Gerardo Iannone

2D and 3D numerical modeling of experimental magnetization cycles in disks and spheres

The use of FEM models to simulate the Bean critical state is used in two particular geometries: the disk and the sphere exposed to a uniform magnetic field. Two FEM approaches have been used, the Adaptive Resistivity Algorithm under the ANSYS framework, and the H-Formulation using the COMSOL software. In this work, the validity of these methods to solve two-dimensional and three-dimensional models is proven through the comparison to the existing theories. In order to reproduce the experimental magnetization cycles, the critical current density dependence on magnetic field has been derived from measurements in YBCO thin disk at 65 K and a Nb spherical samples at 6.0 K. While the YBCO disk critical state is well reproduced by our models, the Nb sample shows more complicated response which cannot be simulated just considering a critical state model.

Quench Behavior of a Conduction Cooled

Extensive applications of YBa2Cu3O7-x (YBCO) tapes require a comprehensive knowledge of their behavior in every possible operating condition. In this paper, the thermal stability behavior of a conduction-cooled pancake coil wound with commercial YBCO coated conductors is reported from both the experimental and numerical point of view. The coil stability against heat disturbances is studied in terms of minimum quench energy and normal zone propagation velocity (NZPV) for different values of the coil currents at different temperatures. The quench dynamics of the tape is compared between experiment and the numerical analysis, obtaining a reasonable agreement for voltage traces, NZPV, and temperatures. The model allows a wide range of case studies that can be used to suggest appropriate solutions for the design of detection and protection systems.

\hbox{YBa}_{2} \hbox{Cu}_{3}\hbox{O}_{7 - {\rm x}}

To broaden the use of an adaptive resistive algorithm (ARA), we present a 3-D model able to reproduce the experimental magnetic moment loop for a finite-size superconducting strip in a perpendicular field. We also develop the same model by using H-formulation, to strengthen the ARA results. We find that 2-D models computed with the two different approaches, i.e., ARA and H-formulation, provide similar results, and both well compare to approximate analytical solutions. Then, we verify that the computed magnetic moment loop by using either 3-D numerical approaches reproduces the experimental curve, i.e., the magnetic loops of a commercial YBCO-coated conductor sample measured at 5 K. Instead, the 2-D numerical data need a scaling factor to match the experimental ones. The 3-D computations provide support to the hypotheses on the current surface profile that has been used to find the scaling factor.

Tape Pancake Coil

The Italian National Institute for Nuclear Physics, within a larger cooperation with other partners, is setting up a new facility at University of Salerno for testing superconducting magnets for accelerators. The setup includes, further to the supercritical He 200 W@4.5 K refrigerator, and the 20 kA power converter, a suitable pair of HTS 20 kA current leads. To keep an optimized system flexibility, the current leads are designed with HTS technology, which allows for reduction of both the conduction heat leak on its cold end, and the Joule heating. In addition to match the cryogenic plant features, the current leads, at current level below 10 kA, are designed to operate with cold He flow provided by the refrigeration plant, thus avoiding LN2 flow. When running the current leads at full current we shall use an additional LN2 bath and evaporation stream to boost the He refrigeration power needed in the copper section of the current leads. This cooling scheme requires a dedicated design of the heat exchangers. In this work we report the numerical analyses of the current leads, concerning only the normal conducting section, to support this refrigeration scheme which have to match two different heat loads.

Modeling experimental magnetization cycles of thin superconducting strips by finite-element simulations

The Italian Institute for Nuclear Physics is working on the development of fast cycled dipoles for the Facility for Antiproton and Ion Research SIS300 synchrotron at Gesellschaft für Schwerionenforschung, Darmstadt. In this framework the development of high current and low ac loss superconducting wires is an important step of the R&D. The main technique to attain these features is to develop fine filaments for the strands and to design suitable resistive barriers among filament islands within the strands. In this paper, we study a newly developed wire in terms of critical currents and ac losses. The critical current is obtained from magnetization cycle and direct transport current. The ac loss mechanisms caused by the interfilament electromagnetic coupling is related to the ρet, the transverse resistance between adjacent filaments. We measure ρet through ac susceptibility technique.

20 kA HTS Current Leads for the INFN Magnet Test Facility

Abstract Nowadays, users’ privacy on the Internet is highly at risk, due to the monetization by advertising companies that support many of the so-called “free” services such as searching or social networking. In fact, several mechanisms are used to monitor users and build detailed profiles to tailor behavioral advertising. Given the increasing use of mobile devices and the increasing revenues from behavioral advertising, large advertising companies are present in this market as well. The increasing use of mobile devices for interacting with the Web and using mobile applications has been also drawing attention to their energy consumption. Several studies have addressed this issue from different point of views, i.e., hardware, software, as well as by analyzing the energy drained by different mobile applications. Our goal in this work is to measure the effectiveness of a methodology that exploits a hardware-based instrumentation to study whether privacy-preserving mechanisms are also able to efficiently reduce communication and computation overhead and, thus, save the battery life of mobile phones with the overall aim of a more sustainable Internet.