IPAC2015 - List of Keywords (superconductivity)

Paper	Title	Other Keywords	Page
WEPHA058	Superconducting Coatings Synthesized by CVD/PECVD for SRF Cavities	niobium, SRF, plasma, accelerating-gradient	3246
	P. Pizzol, P. Chalker, T. Heil The University of Liverpool, Liverpool, United Kingdom A.N. Hannah, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	Funding: STFC Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the samples deposited are superconductive and polycrystalline; the sample obtained with CVD measured RRR=31 and Tc=7.9 K, while the sample obtained with PECVD exhibited RRR=9 and Tc= 9.4 K. In both cases the films grew in a (100) preferred orientation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA058
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WEPHA059	Physical Vapour Deposition of Thin Films for Use in Superconducting RF Cavities	SRF, plasma, power-supply, radio-frequency	3249
	S. Wilde, B. Chesca Loughborough University, Loughborough, Leicestershire, United Kingdom A.N. Hannah, D.O. Malyshev, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. Optimizing superconducting properties of Nb thin-films is therefore essential. Nb films were deposited by magnetron sputtering in pulsed DC mode onto Si (100) and MgO (100) substrates and also by high impulse magnetron sputtering (HiPIMS) onto Si (100), MgO (100) and polycrystalline Cu. The films were characterised using scanning electron microscopy, x-ray diffraction and DC SQUID magnetometry.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA059
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WEPTY021	Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities	cavity, niobium, cryogenics, cryomodule	3309
	M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov Fermilab, Batavia, Illinois, USA M. Checchin, M. Martinello Illinois Institute of Technology, Chicago, Illlinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. In this study we prove that the mechanism at the basis of quality factor degradation due to quench involves the entrapment of ambient magnetic field. The cavity quench in the absence of magnetic field does not introduce any extra losses, and a clear trend between the external field and the extra losses introduced by the quench was observed. It is demonstrated that the quality factor can be totally recovered by quenching in zero applied magnetic field. A dependence of the amount of quality factor degradation on the orientation of the magnetic field with respect to the cavity was also found.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY021
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WEPTY022	Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities	niobium, SRF, cavity, vacuum	3312
	A. Vostrikov, M. Checchin, A. Grassellino, A. Romanenko Fermilab, Batavia, Illinois, USA Y.K. Kim, A. Vostrikov University of Chicago, Chicago, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Discovery at Fermilab of a drastic effect of nitrogen doping leading to unprecedented high Q values in niobium cavities * motivated a strong interest in revealing the physics underlying the effect. In this contribution we present new results obtained by DC magnetometry, AC susceptibility, resistivity and thermal properties measurements on nitrogen doped samples prepared by different recipes/doping levels, which shed light on the possible origin of the effect. * A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001
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WEPTY034	T-map Studies on Gradient-limiting Mechanism in Nitrogen Doped Cavities	cavity, niobium, factory, SRF	3348
	M. Martinello, M. Checchin, A. Grassellino, A. Romanenko Fermilab, Batavia, Illinois, USA
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Nitrogen doping * results in ultra-high quality factors in SRF niobium cavities but currently achievable gradients in doped cavities are, on average, somewhat lower than in EP/120C baked cavities. The origin of this difference is explored in the reported work by detailed temperature mapping studies on several single cell nitrogen doped cavities. * A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY034
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WEPTY066	T-Maps Taken During Cool-down of an SRF cavity: a Tool to Understand Flux Trapping	cavity, SRF, data-analysis, operation	3431
	R.G. Eichhorn, F. Furuta, G.M. Ge Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	During the past years the impact of cool-down procedures on the flux trapping properties of superconducting cavities have been under investigation. We have measured temperature distributions of a multi-cell cavity using a T-map set-up to understand the transition to superconductivity in detail. We will report how the spatial disorder is affected by the cool-down speed and relate our findings to data on flux pinning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY066
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WEPTY075	Hc2 Measurements of Nb3Sn and Nitrogen-doped Niobium using Physical Property Measurement System	niobium, SRF, controls, radio-frequency	3458
	J.T. Maniscalco, D. Gonnella, D.L. Hall, M. Liepe, S. Posen Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	The measurement of the upper critical field of a type-2 superconductor, Hc2, is an important step in determining its superconducting properties, and therefore its suitability as a material in SRF cavities. However, measuring Hc2 directly can be challenging, as performing electrical measurements causes changes in the very properties one seeks to measure. We present a method for extracting Hc2 from resistivity measurements made near the transition temperature for varied applied fields and excitation currents. We also present results of these measurements made on Nb3Sn and nitrogen-doped niobium.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY075
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WEPWI021	An Analysis of the Temperature and Field Dependence of the RF Surface Resistance of Nitrogen-Doped Niobium SRF Cavities with Respect to Existing Theoretical Models	cavity, niobium, SRF, site	3532
	C.E. Reece, A.D. Palczewski JLab, Newport News, Virginia, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 Recent progress with the reduction of rf surface resistance (Rs) of niobium SRF cavities via the use of high temperature surface doping by nitrogen has opened a new regime for energy efficient accelerator applications. For particular doping conditions one observes dramatic decreases in Rs with increasing surface magnetic fields. The observed variations as a function of temperature may be analyzed in the context of recent theoretical treatments in hopes of gaining insight into the underlying beneficial mechanism of the nitrogen treatment. Systematic data sets of Q0 vs. Eacc vs. temperature acquired during the high Q0 R&D work of the past year will be compared with theoretical model predictions. * * B. P. Xiao et al., Physica C: Superconductivity 490 (0), 26-31 (2013) and A. Gurevich, PRL 113 (8), 087001 (2014)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI021
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WEPWI053	HTS/lTS Hybrid High Field Superconducting Magnet Designs for the Proposed 100 TeV Proton Colliders	dipole, proton, collider, magnet-design	3609
	R.C. Gupta, M. Anerella, A.K. Ghosh, W. Sampson, J. Schmalzle BNL, Upton, Long Island, New York, USA J. Kolonko, D. Larson, R.M. Scanlan, R.J. Weggel, E. Willen Particle Beam Lasers, Inc., Northridge, California, USA C.M. Rey e2P, Knoxville, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under contract Number DE-SC0012704, with the U.S. Department of Energy and STTR contract DOE Grant Number DE-SC0011348. Proposed proton-proton colliders with a center-of-mass energy up to 100 TeV in a tunnel of desired size require the dipole magnets to be of very high field–20 teslas in some proposals. This field is beyond the limit of present conventional Low Temperature Superconductors (LTS) and requires using High Temperature Superconductors (HTS). The preliminary magnetic design presented in this paper is an HTS/LTS hybrid design with high strength HTS tape used in higher field regions and less expensive LTS in lower field regions, with a goal of optimizing the performance while reducing the cost. A major concern in the magnets built with the HTS tape is the large field errors associated with the conductor magnetization. The strategy presented here aims to reduce those errors considerably. This paper also presents a proof-of-principle design and program to experimentally evaluate that concept.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI053
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Paper

