SRF2019 - List of Authors (Angle, J.W.)

Paper	Title	Page
TUFUA3	Development of a Qualitative Model for N-Doping Effects on Nb SRF Cavities
	A.D. Palczewski, C.E. Reece, J.K. Spradlin JLab, Newport News, Virginia, USA J.W. Angle Virginia Polytechnic Institute and State University, Blacksburg, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. In early 2018, preliminary RF date from the LCLS-II HE program suggested two new high temperature doping recipes developed at Jefferson Laboratory (3N60) and Fermi Nation Laboratory (2N0) produced quench fields outside expectations.* Both recipes showed quench fields (while maintaining high Q₀) outside the simplified model where the quench field scaled purely with the RF surface doping level. In late 2018 we developed a qualitative going on a quantitative model based on preliminary SIMS/SEM measurements of the new recipes that would explain the quench field distribution. Unfortunately, subsequent measurements invalidated the developing model. We will present our original qualitative model and new data where the model breaks down; showing the multi-variable dynamics which we now think we need to understand in order to fully model and maximize quench fields for high temperature doping. * Palczewski, A.D. and Bafia, D., contributions TESLA Technology Collaboration University of British Columbia, Vancouver, Canada, February 5 - 8 2019
	Slides TUFUA3 [7.176 MB]
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THFUA6	Nb₃Sn Films for SRF Cavities: Genesis and RF Properties	810
	U. Pudasaini, M.J. Kelley The College of William and Mary, Williamsburg, Virginia, USA J.W. Angle, M.J. Kelley, J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA
	Funding: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 to the College of William and DE-SC-0018918 to Virginia Tech. 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 effects of nucleation, growth, process conditions, and impurities. Nb₃Sn films from few hundreds of nm up to ~15 µm were grown and characterized using AFM, SEM/EDS, XPS, EBSD, SIMS, and SAM. Microscopic examinations of samples suggest the mechanisms behind Nb₃Sn thin film nucleation and growth. RF measurements of coated cavities were combined with material characterization of witness samples to adapt the coating process in "Siemens" coating configuration. Understanding obtained from sample studies, applied to cavities, resulted in Nb₃Sn cavity with quality factor 2 ×10¹⁰ at 15 MV/m accelerating gradient at 4 K, without "Wuppertal" Q-slope. We discuss the genesis of the Nb₃Sn thin film in a typical tin vapor diffusion process, and its consequences to the coating of SRF cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUA6
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
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THP017	Crystallographic Characterization of Nb₃Sn Coatings and N-Doped Niobium via EBSD and SIMS	871
SUSP001	use link to see paper's listing under its alternate paper code
	J.W. Angle, M.J. Kelley, J. Tuggle Virginia Polytechnic Institute and State University, Blacksburg, USA G.V. Eremeev, M.J. Kelley, C.E. Reece JLab, Newport News, Virginia, USA M.J. Kelley, U. Pudasaini The College of William and Mary, Williamsburg, Virginia, USA
	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, motivated by potentially higher operating temperatures. More recently niobium has been doped with nitrogen to improve the quality factor (Q). Currently, a need for better understanding still exists for both mechanisms. EBSD has been shown to be a viable technique to determine the crystallographic orientation and the size of the Nb₃Sn grains. The EBSD maps obtained show a bimodal distribution of grain sizes with smaller Nb₃Sn grains found present near the Nb₃Sn/Nb interface. In addition to the Nb₃Sn coatings, N-doped niobium coupons were analyzed by EBSD and found that the coupon had preferred surface orientation. The EBSD analysis was found to be vital as specific grains could be targeted in SIMS to better understand the diffusion of nitrogen with respect to crystal orientation.
	Poster THP017 [2.571 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP017
About •	paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

TUFUA3

Development of a Qualitative Model for N-Doping Effects on Nb SRF Cavities

A.D. Palczewski, C.E. Reece, J.K. Spradlin
JLab, Newport News, Virginia, USA
J.W. Angle
Virginia Polytechnic Institute and State University, Blacksburg, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In early 2018, preliminary RF date from the LCLS-II HE program suggested two new high temperature doping recipes developed at Jefferson Laboratory (3N60) and Fermi Nation Laboratory (2N0) produced quench fields outside expectations.* Both recipes showed quench fields (while maintaining high Q₀) outside the simplified model where the quench field scaled purely with the RF surface doping level. In late 2018 we developed a qualitative going on a quantitative model based on preliminary SIMS/SEM measurements of the new recipes that would explain the quench field distribution. Unfortunately, subsequent measurements invalidated the developing model. We will present our original qualitative model and new data where the model breaks down; showing the multi-variable dynamics which we now think we need to understand in order to fully model and maximize quench fields for high temperature doping.
* Palczewski, A.D. and Bafia, D., contributions TESLA Technology Collaboration University of British Columbia, Vancouver, Canada, February 5 - 8 2019

Slides TUFUA3 [7.176 MB]

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THFUA6

Nb₃Sn Films for SRF Cavities: Genesis and RF Properties

810

U. Pudasaini, M.J. Kelley
The College of William and Mary, Williamsburg, Virginia, USA
J.W. Angle, M.J. Kelley, J. Tuggle
Virginia Polytechnic Institute and State University, Blacksburg, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA

Funding: Partially authored by Jefferson Science Associates under contract no. DE¬AC05¬06OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 to the College of William and DE-SC-0018918 to Virginia Tech.
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 effects of nucleation, growth, process conditions, and impurities. Nb₃Sn films from few hundreds of nm up to ~15 µm were grown and characterized using AFM, SEM/EDS, XPS, EBSD, SIMS, and SAM. Microscopic examinations of samples suggest the mechanisms behind Nb₃Sn thin film nucleation and growth. RF measurements of coated cavities were combined with material characterization of witness samples to adapt the coating process in "Siemens" coating configuration. Understanding obtained from sample studies, applied to cavities, resulted in Nb₃Sn cavity with quality factor 2 ×10¹⁰ at 15 MV/m accelerating gradient at 4 K, without "Wuppertal" Q-slope. We discuss the genesis of the Nb₃Sn thin film in a typical tin vapor diffusion process, and its consequences to the coating of SRF cavities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUA6

About •

paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP017

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

871

SUSP001

use link to see paper's listing under its alternate paper code

J.W. Angle, M.J. Kelley, J. Tuggle
Virginia Polytechnic Institute and State University, Blacksburg, USA
G.V. Eremeev, M.J. Kelley, C.E. Reece
JLab, Newport News, Virginia, USA
M.J. Kelley, U. Pudasaini
The College of William and Mary, Williamsburg, Virginia, USA

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, motivated by potentially higher operating temperatures. More recently niobium has been doped with nitrogen to improve the quality factor (Q). Currently, a need for better understanding still exists for both mechanisms. EBSD has been shown to be a viable technique to determine the crystallographic orientation and the size of the Nb₃Sn grains. The EBSD maps obtained show a bimodal distribution of grain sizes with smaller Nb₃Sn grains found present near the Nb₃Sn/Nb interface. In addition to the Nb₃Sn coatings, N-doped niobium coupons were analyzed by EBSD and found that the coupon had preferred surface orientation. The EBSD analysis was found to be vital as specific grains could be targeted in SIMS to better understand the diffusion of nitrogen with respect to crystal orientation.

Poster THP017 [2.571 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP017

About •

paper received ※ 23 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)