Performance boundaries in Nb3Sn superconductors

Superconducting magnets for High Energy Physics, Fusion, Magnetic Resonance Imaging (NMR) and Nuclear Magnetic Resonance, benefit from the extremely high current densities that can be achieved in superconductors compared to normal conducting materials. These magnets are usually constructed starting with a composite wire of typically 1 mm in diameter, in which the superconducting material is embedded in a copper matrix in the form of micrometer scale filaments. The present superconducting workhorse is Niobium-Titanium

Toward an accurate scaling relation for the critical current in niobium-tin conductors

Until a few years ago, a set of equations commonly referred to as the Summers relations gave the most accurate description of the critical current in Nb/sub 3/Sn conductors as a function of applied field, temperature and axial strain. Although highly empirical, they describe reasonably well the critical current data of past Nb/sub 3/Sn conductors. New data from various types of Nb/sub 3/Sn conductors, as well as recent analysis of the ITER CS model coil results reveal however, that this description lacks the precision, required to correlate the conductor data to the model coil results. This discrepancy, attributed to the highly empirical background for the relations, manifests itself mainly in the strain- and temperature dependence. The development of an alternative, more accurate description of the behavior of the critical current, starting from a more fundamental description of the strain dependence, has been initiated. At the moment, the development concentrates around the improvement of the temperature dependency relations to achieve a better accuracy of the overall descriptions, especially in the high temperature region

The effect of initial and back pressures upon the water rate of a simple steam engine

Thesis (M.E.)--University of Illinois, 1916Typescrip

Scaling of the critical current in ITER type niobium-tin superconductors in relation to the applied field, temperature and uni-axial applied strain

The three dimensional surface of the critical current density versus field and temperature Jc(B,T) of niobium-tin is a function of the strain state of the superconductor. A brief review of literature on this subject is presented. The Jc(B) function is described by the relations for flux pinning. The temperature and strain dependencies are added to this relation, This results in a unifying scaling law for A15 materials, which is verified for different niobium-tin conductors with respect to all the relevant variables, i.e. field, temperature and uni-axial strain. Nb3Sn conductors from 9 manufacturers are measured in the frame work of the third ITER benchmark tests on critical current. The investigated ranges are: applied field from 7 to 13 T, temperature from 4.2 to 8 K and applied strain from -0.4 to +0.8%. Special attention is paid to the region of compressive axial strain, which is the most relevant state of strain for superconductors under thermal compression in practical application

Experimental Verification of the Temperature and Strain Dependence of the Critical Properties in Nb3Sn Wires

The critical current density in Nb3Sn conductors is described with an improved scaling formula for the temperature, magnetic field and strain dependence. In an earlier study, it is concluded that the largest uncertainties in this description arise from the temperature dependence that is described with various slightly different empirical relations. For the optimization of the numerical codes, used to predict the stability of large magnet systems, a more accurate description is required. Therefore, two different bronze processed conductors for the ITER CS model coil are analyzed in detail. The critical current is measured at temperatures from 4.2 K up to the critical temperature, in magnetic fields from 1 T to 13 T and with an applied axial strain from -0.6% to +0.4%. The axial strain is applied by a U-shaped bending spring and a comparison is made between brass and Ti-6Al-4V, as substrate materia

Verzet of participatie? Advies om uw huurders deel te laten nemen aan energiebesparende werkzaamheden!

In de komende jaren wil woningcorporatie Lefier Zuidoost Drenthe, hierna genoemd Lefier, 1750 woningen een energielabel C of hoger verschaffen en daarbij de klanttevredenheid waarborgen. Dit advies is geschreven voor woningcorporatie Lefier Zuidoost Drenthe. Deze woningcorporatie wil een upgrade van energielabels voor bestaande woningen in Emmen en Klazienaveen bewerkstelligen. Lefier wil dit bereiken door het uitvoeren van energiebesparende werkzaamheden. Voordat deze werkzaamheden bij de woningen doorgevoerd kunnen worden, moet 70% van de bewoners hiermee ingestemd hebben. Het probleem is echter dat in de betreffende wijken in Klazienaveen en Emmen deze 70% niet wordt gehaald en de werkzaamheden dus niet plaats kunnen vinden. De grote vraag is dan ook: ‘Welke bijdrage levert de 70% norm aan het besluit van bewoners om wel of niet deel te nemen aan energiebesparende werkzaamheden en welke rol speelt communicatie hierin?’. Om deze probleemstelling te kunnen beantwoorden hebben wij de volgende doelstelling geformuleerd: namelijk het verkrijgen van informatie door middel van een kwantitatief onderzoek om de mening van de huurders te achterhalen over de 70% regeling. Daarnaast is het onderzoek gericht op hoe de huurders het liefst benaderd worden, waardoor een zo hoog mogelijk percentage mee wil werken aan energiebesparende renovatieprojecten. Studentenonderzoek in het kader van het thema Duurzaam bouwen

