Effect of Applied Compressive Stress and Impregnation Material on Internal Strain and Stress State in Nb 3 Sn Rutherford Cable Stacks
TL;DR: In this paper, the elastic strain evolution of Nb3Sn Rutherford type cables with different impregnation and coil blocks extracted from an 11 T dipole short model coil were investigated.
Abstract: The Nb3Sn superconductor in accelerator magnets must resist high mechanical stresses. In order to better understand the effect of the coil impregnation system on the stresses exerted on the strain-sensitive Nb3Sn superconductor, we have measured the elastic strain evolution in the conductor constituents under externally applied loads. For this purpose, a dedicated load frame that enables rotation of the sample load axis with respect to the neutron scattering geometry was installed in the Stress-Spec beamline at the neutron source Heinz Maier-Leibnitz FRM II. The Nb3Sn- and Cu-loading strains were measured in situ by neutron diffraction under monotonic and cyclic compressive loading. So-called ten-stack samples composed of Nb3Sn Rutherford type cables with different impregnation and coil blocks extracted from an 11 T dipole short model coil were investigated.
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TL;DR: Several development programs for these magnets, based on Nb3Sn technology, are being pursued in Europe and in the U.S. as mentioned in this paper summarizes and discusses the status, plans, and preliminary results of these programs.
Abstract: A future circular collider (FCC) with a center-of-mass energy of 100 TeV and a circumference of around 100 km, or an energy upgrade of the LHC (HE-LHC) to 27 TeV require bending magnets providing 16 T in a 50-mm aperture. Several development programs for these magnets, based on Nb3Sn technology, are being pursued in Europe and in the U.S. In these programs, cos–theta, block-type, common-coil, and canted–cos–theta magnets are explored; first model magnets are under manufacture; limits on conductor stress levels are studied; and a conductor with enhanced characteristics is developed. This paper summarizes and discusses the status, plans, and preliminary results of these programs.
37 citations
Cites methods from "Effect of Applied Compressive Stres..."
...Neutron diffraction measurements at the Heinz MaierLeibnitz Zentrum (MLZ) at the instrument STRESS-SPEC have been performed in order to better understand the effect of the epoxy resin on the Nb3Sn and copper lattice strain and stress evolution under compressive stress loading [28]....
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TL;DR: In this paper, the authors measured the stiffness of Nb3Sn Rutherford cable stacks with different epoxy volume fraction and found that the cable stack stiffness is strongly dependent on the load direction.
Abstract: For the optimization of Nb3Sn superconducting accelerator magnet design and assembly parameters the stress-strain behavior of the coils needs to be known. We have measured the stiffness of Nb3Sn Rutherford cable stacks with different epoxy volume fraction. The cable stack stiffness is strongly dependent on the load direction. The highest stiffness of about 95 GPa is measured in axial direction, as predicted by the rule of mixtures. In transverse load direction the stiffness is stress dependent, and about half of the axial stiffness. As expected the stiffness of the cable stacks increases with decreasing epoxy volume fraction. The stiffness of a conductor block extracted from an already cold tested 11 T dipole coil is comparable to that of a ten-stack sample with similar epoxy volume fraction.
12 citations
Cites methods from "Effect of Applied Compressive Stres..."
...This second setup, installed at the STRESS-SPEC neutron diffractometer [15] at the Heinz Maier-Leibnitz Zentrum (MLZ), Munich, was used for simultaneous stress-strain and neutron diffraction experiments [16], [17]....
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TL;DR: In this paper, a three-dimensional model is established and analyzed to better understand the mechanical behavior of Nb3Sn Rutherford cables subjected to different loading conditions during the cabling process.
3 citations
CERN1
TL;DR: In this paper, the elastic anisotropy of different materials used in superconducting magnet coils and in the structural magnet constituents is calculated based on the neutron diffraction data.
Abstract: The materials used in superconducting magnet coils and in the structural magnet constituents are textured to various extents. This causes an angular dependence of the Young's moduli that needs to be taken into account when predicting the stress and strain distribution in the magnets. We have measured by neutron diffraction the texture in metallic materials typically used in superconducting magnets. Based on the neutron diffraction data the elastic anisotropy of the different materials has been calculated. Among the materials studied, the extruded Al oxide dispersion strengthened Cu coil wedges exhibit the strongest elastic anisotropy of 37%. The Young's moduli calculated from single crystal elastic constants and grain orientation distributions are compared with highly accurate Young's moduli derived experimentally from resonance tests.
1 citations
Cites background from "Effect of Applied Compressive Stres..."
...For more information about the Nb3Sn/Cu sample see reference [22]....
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References
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4,690 citations
TL;DR: In this article, anwendungsmoglichkeiten der Methode werden besprochen, in which experimentelle Vergleichswerte weichen von den berechneten etwas ab, was beweist, das die Experimente nicht den von der Theorie geforderten idealen Bedingungen genugt haben.
