687 research outputs found
Proposal of a novel design for linear superconducting motor using 2G tape stacks
This paper presents a new design for a su-
perconducting linear motor (SLM). This SLM uses stacks
of second-generation (2G) superconducting tapes, which
are responsible for replacing yttrium barium copper oxide
bulks. The proposed SLM may operate as a synchronous
motor or as a hysteresis motor, depending on the load
force magnitude. A small-scale linear machine prototype
with 2G stacks was constructed and tested to investigate
the proposed SLM topology. The stator traveling magnetic
field wave was represented by several Nd-Fe-B permanent
magnets. A relative movement was produced between the
stator and the stack, and the force was measured along the
displacement. This system was also simulated by the finite
element method, in order to calculate the induced currents
in the stack and determine the electromagnetic force. The
H-formulation was used to solve the problem, and a power
law relation was applied to take into account the intrin-
sically nonlinearity of the superconductor. The simulated
and measured results were in accordance. Simulated re-
sults were extrapolated, proving to be an interesting tool to
scale up the motor in future projects. The proposed motor
presented an estimated force density of almost 500 N/kg,
which is much higher than any linear motor.This work was supported in part by the following agencies: CNPq/CAPES/INERGE, CNPq—Ci ˆ encias sem Fronteiras, FAPERJ, Catalan Government 2014- SGR-753, CONSOLIDER Excellence Network MAT2014-56063-C2-1-R and MAT2015-68994-REDC, Eurofusion EU COST ACTIONS MP1201/ MP1014/PPPT-WPMAG 2014, EUROTAPES FP7-NMP-Large-2011- 280432, FORTISSIMO FP7-2013-ICT-609029, and Spanish Govern- ment Agencies—Severo Ochoa Programme Centres of Excellence in R&D. (Corresponding author: Guilherme G. Sotelo.
Current distribution in wide YBCO tapes
The need of a better mechanical behaviour and the stabilization of coated conductors for applications, as Magnets, cables or Fault Current Limiters, has motivated the lamination of tapes with stainless steel or copper alloys, increasing so the elastic modulus of the conductors and their mechanical performance. Some of the stainless steels used are magnetic, thus introducing some perturbations of the current flow when energizing the conductor. In order to detect these possible perturbations, the magnetic self field in the surface of the tape has been explored by Hall mapping technique at several current loads in a monotonically driven cyclic sequence. By increasing current steps when loading up, crossing the critical field threshold, and decreasing down to remanent state. Deviation from the expected magnetic map has been observed. In this work, we will report on the resulting measurements, and the current flow is calculated by solving the inverse problem for a 12 mm wide stainless steel reinforced Coated Conductor tape. We discuss on the likely origin of the observed perturbations.We would like to acknowledge the support of Nanoselect project of the CONSOLIDER program, and EU-FP7-ECCOFLOW project, and Xermae
H-Formulation FEM Modeling of the Current Distribution in 2G HTS Tapes and Its Experimental Validation Using Hall Probe Mapping
One of the most widespread mathematical formulations applied to simulate the electromagnetic phenomena of coated conductor in the recent literature is the H one. However, the only validation of the model has been indirect by using measurements taken from the applications, as measurements of the energy losses in ac fields, forces developed in levitation systems or any other parameter related to a specific application. Direct validation of the calculation requires the observation of the local out of plane magnetic field over the surface of the sample and this is only accessible under magneto-optical observations and, in a larger scale and better dynamic range, by the Hall scanning microscopy. We propose here the experimental validation of the H-formulation by comparing the simulated results with measurements made by a Hall probe mapping in a second generation (2G) tape sample for several DC transported currents at 77 K. The paper presents a methodology to simulate the 2G tape by using only measured data obtained from a sample and its normalized J(B) experimental curves. Some boundary conditions that allow a faster convergence of the problem are investigated. Simulated results of the 2G tape modelled considering only the 1 μm HTS layer were compared with other that represent the most important layers of the coated conductor structure in the calculations. The simulated and measured results present a good agreement, proving that this model can calculate precisely the magnetic field and, hence, the current distribution in HTS samples.This work was supported in part by the
