Christian Lacroix

Polytechnique Montréal · Department of Electrical Engineering

A high normal zone propagation velocity (NZPV) is a desirable feature in second generation (2G) high-temperature superconductor (HTS) coated conductors (CCs) in order to reduce the probability of developing destructive hot spots. In this work we investigated experimentally the impact of inserting a highly resistive layer that partially covers the H...

In this paper, we propose a slight change in the architecture of second generation (2G) high temperature superconductor (HTS) coated conductors (CCs), in order to accelerate their normal zone propagation velocity (NZPV) and reduce the probability of developing hot spots. The concept described in this work is to insert a highly resistive layer (call...

The relation between crystallographic texture and magnetic properties of GaP epilayers with embedded MnP nanoclusters grown by metal-organic vapor phase epitaxy is investigated with angle-dependent ferromagnetic resonance (FMR) measurements. A systematic methodology entirely based on magnetic characterization identifies all the crystallographic ori...

We report the measurement and modeling of two ferromagnetic resonance (FMR) modes in an array of amorphous CoFeB ferromagnetic nanowires with the applied static magnetic field transverse to the nanowire axes. The two modes are observed below saturation and are excited independently by the components of the microwave magnetic field parallel and perp...

An effective field model based on intrawire and interwire dipolar interactions has been developed in order to describe the magnetic anisotropy in arrays of homogeneous and multilayer nanowires. Variable angle ferromagnetic resonance (FMR) and vibrating sample magnetometry (VSM) characterization techniques were used to determine the effective intera...

A procedure is reported to obtain MnP nanoparticles in powder form or embedded within a polymer (polystyrene) matrix, referred to as Ps:MnP . Ps:MnP nanoaggregates are obtained starting from bulk crystalline MnP or from polycrystalline films grown from the vapor phase on glass substrates. Laser ablation (100 to 200 mW power) is used to produce the...

Inhomogeneous temperature elevations, also called hot spots, occurring in second generation high-temperature superconductor (2G HTS) tapes may lead to their destruction. A better understanding of inhomogeneous quenches would contribute to develop strategies to better protect superconducting devices based on 2G HTS tapes against hot spots. To do so,...

The primary benefit of a metallic stabilization/shunt in high temperature superconductor (HTS) coated conductors (CCs) is to prevent joule heating damage by providing an alternative path for the current flow during the HTS normal state transition (i.e., quench). However, the shunt presence in combination with unavoidable fluctuations in the critica...

The normal zone propagation velocity (NZPV) of three families of REBCO tape architectures designed for superconducting fault current limiters (SFCLs) and to be used in high voltage direct current (HVDC) transmission systems has been measured experimentally in liquid nitrogen at atmospheric pressure. The measured NZPVs span more than three orders of...

When modeling superconducting devices based on REBCO tapes and operating near or above the critical current value Ic, the power-law is not always accurate. In our previous works, we proposed the overcritical current constitutive law, based on a combination of fast pulsed current measurements and finite element analysis. The overcritical current con...

This paper uses both experimental and numerical approaches to revisit the concept of current transfer length (CTL) in second-generation high-temperature superconductor coated conductors with a current flow diverter (CFD) architecture. The CFD architecture has been implemented on eight commercial coated conductors samples from THEVA. In order to mea...

A good knowledge of material properties is a critical aspect for modeling high-temperature superconductor (HTS) devices. However, the knowledge of the electrical resistivity of coated conductors above the critical current is limited. The major challenge in characterizing this regime lies in the fact that for I>Ic, heating effects and thermal instab...

Copper-stabilized second generation high-temperature superconductor (HTS) coated conductors were modified to enhance their normal zone propagation velocity (NZPV). Experimental results, supported by numerical simulations, indicate that adding copper on the substrate side instead of adding it on the HTS side increases the NZPV by a factor of 2–3. Fu...

This paper presents extensive electrical, microstructural and chemical characterizations of HTS coated conductor samples in which an oxide layer (CeOx) has been added between the superconductor (GdBaCuO) and the silver (Ag) layers, in an attempt to increase the interfacial resistance between these two conductive layers. This increase of interfacial...

The strong photon-magnon coupling between an electromagnetic cavity and two yttrium iron garnet (YIG) spheres has been investigated in the context of a strong mutual dipolar interaction between the spheres. A decrease in the coupling strength between the YIG spheres and the electromagnetic cavity is observed, along with an increase of the total mag...

