SRF2021 - List of Keywords (radio-frequency)

Paper	Title	Other Keywords	Page
SUPCAV008	Design and Construction of Nb₃Sn Vapor Diffusion Coating System at KEK	cavity, vacuum, MMI, target	23
	K. Takahashi, T. Okada Sokendai, Ibaraki, Japan H. Ito, E. Kako, T. Konomi, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Vapor diffusion Nb₃Sn coating system was developed at KEK. At most 1.3GHz 3-cell cavity can be coat with the coating system. The coating system consists of a coating chamber made of Nb, a vacuum furnace for heating the Nb chamber, and a heating device of Tin in the crucible. The Nb chamber vacuum and the furnace vacuum are isolated to prevent contamination from the furnace. There is a heating device for increasing Tin vapor pressure. In this presentation, the design and construction of the coating system are reported.
	Poster SUPCAV008 [0.986 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV008
About •	Received ※ 21 June 2021 — Accepted ※ 18 November 2021 — Issue date ※ 11 April 2022
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SUPCAV009	First Nb₃Sn Coating and Cavity Performance Result at KEK	cavity, SRF, experiment, factory	27
	K. Takahashi, T. Okada Sokendai, Ibaraki, Japan H. Ito, E. Kako, T. Konomi, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	At KEK, Nb₃Sn vapor diffusion R&D for High-Q has just started. We have performed Nb₃Sn coating on niobium samples and characterized these samples. We optimized the cavity coating parameter from the result of characterized samples. After optimizing the parameter, we have performed Nb₃Sn coating on a TESLA-like single-cell Nb cavity and measured cavity performance in vertical tests. This presentation presents the result of the cavity coating and performance results.
	Poster SUPCAV009 [1.481 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV009
About •	Received ※ 21 June 2021 — Accepted ※ 18 March 2022 — Issue date ※ 16 May 2022
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SUPFDV003	Effect of Mean Free Path on Nonlinear Losses of Trapped Vortices Driven by a RF Field Field	cavity, ECR, linear-dynamics, simulation	67
	M.R.P. Walive Pathiranage, A.V. Gurevich ODU, Norfolk, Virginia, USA
	Funding: This work was supported by NSF under Grants PHY 100614-010 and PHY 1734075, and by DOE under Grant DE-SC 100387-020. We report extensive numerical simulations on nonlinear dynamics of a trapped elastic vortex under rf field, and its dependence on electron mean free path li. Our calculations of the field-dependent residual surface resistance Ri(H) take into account the vortex line tension, the linear Bardeen-Stephen viscous drag and random distributions of pinning centers. We showed that Ri(H) decreases significantly at small fields as the material gets dirtier while showing field independent behavior at higher fields for clean and dirty limit. At low frequencies Ri(H) increases smoothly with the field amplitude at small H and levels off at higher fields. The mean free path dependency of viscosity and pinning strength can result in a nonmonotonic mean free path dependence of Ri, which decreases with li at higher fields and weak pinning strength.
	Poster SUPFDV003 [1.344 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV003
About •	Received ※ 20 June 2021 — Accepted ※ 19 December 2021 — Issue date ※ 09 April 2022
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SUPFDV006	Investigation of SIS Multilayer Films at HZB	SRF, cavity, superconductivity, quadrupole	72
	D.B. Tikhonov, S. Keckert, J. Knobloch, O. Kugeler HZB, Berlin, Germany E. Chyhyrynets, C. Pira INFN/LNL, Legnaro (PD), Italy J. Knobloch University of Siegen, Siegen, Germany S.B. Leith, M. Vogel University Siegen, Siegen, Germany
	Funding: The manufacture of the QPR samples received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871 The systematic study of multilayer SIS films (Superconductor-Insulator-Superconductor) is being conducted in Helmholtz-Zentrum Berlin. Such films theoretically should boost the performance of superconducting cavities, and reduce some problems related to bulk Nb such as magnetic flux trapping. Up to now such films have been presented in theory, but the RF performance of those structures have not been widely studied. In this contribution we present the results of the latest tests of AlN-NbN films, deposited on micrometers-thick Nb layers on copper. It has, also, been shown previously at HZB that such SIS films may show some unexpected behavior in surface resistance versus temperature parameter space. In this contribution we continue to investigate those effects with the variation of different parameters of films (such as insulator thickness) and production recipes.
	Poster SUPFDV006 [2.234 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV006
About •	Received ※ 21 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 21 December 2021
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SUPFDV009	Thermal Annealing of Sputtered Nb₃Sn and V₃Si Thin Films for Superconducting RF Cavities	SRF, cavity, ECR, target	82