Abstract: Mit Hilfe des Begriffes der elastischen Polarisierbarkeit konnen die elastischen Konstanten des makroskopisch isotropen Vielkristalls aus den Einkristallkonstanten exakt ausgerechnet werden. Im Falle des Aggregats aus kubischen Kristalliten, in dem die Bestimmung des Kompressionsmoduls trivial ist, folgt der Schubmodul aus einer Gleichung 3. Grades [Gl. (22)], in der Kombinationen der Einkristallhauptkonstanten als Koeffizienten auftreten. Die experimentellen Vergleichswerte weichen von den berechneten etwas ab, was beweist, das die Experimente nicht den von der Theorie geforderten idealen Bedingungen genugt haben. Weitere Anwendungsmoglichkeiten der Methode werden besprochen.
1,433 citations
"Effect of Applied Compressive Stres..." refers methods in this paper
...Table I summarizes Young’s moduli Ehkl and Poisson’s ratio νhkl that are calculated from single crystal constants by the Kroener model [17], which was used as it is the most accepted approach [16] to calculate the elastic constants....
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1,299 citations
Book•
28 Feb 2005TL;DR: In this article, the authors discuss the development of stress measurement by diffraction and the characteristics of Neutron Strain Measurement, including extinction, texture, and multiple scattering.
Abstract: INTRODUCTION Residual Stress: Friend or Foe? Historical Development of Stress Measurement by Diffraction Special Characteristics of Neutron Strain Measurement Nature and Origin of Residual Stress Effects of Residual Stress FUNDAMENTALS OF NEUTRON DIFFRACTION Introduction Scattering and Absorption of Neutrons and X-Rays by Atoms Neutron Diffraction from Crystalline Solids Penetration of Neutron Beams Effects of Lattice Vibrations Extinction, Texture, and Multiple Scattering DIFFRACTION TECHNIQUES AND INSTRUMENT DESIGN Neutron Sources Diffractometers for Strain Measurement Neutron Detectors The Instrumental Resolution Instrument Gauge Volumes Sampled Gauge Volume and Effective Measurement Position Specialized Instruments for Strain Measurement PRACTICAL ASPECTS OF STRAIN MEASUREMENT USING NEUTRON DIFFRACTION Introduction Measurement of Diffraction Bragg Peak Profile Analyzing Bragg Peak Profiles Accuracy of Diffraction Peak Center Determination Analysis of Complete Diffraction Profiles for Strain Strain-Free Reference Reproducibility Tests INTERPRETATION AND ANALYSIS OF LATTICE STRAIN DATA Inferring Stresses from Lattice Strains Introduction to Mechanics of Crystallite Deformation Elastic Anisotropy of Single Crystals The Bulk Elastic Response of Polycrystals hkl-Specific Response in a Polycrystal Undergoing Elastic Deformation hkl-Specific Response in a Polycrystal Undergoing Plastic Deformation APPLICATIONS TO PROBLEMS IN MATERIALS SCIENCE AND ENGINEERING Introduction Welded Structures Composites and Other Multiphase Materials Plastically Deformed Components and Materials Near-Surface Stresses In Situ and Through-Process or Life Studies THE FUTURE SYMBOLS AND ABBREVIATIONS GLOSSARY APPENDICES Note on Reactor Flux Spectrum Relation between the Centroid of Sampled Gauge Volume and Translator Reading Points for Consideration When Making a Neutron Diffraction Stress Measurement Macroscopic Scattering Cross-Sections of All Elements Index
659 citations
"Effect of Applied Compressive Stres..." refers methods in this paper
...Table I summarizes Young’s moduli Ehkl and Poisson’s ratio νhkl that are calculated from single crystal constants by the Kroener model [17], which was used as it is the most accepted approach [16] to calculate the elastic constants....
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...The loading strain is determined from the scattering angles of the Nb3Sn (321) and Cu (220) lattice planes [16] and represents an average elastic strain in the gauge volume of 5 × 5 × 5 mm3 defined by beam and detector characteristics....
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CERN1
TL;DR: In this article, the authors reviewed the last ten year of Nb3Sn accelerator magnet R&D and compared it to the needs of the upgrades and critically assessed the results of the Nb 3Sn and HTS technology and the planned R&DD programs also based on the inputs of first year of LHC operation.
Abstract: The Large Hadron Collider is working at about half its design value, limited by the defective splices of the magnet interconnections. While the full energy will be attained after the splice consolidation in 2014, CERN is preparing a plan for a Luminosity upgrade (High Luminosity LHC) around 2020 and has launched a pre-study for exploring an Energy upgrade (High Energy LHC) around 2030. Both upgrades strongly rely on advanced accelerator magnet technology, requiring dipoles and quadrupoles of accelerator quality and operating fields in the 11-13 T range for the luminosity upgrade and 16-20 T range for the energy upgrade. The paper will review the last ten year of Nb3Sn accelerator magnet R&D and compare it to the needs of the upgrades and will critically assess the results of the Nb3Sn and HTS technology and the planned R&D programs also based on the inputs of first year of LHC operation.
208 citations
"Effect of Applied Compressive Stres..." refers background in this paper
...IN ACCELERATOR magnets [1] like the Nb3Sn magnets presently under construction for the LHC High Luminosity upgrade (HL-LHC) [2], and those foreseen for the Future Circular Collider (FCC) [3], the dominant mechanical load case to which the coils are exposed is transverse compression....
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