Title

Other Keywords

Page

WEPHA058

Superconducting Coatings Synthesized by CVD/PECVD for SRF Cavities

niobium, SRF, plasma, accelerating-gradient

3246

P. Pizzol, P. Chalker, T. Heil
The University of Liverpool, Liverpool, United Kingdom
A.N. Hannah, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

Funding: STFC
Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the samples deposited are superconductive and polycrystalline; the sample obtained with CVD measured RRR=31 and Tc=7.9 K, while the sample obtained with PECVD exhibited RRR=9 and Tc= 9.4 K. In both cases the films grew in a (100) preferred orientation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA058

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WEPHA059

Physical Vapour Deposition of Thin Films for Use in Superconducting RF Cavities

SRF, plasma, power-supply, radio-frequency

3249

S. Wilde, B. Chesca
Loughborough University, Loughborough, Leicestershire, United Kingdom
A.N. Hannah, D.O. Malyshev, O.B. Malyshev, S.M. Pattalwar, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. Optimizing superconducting properties of Nb thin-films is therefore essential. Nb films were deposited by magnetron sputtering in pulsed DC mode onto Si (100) and MgO (100) substrates and also by high impulse magnetron sputtering (HiPIMS) onto Si (100), MgO (100) and polycrystalline Cu. The films were characterised using scanning electron microscopy, x-ray diffraction and DC SQUID magnetometry.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA059

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WEPTY021

Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities

cavity, niobium, cryogenics, cryomodule

3309

M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA
M. Checchin, M. Martinello
Illinois Institute of Technology, Chicago, Illlinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
In this study we prove that the mechanism at the basis of quality factor degradation due to quench involves the entrapment of ambient magnetic field. The cavity quench in the absence of magnetic field does not introduce any extra losses, and a clear trend between the external field and the extra losses introduced by the quench was observed. It is demonstrated that the quality factor can be totally recovered by quenching in zero applied magnetic field. A dependence of the amount of quality factor degradation on the orientation of the magnetic field with respect to the cavity was also found.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY021