followings grants: “Science Without Borders” from the Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq); by the European Agency
(EU) through the Factories of the Future Resources, Technology, Infrastructure
and Services for Simulation and Modelling (FORTISSIMO) Project under
Grant EU FP7-2013-ICT-609029, the European Development of Superconducting
Tapes (EUROTAPES) Project under Grant EU-FP7 NMP-LA-2012-
280432, the European Consortium for the Development of Fusion Energy
(EUROfusion, PPPT-WPMAG 2014), and EU COST ACTIONS MP1201 and
MP1014; by the Spanish Ministry of Economy and Competitiveness through
the “Severo Ochoa” Programme for Centres of Excellence in R&D under Grant
SEV-2015-0496, CONSOLIDER Excellence Network under Grant MAT2015-
68994-REDC, COACHSUPENERGY project under Grant MAT2014-56063-
C2-1-R, co-financed by the European Regional Development Fund; by the
Catalan Government under Grant 2014-SGR-753 and Xarmae
Effect of strain and magnetic field on the critical current and electric resistance of the joints between HTS coated conductors
Engineering of devices and systems such as magnets, fault current limiters or cables, based
on High Temperature Superconducting wires requires a deep characterization of the possible
degradation of their properties by handling at room temperature as well as during the service
life thus establishing the limits for building up functional devices and systems.
In the present work we report our study regarding the mechanical behavior of spliced joints
between commercial HTS coated conductors based on YBCO at room temperature and service
temperature, 77 K.
Tensile tests under axial stress and the evolution of the critical current and the electric resistance
of the joints have been measured. The complete strain contour for the tape and the joints
has been obtained by using Digital Image Correlation. Also, tensile tests under external magnetic
field have been performed and the effect of the applied field on the critical current and
the electric resistance of the joints has been studied. Additionally, fatigue tests under constant
cyclic stress and loading-unloading ramps have been carried out in order to evaluate the electromechanical
behavior of the joints and the effect of maximum applied stress on the critical current.
Finally, a preliminary numerical study by means of the Finite Element Method (FEM) of the
electromechanical behavior of the joints between commercial HTS is presented
Effect of strain and magnetic field on the critical current and electric resistance of the joints between HTS coated conductors
Engineering of devices and systems such as magnets, fault current limiters or cables, based on
High Temperature Superconducting wires requires a deep characterization of the possible
degradation of their properties by handling at room temperature as well as during the service
life thus establishing the limits for building up functional devices and systems.
In the present work we report our study regarding the mechanical behavior of spliced joints
between commercial HTS coated conductors based on YBCO at room temperature and
service temperature, 77 K.
Tensile tests under axial stress and the evolution of the critical current and the electric
resistance of the joints have been measured. The complete strain contour for the tape and the
joint has been obtained by using Digital Image Correlation. Also, tensile tests under external
magnetic field have been performed and the effect of the applied field on the critical current
and the electric resistance of the joints has been studied.
Finally, a preliminary numerical study by means of Finite Element Method (FEM) of the
mechanical behavior of the joints between commercial HTS is presented
Singular spectrum analysis filtering and Fourier inversion: an efficient and fast way to improve resolution and quality of current density maps with low-cost Hall scanning systems
We provide a Biot–Savart inversion scheme that, for any two-dimensional, or bulk with planar crystallization, high-temperature superconducting (HTS) sample, determines current density maps with a higher resolution and accuracy than previous procedures and at a fraction of its computational cost.
The starting point of our scheme is a Hall scanning microscopy map of the out-of-plane component of the magnetic field generated by the current. Such maps are noisy in scans of real samples with commercial-grade equipment, and their error is the limiting factor in any Biot–Savart inversion scheme. The main innovation of our proposed scheme is a singular spectrum analysis (SSA) filtering of the Hall probe maps, which cancels measurement errors such as noise or drifts without introducing any artifacts in the field map.
The SSA filtering of the Hall probe data is so successful in this task that the resulting magnetic field map does not require an overdetermined QR inversion, allowing Fourier inversion of the Biot–Savart problem.
