SRF2019 - List of Authors (Oseroff, T.E.)

Paper	Title	Page
MOP014	Electroplating of Sn Film on Nb Substrate for Generating Nb₃Sn Thin Films and Post Laser Annealing	51
SUSP036	use link to see paper's listing under its alternate paper code
	Z. Sun, M. Liepe, T.E. Oseroff, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T. Arias, A.B. Connolly, J.M. Scholtz, N. Sitaraman, M.O. Thompson Cornell University, Ithaca, USA X. Deng University of Virginia, Charlottesville, Virginia, USA K.D. Dobson University of Delaware, Newark, Delaware, USA
	Controlling film quality of Nb₃Sn is critical to its SRF cavity performance. The state-of-the-art vapor diffusion approach for Nb₃Sn deposition observed surface roughness, thin grain regions, and misfit dislocations which negatively affect the RF performance. The Sn deficiency and non-uniformity at the nucleation stage of vapor deposition is believed to be the fundamental reason to cause these roughness and defects issues. Thus, we propose to pre-deposit a uniform Sn film on the Nb substrate, which is able to provide sufficient Sn source during the following heat treatment for Nb₃Sn nucleation and growth. Here, we demonstrated successful electrodeposition of a low-roughness, dendrite-free, excellent-adhesion Sn film on the Nb substrate. More importantly, we further achieved a uniform, low-roughness (Ra = 66 nm), pure-stoichiometric Nb₃Sn film through thermal treatment of this electroplated Sn film in the furnace. Additionally, we provide preliminary results of laser annealing as a post treatment for epitaxial grain growth and roughness reduction.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP014
About •	paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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TUFUB8	CVD Coated Copper Substrate SRF Cavity Research at Cornell University	381
	M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V.M. Arrieta, S.R. McNeal Ultramet, Pacoima, California, USA
	Chemical vapor deposition (CVD) is a promising alternative to conventional sputter techniques for coating copper substrate cavities with high-quality superconducting films. Through multiple SRF-related DOE SBIR projects, Ultramet has developed CVD processes and CVD reactor designs for SRF cavities, and Cornell University has conducted extensive RF testing of CVD coated surfaces. Here we report results from thin-film CVD Nb₃Sn coated copper test plates, and for thick-film CVD niobium on copper including full-scale single cell 1.3 GHz copper substrate cavities. Detailed optical inspection and surface characterization show high-quality and well-adhered coatings. No copper contamination is found. The Nb₃Sn coated plates have a uniform Nb₃Sn coating with a slightly low tin concentration (19 -22%), but a BCS resistance well in agreement with predictions. The CVD Nb coatings on copper plates demonstrate excellent adhesion characteristics and exceeded surface fields of 50 mT without showing signs of a strong Q-slope that is frequently observed in sputtered Nb cavities. Multiple single-cell 1.3 GHz copper cavities have been coated to date at Ultramet, and results from RF testing of these are presented and discussed.
	Slides TUFUB8 [12.488 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB8
About •	paper received ※ 01 July 2019 paper accepted ※ 05 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP044	RF Characterization of Novel Superconducting Materials and Multilayers	950
SUSP021	use link to see paper's listing under its alternate paper code
	T.E. Oseroff, M. Liepe, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA B. Moeckly STI, Santa Barbara, California, USA M.J. Sowa Veeco-CNT, Medford, USA
	Cutting edge SRF technology is likely approaching the fundamental limitations of niobium cavities operating in the Meissner state. This combined with the obvious advantages of using higher critical temperature superconductors and thin film depositions leads to interest in the RF characterization of such materials. A TE mode niobium sample host cavity was used to characterize the RF performance of 5" (12.7 cm) diameter sample plates as a function of field and temperature at 4 GHz. Materials studied include MgB₂ and thin film atomic layer deposition (ALD) NbN and NbTiN on Nb substrates. These higher critical temperature superconductors all having coherence lengths on the order of a few nm. It is therefore likely that defects on the order of the coherence lengths will cause early flux penetration well before the theorized superheating field of an ideal superconducting surface. Superconductor-insulator-superconductor (SIS) multilayers have been proposed as a mechanism of arresting these early penetration flux avalanches and are therefore studied here as well, using the same NbN and NbTiN films, but over thin layers of insulating AlN on Nb substrates.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP044
About •	paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP045	Improvements to the Cornell Sample Host System	956
	T.E. Oseroff, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	RF characterization of arbitrary superconducting samples has been of interest for many years but, due to the experimental complexities, has never been achieved to its full potential. A TE mode niobium sample host cavity has been used at Cornell to characterize the RF performance of 5" (12.7 cm) diameter sample plates. It was designed and built in 2012 – 2013 and since then has encountered a range of problems. The focus of this work is to highlight these and to present solutions to assist future researchers hoping to design novel RF characterization instruments. Topics covered include coupler design, cryostat support structure, sample preparation, and a discussion of potential systematic errors introduced by the data extraction and calibration methods applied to this device.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP045
About •	paper received ※ 01 July 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP046	Magnetic Field Mapping System for Cornell Sample Host Cavity	961
	S.N. Lobo, M. Liepe, T.E. Oseroff Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Cornell Laboratory for Accelerator-Based Sciences and Education Dissipation due to flux trapping is a persistent problem experienced in SRF cavity testing and cryomodule operation. This work addresses accurately and cheaply measuring magnetic fields in a cryostat without using delicate and expensive fluxgate magnetometers. Anisotropic Magnetoresistive (AMR) magnetic field sensors were investigated for the detection of small fields in a cryogenic environment. Initial development of instrumentation using 16 AMR sensors is presented for the purpose of measuring magnetic fields perpendicular the normal of a 5" diameter sample plate on the Cornell sample host cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP046
About •	paper received ※ 29 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