	K. Howard, M. Liepe, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams and Cornell Center for Materials Research Shared Facilities supported through the NSF MRSEC program (DMR-1719875) Nb₃Sn and V₃Si thin films are alternative material candidates for the next-generation of superconducting radio frequency (SRF) cavities. However, past sputtered films suffer from stoichiometry and strain issues during deposition and post annealing. As such, we aim to explore the structural and chemical effects of thermal annealing, both in-situ and post-sputtering, on DC-sputtered Nb₃Sn and V₃Si with varying thickness on Nb or Cu substrates. We successfully enabled recrystallization of 100 nm thin Nb₃Sn films with stoichiometric and strain-free grains at 950 C annealing. For 2 um films, we observed removal of strain and slight increase in grain size with increasing temperature. A phase transformation from unstable to stable structure appeared on thick V₃Si samples, while we observed significant Sn loss in thick Nb₃Sn films at high temperature anneals. For films on Cu substrates, we observed similar Sn and Si loss during annealing likely due to Cu-Sn and Cu-Si phase generation and subsequent Sn and Si evaporation. These results encourage us to refine our process to obtain high quality films for SRF use.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV009
About •	Received ※ 22 June 2021 — Revised ※ 06 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 17 March 2022
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SUPTEV010	Electrical and Thermal Properties of Cold-Sprayed Bulk Copper and Copper-Tungsten Samples at Cryogenic Temperatures	cavity, site, SRF, vacuum	142
	H. Pokhrel ODU, Norfolk, Virginia, USA G. Ciovati, P. Dhakal, J.K. Spradlin JLab, Newport News, Virginia, USA C.-J. Jing, A. Kanareykin Euclid TechLabs, Solon, Ohio, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, SBIR grant DE-SC00195589 The development of high thermal conductivity coatings with pure copper or copper-tungsten alloy could be beneficial to improve the heat transfer of bulk Nb cavities for conduction cooling applications and to increase the stiffness of bulk Nb cavities cooled by liquid helium. Cold-spray is an additive manufacturing technique suitable to grow thick coatings of either Cu or CuW on a Nb substrate. Bulk (~5 mm thick) coatings of Cu and CuW were deposited on standard 3 mm thick, high-purity Nb samples and smaller samples with 2 mm x 2 mm cross section were cut for measuring the thermal conductivity and the residual resistivity ratio. The samples were subjected to annealing at different temperatures and a maximum RRR of ~130 and ~40 were measured for the Cu samples and CuW samples, respectively.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV010
About •	Received ※ 21 June 2021 — Revised ※ 13 August 2021 — Accepted ※ 15 November 2021 — Issue date ※ 21 March 2022
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MOPTEV017	Development and Operation of PIP-II Injector Test, SSR1 Cryomodule, 325 MHz Amplifiers	cavity, rf-amplifier, operation, cryomodule	245
	J. Steimel, V.M. Grzelak, D.W. Peterson Fermilab, Batavia, Illinois, USA V.R. Bala, S.K. Bharade, G. Joshi, R. Keshwani, J.K. Mishra, M.M. Pande, S. Shrotriya, H. Shukla, S. Singh, C.I. Sujo BARC, Mumbai, India D. Balakrishna, N. Chikte, S. Dubey, C. G, V. Gollapalli, J. K Chandra, V. Kumar, M. M, A. Maheshwari, S.N. Nagaratnam, G. Poornima, T.V.S. Thalluri ECIL, Hyderabad, India
	Funding: 1Fermilab, U.S.Department of Energy 2 Bhabha Atomic Research Centre, Department of Atomic Energy, Government of India 3 Electronic Corporation of India, Department of Atomic Energy, Government of India The PIP-II Injector Test (PIP2IT) has successfully accelerated ionized hydrogen up to 17MeV through a superconducting, single spoke resonator (SSR1) cryomodule at Fermi National Accelerator Laboratory (FNAL). Each of the SSR1 cavities is tuned to 325MHz and requires up to 6 kW of RF power to accelerate 2mA of ionized hydrogen at the design gradients. RF power amplifiers, specialized for SRF cavity beam operations, were designed by Bhabha Atomic Research Center (BARC) and constructed in a collaboration between the BARC in Mumbai, India and the Electronics Corporation of India Limited (ECIL) in Hyderabad, India. The RF amplifiers meet the specifications and requirements mutually approved between BARC and FNAL. They operate at 325 MHz with a linear power output of 7 kW in both CW and pulse mode. The amplifiers are compatible with the FNAL accelerator personnel safety system and the cavity protection interlocks. Access to controls and internal diagnostic instrumentation are compatible with EPICS control standards. This paper gives details about RF power amplifier development within the Department of Atomic Energy (DAE), India and the operational details with PIP2IT at FNAL.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV017
About •	Received ※ 28 June 2021 — Revised ※ 08 September 2021 — Accepted ※ 18 November 2021 — Issue date ※ 14 May 2022
