IPAC2015 - List of Authors (Grassellino, A.)

Paper	Title	Page
MOYGB2	High Q Developments
	A. Grassellino Fermilab, Batavia, Illinois, USA
	This presentation will cover recent breakthroughs in the SRF field that have revolutionized the achievable quality factors in bulk niobium cavities. It will cover two main breakthroughs: one involving the controlled nitrogen doping of the niobium cavity surface, and second the efficient magnetic flux expulsion from the niobium walls via controlled cavity cooling though transition temperature. The talk will give an overview from the discovery of these effects at FNAL to the development into a cryomodule ready technology by the partner labs Cornell, Jlab, FNAL and SLAC for implementation in the LCLS-2 accelerator. New results will be presented from surface analysis, cavity diagnostics tools and very high Q obtained in dressed cavities in cryomodule environment.
	Slides MOYGB2 [11.862 MB]
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WEPTY021	Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities	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	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
DOI •	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	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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WEPTY072	Update on Nitrogen-doped 9-cell Cavity Performance in the Cornell Horizontal Test Cryomodule	3446
	D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, J.T. Maniscalco, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Grassellino, C.J. Grimm, O.S. Melnychuk, A. Romanenko Fermilab, Batavia, Illinois, USA
	Funding: U.S. Department of Energy The Linac Coherent Light Source-II (LCLS-II) is a new x-ray source that is planned to be constructed in the existing SLAC tunnel. To meet the quality factor specifications (2.7x 10¹⁰ at 2.0 K and 16 MV/m), nitrogen-doping has been proposed as a preparation method for the SRF cavities. In order to demonstrate the feasibility of these goals, four 9-cell cavity tests have been completed in the Cornell Horizontal Test Cryomodule (HTC), which serves as a test bench for the full LCLS-II cryomodule. Here we report on the most recent two cavity tests in the HTC: one cavity nitrogen-doped at Cornell and tested with high Q input coupler and then again tested with high power LCLS-II input coupler. Transition to test in horizontal cryomodule resulted in no degradation in Q0 from vertical test. Additionally, increased dissipated power due to the high power input coupler was small and in good agreement with simulations. These results represent a crucial step on the way to demonstrating technical readiness for LCLS-II.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY072
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Paper

Title

Page

MOYGB2

High Q Developments

A. Grassellino
Fermilab, Batavia, Illinois, USA

This presentation will cover recent breakthroughs in the SRF field that have revolutionized the achievable quality factors in bulk niobium cavities. It will cover two main breakthroughs: one involving the controlled nitrogen doping of the niobium cavity surface, and second the efficient magnetic flux expulsion from the niobium walls via controlled cavity cooling though transition temperature. The talk will give an overview from the discovery of these effects at FNAL to the development into a cryomodule ready technology by the partner labs Cornell, Jlab, FNAL and SLAC for implementation in the LCLS-2 accelerator. New results will be presented from surface analysis, cavity diagnostics tools and very high Q obtained in dressed cavities in cryomodule environment.

Slides MOYGB2 [11.862 MB]

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WEPTY021

Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities

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

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

DOI •

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

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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WEPTY072

Update on Nitrogen-doped 9-cell Cavity Performance in the Cornell Horizontal Test Cryomodule

3446

D. Gonnella, R.G. Eichhorn, F. Furuta, G.M. Ge, D.L. Hall, Y. He, K.M.V. Ho, G.H. Hoffstaetter, M. Liepe, J.T. Maniscalco, T.I. O'Connel, S. Posen, P. Quigley, J. Sears, V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Grassellino, C.J. Grimm, O.S. Melnychuk, A. Romanenko
Fermilab, Batavia, Illinois, USA

Funding: U.S. Department of Energy
The Linac Coherent Light Source-II (LCLS-II) is a new x-ray source that is planned to be constructed in the existing SLAC tunnel. To meet the quality factor specifications (2.7x 10¹⁰ at 2.0 K and 16 MV/m), nitrogen-doping has been proposed as a preparation method for the SRF cavities. In order to demonstrate the feasibility of these goals, four 9-cell cavity tests have been completed in the Cornell Horizontal Test Cryomodule (HTC), which serves as a test bench for the full LCLS-II cryomodule. Here we report on the most recent two cavity tests in the HTC: one cavity nitrogen-doped at Cornell and tested with high Q input coupler and then again tested with high power LCLS-II input coupler. Transition to test in horizontal cryomodule resulted in no degradation in Q0 from vertical test. Additionally, increased dissipated power due to the high power input coupler was small and in good agreement with simulations. These results represent a crucial step on the way to demonstrating technical readiness for LCLS-II.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY072

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