Interstitial Solutes and Deformation in Nb and Nb Single Crystals

Ricker, Richard E.; Pitchure, David J.; Myneni, Ganapati Rao

doi:10.1063/1.2770679

Cited by 3 publications

(2 citation statements)

References 15 publications

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“…The E beam melting practice for interstitial degassing is known to function efficiently because of the excellent bulk mechanical yielding properties [51] of niobium. The E beam melting practice for interstitial degassing is known to function efficiently because of the excellent bulk mechanical yielding properties [51] of niobium.…”

Section: Melting Cutting and Formingmentioning

confidence: 99%

Proton in SRF Niobium

Wallace¹,

Myneni²,

Ciovati³

et al. 2011

AIP Conference Proceedings

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Hydrogen is a difficult impurity to physically deal with in superconducting radio frequency (SRF) niobium, therefore, its properties in the metals should be well understood to allow the metal's superconducting properties to be optimized for minimum loss in the construction of resonant accelerator cavities. It is known that hydrogen is a paramagnetic impurity in niobium from NMR studies. This paramagnetism and its effect on superconducting properties are important to understand. To that end analytical induction measurements aimed at isolating the magnetic properties of hydrogen in SRF niobium are introduced along with optical reflection spectroscopy which is also sensitive to the presence of hydrogen. From the variety, magnitude and rapid kinetics found in the optical and magnetic properties of niobium contaminated with hydrogen forced a search for an atomic model. This yielded quantum mechanical description that correctly generates the activation energy for diffusion of the proton and its isotopes not only in niobium but the remaining metals for which data is available. This interpretation provides a frame work for understanding the individual and collective behavior of protons in metals. 1

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Section: Melting Cutting and Formingmentioning

confidence: 99%

Proton in SRF Niobium

Wallace¹,

Myneni²,

Ciovati³

et al. 2011

AIP Conference Proceedings

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“…This prompted a second series of tests in which additional specimen were EDM cut with subsequent vacuum annealing. The purpose of these tests was a thorough outgassing of volatile interstials which are known to affect the mechanical properties of high purity niobium [3]. The first annealing test was done for 1 hour at 700 °C at 10 -6 Torr; the second test with a different set of samples was done for 24 hours at 1000 °C.…”

Section: Tensile Testsmentioning

confidence: 99%

Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities

Gnäupel‐Herold¹,

Myneni²,

Ricker³

2007

AIP Conference Proceedings

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This work investigates properties of large grained, high purity niobium with respect to the forming of superconducting radio frequency (SRF) cavities from such large grained sheets. The yield stresses were examined using tensile specimens that were essentially single crystals in orientations evenly distributed in the standard projection triangle. No distinct yield anisotropy was found, however, vacuum annealing increased the yield strength by a factor 2..3. The deep drawing forming operation of the half cells raises the issues of elastic shape changes after the release of the forming tool (springback) and residual stresses, both of which are indicated to be negligible. This is a consequence of the low yield stress (< 100 MPa) and the large thickness (compared to typical thicknesses in sheet metal forming). However, the significant anisotropy of the transversal plastic strains after uniaxial deformation points to potentially critical thickness variations for large grained / single crystal half cells, thus raising the issue of controlling grain orientation or using single crystal sheet material.

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Review of ingot niobium as a material for superconducting radiofrequency accelerating cavities

Kneisel

Ciovati

Dhakal

et al. 2015

Nuclear Instruments and Methods in Physics Research Section A:

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As a result of a collaboration between Jefferson Lab and niobium manufacturer CBMM, ingot niobium was explored as a possible material for superconducting radiofrequency (SRF) cavity fabrication. The first single cell cavity from large grain high purity niobium was fabricated and successfully tested at Jefferson Lab in 2004. This pioneering work triggered research activities in other SRF laboratories around the world. Large grain niobium became not only an interesting alternative material for cavity builders, but also material scientists and surface scientists were eager to participate in the development of this material. Most of the original expectations for this material of being less costly and allowing less expensive fabrication and treatment procedures at the same performance levels in cavities have been met. Many single cell cavities made from material of different suppliers have been tested successfully and several multi-cell cavities have shown the performances comparable to the best cavities made from standard polycrystalline niobium. Several 9-cell cavities fabricated by Research Instruments and tested at DESY exceeded the best performing fine grain cavities with a record accelerating gradient of E acc = 45.6 MV/m. Recently-at JLab-by using a new furnace treatment procedure a single cell cavity made of ingot niobium performed at a remarkably high Q 0value (~5×10 10 ) at an accelerating gradient of ~20 MV/m, at 2K. Such performance levels push the state-of-the art of SRF technology to new limits and are of great interest for future accelerators. This contribution reviews the development of ingot niobium technology and attempts to make a case for this material being the choice for future accelerators. PACS numbers: 84.40.-x, 84.71.-b 2

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Interstitial Solutes and Deformation in Nb and Nb Single Crystals

Cited by 3 publications

References 15 publications

Proton in SRF Niobium

Proton in SRF Niobium

Investigations of Residual Stresses and Mechanical Properties of Single Crystal Niobium for SRF Cavities

Review of ingot niobium as a material for superconducting radiofrequency accelerating cavities

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