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TUPFAV006	The Superconducting Radio Frequency System of Shenzhen Industrial Synchrotron Radiation Source FacilityRIAL SYNCHROTRON RADIATION SOURCE FACILITY	cavity, radiation, synchrotron, storage-ring	392
	W. Ma, Y.B. Sun, N. Yuan Sun Yat-sen University, Zhuhai, Guangdong, People’s Republic of China G.M. Liu SSRF, Shanghai, People’s Republic of China L. Lu, L. Yang, Z.L. Zhang IMP/CAS, Lanzhou, People’s Republic of China
	Shenzhen industrial synchrotron radiation source is a 3 GeV synchrotron radiation diffraction-limited source. It consists of three parts, linear accelerator, booster, and storage ring. As a basic part of the storage ring, the superconducting radio frequency system provides energy for the beam to supplement the beam power loss caused by synchrotron radiation and higher-order modes, and provide the longitudinal bunch for the electron beam. The superconducting radio frequency cavity of the storage ring consists of two 500 MHz single-cell cavities and a third harmonic 1500 MHz double-cell cavity. This paper will introduce the superconducting cavity, radio frequency amplifier, and low-level radio frequency system in the Shenzhen industrial synchrotron radiation source facility.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFAV006
About •	Received ※ 20 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 26 November 2021
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TUPFDV007	Surface Impedance of Nb₃Sn and YBa₂Cu₃O_7-δ in High Magnetic Fields	impedance, cavity, framework, collider	416
	N. Pompeo, A. Alimenti, E. Silva, K. Torokhtii Università degli Studi Roma III, Roma, Italy G. Celentano, V. Pinto, F. Rizzo ENEA C.R. Frascati, Frascati (Roma), Italy R. Flükiger UNIGE, Geneva, Switzerland T. Spina Fermilab, Batavia, Illinois, USA
	Funding: This work has been partially carried out within the framework of the EUROfusion consortium, funding from the Euratom research and training programme 2014-18 and 2019-20 under grant agreement No 633053 New potential rf applications of superconductors emerged with the need to operate in high dc magnetic fields (up to 16 T) where vortex motion dictates the response: the beam screen coating of the Future Circular Collider (FCC) [1] and haloscopes, i.e. rf cavities for the axions detection [2]. However, very few data are available in the required regimes. We present in this work measurements of the surface impedance Z up to 12 T on bulk Nb₃Sn and YBCO thin films grown by different techniques. The measurements are performed with a dielectric loaded resonator operating at 15 GHz. We obtained the vortex motion resistivity and extracted the high frequency vortex motion parameters [3]: the depinning frequency, the flux-flow resistivity and the pinning constant, as well as their temperature and field dependences. Substantial differences are highlighted in the high frequency pinning properties of the studied materials, providing useful information on possible improvements in view of applications. A comparison with the results obtained in the microwave frequency range at lower fields (up to 1 T) is given. [1] S. Calatroni, IEEE Trans. Appl. Supercond., vol. 26 p. 3500204, 2016. [2] D. Alesini et al., Phys. Rev. D, vol. 99, p. 101101, 2019. [3] J.I. Gittleman and B. Rosenblum, Phys. Rev. Lett., vol. 16, p.734, 1966.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV007
About •	Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date ※ 02 January 2022
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TUPTEV003	Progress of MgB₂ Deposition Technique for SRF Cavities at LANL	cavity, SRF, experiment, superconductivity	482
	P. Pizzol, L. Civale, D.N. Kelly, I. Nekrashevich, A. Poudel, H.R. Salazar, R.K. Schulze, T. Tajima LANL, Los Alamos, New Mexico, USA
	Since its discovery in 2001, Magnesium Diboride (MgB₂) has had the potential to become a material for cavity manufacturing. Having a transition temperature (Tc) at ~39 K, there is a potential to operate the cavity at ~20 K with cryocoolers. This will open up a variety of applications that benefit from compact high-efficiency superconducting accelerators. We have found a 2-step deposition technique as a viable technique for cavity coating, i.e., coating of a pure boron layer with chemical vapor deposition using a diborane gas in the first step and react it with Mg vapor in the second step. In this paper, we will show some recent results with up to Tc ~38 K using a small furnace and describe a new coating system under construction with a new 3-zone furnace to coat a 1.3-GHz single-cell cavity.
	Poster TUPTEV003 [0.456 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV003
About •	Received ※ 21 June 2021 — Accepted ※ 16 October 2021 — Issue date ※ 02 May 2022
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WEPFDV008	Thermal Conductivity of Electroplated Copper Onto Bulk Niobium at Cryogenic Temperatures	cavity, SRF, niobium, site	576
	G. Ciovati, P. Dhakal JLab, Newport News, Virginia, USA I.P. Parajuli, M.R.P. Walive Pathiranage ODU, Norfolk, Virginia, USA T. Saeki KEK, Ibaraki, Japan