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WEPTY022

Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities

niobium, SRF, cavity, vacuum

3312

A. Vostrikov, M. Checchin, A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA
Y.K. Kim, A. Vostrikov
University of Chicago, Chicago, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Discovery at Fermilab of a drastic effect of nitrogen doping leading to unprecedented high Q values in niobium cavities * motivated a strong interest in revealing the physics underlying the effect. In this contribution we present new results obtained by DC magnetometry, AC susceptibility, resistivity and thermal properties measurements on nitrogen doped samples prepared by different recipes/doping levels, which shed light on the possible origin of the effect.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY022

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WEPTY034

T-map Studies on Gradient-limiting Mechanism in Nitrogen Doped Cavities

cavity, niobium, factory, SRF

3348

M. Martinello, M. Checchin, A. Grassellino, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Nitrogen doping * results in ultra-high quality factors in SRF niobium cavities but currently achievable gradients in doped cavities are, on average, somewhat lower than in EP/120C baked cavities. The origin of this difference is explored in the reported work by detailed temperature mapping studies on several single cell nitrogen doped cavities.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY034

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WEPTY066

T-Maps Taken During Cool-down of an SRF cavity: a Tool to Understand Flux Trapping

cavity, SRF, data-analysis, operation

3431

R.G. Eichhorn, F. Furuta, G.M. Ge
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

During the past years the impact of cool-down procedures on the flux trapping properties of superconducting cavities have been under investigation. We have measured temperature distributions of a multi-cell cavity using a T-map set-up to understand the transition to superconductivity in detail. We will report how the spatial disorder is affected by the cool-down speed and relate our findings to data on flux pinning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY066

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WEPTY075

Hc2 Measurements of Nb3Sn and Nitrogen-doped Niobium using Physical Property Measurement System

niobium, SRF, controls, radio-frequency

3458

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

The measurement of the upper critical field of a type-2 superconductor, Hc2, is an important step in determining its superconducting properties, and therefore its suitability as a material in SRF cavities. However, measuring Hc2 directly can be challenging, as performing electrical measurements causes changes in the very properties one seeks to measure. We present a method for extracting Hc2 from resistivity measurements made near the transition temperature for varied applied fields and excitation currents. We also present results of these measurements made on Nb3Sn and nitrogen-doped niobium.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY075

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

WEPWI021

An Analysis of the Temperature and Field Dependence of the RF Surface Resistance of Nitrogen-Doped Niobium SRF Cavities with Respect to Existing Theoretical Models

cavity, niobium, SRF, site

3532

C.E. Reece, A.D. Palczewski
JLab, Newport News, Virginia, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177
Recent progress with the reduction of rf surface resistance (Rs) of niobium SRF cavities via the use of high temperature surface doping by nitrogen has opened a new regime for energy efficient accelerator applications. For particular doping conditions one observes dramatic decreases in Rs with increasing surface magnetic fields. The observed variations as a function of temperature may be analyzed in the context of recent theoretical treatments in hopes of gaining insight into the underlying beneficial mechanism of the nitrogen treatment. Systematic data sets of Q0 vs. Eacc vs. temperature acquired during the high Q0 R&D work of the past year will be compared with theoretical model predictions. *
* B. P. Xiao et al., Physica C: Superconductivity 490 (0), 26-31 (2013) and
A. Gurevich, PRL 113 (8), 087001 (2014)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI021

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WEPWI053

HTS/lTS Hybrid High Field Superconducting Magnet Designs for the Proposed 100 TeV Proton Colliders

dipole, proton, collider, magnet-design

3609

R.C. Gupta, M. Anerella, A.K. Ghosh, W. Sampson, J. Schmalzle
BNL, Upton, Long Island, New York, USA
J. Kolonko, D. Larson, R.M. Scanlan, R.J. Weggel, E. Willen
Particle Beam Lasers, Inc., Northridge, California, USA
C.M. Rey
e2P, Knoxville, USA

Funding: Work supported by Brookhaven Science Associates, LLC under contract Number DE-SC0012704, with the U.S. Department of Energy and STTR contract DOE Grant Number DE-SC0011348.
Proposed proton-proton colliders with a center-of-mass energy up to 100 TeV in a tunnel of desired size require the dipole magnets to be of very high field–20 teslas in some proposals. This field is beyond the limit of present conventional Low Temperature Superconductors (LTS) and requires using High Temperature Superconductors (HTS). The preliminary magnetic design presented in this paper is an HTS/LTS hybrid design with high strength HTS tape used in higher field regions and less expensive LTS in lower field regions, with a goal of optimizing the performance while reducing the cost. A major concern in the magnets built with the HTS tape is the large field errors associated with the conductor magnetization. The strategy presented here aims to reduce those errors considerably. This paper also presents a proof-of-principle design and program to experimentally evaluate that concept.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI053

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