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Abstract:The paper presents laboratory tests for the characterization of commercial Rogowski coils and a specially designed B-Dot sensor for the measurement of lightning currents on the Säntis telecommunications tower in Switzerland. In order to overcome the limited high frequency response of the Rogowski coils, we propose to use magnetic loops located very close to the tower. We introduce the design of a B-Dot sensor based on improvements proposed by C. E. Baum, in which the inductance is lowered by extending the vertical dimension of the loop, with the overall effect of extending the operating frequency range. To overcome the integrating behavior of the B-Dot loop when connected to lowimpedance loads (such as 50 Ohm), an arrangement of 100-Ohm-impedance cables connected across conicaltransmission-line gaps is used. The designed sensor is characterized by an upper frequency cutoff of 20 MHz and a 50 Ohm matched termination. Simulation results and laboratory tests carried out in the high voltage laboratories of the EPFL and Montena EMC show the effectiveness of the simultaneous use of Rogowski coils and B-Dot sensors for the measurement of lightning currents.

Zircon U‐Pb geochronology is a very robust dating method but the accuracy of determined ages can sometimes be compromised. This is because, as commonly observed, the U‐Pb isotope system can be reopened during the post‐crystallization evolution of a zircon. The present manuscript investigates the capability of traverses by LA‐ICP‐MS to identify zones of well‐preserved U‐Pb isotope systematics within zircon crystals. The data for the different zones can be used to construct internal Discordia lines that provide age information about crystallization and metamorphism of single zircon crystals. To test our approach, we analyzed zircons from three ca. 3.96 Ga Acasta gneisses. Results demonstrate that such a method allows retrieval of original crystallization age in most of the studied zircons, even in those that experienced ancient U‐Pb disturbances resulting in discordant U‐Pb data. It was also possible to estimate disturbance ages, though not as precisely as for the igneous crystallization, in many of the studied crystals.

In order to clarify the link between 40 Ar/ 39 Ar record in white mica and deformation, we performed in situ and bulkwise 40 Ar/ 39 Ar dating over the East Tenda Shear Zone (Tenda massif, Alpine Corsica). White micas from 11 samples were selected and extensively analyzed using in situ techniques across nested scales of strain-intensity gradients developed at the expense of a late-Variscan protolith. 40 Ar/ 39 Ar systematics are unaffected by inherited Ar and directly linked to deformation with little or no Ar lattice (volume) diffusion. Extensive sampling allows constraining the end of deformation related to burial and exhumation, respectively, at~34 and~22 Ma, bracketing the duration of regional extensional shear to~12 Myr. Results also highlight a regional strain localization toward the upper contact of the unit with smaller-scale localization in specific lithologies, notably meta-aplites. Second-order complications exist, such as local ill-defined correlations between ages and finite-strain microstructures. Thus, the use of a strain gradient as a proxy for strain localization in time is regionally valid but sometimes locally too complex to track or resolve strain partitioning/localization trends at the meter (outcrop) scale and below. Age mixing and incomplete isotopic homogenization by dissolution/precipitation are identified as the main causes of local discrepancies that complicate the link between age and microstructure and the derivation of strain localization rates. Tracking temporal trends in shear distribution across regional-scale deformation gradients in such settings is possible but requires a multi-scale approach as implemented here to reveal younging patterns associated to strain localization.

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We present an analysis of the thermal response of a hot-wire electroexplosive device (EED) excited with different transient signals. First-order and second-order analytical models to calculate the thermal response of an EED are assessed taking as reference numerical simulations obtained using ANSYS. For the early-time response, when the time is much smaller than the thermal constant of the EED, the best approach corresponds to a first-order differential model in which the thermal capacitance is calculated with short-pulse excitations. A linear simplification to calculate the maximum temperature due to short excitations is also shown to be adequate. On the other hand, the most appropriate model for the late-time response is a second-order model. The models are used to assess the electromagnetic susceptibility of a wired EED for different electromagnetic pulsed environments. Radiated signals produced by a mesoband radiator, two types of radars, and a hyperband radiator are considered. The radar signal proved to be the most disturbing source because of its highest duty cycle and its flat spectral response around a specific frequency. Even the temperature firing threshold can be exceeded with the radiated field produced by a radar of 200 kW of output power located at a distance of 5 m.Index Terms-Electroexplosive device (EED), electromagnetic compatibility, intentional electromagnetic interference (IEMI), thermal model.

Materials exhibiting a gradient in permittivity are synthesized through the application of an external magnetic field to a suspension of Fe3O4@TiO2 nanoparticles in an epoxy matrix. It is shown how the application of the magnetic field not only induces the magnetophoretic motion of the particles, but causes also their alignment in high aspect ratio structures. The combination of these two effects gives rise to graded nanocomposites exhibiting gradients in permittivity that go beyond the ones predicted for nanocomposites with homogeneously distributed and isotropic inclusions. Moreover, it is demonstrated through numerical simulations how such nanocomposites, employed as electrical insulators, can efficiently reduce the electrical field stress at the interface between the electrode and the insulator, being therefore suitable candidates as long-lasting high-voltage dielectrics.