G. De Marzi

Bio: G. De Marzi is an academic researcher from ENEA. The author has contributed to research in topics: Magnetization & Magnet. The author has an hindex of 16, co-authored 57 publications receiving 918 citations. Previous affiliations of G. De Marzi include Sapienza University of Rome & University of Paris-Sud.

Design of an Industrially Feasible Twisted-Stack HTS Cable-in-Conduit Conductor for Fusion Application

Abstract: Taking advantage of the large experience of the ENEA Superconducting Laboratory in the manufacture and characterization of large scale superconducting systems, a project was launched, aimed at using High Temperature Superconductor (HTS) 2G wires for the manufacture of a cable-in-conduit conductor (CICC). In particular, the main aim was the definition of a conductor design fully compatible with existing cabling technologies, to be promptly transferred to an industrial scale production. The considered layout is based on 150 HTS tapes, arranged as five layered structures of twisted tapes wound on a helically slotted core with external round jacket. All manufacturing steps (slotted core production, tape stacking and insertion into the ducts, external wrapping and jacketing) are fulfilled by using equipments and technologies available at TRATOS Cavi S.p.A. These CICCs are intended for operation using forced flow of Helium. A 2D local thermal model has been developed for the optimization of the cooling configuration. This conductor is designed to target 20 kA at 4.2 K and 15 T (or, alternatively, higher temperature, in self-field and LN2 cooling) corresponding to a Je of about 55 A/mm2. The production of a short dummy sample revealed that the exploited industrial production process is very promising for the development of HTS CICC.

Probing intrinsic transport properties of single metal nanowires: Direct-write contact formation using a focused ion beam

Abstract: The transport characteristics of 70-nm-diameter platinum nanowires (NWs), fabricated using a pore-templated electrodeposition process and individually contacted using a focused ion beam (FIB) method, are reported. This approach yields nanowire devices with low contact resistances (∼400Ω) and linear current–voltage characteristics for current densities up to 65kA∕cm2. The intrinsic nanowire resistivity (33±5μΩcm) indicates significant contributions from surface- and grain-boundary scattering mechanisms. Fits to the temperature dependence of the intrinsic NW resistance confirm that grain-boundary scattering dominates surface scattering (by more than a factor of 2) at all temperatures. Our results demonstrate that FIB presents a rapid and flexible method for the formation of low-resistance ohmic contacts to individual metal nanowires, allowing intrinsic nanowire transport properties to be probed.

Water Confined in Lamellar Structures of AOT Surfactants: An Infrared Investigation

Abstract: Both X-ray diffraction and infrared spectroscopy on water confined between the lamellar bilayers of aerosol-OT (AOT) allowed us to explore the differences in connectivity between bulk and confined water when water layer thicknesses are allowed to vary from 19.0 to 1.5 nm. Compared with previous studies on AOT reverse micelles, the present report in the lamellar mesophase allows one to cancel the micelle curvature contribution, which disrupts the water connectivity, too. The influence of AOT surface on the water connectivity degree was thus quantified alone in the mid infrared region (3000−3800 cm-1) in the OH stretching mode. The OH stretching mode peak can be fitted by three Gaussian peaks that describe three main connecting populations, namely the “multimer” water at c.a. 3585 cm-1, the “intermediary” water at c.a. 3465 cm-1, and the “network” water at c.a. 3320 cm-1. It is shown that interactions with the surfactant heads do not alter the water structure until the water layer shrinks below 4.0 nm and t...

Cable-in-conduit conductors: lessons from the recent past for future developments with low and high temperature superconductors

Abstract: We review progress in the design of high field superconducting cable-in-conduit conductors (CICCs) for fusion applications, with special attention to the results of recent key experiments, leading to the state-of-the-art CICC technology: the ITER Toroidal Field and Central Solenoid programs, the EFDA Dipole conductor development program, the NHFML Hybrid Magnet project, the EU-TF Alt conductor demonstration, and the CRPP React & Wind flat cable test. For these projects, the main CICC design driver was the mitigation of Nb3Sn conductor performance degradation with electro-magnetic loading cycles. This was achieved by proper choice of cable layout and of conductor geometry, depending on the specific operating conditions and project requirements. In all cases, the necessity to limit cable movements inside the conductor jacket was identified to be of crucial importance. The main aspects of CICC manufacture are also discussed here, at least for what is the experience gained by the authors in both CICC jacketing and cabling processes. Finally, the state of the art of high-temperature superconducting (HTS) cables is discussed: at present, this technology is still in its infancy, but it is highly likely that major technological improvements could eventually lead to a widespread use of HTS CICCs.

Infrared-active phonons of LaMnO 3 and CaMnO 3

Abstract: The infrared absorption spectra of polycrystalline ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{CaMnO}}_{3}$ measured in the frequency range of the transverse optical phonons are reported, discussed, and compared with calculations of the lattice dynamics. For ${\mathrm{LaMnO}}_{3}$ the measured spectrum is consistent with the expected orthorhombic structure. For ${\mathrm{CaMnO}}_{3}$ the spectrum reflects a symmetry lower than that of a cubic perovskite. We find a close correspondence between the spectra of the two materials which suggests a similarity in their structures.

Signatures of the hydrogen bonding in the infrared bands of water.

Abstract: Infrared spectroscopy measurements have been completed over a wide range of frequencies allowing to measure the evolution of both intramolecular and intermolecular vibrational modes in water as a function of temperature. Emphasis is made on the high frequency OH stretching band and the so-called connectivity band that lies in the far infrared region. The substructures of the two infrared bands are analyzed in terms of different levels of connectivity of the water molecules, along the statements of the percolation model. Both band profiles appear to be related to the different degrees of connectivity of water molecules. Comparison of the data with the predictions of the percolation model shows good agreement as for the temperature evolution of liquid water. This work provides additional support to the interpretation of water bands substructures as signatures of its very specific connectivity pattern.

Porosity and Mechanical Properties of Mesoporous Thin Films Assessed by Environmental Ellipsometric Porosimetry

Abstract: Mesoordered silica thin films with cubic structures were prepared by evaporation induced self-assembly (EISA) with two types of structuring agent (CTAB and block copolymer F127). A complete and accurate description of these films was obtained by combining 2D-SAXS analyses, variable angle spectroscopic ellipsometry, and a specially designed environmental ellipsometric porosimetry (EEP) experiment. The EEP analysis is rapid and cheap and operates at ambient pressure and temperature. This latter experiment was performed with water and produced a set of water adsorption-desorption isotherms. A modified Kelvin equation, coupled with a modelisation of pores contraction, enabled the determination of the structural parameters of films porous networks: ellipsoidal pore diameters, porous volume, and surface area. Young moduli of films in the direction perpendicular to the substrates were calculated from these parameters.