Explanipedia

Niobium's intrinsic coherence length and penetration depth revisited using low-energy muon spin spectroscopy Open

Ryan M. L. McFadden, Jonathan W. Angle, Eric Lechner, Michael J. Kelley, Charles Reece , et al. · 2025

We report measurements of the London penetration depth ($λ_L$) and Bardeen-Cooper-Schrieffer (BCS) coherence length ($ξ_0$) in oxygen-doped niobium, with impurity concentrations spanning the "clean" to "dirty" limits. Depth-resolved low-en…

Analysis of Thermal Grooving Effects on Vortex Penetration in Vapor-Diffused Nb3Sn Open

Eric Lechner, O. M. Trofimova, Jonathan W. Angle, Madison C. DiGuilio, Uttar Pudasaini · 2024

While Nb3Sn theoretically offers better superconducting RF cavity performance (Q0 and Eacc) to Nb at any given temperature, peak RF magnetic fields consistently fall short of the 400 mT prediction. The relatively rough topography of vapor-…

Materials Science of the Interstitial Doping Process Open

Michael J. Kelley, Jonathan W. Angle, Eric Lechner, Charles Reece · 2024

Particle accelerators are an increasingly important tool for frontier science. Growing initial and operating costs are a significant barrier for upgrades and for new machines. While everything matters, the major cost contributor is the SRF…

SIMS CHARACTERIZATION OF NITROGEN DOPING OF LCLS-II-HE PRODUCTION CAVITIES Open

Charles Reece, Eric Lechner, Michael J. Kelley, Jonathan W. Angle · 2023

The thermal diffusion of nitrogen into the surface of niobium has been shown to yield superior low-loss SRF performance. An effective solution was identified and promptly employed in the production of cryomodules for LCLS-II. With added ex…

Analysis of furnace contamination on superconducting radio frequency niobium using secondary-ion mass spectrometry Open

Jonathan W. Angle, Eric Lechner, Charles Reece, F. A. Stevie, Michael J. Kelley · 2023

Detection of surface contamination on niobium materials used in superconducting radio frequency (SRF) applications is difficult due to quantitative sensitivity and near-atomic depth resolution needed. Inspection of samples known to have ex…

SIMS Characterization of Nitrogen Doping of LCLS-II-HE Production Cavities Open

Charles Reece, Eric Lechner, Michael J. Kelley, Jonathan W. Angle · 2023

The thermal diffusion of nitrogen into the surface of niobium has been shown to yield superior low-loss SRF performance. An effective solution was identified and promptly employed in the production of cryomodules for LCLS-II. With added ex…

Topographic Evolution of Nitrogen Doped Nb Subjected to Electropolishing Open

Eric Lechner, Jonathan W. Angle, Carrie Baxley, Michael J. Kelley, Charles Reece · 2023

Surface quality is paramount in facilitating high perfor-mance SRF cavity operation. Here, we investigate the topographic evolution of samples subjected to N-doping and 600 °C vacuum anneal. We show that in N-doped Nb, niobium nitrides may…

Improved quantitation of SIMS depth profile measurements of niobium via sample holder design improvements and characterization of grain orientation effects Open

Jonathan W. Angle, Eric Lechner, Ari Palczewski, Charles Reece, F. A. Stevie , et al. · 2022

The importance of SIMS analyses for “N-doped” impurity alloyed niobium and other surface-alloyed materials continues to increase. A major hurdle is the uncertainty of instrument calibration due to changes in sample height either from sampl…

Challenges to Reliable Production Nitrogen Doping of Nb for SRF Accelerating Cavities Open

Charles Reece, Jonathan W. Angle, Eric Lechner, Ari Palczewski, F. A. Stevie , et al. · 2022

Over the last several years, alloying of the surface layer of niobium SRF cavities has been demonstrated to beneficially lower the superconducting RF surface resistance. Nitrogen, titanium, and oxygen have all been demonstrated as effectiv…

Modeling O and N Alloying in Nb for SRF Applications Open

Eric Lechner, Jonathan W. Angle, Michael J. Kelley, Ari Palczewski, Charles Reece , et al. · 2022