High-voltage direct current transmission systems are expected to allow the transmission of huge volumes of electricity over long distances. The use of superconducting fault current limiters (SFCLs) based on second-generation (2G) high-temperature superconductor (HTS) coated conductors (CCs) is a promising solution to mitigate fault currents in DC t...

The strong photon-magnon coupling between an electromagnetic cavity and two yttrium iron garnet (YIG) spheres has been investigated in the context of a strong mutual dipolar interaction between the spheres. A decrease in the coupling strength between the YIG spheres and the electromagnetic cavity is observed, along with an increase of the total mag...

This work presents a generalization of the concept of current transfer length (CTL) between the stabilizer and the superconducting layer of high temperature superconductor (HTS) coated conductor tapes with a current flow diverter (CFD) architecture. The CFD architecture consists in a non-uniform interfacial resistance between the two layers, namely...

A detailed knowledge of the resistivity of high-temperature superconductors in the overcritical current regime is important to achieve reliable numerical simulations of applications such as superconducting fault current limiters. We have previously shown that the combination of fast pulsed current measurements and finite element analysis allows acc...

This paper presents a simple but rigorous method to extract correctly the resistivity of the superconducting Rare-Earth Barium Copper Oxide (REBCO) layer of High Temperature Superconductor coated conductors, when the latter are characterized in over-critical current conditions using ultrafast V-I pulsed current measurements. The pulsed current meas...

In this work, we use numerical simulations to compare the performance of different promising architectures of HTS tape for DC fault current limitation. A 1D finite-element model which solves the heat equation through the thickness of a high temperature superconducting (HTS) tape at the location of a hot spot was coupled with a simple electrical cir...

Understanding the electro-thermal behavior of high temperature superconductor (HTS) materials is a critical aspect for designing efficient and reliable applications. In order to optimize cost and performance, one needs to understand the role played by the various layers of a HTS tape during a quench. On the one hand, the electrical and thermal prop...

This paper presents a simple and effective approach to increase the normal zone propagation velocity (NZPV) in (RE)BaCuO thin films grown on a flexible metallic substrate. The concept is an extension of the current-flow-diverter concept already known in the literature. The key idea behind the novel approach is to use a specific geometry of the silv...

Epitaxial growth of aluminum substituted epsilon ferrite by pulsed laser deposition on strontium titanate and yttrium-stabilized zirconium substrates is demonstrated for a wide range of aluminum substitution. Linear decrease of the out-of-plane lattice parameter with aluminum substitution correlates with the decrease of the coercive magnetic field,...

This paper presents a simple approach to increase the normal zone propagation velocity in (RE)BaCuO thin films grown on a flexible metallic substrate, also called superconducting tapes. The key idea behind this approach is to use a specific geometry of the silver thermal stabilizer that surrounds the superconducting tape. More specifically, a very...

Epsilon ferrite (ε-Fe2O3) is a metastable phase of iron(III) oxide, intermediate between maghemite and hematite. It has recently attracted interest because of its magnetocrystalline anisotropy, which distinguishes it from the other polymorphs, and results in a gigantic coercive field and a natural ferromagnetic resonance frequency in the THz range....

The effects of operating conditions, critical current and stabilizer geometry on the normal zone propagation velocity (NZPV) of second generation (2G) high-temperature superconductor (HTS) coated conductors (CCs) are investigated using finite element simulations. The NZPV of tapes with a low interfacial resistance between the HTS and stabilizer lay...

In order to plan the integration of superconducting fault current limiters (SFCLs) in power systems, accurate models of SFCLs must be made available in commercial power system transient simulators. In this context, we developed such a model for the EMTP-RV software package, a power system transient simulator widely used by power utilities. The mode...

Hysteresis loops characterize a wide variety of behaviors in fields ranging from physics and chemistry to economics and sociology. In particular, they represent the main characteristic of ferroic materials such as ferromagnetic and ferroelectric, which, in recent years, have attracted much interest due to their multifunctional properties. Although...

We investigate the quasi-static magnetic behavior of ensembles of non-interacting ferromagnetic nanoparticles consisting of MnP nanoclusters embedded in GaP(001) epilayers grown at 600, 650 and 700{\deg}C. We use a phenomenological model, in which surface effects are included, to reproduce the experimental hysteresis curves measured as a function o...

There is described herein a superconducting segment and method of making same comprising one or several layers with very high electrical resistivity, acting as a current flow diverter when the current transfers from the superconductor to the stabilizer. The purpose of this current flow diverter is: i) to increase the contact resistance between the...

