IPAC2016 - List of Authors (Maniscalco, J.T.)

Paper	Title	Page
WEPMR023	Surface Analysis Studies of Nb3Sn Thin Films	2316
	D.L. Hall, J.J. Kaufman, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	A recent study to optimise the coating of thin-film Nb3Sn cavities has resulted in coating procedures that can fabricate 1.3 GHz cavities capable of reproducibly achieving fields of >16 MV/m with record high Qs >10¹⁰ at 4.2 K. However, the performance of these next generation SRF cavities is as yet well below the theoretical maximum performance expected of Nb3Sn, thus giving ample room for further advancements. Current measurements strongly suggest that the current limits are due to local defects and irregularities in the coated surface. In this paper we analyse, using methods including SEM/EDS, TEM, XRD and EBSD, the surface of both sample coupons and cavity cut-outs, with a view to identifying and understanding the origin of surface non-uniformities that would lead to increased surface resistance and cavity quench.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR023
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WEPMR024	RF Measurements on High Performance Nb3Sn Cavities	2320
SUPSS092	use link to see paper's listing under its alternate paper code
	D.L. Hall, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	A single-cell 1.3 GHz ILC-shape thin-film Nb3Sn-on-Nb cavity recently achieved accelerating gradients of >16 MV/m with a record Q0 of approx. 2·10¹⁰ at 4.2 K, exceeding the power efficiency seen in the current most efficient niobium cavities. A concurrent study of the coating process has resulted in a coating procedure that is capable of replicating this performance in other single-cell cavities. In this paper we demonstrate the RF performance and behaviour of these next generation SRF cavities, with an emphasis on both the impact from both external magnetic fields and the cavity cool down procedure on cavity performance.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR024
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WEPMR025	Improved N-Doping Protocols for SRF Cavities	2323
	D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF, DOE Nitrogen-doping has been shown to consistently produce better quality factors in SRF cavities than is achievable with standard preparation techniques. Unfortunately, nitrogen-doping typically brings with it lower quench fields and higher sensitivities of residual resistance to trapped magnetic flux. Here we present work to understand these effects in hopes of mitigating them while maintaining the high Q desired by future projects. Using a nitrogen diffusion simulation, material parameters of nitrogen-doped cavities can be predicted prior to doping. These simulations results are consistent with SIMS data taken from samples treated with cavities. The nature of doping's effect on quench field has also been studied using CW and pulsed measurements. These results have allowed us to better understand the nature of nitrogen-doping and its effect on cavity performance.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR025
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WEPMR027	Dependence of Surface Resistance on N-Doping Level	2331
	D. Gonnella, F. Furuta, G.M. Ge, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF, DOE Nitrogen-doping has become a standard tool for reaching high quality factors in SRF cavities in the medium field region at 2 K. This high Q has been shown to be a result of lowering of the temperature dependent BCS resistance. Here we show that this lowering of the BCS resistance is due to interstitial nitrogen in the niobium lowering the mean free path. The BCS resistance extracted from experimental data is shown to be consistent with theoretical predictions from BCS theory; that there is an optimal doping of which the mean free path is lowered to about half the intrinsic coherence length. These results provide insight into understanding the mechanisms behind nitrogen-doping and allow us to more accurately predict doping parameters to reach optimal cavity performance.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR027
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WEPMR028	Studies on the Field Dependence of the BCS Surface Resistance	2335
SUPSS116	use link to see paper's listing under its alternate paper code
	J.T. Maniscalco, D. Gonnella, G.H. Hoffstaetter, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Experiments have shown that the temperature-dependent portion of the RF surface resistance of SRF materials also exhibits a dependence on the magnitude of the surface field, manifested as a "Q-slope" or "anti-Q-slope" in the medium field region. Recent theoretical work proposes an explanation of the anti-Q-slope in dirty-limit superconductors. In this report, we compare theoretical predictions with the results of systematic experimental studies on the RF field dependence of the surface resistance using 1.3 GHz niobium SRF cavities with a wide range of mean free paths. We find very good agreement between theory and experiment in the dirty limit, with some divergence as the cavities approach the clean limit.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR028
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WEPMR029	New Material Studies in the Cornell Sample Host Cavity	2338
	J.T. Maniscalco, D.L. Hall, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA O.B. Malyshev, R. Valizadeh, S. Wilde STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom S. Wilde Loughborough University, Loughborough, Leicestershire, United Kingdom
	Cornell has developed a TE mode sample host microwave cavity in order to study large, flat samples of novel SRF materials. In recent calibration tests, the cavity was shown to reach peak magnetic fields on the sample plate of >100 mT and a quality factor Q₀ greater than 10¹⁰, making it a powerful system to study the performance of superconductors at high RF fields with nOhms sensitivity. In this report we present results of measurements of two samples of thin-film Nb deposited on Cu using HiPIMS at 500 C and at 800 C.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR029
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WEPMR030	Pulsed Field Limits in SRF Cavities	2341
	J.T. Maniscalco, D. Gonnella, D.L. Hall, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	High-power pulsed (HPP) measurements of SRF cavities offer several different avenues of experimentation from standard continuous wave (CW) measurements by probing higher fields and reducing thermal effects. In this paper we report upon recent measurements of N-doped Nb and Nb3Sn cavities, investigating the limitations of the superheating field, flux entry field, and other maximum fields. We also investigate the potential of these materials for operation in a pulsed accelerator, which would partially or fully mitigate the effects of defects (i.e. thermal quenches).
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR030
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THOBB02	Impurity Doping of Superconducting Radio Frequency Cavities	3195
SUPSS093	use link to see paper's listing under its alternate paper code
	P.N. Koufalis, F. Furuta, G.M. Ge, D. Gonnella, J.J. Kaufman, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF PHYS-1416318 Impurity doping of bulk-niobium superconducting radio frequency (SRF) cavities is a relatively new field of study and the underlying physics is not yet fully understood. Previous studies have shown an increase in the intrinsic quality factor and the corresponding decrease of the temperature-dependent component of the surface resistance of nitrogen-doped cavities with increasing accelerating field.* Here we investigate the effects of alternative inert dopants on the surface resistance and thus the intrinsic quality factor of SRF cavities in pursuit of the optimal dopant and doping level. A. Grassellino et al., Nitrogen and Argon Doping of Niobium for Superconducting Radio Frequency Cavities. Supercond. Sci. Technol., 26(102001), 2013
	Slides THOBB02 [4.048 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THOBB02
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Paper