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Superconducting radio-frequency (SRF) cavities made of high-purity bulk niobium are widely used in modern particle accelerators. The development of metallic outer coatings with high thermal conductivity would have a beneficial impact in terms of improved thermal stability, reduced material cost and for the development of conduction-cooled, cryogenic-free SRF cavities. Several high-purity, fine-grain Nb samples have been coated with 2’4 mm thick copper by electroplating. Measurements of the thermal conductivity of the bimetallic Nb/Cu samples in the range 2’7 K showed values of the order of 1 kW/(m K) at 4.3 K. Very good adhesion between copper and niobium was achieved by depositing a thin Cu layer by cold spray on the niobium, prior to electroplating the bulk Cu layer.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPFDV008
About •	Received ※ 17 June 2021 — Accepted ※ 10 September 2021 — Issue date ※ 01 March 2022
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THPFDV003	SIMS Investigation of Furnace-Baked Nb	cavity, vacuum, niobium, SRF	761
	E.M. Lechner, M.J. Kelley, A.D. Palczewski, C.E. Reece JLab, Newport News, Virginia, USA J.W. Angle, M.J. Kelley Virginia Polytechnic Institute and State University, Blacksburg, USA F.A. Stevie NCSU AIF, Raleigh, North Carolina, USA
	Funding: U.S. DOE Contract No. DE-AC05-06OR23177 Results recently published by Ito et al. showed that "furnace baking" Nb SRF cavities after electropolishing yields high quality factors and anti-Q-slopes resembling that of N doped cavities. Small Nb samples were prepared following the recipe outlined by Ito. These samples were measured by SIMS to examine impurity contributions to the RF penetration layer. These diffusion profiles are modeled, and their consequences on RF properties discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV003
About •	Received ※ 22 June 2021 — Accepted ※ 24 November 2021 — Issue date ※ 15 May 2022
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THPTEV015	Cylindrical Magnetron Development for Nb3sn Deposition via Magnetron Sputtering	cavity, SRF, target, site	868
	Md.N. Sayeed, H. Elsayed-Ali ODU, Norfolk, Virginia, USA C. Côté, M.A. Farzad, A. Sarkissian PLASMIONIQUE Inc., Varennes, Québec, Canada G.V. Eremeev Fermilab, Batavia, Illinois, USA A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177. Due to its better superconducting properties (critical temperature Tc~ 18.3 K, superheating field Hsh~ 400 mT), Nb₃Sn is considered as a potential alternative to niobium (Tc~ 9.25 K, Hsh~ 200 mT) for superconducting radiofrequency (SRF) cavities for particle acceleration. Magnetron sputtering is an effective method to produce superconducting Nb₃Sn films. We deposited superconducting Nb₃Sn films on samples with magnetron sputtering using co-sputtering, sequential sputtering, and sputtering from a stoichiometric target. Nb₃Sn films produced by magnetron sputtering in our previous experiments have achieved DC superconducting critical temperature up to 17.93 K and RF superconducting transition at 17.2 K. A magnetron sputtering system with two identical cylindrical cathodes that can be used to sputter Nb₃Sn films on cavities has been designed and is under development now. We report on the design and the current progress on the development of the system.
	Poster THPTEV015 [1.131 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV015
About •	Received ※ 22 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 27 September 2021
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THPTEV016	The Role of Oxygen Concentration in Enabling High Gradients in Niobium SRF Cavities	cavity, niobium, SRF, ECR	871
	D. Bafia, A. Grassellino, A.S. Romanenko Fermilab, Batavia, Illinois, USA
	We studied the role of O concentration with depth in the performance of Nb SRF cavities. An ensemble of electropolished 1.3 GHz cavities, which initially showed high field Q-slope (HFQS), was subjected to sequential testing and treatment with in-situ low temperature baking at various temperatures. We find that increasing the bake duration causes (i) an increase in the onset of HFQS until it is absent up to quench (ii) a non-monotonic relationship with the quench field (iii) an evolution of the RBCS toward a non-equilibrium behavior that drives anti-Q slope. Our data is qualitatively explained by assuming an O diffusion model and suggests that the mitigation of HFQS that arises from 120°C in-situ LTB is mediated by the diffusion of O from the native oxide which prevents the precipitation of proximity-coupled Nb nano-hydrides, in turn enabling higher quench fields. The decrease in quench field for cavities in which O has been diffused >90 nm from the RF surface may be due to a reduction of the field limit in the SS bilayer structure. We also suggest that the evolution of the RBCS occurs due to the absence of proximity coupled inclusions, bringing about non-equilibrium effects.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV016
About •	Received ※ 22 June 2021 — Revised ※ 13 September 2021 — Accepted ※ 13 October 2021 — Issue date ※ 23 November 2021
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Paper

