Ultrasonic non destructive testing based on sparse deconvolution

Abstract. The acoustic modality yields non destructive testing techniques of choice for indepth investigation. Given a precise model of acoustic wave propagation in materials of possibly complex structures, acoustical imaging amounts to the so-called acoustic wave inversion. A less ambitious approach consists in processing pulse-echo data (typically, A-or B-scans) to detect localised echoes with the maximum temporal (and lateral) precision. This is a resolution enhancement problem, and more precisely a sparse deconvolution problem which is naturally addressed in the inversion framework. The paper focuses on the main sparse deconvolution methods and algorithms, with a view to apply them to ultrasonic non-destructive testing

Simultaneous Measurements of Nuclear Heating and Thermal Neutron Flux Obtained with the CALMOS-2 Measurement Device inside the OSIRIS Reactor

International audienceNuclear heating inside an MTR reactor needs to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. To improve the nuclear heating knowledge, an innovative calorimetric system CALMOS has been studied, manufactured and tested for the 70MWth OSIRIS reactor operated by CEA. This device is based on a mobile calorimetric probe which can be inserted in any in-core experimental location and can be moved axially from the bottom of the core to 1000mm above the core mid-plane. Analysis of obtained results and advantages brought by the first CALMOS-1 mobile equipment have been already presented. However, some difficulties appeared with this first version. A thermal limitation in the cell did not allow to monitor nuclear heating up to the 70MW nominal power, and some significant discrepancies were observed at high heating rates between results deduced from the calibration and those obtained by the zero method. Feedback based, the new CALMOS-2 calorimeter has been designed both for extending the heating range up to 13W.g-1 and improving the zero method measurement thanks to a 4-wires technique. In addition, the CALMOS-2 calorimeter has been designed as a real operational measurement system, well suited to characterize and to follow the radiation field evolution throughout the reactor cycle. To meet this requirement, a programmable system associated with a specific software allows automatic complete cell mobility in the core, the data acquisition and the measurements processing. This paper presents the analysis of results collected during the 2015 comprehensive measurement campaign carried out with the new CALMOS-2 prototype. The 4-wires technique was tested up to around a 4 W.g-1 heating level and allowed to quantify discrepancies between zero and calibration methods. Thermal neutron flux and nuclear heating measurements from CALMOS-1 and CALMOS-2 are compared. Thermal neutron flux distributions, obtained with the Self-Power Neutron Detector suited to the CALMOS-2 calorimetric cell, are compared with those obtained with current devices. Finally, this analysis tends to emphasize advantages brought by the human machine interface automation, which deeply refined the profiles definition

Last Improvements of the CALMOS Calorimeter Dedicated to Thermal Neutron Flux and Nuclear Heating Measurements inside the OSIRIS Reactor

Nuclear heating inside an MTR reactor needs to be known in order to design and to run irradiation experiments which have to fulfill target temperature constraints. To improve the nuclear heating knowledge, an innovative calorimetric system CALMOS has been studied, manufactured and tested for the 70MWth OSIRIS reactor operated by CEA. This device is based on a mobile calorimetric probe which can be inserted in any in-core experimental location and can be moved axially from the bottom of the core to 1000 mm above the core mid-plane. Obtained results and advantages brought by the first CALMOS-1 equipment have been already presented. However, some difficulties appeared with this first version. A thermal limitation in cells did not allow to monitor nuclear heating up to the 70 MW nominal power, and some significant discrepancies were observed at high heating rates between results deduced from the calibration and those obtained by the “zero method”. Taking this feedback into account, the new CALMOS-2 calorimeter has been designed both for extending the heating range up to 13W.g-1 and for improving the “zero method” measurement thanks to the implementation of a 4-wires technique. In addition, the new calorimeter has been designed as a real operational measurement system, well suited to characterize and to follow the radiation field evolution throughout the reactor cycle. To meet this requirement, a programmable system associated with a specific software allows automatic complete cell mobility in the core, the data acquisition and the measurements processing. This paper presents the analysis of results collected during the 2015 comprehensive measurement campaign. The 4-wires technique was tested up to around a 4 W.g-1 heating level and allowed to quantify discrepancies between “zero” and calibration methods. Thermal neutron flux and nuclear heating measurements from CALMOS-1 and CALMOS-2 are compared. Thermal neutron flux distributions, obtained with the Self-Power Neutron Detector suited to the CALMOS-2 calorimetric probe, are compared with those obtained with current devices. This campaign allowed to highlight advantages brought by the human machine interface automation, which deeply refined the profiles definition. Finally, the decay of the reactor residual power after shutdown could be performed after shutdown, demonstrating the ability of such type of calorimeter to follow the heating level whatever the thermohydraulic conditions, forced or natural convection regimes

Isolation and characterization of microsatellite loci in the seed chalcid Megastigmus wachtli (Hymenoptera)

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Mid-IR s-SNOM imaging of photo-induced refractive index variation in chalcogenide glass

International audienceWe report the mid-IR s-SNOM surface characterization of a chalcogenide glass photo-inscribed by ultrashort laser pulses. Imaging allows to access to the morphology and the optical properties of the material at nanoscale, unravelling topographical and optical contrasts resulting from the laser inscription process. © 2019 IEEE

Elaboration of chalcogenide microstructured optical fibers preform by 3D additive manufacturing

International audienceFor several years, chalcogenide glasses have been studied as good candidates for numerous applications in the midinfrared region. Indeed, these glasses are transparent from 1 to 20 μm (depending on the composition), a mid- IR windows well-suited for sensing molecules whose optical signatures are located in the 2-16 μm range. In addition, thanks to appropriate thermal properties, chalcogenide glasses can be drawn into fibers, including microstructured optical fibers. In this work, a new method based on 3D-printing process is investigated to produce hollow chalcogenide glass preforms, which are then drawn into hollow-core fibers. The transmission of the "printed"hollow-core fiber has been measured and compared to the initial glass. A significant, but still manageable, increase by a factor of 2.5 is observed. This works opens a promising way for the fabrication of chalcogenide MOFs, more particularly for the elaboration of hollow core fibers. © 2021 SPIE