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인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today’s technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.

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FCC-ee: The Lepton Collider: Future Circular Collider Conceptual Design Report Volume 2

We performed high-field magnetotransport and magnetization measurements on a single crystal of the 122-phase iron pnictide Ba(Fe1−xCox)2As2. Unlike the high-temperature superconductor cuprates and 1111-phase oxypnictides, Ba(Fe1−xCox)2As2 showed practically no broadening of the resistive transitions under magnetic fields up to 45 T. We report the temperature dependencies of the upper critical field Hc2 both parallel and perpendicular to the c-axis, the irreversibility field Hirrc(T), and a rather unusual symmetric volume pinning force curve Fp(H) suggestive of a strong pinning nanostructure. The anisotropy parameter γ=Hc2ab/Hc2c deduced from the slopes of dHc2ab/dT=4.9 T/K and dHc2c/dT=2.5 T/K decreases from ∼2 near Tc, to ∼1.5 at lower temperatures, much smaller than γ for 1111pnictides and high-Tc cuprates.

Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1−xCox)2As2

Transition temperature of strong-coupled superconductors.

Significant efforts can be found throughout the literature to optimize the current-carrying capacity of Nb3Sn superconducting wires. The achievable transport current density in wires depends on the A15 composition, morphology and strain state. The A15 sections in wires contain, due to compositional inhomogeneities resulting from solid-state diffusion A15 formation reactions, a distribution of superconducting properties. The A15 grain size can be different from wire to wire, and is also not necessarily homogeneous across the A15 regions. Strain is always present in composite wires, and the strain state changes as a result of thermal contraction differences and Lorentz forces in magnet systems. To optimize the transport properties, it is thus required to identify how composition, grain size and strain state influence the superconducting properties. This is not possible accurately in inhomogeneous and spatially complex systems such as wires. This article therefore gives an overview of the available literature on simplified, well-defined (quasi-)homogeneous laboratory samples. After more than 50 years of research on superconductivity in Nb3Sn, a significant amount of results are available, but these are scattered over a multitude of publications. Two reviews exist on the basic properties of A15 materials in general, but no specific review for Nb3Sn is available. This article is intended to provide such an overview. It starts with a basic description of the niobium–tin intermetallic. After that, it maps the influence of Sn content on the electron–phonon interaction strength and on the field–temperature phase boundary. The literature on the influence of Cu, Ti and Ta additions will then be summarized briefly. This is followed by a review of the effects of grain size and strain. The article concludes with a summary of the main results.

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A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State

Sn wires and include recent findings on the variation of the upper critical field (Hc2) with temperature (T) and A15 composition. Measurements of Hc2(T) in inevitably inhomogeneous wires, as well as analysis of literature results, have shown that all available Hc2(T) data can be accurately described by a single relation from the microscopic theory. This relation also holds for inhomogeneity averaged, effective, Hc2*(T) results and can be approximated by , with t = T/Tc. Knowing Hc2*(T) implies that Jc(T) is also known. We highlight deficiencies in the Summers/Ekin relations, which are not able to account for the correct Jc(T) dependence. Available Jc(H) results indicate that the magnetic field dependence for all wires from T up to about 80% of the maximum Hc2 can be described with Kramer's flux shear model, if nonlinearities in Kramer plots when approaching the maximum Hc2 are attributed to A15 inhomogeneities. The strain () dependence is introduced through a temperature and strain dependent Hc2*(T,) and Ginzburg–Landau (GL) parameter κ1(T,) and a strain dependent critical temperature Tc(). This is more consistent than the usual Ekin unification of strain and temperature dependence, which uses two separate and different dependences on Hc2*(T) and Hc2*(). Using a correct temperature dependence and accounting for the A15 inhomogeneities leads to the remarkably simple relation , where C is a constant, s() represents the normalized strain dependence of Hc2*(0) and h = H/Hc2*(T,). Finally, a new relation for s() is proposed, which is an asymmetric version of our earlier deviatoric strain model and based on the first, second and third strain invariants. The new scaling relation solves a number of much debated issues with respect to Jc scaling in Nb3Sn and is therefore of importance to the applied community, who use scaling relations to analyse magnet performance from wire results.