MOP014

Electroplating of Sn Film on Nb Substrate for Generating Nb₃Sn Thin Films and Post Laser Annealing

51

SUSP036

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

Z. Sun, M. Liepe, T.E. Oseroff, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, A.B. Connolly, J.M. Scholtz, N. Sitaraman, M.O. Thompson
Cornell University, Ithaca, USA
X. Deng
University of Virginia, Charlottesville, Virginia, USA
K.D. Dobson
University of Delaware, Newark, Delaware, USA

Controlling film quality of Nb₃Sn is critical to its SRF cavity performance. The state-of-the-art vapor diffusion approach for Nb₃Sn deposition observed surface roughness, thin grain regions, and misfit dislocations which negatively affect the RF performance. The Sn deficiency and non-uniformity at the nucleation stage of vapor deposition is believed to be the fundamental reason to cause these roughness and defects issues. Thus, we propose to pre-deposit a uniform Sn film on the Nb substrate, which is able to provide sufficient Sn source during the following heat treatment for Nb₃Sn nucleation and growth. Here, we demonstrated successful electrodeposition of a low-roughness, dendrite-free, excellent-adhesion Sn film on the Nb substrate. More importantly, we further achieved a uniform, low-roughness (Ra = 66 nm), pure-stoichiometric Nb₃Sn film through thermal treatment of this electroplated Sn film in the furnace. Additionally, we provide preliminary results of laser annealing as a post treatment for epitaxial grain growth and roughness reduction.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP014

About •

paper received ※ 22 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

TUFUB8

CVD Coated Copper Substrate SRF Cavity Research at Cornell University

381

M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, T.E. Oseroff, R.D. Porter, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V.M. Arrieta, S.R. McNeal
Ultramet, Pacoima, California, USA

