IPAC2017 - List of Authors (Maniscalco, J.T.)

Paper	Title	Page
MOPVA116	Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion	1119
	D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna Cornell University, Ithaca, New York, USA
	The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA116
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MOPVA119	Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion	1130
	D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA T. Arias, P. Cueva, D.A. Muller, N. Sitaraman Cornell University, Ithaca, New York, USA
	As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA119
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MOPVA123	Cornell Sample Host Cavity: Recent Results	1142
	J.T. Maniscalco, D.L. Hall, M. Liepe, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V.M. Arrieta, S.R. McNeal, W.E. Williams Ultramet, Pacoima, California, USA
	Funding: NSF-PHY 1416318 NSF-PHY 1549132 The Cornell sample host cavity is a 3.9~GHz testing system for RF analysis of novel superconducting surfaces. The cavity applies fields up to 100~mT on a removable and replaceable 5-inch sample plate in order to measure the surface resistance of the material under investigation. The cavity also includes a temperature-mapping system for localization of quench events and surface defects. In this paper, we present recent experimental results from the host cavity of niobium deposited onto molybdenum and copper substrates using chemical vapor deposition, in collaboration with industry partner Ultramet. The results indicate low BCS resistance and good adhesion but also areas of high residual resistance due to chemical and morphological defects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA123
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MOPVA124	Effectiveness of Chemical Treatments for Reducing the Surface Roughness of Nb3Sn	1145
SUSPSIK104	use link to see paper's listing under its alternate paper code
	R.D. Porter, F. Furuta, D.L. Hall, M. Liepe, J.T. Maniscalco Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: DOE DE-SC008431, NSF-PHY 1549132, NSF DMR-1120296 Current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities have rougher surfaces than conventional electropolished Niobium accelerator cavities. The surface roughness can cause enhancement of the surface magnetic field, pushing it beyond the critical field. If this occurs over a large enough area it can cause the cavity to quench. The surface roughness may cause other effects that negatively impact cavity quality factor (Q) performance. Reducing surface roughness of Nb3Sn cavities may be necessary to achieve higher gradient with high Q. Current chemical treatments for reducing the surface roughness of Niobium are challenging for Nb3Sn: the Nb3Sn layer is only ~2 um thick while it is difficult to remove less than 1 mu uniformly with most chemical treatments. This paper presents measurements of the surface roughness before and after Buffered Chemical Polish, Electropolishing and oxipolishing.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA124
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MOPVA126	Sample Host Cavity Design for Measuring Flux Entry and Quench	1149
	R.D. Porter, M. Liepe, J.T. Maniscalco, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF-PHY 1549132 Current state-of-the-art Niobium superconducting radio-frequency (SRF) accelerator cavities have reached surface magnetic field close to the theoretical maximum set by the superheating field. Further increasing accelerating gradients will require new superconducting materials for accelerator cavities that can support higher surface magnetic fields. This necessitates measuring the quench fields of new materials in high power RF fields. In this paper, we present designs and simulations of a sample host cavity. The cavity design is optimized to maximize the surface magnetic field achieved on the sample.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA126
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WEPVA145	Analysis of Mean Free Path and Field Dependent Surface Resistance	3609
	J.T. Maniscalco, F. Furuta, D.L. Hall, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF-PHY 1416318 Work from Cornell in 2016 built on recent theoretical research in the field of SRF to link the electron mean free path to the field-dependent BCS surface resistance. This research relates the magnitude of the ‘‘anti-Q-slope'', the puzzling reduction of surface resistance with increasing RF field intensity observed in certain cavities, to the doping level of nitrogen-doped niobium, quantified by the mean free path: shorter mean free paths correspond directly with stronger anti-Q-slopes. The theoretical connection comes through the overheating of the quasiparticles, which more effectively transfer their energy to the lattice at short mean free paths. In this report, we present an update of this analysis, investigating recent test results of low-temperature-doped single-cell and nine-cell cavities. We also study the theoretical implications for cavities at frequencies higher and lower than the often-studied 1.3~GHz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA145
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Paper

Title

Page

Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion

1119

D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna
Cornell University, Ithaca, New York, USA

The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA116

Export •

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

MOPVA119

Surface Analysis of Features Seen on Nb3Sn Sample Coupons Grown by Vapour Diffusion