Our implementation of SSA filtering of the Hall scan measurements, followed by Biot–Savart inversion using the fast Fourier transform (FFT), is applied to both simulations and real samples of HTS tape stacks. The algorithm works in cases where ill conditioning ruled out the application of Fourier inversion, and achieves a finer resolution for a fraction of the cost of the QR inversion used to date. The computation passes physical and statistical validity tests in all cases, and in three-dimensional samples it is shown to yield the average, with a depth-dependent weight, of the current density circulating in the different layers of the sample.We acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme (SEV-2015-0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-51778-C2-1-R, co-financed by FEDER), GAP project (MTM2015-69135-P) and SUPERINKS project (RTC-2015-3640-3, co-financed by FEDER); the European Union for the FASTGRID project (H2020-NMBP-18-2016-IA-72109) and WPMAG 5 (H2020-EUROfusion); and the Catalan Government with 2017-SGR-932, 2014-SGR-753 and Xarmae
Simple, Robust, and Plasticizer-Free Iodide-Selective Sensor Based on Copolymerized Triazole-Based Ionic Liquid
Novel solid-contact iodide-selective electrodes based on covalently attached 1,2,3 triazole ionic liquid (IL) were prepared and investigated in this study. Triazole-based IL moieties were synthesized using click chemistry and were further copolymerized with lauryl methacrylate via a simple one-step free radical polymerization to produce a "self-plasticized" copolymer. The mechanical properties of the copolymer are suitable for the fabrication of plasticizer-free ion-selective membrane electrodes. We demonstrate that covalently attached IL moieties provide adequate functionality to the ion-selective membrane, thus achieving a very simple, one-component sensing membrane. We also demonstrate that the presence of iodide as the counterion in the triazole moiety has direct influence on the membrane's functionality. Potentiometric experiments revealed that each electrode displays high selectivity toward iodide anions over a number of inorganic anions. Moreover, the inherent presence of the iodide in the membrane reduces the need for conditioning. The nonconditioned electrodes show strikingly similar response characteristics compared to the conditioned ones. The electrodes exhibited a near Nernstian behavior with a slope of -56.1 mV per decade across a large concentration range with lower detection limits found at approximately 6.3 × 10(-8) M or 8 ppb. These all-solid-state sensors were utilized for the selective potentiometric determination of iodide ions in artificial urine samples in the nanomolar concentration range
Crossover in the nature of the metallic phases in the perovskite-type RNiO_3
We have measured the photoemission spectra of NdSmNiO,
where the metal-insulator transition and the N\'{e}el ordering occur at the
same temperature for and the metal-insulator transition
temperature () is higher than the N\'{e}el temperature for . For , the spectral intensity at the Fermi level is high in the
metallic phase above and gradually decreases with cooling in the
insulating phase below while for it shows a pseudogap-like
behavior above and further diminishes below . The results
clearly establish that there is a sharp change in the nature of the electronic
correlations in the middle () of the metallic phase of the
NiO system.Comment: 4 pages, 4 figure, submitted to Phys. Rev.
High-order harmonic generation in Xe, Kr, and Ar driven by a 2.1-\mu m source: high-order harmonic spectroscopy under macroscopic effects
We experimentally and numerically study the atomic response and pulse
propagation effects of high-order harmonics generated in Xe, Kr, and Ar driven
by a 2.1-\mu m infrared femtosecond light source. The light source is an
optical parametric chirped-pulse amplifier, and a modified strong-field
approximation and 3-dimensional pulse propagation code are used for the
numerical simulations. The extended cutoff in the long-wavelength driven
high-harmonic generation has revealed the spectral shaping of high-order
harmonics due to the atomic structure (or photo-recombination cross-section)
and the macroscopic effects, which are the main factors of determining the
conversion efficiency besides the driving wavelength. Using precise numerical
simulations to determine the macroscopic electron wavepacket, we are able to
extract the photo-recombination cross-sections from experimental high-order
harmonic spectra in the presence of macroscopic effects. We have experimentally
observed that the macroscopic effects shift the observed Cooper minimum of Kr
from 80 eV to 60-70 eV and wash out the Cooper minimum of Ar. Measured
high-harmonic conversion efficiencies per harmonic near the cutoff are ~10^{-9}
for all three gases.Comment: 19 pages, 8 figure
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