SRF2021 - List of Authors (Holic, A.T.)

Paper	Title	Page
SUPTEV007	Development of a System for Coating SRF Cavities Using Remote Plasma CVD	129
	G. Gaitan, P. Bishop, A.T. Holic, G. Kulina, M. Liepe, J. Sears, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the National Science Foundation under Grant No. PHY-1549132. Next-generation, thin-film surfaces employing Nb₃Sn, NbN, NbTiN, and other compound superconductors are destined to allow reaching superior RF performance levels in SRF cavities. Optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a remote plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a clean vacuum and furnace loading system. The use of plasma alongside reacting precursors will significantly reduce the required processing temperature and promote precursor decomposition. A vacuum quality monitor (VQM) is used to characterize the residual gases before coating. The CVD system has been designed and is currently under assembly and commissioning.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV007
About •	Received ※ 09 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 10 February 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPTEV008	CW Operation of Conduction-Cooled Nb₃Sn SRF Cavity	133
	N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Significant progress in the performance of SRF cavities coated with Nb₃Sn films during the last few years has provided an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This allows for the use of new cryogenic cooling schemes based on conduction cooling with robust, commercialized turn-key style cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m with measured thermal dynamics which match numerical simulations. These results also serve as a foundation for designing a new standalone SRF cryomodule which will use a pair of cryocoolers to cool a 1.3 GHz Nb₃Sn cavity with an input coupler capable of supporting high beam current operation.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV008
About •	Received ※ 22 June 2021 — Accepted ※ 13 August 2021 — Issue date ※ 08 November 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPFDV005	Superconducting RF Performance of Cornell 500 MHz N-Doped B-Cell SRF Cavitiy	764
	M. Ge, T. Gruber, A.T. Holic, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The Cornell SRF group is working on rebuilding a 500 MHz B-cell cryomodule (CRYO-2 BB1-5) as a spared cryomodule for the operation of the CESR ring. To minimize BCS surface resistance, achieve a high quality-factor (Q₀), and increase maximum fields, we prepared the cavity’s surface with electropolishing and performed a 2/6 N2-doping. In this work, we report 4.2 K and 2 K cavity test results with detailed surface resistance analysis, showing improved performance, including significant higher fields.
	Poster THPFDV005 [0.718 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV005
About •	Received ※ 05 July 2021 — Revised ※ 10 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 22 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPFDV006	Seebeck Coefficient Measurement at Cryogenic Temperatures for the LCLS-II HE Project	768
	M. Ge, A.T. Holic, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Reducing thermoelectric currents during cooldown is important to maintain high-quality factors (Q₀) of the cavities in the LCLS-II HE cryomodules. The temperature-dependent Seebeck coefficients of the materials used in the cryomodules are needed for quantitative estimations of thermoelectric currents. In this work, we present a setup for cryogenic Seebeck coefficient measurements as well as the measured Seebeck coefficients of high-pure niobium at cryogenic temperatures between 4K and 200K.
	Poster THPFDV006 [0.511 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV006
About •	Received ※ 29 June 2021 — Revised ※ 10 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 26 November 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Development of a System for Coating SRF Cavities Using Remote Plasma CVD

129

G. Gaitan, P. Bishop, A.T. Holic, G. Kulina, M. Liepe, J. Sears, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the National Science Foundation under Grant No. PHY-1549132.
Next-generation, thin-film surfaces employing Nb₃Sn, NbN, NbTiN, and other compound superconductors are destined to allow reaching superior RF performance levels in SRF cavities. Optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University is developing a remote plasma-enhanced chemical vapor deposition (CVD) system that facilitates coating on complicated geometries with a high deposition rate. This system is based on a high-temperature tube furnace with a clean vacuum and furnace loading system. The use of plasma alongside reacting precursors will significantly reduce the required processing temperature and promote precursor decomposition. A vacuum quality monitor (VQM) is used to characterize the residual gases before coating. The CVD system has been designed and is currently under assembly and commissioning.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV007

About •

Received ※ 09 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 10 February 2022

Cite •

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

SUPTEV008

CW Operation of Conduction-Cooled Nb₃Sn SRF Cavity

133

N.A. Stilin, A.T. Holic, M. Liepe, R.D. Porter, J. Sears, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Significant progress in the performance of SRF cavities coated with Nb₃Sn films during the last few years has provided an energy efficient alternative to traditional Nb cavities, thereby initiating a fundamental shift in SRF technology. These Nb₃Sn cavities can operate at significantly higher temperatures than Nb cavities while simultaneously requiring less cooling power. This allows for the use of new cryogenic cooling schemes based on conduction cooling with robust, commercialized turn-key style cryocoolers. Cornell University has developed and tested a 2.6 GHz Nb₃Sn cavity assembly which utilizes such cooling methods. These tests have demonstrated stable RF operation at 10 MV/m with measured thermal dynamics which match numerical simulations. These results also serve as a foundation for designing a new standalone SRF cryomodule which will use a pair of cryocoolers to cool a 1.3 GHz Nb₃Sn cavity with an input coupler capable of supporting high beam current operation.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV008

About •

Received ※ 22 June 2021 — Accepted ※ 13 August 2021 — Issue date ※ 08 November 2021

Cite •

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

THPFDV005

Superconducting RF Performance of Cornell 500 MHz N-Doped B-Cell SRF Cavitiy

764

M. Ge, T. Gruber, A.T. Holic, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The Cornell SRF group is working on rebuilding a 500 MHz B-cell cryomodule (CRYO-2 BB1-5) as a spared cryomodule for the operation of the CESR ring. To minimize BCS surface resistance, achieve a high quality-factor (Q₀), and increase maximum fields, we prepared the cavity’s surface with electropolishing and performed a 2/6 N2-doping. In this work, we report 4.2 K and 2 K cavity test results with detailed surface resistance analysis, showing improved performance, including significant higher fields.

Poster THPFDV005 [0.718 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV005

About •

Received ※ 05 July 2021 — Revised ※ 10 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 22 April 2022

Cite •

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

THPFDV006

Seebeck Coefficient Measurement at Cryogenic Temperatures for the LCLS-II HE Project

768

M. Ge, A.T. Holic, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Reducing thermoelectric currents during cooldown is important to maintain high-quality factors (Q₀) of the cavities in the LCLS-II HE cryomodules. The temperature-dependent Seebeck coefficients of the materials used in the cryomodules are needed for quantitative estimations of thermoelectric currents. In this work, we present a setup for cryogenic Seebeck coefficient measurements as well as the measured Seebeck coefficients of high-pure niobium at cryogenic temperatures between 4K and 200K.

Poster THPFDV006 [0.511 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV006

About •

Received ※ 29 June 2021 — Revised ※ 10 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 26 November 2021

Cite •

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