Title

Page

Surface Analysis Studies of Nb3Sn Thin Films

2316

D.L. Hall, J.J. Kaufman, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A recent study to optimise the coating of thin-film Nb3Sn cavities has resulted in coating procedures that can fabricate 1.3 GHz cavities capable of reproducibly achieving fields of >16 MV/m with record high Qs >10¹⁰ at 4.2 K. However, the performance of these next generation SRF cavities is as yet well below the theoretical maximum performance expected of Nb3Sn, thus giving ample room for further advancements. Current measurements strongly suggest that the current limits are due to local defects and irregularities in the coated surface. In this paper we analyse, using methods including SEM/EDS, TEM, XRD and EBSD, the surface of both sample coupons and cavity cut-outs, with a view to identifying and understanding the origin of surface non-uniformities that would lead to increased surface resistance and cavity quench.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR023

Export •

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

WEPMR024

RF Measurements on High Performance Nb3Sn Cavities

2320

SUPSS092

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

D.L. Hall, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

A single-cell 1.3 GHz ILC-shape thin-film Nb3Sn-on-Nb cavity recently achieved accelerating gradients of >16 MV/m with a record Q0 of approx. 2·10¹⁰ at 4.2 K, exceeding the power efficiency seen in the current most efficient niobium cavities. A concurrent study of the coating process has resulted in a coating procedure that is capable of replicating this performance in other single-cell cavities. In this paper we demonstrate the RF performance and behaviour of these next generation SRF cavities, with an emphasis on both the impact from both external magnetic fields and the cavity cool down procedure on cavity performance.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR024

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WEPMR025

Improved N-Doping Protocols for SRF Cavities

2323

D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF, DOE
Nitrogen-doping has been shown to consistently produce better quality factors in SRF cavities than is achievable with standard preparation techniques. Unfortunately, nitrogen-doping typically brings with it lower quench fields and higher sensitivities of residual resistance to trapped magnetic flux. Here we present work to understand these effects in hopes of mitigating them while maintaining the high Q desired by future projects. Using a nitrogen diffusion simulation, material parameters of nitrogen-doped cavities can be predicted prior to doping. These simulations results are consistent with SIMS data taken from samples treated with cavities. The nature of doping's effect on quench field has also been studied using CW and pulsed measurements. These results have allowed us to better understand the nature of nitrogen-doping and its effect on cavity performance.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR025

