SRF2023 - List of Keywords (factory)

Paper	Title	Other Keywords	Page
MOPMB024	Flux Expulsion Studies of Niobium Material of 650 MHz Cavities for PIP-II	cavity, niobium, simulation, radio-frequency	141
	K.E. McGee FRIB, East Lansing, Michigan, USA F. Furuta, M. Martinello, O.S. Melnychuk, A.V. Netepenko, G. Wu, Y. Xie Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Two different vendors supplied the niobium sheet material for PIP-II 5-cell 650 MHz cavities, which was characterized by multiple different ASTM sizes. Cavities subsequently fabricated from these sheets were heat-treated at various temperatures, then the cavities’ flux-expulsion performance was measured. Where the initial measurements of vendor O materials showed that nearly all flux remained trapped despite a high thermal gradient, 900C heat treatment subsequently improved the flux expulsion to an acceptable rate. Understanding and characterizing vendor O materials in this way is key for upcoming and future projects planning to employ niobium sheet from this supplier.
	Poster MOPMB024 [4.064 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB024
About •	Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB040	Comparing the Effectiveness of Low Temperature Bake in EP and BCP Cavities	cavity, SRF, niobium, radio-frequency	187
	H. Hu, Y.K. Kim University of Chicago, Chicago, Illinois, USA D. Bafia Fermilab, Batavia, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Electropolishing (EP) and buffered chemical polishing (BCP) are conventional surface preparation techniques for superconducting radiofrequency (SRF) cavities. Both EP and BCP treated SRF cavities display high field Q-slope (HFQS) which degrades performance at high gradients. While high gradient performance in EP cavities can be improved by introducing oxygen via a low temperature bake (LTB) of 120^°C by 48 hours, LTB does not consistently remove HFQS in BCP cavities. There is no consensus as to why LTB is not effective on BCP prepared cavities. We examine quench in EP, BCP, EP+LTB, and BCP+LTB treated 1.3 GHz single-cell Nb cavities by studying the heating behavior with field using a temperature mapping system. Cavity performance is correlated to characterizations of surface impurity profile obtained via time of flight secondary ion mass spectrometry studies. We observe a difference in near surface hydrogen concentration following BCP compared to EP that may suggest that the causes of quench in EP and BCP cavities are different.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB040
About •	Received ※ 14 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPMB047	Commissioning of Dedicated Furnace for Nb₃Sn Coatings of 2.6 GHz Single Cell Cavities	cavity, niobium, SRF, MMI	216
	P.A. Kulyavtsev, G.V. Eremeev, S. Posen, B. Tennis Fermilab, Batavia, Illinois, USA J. Zasadzinski IIT, Chicago, Illinois, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. We present the results of commissioning a dedicated furnace for Nb₃Sn coatings of 2.6GHz single cell cavities. Nb₃Sn is a desired coating due to its high critical temperature and smaller surface resistance compared to bulk Nb. Usage of Nb₃Sn coated cavities will greatly reduce operating costs due to its higher operating temperature providing decreased cooling costs. Tin is deposited in the bulk Nb cavity by use of a tin chloride nucleation agent and tin vapor diffusion. Analysis of the resultant coating was performed using SEM/EDS to verify successful formation of desired Nb:Sn phase. Witness samples located in line of sight of the source were analyzed in order to understand the coating efficacy. The cavity’s performance was assessed in the Vertical Test Stand (VTS) at Fermilab.
	Poster MOPMB047 [4.858 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB047
About •	Received ※ 26 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 08 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUCBA01	Measurements of the Amplitude-Dependent Microwave Surface Resistance of a Proximity-Coupled Au/Nb Bilayer	niobium, cavity, SRF, extraction	369
	T.E. Oseroff, M. Liepe, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	A sample host cavity is used to measure the surface resistance of a niobium substrate with a gold film deposited in place of its surface oxide. This talk will report about this measurement result. The film thickness of the gold layer was increased from 0.1 nm to 2.0 nm in five steps to study the impact of the normal layer thickness. The 0.1 nm film was found to reduce the surface resistance below its value with the surface oxide present and to enhance the quench field. The magnitude of the surface resistance increased substantially with gold film thickness. The surface resistance field-dependence appeared to be independent from the normal layer thickness. The observations reported in this work have profound implications for both low-field and high-field S.C. microwave devices. By controlling or eliminating the niobium oxide using a gold layer to passivate the niobium surface, it may be possible to improve the performance of SRF cavities used for particle acceleration. This method to reduce surface oxidation while maintaining low surface resistance could also be relevant for minimizing dissipation due to two-level systems observed in low-field low-temperature devices.
	Slides TUCBA01 [2.292 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCBA01
About •	Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 26 July 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEIAA03	Surface Roughness Reduction and Performance of Vapor-Diffusion Coating of Nb₃Sn Film for SRF Application	cavity, SRF, site, accelerating-gradient	593
	U. Pudasaini, M.J. Kelley, E.M. Lechner, C.E. Reece, O. Trofimova, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: This work is authored by Jefferson Science Associates LLC under U.S. DOE Contract No. DE-AC05- 06OR23177. Nb₃Sn offers the prospect of better RF performance (Q and E_acc) than niobium at any given temperature because of its superior superconducting properties. Nb₃Sn-coated SRF cavities are routinely produced by growing a few microns thick Nb₃Sn film on Nb cavities via tin vapor diffusion. It has been observed that a clean and smooth surface can enhance the performance of the Nb₃Sn-coated cavity, typically, the attainable acceleration gradient. The reduction of surface roughness is often linked with a correlative reduction in average coating thickness and grain size. Besides Sn supply’s careful tuning, the temperature profiles were varied to reduce the surface roughness as low as ~40 nm in 20 µm × 20 µm AFM scans, one-third that of the typical coating. Samples were systematically coated inside a mock single-cell cavity and examined using different material characterization techniques. A few sets of coating parameters were used to coat 1.3 GHz single-cell cavities to understand the effects of roughness variation on the RF performance. This presentation will discuss ways to reduce surface roughness with results from a systematic analysis of the samples and Nb₃Sn-coated single-cell cavities.
	Slides WEIAA03 [7.231 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIAA03
About •	Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPWB121	Niobium Chronicles: Surface Quality Investigation and Recovery During Material Procurement for the PIP-II High Beta 650 MHz Cavities	cavity, niobium, controls, synchrotron	880
	A.D. Shabalina STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	The surface quality of high-purity niobium for superconducting radiofrequency cavities experienced a sudden and significant decline in 2021. The recovery process and root cause analysis were challenging due to a variety of factors such as COVID-19 travel restrictions, cultural differences, and bureaucratic processes. Effective open communication was crucial to resolving the issue, especially with direct vendor oversight being impossible.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB121
About •	Received ※ 28 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 20 August 2023
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPMB024