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A general scaling relation for the critical current density in Nb3Sn

We review the scaling relations for the critical current density (Jc) in Nb3Sn wires and include recent findings on the variation of the upper critical field (Hc2) with temperature (T) and A15 composition. Measurements of Hc2(T) in inevitably inhomogeneous wires, as well as analysis of literature results, have shown that all available Hc2(T) data can be accurately described by a single relation from the microscopic theory. This relation also holds for inhomogeneity averaged, effective, Hc2*(T) results and can be approximated by Hc2(t)=Hc2(0) = 1-t1.52, with t = T=Tc.Knowing Hc2*(T) implies that also Jc(T) is known. We highlight deficiencies in the Summers/Ekin relations, which are not able to account for the correct Jc(T) dependence. Available Jc(H) results indicate that the magnetic field dependence for all wires from mu0H = 1 T up to about 80 percent of the maximum Hc2 can be described with Kramer's flux shear model, if non-linearities in Kramer plots when approaching the maximum Hc2 are attributed to A15 inhomogeneities. The strain (e) dependence is introduced through a temperature and strain dependent Hc2*(T,e) and Ginzburg-Landau parameter kappa1(T,e) and a strain dependent critical temperature Tc(e). This is more consistent than the usual Ekin unification of strain and temperature dependence, which uses two separate and different dependencies on Hc2*(T) and Hc2*(e). Using a correct temperature dependence and accounting for the A15 inhomogeneities leads to the remarkable simple relation Jc(H,T,e)= (C/mu0H)s(e)(1-t1.52)(1-t2)h0.5(1-h)2, where C is a constant, s(e) represents the normalized strain dependence of Hc2*(0) andh = H/Hc2*(T,e). Finally, a new relation for s(e) is proposed, which is an asymmetric version of our earlier deviatoric strain model and based on the first, second and third strain invariants. The new scaling relation solves a number of much debated issues withrespect to Jc scaling in Nb3Sn and is therefore of importance to the applied community, who use scaling relations to analyze magnet performance from wire results.

The critical current (Ic) of six different Nb3Sn multifilamentary wires is investigated as a function of temperature, magnetic field, and strain. A relation for a critical temperature (Tc) that depends on the deviatoric strain is proposed and applied to interpret the results. First, a short review is given on the flux-pinning relations that are used to introduce a strain dependent Tc in a relation for the Ic as a function of field and temperature. The conductor samples are investigated in two different deformation states, namely, in a spiraled shape on a Ti sample holder and a straight section soldered onto a brass substrate. The brass substrate is used to apply a compressive or tensile axial strain to the conductor. The Ic in the different samples prepared from a single conductor type can be described very well with a single set of critical properties and strain parameters. In particular, in the strain regime where the matrix deformation is limited and the superconductor is axially compressed, the proposed strain relation is very accurate. The small variation in the strain parameter between the six conductors investigated suggests that this strain parameter is an intrinsic property of Nb3Sn.

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The strain dependence of the critical properties of Nb3Sn conductors

We have examined the upper critical field of a large and representative set of present multifilamentary Nb3Sn wires and one bulk sample over a temperature range from 1.4 K up to the zero-field critical temperature. Since all present wires use a solid-state diffusion reaction to form the A15 layers, inhomogeneities with respect to Sn content are inevitable, in contrast to some previously studied homogeneous samples. Our study emphasizes the effects that these inevitable inhomogeneities have on the field-temperature phase boundary. The property inhomogeneities are extracted from field-dependent resistive transitions which we find broaden with increasing inhomogeneity. The upper 90%–99% of the transitions clearly separates alloyed and binary wires but a pure, Cu-free binary bulk sample also exhibits a zero-temperature critical field that is comparable to the ternary wires. The highest μ0Hc2 detected in the ternary wires are remarkably constant: The highest zero-temperature upper critical fields and zero-fiel...

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Arno Godeke

Papers

A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State

A general scaling relation for the critical current density in Nb3Sn

A general scaling relation for the critical current density in Nb3Sn

The strain dependence of the critical properties of Nb3Sn conductors

The upper critical field of filamentary Nb3Sn conductors