N and O-alloyed superconducting radio frequency cavities exhibit extraordinary quality factors. Developing diffusion models that describe interstitial N and O in Nb is important for optimizing alloyed cavity quality factors and acceleratin…

RF surface resistance tuning of superconducting niobium via thermal diffusion of native oxide Open

Eric Lechner, Jonathan W. Angle, F. A. Stevie, Michael J. Kelley, Charles Reece , et al. · 2021

Recently, Nb superconducting radio frequency cavities vacuum heat treated between 300 and 400 °C for a few hours have exhibited very high quality factors (∼5 × 1010 at 2.0 K). Secondary ion mass spectrometry measurements of O, N, and C sho…

SIMS Investigation of Furnace-Baked Nb Open

Eric Lechner, Michael S. P. Kelley, Ari Palczewski, C. E. Reece, Jonathan W. Angle , et al. · 2021

Results recently published by Ito et al. showed that "furnace baking" Nb SRF cavities after electropolishing yields high quality factors and anti-Q-slopes resembling that of N doped cavities. Small Nb samples were prepared following the re…

Advances in secondary ion mass spectrometry for N-doped niobium Open

Jonathan W. Angle, Ari Palczewski, Charles Reece, F. A. Stevie, Michael J. Kelley · 2021

Accurate secondary ion mass spectroscopy measurement of nitrogen in niobium relies on the use of closely equivalent standards, made by ion implantation, to convert nitrogen signal intensity to nitrogen content by determination of relative …

Advances in secondary ion mass spectroscopy Open

Jonathan W. Angle, Ari Palczewski, Charles Reece, Fred A. Stevies, Michael J. Kelley · 2020

Accurate SIMS measurement of nitrogen in niobium relies on the use of closely equivalent standards, made by ion implantation, to convert nitrogen signal intensity to nitrogen content by determination of relative sensitivity factors (RSF). …

Pulmonary Exposure to Magnéli Phase Titanium Suboxides Results in Significant Macrophage Abnormalities and Decreased Lung Function Open

Dylan K. McDaniel, Veronica M. Ringel‐Scaia, Holly A. Morrison, Sheryl Coutermarsh‐Ott, McAlister Council‐Troche , et al. · 2019

Coal is one of the most abundant and economic sources for global energy production. However, the burning of coal is widely recognized as a significant contributor to atmospheric particulate matter linked to deleterious respiratory impacts.…

Electron backscatter diffraction of Nb3Sn coated niobium: Revealing structure as a function of depth Open

Jay Tuggle, Uttar Pudasaini, Jonathan W. Angle, Grigory Eremeev, Charlie Reece , et al. · 2019

Over the last two decades, advances in Electron Backscatter Diffraction (EBSD) have moved the technique from a research tool to an essential characterization technique in many fields of material research. EBSD is the best suited technique …

Crystallographic Characterization of Nb₃Sn Coatings and N-Doped Niobium via EBSD and SIMS Open

Jonathan W. Angle, Grigory Eremeev, Michael H. Kelley, Uttar Pudasaini, Charles Reece , et al. · 2019

Historically, niobium has been used as the superconducting material in SRF cavities. Due the high operational costs, other materials are currently being considered. Nb₃Sn coatings have been investigated over the past several decades, motiv…

Nb₃Sn Films for SRF Cavities: Genesis and RF Properties Open

Uttar Pudasaini, Jonathan W. Angle, Grigory Eremeev, Michael J. Kelley, Charles Reece , et al. · 2019

Understanding of Nb₃Sn nucleation and growth is essential to the progress with Nb₃Sn vapor diffusion coatings of SRF cavities. Samples representing different stages of Nb₃Sn formation have been produced and examined to elucidate the effect…

Microstructural Engineering of Titanium-Cellulose Nanocrystals Alloys via Mechanical Alloying and Powder Processing Open

Jonathan W. Angle · 2018

Titanium been used industrially for nearly a century. Ever since it was first reduced to its elemental form, concerted efforts have been made to improve the material and to reduce the cost of production. In this thesis, titanium is mechani…

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