We report on the effects of crossed magnetic fields on a commercial Bi:2223/Ag tape superconductor. The large magnetic moments which are generated in the specimen by the application or change of an external magnetic field (denoted H z ) directed perpendicularly to the plane of the tapes, hence along the c -axis of the crystallites, are considerably...

C Lacroix and F Sirois apologize for the error in their paper titled 'Concept of a current flow diverter for accelerating the normal zone propagation velocity in 2G HTS coated conductors'. They point out that in the published paper, the values of the critical current density at T = T0 (Jc0) in table 2 and the critical current Ic0 are incorrect. The...

Solids and powders can be analysed directly and with good accuracy by neutron activation analysis without sample preparation because of the excellent penetrating powers of neutrons and gamma rays. However, if the sample contains high concentrations of gamma-absorbing heavy elements or neutron-absorbing elements, the analysis results must be correct...

A fast normal zone propagation velocity (NZPV) in second-generation (2G) high-temperature superconductor (HTS) coated conductors (CC) is desirable in order to prevent the appearance of destructive hot spots upon a local quench. It was predicted theoretically that an increase of the interfacial resistance between the superconductor and the stabilize...

Triangular-shaped current pulses were used to obtain the electrical characteristics ( E-I curves) of second-generation high-temperature superconductor coated conductors above their critical current. The dependence of these E-I curves on magnetic field was also characterized (up to 150 mT). Current pulses with rising rates of hundreds of amperes per...

Several issues remain to be addressed for the commercial development of Resistive Fault Current Limiters based on superconducting technologies (RFCL). In particular, the inhomogeneity of high temperature superconducting coated conductors (HTS-CC) combined with the difficulty to predict RFCLs behaviour when interfaced with the existing electrical gr...

Full three dimensional x-ray diffraction reciprocal space maps combined with transmission electron microscopy measurements provide a systematic determination of the texture of GaP epilayers containing embedded MnP nanoclusters grown on GaP(001) by organometallic vapor phase epitaxy. This approach reveals that the texture of the MnP clusters depends...

The superconducting state occurs for many elements, alloys, and compounds when cooled to sufficiently low temperatures, specifically, below the critical temperature, Tc. The initial discoveries by Onnes in 1911 and 1914 were of the loss of electrical resistance at very low temperatures and of its reestablishment by applying a strong enough magnetic...

SiCN magnetic ceramics doped with Fe ions were synthesized at different pyrolysis temperatures in the range from 600 to 1600°C. Several phases of ceramics were detected using the techniques of electron paramagnetic resonance/ferromagnetic resonance, Raman, Fourier-transform infrared and X-ray diffractometry, listed as follows: (a) transformation to...

We report a giant magneto-optical (MO) effect in a GaP(011) epilayer with embedded MnP nanoclusters (GaP:MnP) grown on a GaP(011) substrate using metal-organic vapor phase epitaxy. The MO effect exhibits a hysteretic behavior when sweeping the applied magnetic field, thereby indicating a clear dependence upon the magnetization of the sample. The me...

RÉSUMÉ : L’introduction du ferromagnétisme dans la technologie actuelle des couches minces semiconductrices est un défi qui suscite beaucoup de recherche à l’heure actuelle. Ceci ouvrirait la voie à la conception et le développement de nouveaux dispositifs intégrés ayant des fonctionnalités nouvelles ou améliorées. Jusqu’à maintenant, un effort con...

GaP:MnP samples, which consist of GaP(001) epilayers with embedded MnP nanoclusters occupying approximately 7% of the epilayer volume, were grown at three different substrate temperatures (600, 650, and 700 °C) using metal-organic vapor phase epitaxy. Angle dependent ferromagnetic resonance (FMR) spectroscopy indicates that, in all samples, MnP clu...

Hybrid ferromagnetic-semiconductor GaP:MnP thin films were grown at 650 ° C by metal-organic vapor phase epitaxy on GaP(001) using trimethylgallium, tertiarybutylphosphine, and methyl cyclopentadienyl manganese tricarbonyl (MCTMn). Overall Mn concentrations in the hybrid films, determined by Rutherford backscattering spectrometry, were found to be...

We report on the angular dependence of ferromagnetic resonance (FMR) of GaP(001) epilayers with embedded MnP nanoclusters (GaP:MnP) grown on a GaP(001) substrate using metal-organic vapor phase epitaxy (MOVPE). Angle dependent FMR spectra obtained at 292 K show several peaks and indicate a strong magnetic anisotropy. The measured angular dependence...