1130

D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
T. Arias, P. Cueva, D.A. Muller, N. Sitaraman
Cornell University, Ithaca, New York, USA

As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading non-uniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons. In the interests of understanding how to control the presence and nature of such features, it is necessary to know how they form. In this paper we stop the coating at defined instances to gain a stop-motion image of the growth of the layer, and use SEM and TEM techniques to image the development of the features seen in previously coated samples. We demonstrate that surface pre-anodisation can suppress the formation of thin film regions, and apply this technique to a single-cell cavity. Contemporarily, we use TEM with EDS mapping to monitor grain boundaries and tin-depleted regions within the layer.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA119

Export •

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

MOPVA123

Cornell Sample Host Cavity: Recent Results

1142

J.T. Maniscalco, D.L. Hall, M. Liepe, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V.M. Arrieta, S.R. McNeal, W.E. Williams
Ultramet, Pacoima, California, USA

Funding: NSF-PHY 1416318 NSF-PHY 1549132
The Cornell sample host cavity is a 3.9~GHz testing system for RF analysis of novel superconducting surfaces. The cavity applies fields up to 100~mT on a removable and replaceable 5-inch sample plate in order to measure the surface resistance of the material under investigation. The cavity also includes a temperature-mapping system for localization of quench events and surface defects. In this paper, we present recent experimental results from the host cavity of niobium deposited onto molybdenum and copper substrates using chemical vapor deposition, in collaboration with industry partner Ultramet. The results indicate low BCS resistance and good adhesion but also areas of high residual resistance due to chemical and morphological defects.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA123

Export •

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

MOPVA124

Effectiveness of Chemical Treatments for Reducing the Surface Roughness of Nb3Sn

1145

SUSPSIK104

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

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

Funding: DOE DE-SC008431, NSF-PHY 1549132, NSF DMR-1120296
Current Niobium-3 Tin (Nb3Sn) superconducting radio-frequency (SRF) accelerator cavities have rougher surfaces than conventional electropolished Niobium accelerator cavities. The surface roughness can cause enhancement of the surface magnetic field, pushing it beyond the critical field. If this occurs over a large enough area it can cause the cavity to quench. The surface roughness may cause other effects that negatively impact cavity quality factor (Q) performance. Reducing surface roughness of Nb3Sn cavities may be necessary to achieve higher gradient with high Q. Current chemical treatments for reducing the surface roughness of Niobium are challenging for Nb3Sn: the Nb3Sn layer is only ~2 um thick while it is difficult to remove less than 1 mu uniformly with most chemical treatments. This paper presents measurements of the surface roughness before and after Buffered Chemical Polish, Electropolishing and oxipolishing.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA124

Export •

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

MOPVA126

Sample Host Cavity Design for Measuring Flux Entry and Quench

1149

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

Funding: NSF-PHY 1549132
Current state-of-the-art Niobium superconducting radio-frequency (SRF) accelerator cavities have reached surface magnetic field close to the theoretical maximum set by the superheating field. Further increasing accelerating gradients will require new superconducting materials for accelerator cavities that can support higher surface magnetic fields. This necessitates measuring the quench fields of new materials in high power RF fields. In this paper, we present designs and simulations of a sample host cavity. The cavity design is optimized to maximize the surface magnetic field achieved on the sample.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA126

Export •

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

WEPVA145

Analysis of Mean Free Path and Field Dependent Surface Resistance

3609

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

Funding: NSF-PHY 1416318
Work from Cornell in 2016 built on recent theoretical research in the field of SRF to link the electron mean free path to the field-dependent BCS surface resistance. This research relates the magnitude of the ‘‘anti-Q-slope'', the puzzling reduction of surface resistance with increasing RF field intensity observed in certain cavities, to the doping level of nitrogen-doped niobium, quantified by the mean free path: shorter mean free paths correspond directly with stronger anti-Q-slopes. The theoretical connection comes through the overheating of the quasiparticles, which more effectively transfer their energy to the lattice at short mean free paths. In this report, we present an update of this analysis, investigating recent test results of low-temperature-doped single-cell and nine-cell cavities. We also study the theoretical implications for cavities at frequencies higher and lower than the often-studied 1.3~GHz.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA145

Export •

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