concentrations of trace elements in pyrite grains and a elements used as geothermometers. Geothermometry allowed to assess the cooling rates in iron meteorites and the mineralisation conditions in metamorphic rocks, altempting to describe the tectinic history of the terranes, with application in petrologic studies and geological prospecting