Flux Expulsion Studies of Niobium Material of 650 MHz Cavities for PIP-II

cavity, niobium, simulation, radio-frequency

141

K.E. McGee
FRIB, East Lansing, Michigan, USA
F. Furuta, M. Martinello, O.S. Melnychuk, A.V. Netepenko, G. Wu, Y. Xie
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Two different vendors supplied the niobium sheet material for PIP-II 5-cell 650 MHz cavities, which was characterized by multiple different ASTM sizes. Cavities subsequently fabricated from these sheets were heat-treated at various temperatures, then the cavities’ flux-expulsion performance was measured. Where the initial measurements of vendor O materials showed that nearly all flux remained trapped despite a high thermal gradient, 900C heat treatment subsequently improved the flux expulsion to an acceptable rate. Understanding and characterizing vendor O materials in this way is key for upcoming and future projects planning to employ niobium sheet from this supplier.

Poster MOPMB024 [4.064 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB024

About •

Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023

Cite •

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

MOPMB040

Comparing the Effectiveness of Low Temperature Bake in EP and BCP Cavities

cavity, SRF, niobium, radio-frequency

187

H. Hu, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
D. Bafia
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Electropolishing (EP) and buffered chemical polishing (BCP) are conventional surface preparation techniques for superconducting radiofrequency (SRF) cavities. Both EP and BCP treated SRF cavities display high field Q-slope (HFQS) which degrades performance at high gradients. While high gradient performance in EP cavities can be improved by introducing oxygen via a low temperature bake (LTB) of 120^°C by 48 hours, LTB does not consistently remove HFQS in BCP cavities. There is no consensus as to why LTB is not effective on BCP prepared cavities. We examine quench in EP, BCP, EP+LTB, and BCP+LTB treated 1.3 GHz single-cell Nb cavities by studying the heating behavior with field using a temperature mapping system. Cavity performance is correlated to characterizations of surface impurity profile obtained via time of flight secondary ion mass spectrometry studies. We observe a difference in near surface hydrogen concentration following BCP compared to EP that may suggest that the causes of quench in EP and BCP cavities are different.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB040