Calculation of the Critical Current Reduction in a Brittle Round Multifilamentary Wire due to External Forces

A simple model is presented that can describe the electro-mechanical state of a multifilamentary wire. An elastic cylinder model is used to derive the strain state analytically. Axial and transverse forces came a position dependent critical current density in the wire. The integral critical current of such a wire is calculated. The effect of two different parameters, the hydrostatic and the deviatoric strain, on the critical current is compared. The critical current reduction of a model wire due to various external loads in a Nb 3Sn wire is analysed. Finally the position of the superconducting filaments is considere

The critical current of Nb3Sn wires for ITER as a function of the axial tension and compression

The influence of compressive and tensile axial strains on the critical current of various Nb3Sn conductors is investigated. The investigated multifilamentary wires are especially developed for the ITER project. The critical current is determined as a function of an axial tension in a standard pull set-up. These results are compared with the results that are obtained on a bending spring-type strain device. In this second device an axial compression larger than the integral thermal shrinkage of the matrix, can be achieved. A study of the field dependence of the critical current yields the strain dependence of the extrapolated upper-critical field versus the axial strain. A good correlation is found between the two different strain devices in the tensile strain regime. There is a difference in the (limited) compressive strain regime where such a comparison can be mad

An optimized BSCCO/Ag resonator coil for utility use

AC coils made with BSCCO-2223/Ag tapes and operating in liquid nitrogen have a potential for power related applications, e.g., inductors, transformers and current limiters. High-Tc tapes are available from several producers, while access to the coil building know-help is still rather limited, The relevant knowledge and technology suitable for making HTS coils for 50-60 Hz operation is being developed as a part of the current project. To verify the technology, several test solenoids and a first full-scale sub-coil have been manufactured. Electromagnetic, thermal and mechanical analysis of the coils is performed. The electromagnetic analysis focuses on the reduction of the radial magnetic field component in the windings. Voltage-current characteristics and the AC loss data obtained from relevant short sample measurements are applied. A good agreement between calculated and measured V-I curves and losses of the coils is found. A remarkable increase of the critical current and the reduction of the AC loss at the coil edges are predicted and confirmed experimentally. With the losses defined, thermal analysis and optimization of the coil structure are performed numerically followed by measurements for verification. The paper reports on the series of coils developed and explains the features of the projec

Thin film growth by pulsed laser deposition and properties of 122-type iron-based superconductor AE(Fe1--xCox)2As2 (AE = alkaline earth)

This paper reports comprehensive results on thin-film growth of 122-type iron-pnictide superconductors, AE(Fe1-xCox)2As2 (AE = Ca, Sr, and Ba, AEFe2As2:Co) by a pulsed laser deposition method using a neodymium-doped yttrium aluminum garnet laser as an excitation source. The most critical parameter to produce the SrFe2As2:Co and BaFe2As2:Co phases is the substrate temperature (Ts). It is difficult to produce highly-pure CaFe2As2:Co phase thin film at any Ts. For BaFe2As2:Co epitaxial films, controlling Ts at 800-850 {\deg}C and growth rate to 2.8-3.3 {\AA}/s produced high-quality films with good crystallinity, flat surfaces, and high critical current densities > 1 MA/cm2, which were obtained for film thicknesses from 100 to 500 nm. The doping concentration x was optimized for Ba(Fe1-xCox)2As2 epitaxial films, leading to the highest critical temperature of 25.5 K in the epitaxial films with the nominal x = 0.075.Comment: will be published in the special issue of Superconductor Science and Technology, `Iron12