Chemical vapor deposition (CVD) is a promising alternative to conventional sputter techniques for coating copper substrate cavities with high-quality superconducting films. Through multiple SRF-related DOE SBIR projects, Ultramet has developed CVD processes and CVD reactor designs for SRF cavities, and Cornell University has conducted extensive RF testing of CVD coated surfaces. Here we report results from thin-film CVD Nb₃Sn coated copper test plates, and for thick-film CVD niobium on copper including full-scale single cell 1.3 GHz copper substrate cavities. Detailed optical inspection and surface characterization show high-quality and well-adhered coatings. No copper contamination is found. The Nb₃Sn coated plates have a uniform Nb₃Sn coating with a slightly low tin concentration (19 -22%), but a BCS resistance well in agreement with predictions. The CVD Nb coatings on copper plates demonstrate excellent adhesion characteristics and exceeded surface fields of 50 mT without showing signs of a strong Q-slope that is frequently observed in sputtered Nb cavities. Multiple single-cell 1.3 GHz copper cavities have been coated to date at Ultramet, and results from RF testing of these are presented and discussed.

Slides TUFUB8 [12.488 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUFUB8

About •

paper received ※ 01 July 2019 paper accepted ※ 05 July 2019 issue date ※ 14 August 2019

Export •

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

THP044

RF Characterization of Novel Superconducting Materials and Multilayers

950

SUSP021

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

T.E. Oseroff, M. Liepe, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
B. Moeckly
STI, Santa Barbara, California, USA
M.J. Sowa
Veeco-CNT, Medford, USA

Cutting edge SRF technology is likely approaching the fundamental limitations of niobium cavities operating in the Meissner state. This combined with the obvious advantages of using higher critical temperature superconductors and thin film depositions leads to interest in the RF characterization of such materials. A TE mode niobium sample host cavity was used to characterize the RF performance of 5" (12.7 cm) diameter sample plates as a function of field and temperature at 4 GHz. Materials studied include MgB₂ and thin film atomic layer deposition (ALD) NbN and NbTiN on Nb substrates. These higher critical temperature superconductors all having coherence lengths on the order of a few nm. It is therefore likely that defects on the order of the coherence lengths will cause early flux penetration well before the theorized superheating field of an ideal superconducting surface. Superconductor-insulator-superconductor (SIS) multilayers have been proposed as a mechanism of arresting these early penetration flux avalanches and are therefore studied here as well, using the same NbN and NbTiN films, but over thin layers of insulating AlN on Nb substrates.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP044

About •

paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

Export •

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

THP045

Improvements to the Cornell Sample Host System

956

T.E. Oseroff, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

RF characterization of arbitrary superconducting samples has been of interest for many years but, due to the experimental complexities, has never been achieved to its full potential. A TE mode niobium sample host cavity has been used at Cornell to characterize the RF performance of 5" (12.7 cm) diameter sample plates. It was designed and built in 2012 – 2013 and since then has encountered a range of problems. The focus of this work is to highlight these and to present solutions to assist future researchers hoping to design novel RF characterization instruments. Topics covered include coupler design, cryostat support structure, sample preparation, and a discussion of potential systematic errors introduced by the data extraction and calibration methods applied to this device.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP045

About •

paper received ※ 01 July 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

Export •

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

THP046

Magnetic Field Mapping System for Cornell Sample Host Cavity

961

S.N. Lobo, M. Liepe, T.E. Oseroff
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Cornell Laboratory for Accelerator-Based Sciences and Education
Dissipation due to flux trapping is a persistent problem experienced in SRF cavity testing and cryomodule operation. This work addresses accurately and cheaply measuring magnetic fields in a cryostat without using delicate and expensive fluxgate magnetometers. Anisotropic Magnetoresistive (AMR) magnetic field sensors were investigated for the detection of small fields in a cryogenic environment. Initial development of instrumentation using 16 AMR sensors is presented for the purpose of measuring magnetic fields perpendicular the normal of a 5" diameter sample plate on the Cornell sample host cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP046

About •

paper received ※ 29 June 2019 paper accepted ※ 01 July 2019 issue date ※ 14 August 2019

Export •

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