About •

Received ※ 14 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023

Cite •

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

MOPMB047

Commissioning of Dedicated Furnace for Nb₃Sn Coatings of 2.6 GHz Single Cell Cavities

cavity, niobium, SRF, MMI

216

P.A. Kulyavtsev, G.V. Eremeev, S. Posen, B. Tennis
Fermilab, Batavia, Illinois, USA
J. Zasadzinski
IIT, Chicago, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
We present the results of commissioning a dedicated furnace for Nb₃Sn coatings of 2.6GHz single cell cavities. Nb₃Sn is a desired coating due to its high critical temperature and smaller surface resistance compared to bulk Nb. Usage of Nb₃Sn coated cavities will greatly reduce operating costs due to its higher operating temperature providing decreased cooling costs. Tin is deposited in the bulk Nb cavity by use of a tin chloride nucleation agent and tin vapor diffusion. Analysis of the resultant coating was performed using SEM/EDS to verify successful formation of desired Nb:Sn phase. Witness samples located in line of sight of the source were analyzed in order to understand the coating efficacy. The cavity’s performance was assessed in the Vertical Test Stand (VTS) at Fermilab.

Poster MOPMB047 [4.858 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB047

About •

Received ※ 26 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 08 July 2023

Cite •

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

TUCBA01

Measurements of the Amplitude-Dependent Microwave Surface Resistance of a Proximity-Coupled Au/Nb Bilayer

niobium, cavity, SRF, extraction

369

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

A sample host cavity is used to measure the surface resistance of a niobium substrate with a gold film deposited in place of its surface oxide. This talk will report about this measurement result. The film thickness of the gold layer was increased from 0.1 nm to 2.0 nm in five steps to study the impact of the normal layer thickness. The 0.1 nm film was found to reduce the surface resistance below its value with the surface oxide present and to enhance the quench field. The magnitude of the surface resistance increased substantially with gold film thickness. The surface resistance field-dependence appeared to be independent from the normal layer thickness. The observations reported in this work have profound implications for both low-field and high-field S.C. microwave devices. By controlling or eliminating the niobium oxide using a gold layer to passivate the niobium surface, it may be possible to improve the performance of SRF cavities used for particle acceleration. This method to reduce surface oxidation while maintaining low surface resistance could also be relevant for minimizing dissipation due to two-level systems observed in low-field low-temperature devices.

Slides TUCBA01 [2.292 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCBA01

About •

Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 26 July 2023

Cite •

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

WEIAA03

Surface Roughness Reduction and Performance of Vapor-Diffusion Coating of Nb₃Sn Film for SRF Application

cavity, SRF, site, accelerating-gradient

593

U. Pudasaini, M.J. Kelley, E.M. Lechner, C.E. Reece, O. Trofimova, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates LLC under U.S. DOE Contract No. DE-AC05- 06OR23177.
Nb₃Sn offers the prospect of better RF performance (Q and E_acc) than niobium at any given temperature because of its superior superconducting properties. Nb₃Sn-coated SRF cavities are routinely produced by growing a few microns thick Nb₃Sn film on Nb cavities via tin vapor diffusion. It has been observed that a clean and smooth surface can enhance the performance of the Nb₃Sn-coated cavity, typically, the attainable acceleration gradient. The reduction of surface roughness is often linked with a correlative reduction in average coating thickness and grain size. Besides Sn supply’s careful tuning, the temperature profiles were varied to reduce the surface roughness as low as ~40 nm in 20 µm × 20 µm AFM scans, one-third that of the typical coating. Samples were systematically coated inside a mock single-cell cavity and examined using different material characterization techniques. A few sets of coating parameters were used to coat 1.3 GHz single-cell cavities to understand the effects of roughness variation on the RF performance. This presentation will discuss ways to reduce surface roughness with results from a systematic analysis of the samples and Nb₃Sn-coated single-cell cavities.

Slides WEIAA03 [7.231 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIAA03

About •

Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023

Cite •

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

WEPWB121

Niobium Chronicles: Surface Quality Investigation and Recovery During Material Procurement for the PIP-II High Beta 650 MHz Cavities

cavity, niobium, controls, synchrotron

880

A.D. Shabalina
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The surface quality of high-purity niobium for superconducting radiofrequency cavities experienced a sudden and significant decline in 2021. The recovery process and root cause analysis were challenging due to a variety of factors such as COVID-19 travel restrictions, cultural differences, and bureaucratic processes. Effective open communication was crucial to resolving the issue, especially with direct vendor oversight being impossible.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB121

About •

Received ※ 28 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 20 August 2023

Cite •

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