Muons tomography applied to geosciences and volcanology

Imaging the inner part of large geological targets is an important issue in geosciences with various applications. Dif- ferent approaches already exist (e.g. gravimetry, electrical tomography) that give access to a wide range of informations but with identified limitations or drawbacks (e.g. intrinsic ambiguity of the inverse problem, time consuming deployment of sensors over large distances). Here we present an alternative and complementary tomography method based on the measurement of the cosmic muons flux attenuation through the geological structures. We detail the basics of this muon tomography with a special emphasis on the photo-active detectors.Comment: Invited talk at the 6th conference on New Developments In Photodetection (NDIP'11), Lyon-France, July 4-8, 2011; Nuclear Instruments and Methods in Physics Research Section A, 201

Experimental contribution to the study of S-state ions in ionic single crystals?

Abstract. Experimental results are reported on S-state ions incorporated into PbFC 1-type tetragonal single crystals. The spin Hamiltonian parameters of these ions are determined and correlated with structural and physico-chemical properties of the studied compounds. The experimental bi spin Hamiltonian parameters vary linearly with the lattice constant a of the host unit cell. Further, the dependence of the spin Hamiltonian parameters on temperature has been investigated and parametrised. The results of a Raman investigation of the hosts are presented

Systematics, biostratigraphy and biogeography of four Famennian spiriferid brachiopods from Morocco

New data on systematics, biostratigraphy and biogeography are presented in this paper. They concern four Famennian spiriferid species from South-West Morocco, discovered in Hollard's collections housed in Lille and useful for biostratigraphic and palaeobiogeographic correlations. Two of them are new : Cyrtospirifer kelbaensis n. sp., close to C. pamiricus sensu Abramian (1974, pl. 20, fig. 5, non fig. 4) not Reed, 1922 and Dichospirifer zemoulensis n. sp. close to D. cardiosinusoides (ABRAMIAN, 1957). Their systematic study is completed by a justification of their generic and specific attribution with precisions on their geographic and biostratigraphic distribution in Morocco: upper part of the Lower Famennian and lower part of the Upper Famennian (ds II — ? III sensu Hollard, 1981) for C kelbaensis, upper part of Lower Famennian to Upper Famennian (ds II to ds V sensu Hollard, 1981) for D. zemoulensis. Two other species, recognized for the first time in Morocco, Prospira struniana (GOSSELET, 1879) and Dmitria seminoi (VERNEUIL, 1850), are compared with their type material. Their geographic and biostratigraphic distribution are stated to be in Morocco and central part of North Gondwana (North Africa and Central Asia)

Effect of fibre configurations on mechanical properties of flax/tannin composites.

Flax reinforced tannin-based composites have a potential to be used in vehicle applications due to the environmental advantages and good mechanical properties. In this paper, the effects of fibre configuration on mechanical properties of flax/tannin composites were investigated for nonwoven and woven fabric lay-up angles (UD, [0°, 90°]2 and [0°, +45°, 90°, -45°]2). The tannin/flax composites were prepared by compression moulding. The manufactured specimens were then characterized for quasi-static tensile properties, dynamic mechanical properties and low-energy impact performance. Failure mechanism was further investigated using microscopy and demonstrated the need for further adhesion improvements. The study shows that the UD fabric reinforced composite performs better in tensile strength and modulus whereas [0°, +45°, 90°, -45°]2 composite provides the best impact energy absorption performance

Muon tomography of the Soufrière of Guadeloupe (Lesser Antilles): Comparison with other geophysical imaging methods and assessment of volcanic risks

International audienceDensity tomography of rock with muons of cosmic origin measures the attenuation of the flux of particles crossing the object of interest to derive its opacity, i.e. the quantity of matter encountered by the particles along their trajectories. Recent progress in micro-electronics and particle detectors make field measurement possible and muon density tomography is gaining a growing interest (e.g. Tanaka et al., 2010; Gibert et al., 2010). We have constructed field telescopes based on the detectors of the OPERA experiment devoted to study neutrino oscillation (Lesparre et al., 2011a). Each telescope may be equipped with a variable number of detection matrices with 256 pixels. The spatial resolution is adaptable and is typically of about 20 meters (Lesparre et al., 2010). The telescopes are portable autonomous devices able to operate in harsh field conditions encountered on tropical volcanoes. The total power consumption is less than 40W, and an Ethernet link allows data downloading and remote control of the electronic devices and on-board computers. Larger high-resolution telescopes are under construction. The instruments have been successfully tested on the Etna and Soufrière of Guadeloupe volcanoes were a telescope is operating continuously since Summer 2010. Muon radiographies of the Soufrière lava dome reveal its very heterogeneous density structure produced by an intense hydrothermal circulation of acid fluids which alters its mechanical integrity leading to a high risk level of destabilisation. Small-size features are visible on the images and provide precious informations on the structure of the upper hydrothermal systems. Joined interpretation with other geophysical data available on the Soufrière - seismic tomography, electrical resistivity tomography, gravity data - is presented and discussed. Density muon tomography of the internal structure of volcanoes like the Soufrière brings important informations for the hazard evaluation an is particularly adapted to brought constraints on flank destabilization and hydrothermal circulation models. Tanaka et al., Three dimensional computational axial tomography scan of a volcano with cosmic ray muon radiography, J. Geophys. Res., 115, B12332, doi:10.1029/2010JB007677, 2010. Gibert et al., Muon Tomography: Plans for Observations in the Lesser Antilles, Earth Planets and Space, Vol. 52, 153-165, doi: 10.5047/eps.2009.07.003, 2010. Lesparre et al., Geophysical muon imaging: feasibility and limits, Geophysical Journal International, Vol. 183, 1348-1361, doi: 10.1111/j.1365-246X.2010.04790.x, 2010. Lesparre et al., Design and Operation of a Field Telescope for Cosmic Ray Geophysical Tomography, Nuclear Instruments and Methods in Physics Research A, to appear, 2011a. Lesparre et al., Bayesian Dual Inversion of Experimental Telescope Acceptance and Integrated Flux for Geophysical Muon Tomography, Geophysical Journal International, to appear, 2011b