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

WEPMR027

Dependence of Surface Resistance on N-Doping Level

2331

D. Gonnella, F. Furuta, G.M. Ge, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF, DOE
Nitrogen-doping has become a standard tool for reaching high quality factors in SRF cavities in the medium field region at 2 K. This high Q has been shown to be a result of lowering of the temperature dependent BCS resistance. Here we show that this lowering of the BCS resistance is due to interstitial nitrogen in the niobium lowering the mean free path. The BCS resistance extracted from experimental data is shown to be consistent with theoretical predictions from BCS theory; that there is an optimal doping of which the mean free path is lowered to about half the intrinsic coherence length. These results provide insight into understanding the mechanisms behind nitrogen-doping and allow us to more accurately predict doping parameters to reach optimal cavity performance.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR027

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WEPMR028

Studies on the Field Dependence of the BCS Surface Resistance

2335

SUPSS116

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

J.T. Maniscalco, D. Gonnella, G.H. Hoffstaetter, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Experiments have shown that the temperature-dependent portion of the RF surface resistance of SRF materials also exhibits a dependence on the magnitude of the surface field, manifested as a "Q-slope" or "anti-Q-slope" in the medium field region. Recent theoretical work proposes an explanation of the anti-Q-slope in dirty-limit superconductors. In this report, we compare theoretical predictions with the results of systematic experimental studies on the RF field dependence of the surface resistance using 1.3 GHz niobium SRF cavities with a wide range of mean free paths. We find very good agreement between theory and experiment in the dirty limit, with some divergence as the cavities approach the clean limit.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR028

Export •

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

WEPMR029

New Material Studies in the Cornell Sample Host Cavity

2338

J.T. Maniscalco, D.L. Hall, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
O.B. Malyshev, R. Valizadeh, S. Wilde
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
S. Wilde
Loughborough University, Loughborough, Leicestershire, United Kingdom

Cornell has developed a TE mode sample host microwave cavity in order to study large, flat samples of novel SRF materials. In recent calibration tests, the cavity was shown to reach peak magnetic fields on the sample plate of >100 mT and a quality factor Q₀ greater than 10¹⁰, making it a powerful system to study the performance of superconductors at high RF fields with nOhms sensitivity. In this report we present results of measurements of two samples of thin-film Nb deposited on Cu using HiPIMS at 500 C and at 800 C.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR029

Export •

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

WEPMR030

Pulsed Field Limits in SRF Cavities

2341

J.T. Maniscalco, D. Gonnella, D.L. Hall, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

High-power pulsed (HPP) measurements of SRF cavities offer several different avenues of experimentation from standard continuous wave (CW) measurements by probing higher fields and reducing thermal effects. In this paper we report upon recent measurements of N-doped Nb and Nb3Sn cavities, investigating the limitations of the superheating field, flux entry field, and other maximum fields. We also investigate the potential of these materials for operation in a pulsed accelerator, which would partially or fully mitigate the effects of defects (i.e. thermal quenches).

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR030

Export •

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

THOBB02

Impurity Doping of Superconducting Radio Frequency Cavities

3195

SUPSS093

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

P.N. Koufalis, F. Furuta, G.M. Ge, D. Gonnella, J.J. Kaufman, M. Liepe, J.T. Maniscalco
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF PHYS-1416318
Impurity doping of bulk-niobium superconducting radio frequency (SRF) cavities is a relatively new field of study and the underlying physics is not yet fully understood. Previous studies have shown an increase in the intrinsic quality factor and the corresponding decrease of the temperature-dependent component of the surface resistance of nitrogen-doped cavities with increasing accelerating field.* Here we investigate the effects of alternative inert dopants on the surface resistance and thus the intrinsic quality factor of SRF cavities in pursuit of the optimal dopant and doping level.
A. Grassellino et al., Nitrogen and Argon Doping of Niobium for Superconducting Radio Frequency Cavities. Supercond. Sci. Technol., 26(102001), 2013

Slides THOBB02 [4.048 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THOBB02

Export •

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