Title

Other Keywords

Page

SUPCAV008

Design and Construction of Nb₃Sn Vapor Diffusion Coating System at KEK

cavity, vacuum, MMI, target

23

K. Takahashi, T. Okada
Sokendai, Ibaraki, Japan
H. Ito, E. Kako, T. Konomi, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Vapor diffusion Nb₃Sn coating system was developed at KEK. At most 1.3GHz 3-cell cavity can be coat with the coating system. The coating system consists of a coating chamber made of Nb, a vacuum furnace for heating the Nb chamber, and a heating device of Tin in the crucible. The Nb chamber vacuum and the furnace vacuum are isolated to prevent contamination from the furnace. There is a heating device for increasing Tin vapor pressure. In this presentation, the design and construction of the coating system are reported.

Poster SUPCAV008 [0.986 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV008

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Received ※ 21 June 2021 — Accepted ※ 18 November 2021 — Issue date ※ 11 April 2022

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

SUPCAV009

First Nb₃Sn Coating and Cavity Performance Result at KEK

cavity, SRF, experiment, factory

27

K. Takahashi, T. Okada
Sokendai, Ibaraki, Japan
H. Ito, E. Kako, T. Konomi, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

At KEK, Nb₃Sn vapor diffusion R&D for High-Q has just started. We have performed Nb₃Sn coating on niobium samples and characterized these samples. We optimized the cavity coating parameter from the result of characterized samples. After optimizing the parameter, we have performed Nb₃Sn coating on a TESLA-like single-cell Nb cavity and measured cavity performance in vertical tests. This presentation presents the result of the cavity coating and performance results.

Poster SUPCAV009 [1.481 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV009

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Received ※ 21 June 2021 — Accepted ※ 18 March 2022 — Issue date ※ 16 May 2022

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

SUPFDV003

Effect of Mean Free Path on Nonlinear Losses of Trapped Vortices Driven by a RF Field Field

cavity, ECR, linear-dynamics, simulation

67

M.R.P. Walive Pathiranage, A.V. Gurevich
ODU, Norfolk, Virginia, USA

Funding: This work was supported by NSF under Grants PHY 100614-010 and PHY 1734075, and by DOE under Grant DE-SC 100387-020.
We report extensive numerical simulations on nonlinear dynamics of a trapped elastic vortex under rf field, and its dependence on electron mean free path li. Our calculations of the field-dependent residual surface resistance Ri(H) take into account the vortex line tension, the linear Bardeen-Stephen viscous drag and random distributions of pinning centers. We showed that Ri(H) decreases significantly at small fields as the material gets dirtier while showing field independent behavior at higher fields for clean and dirty limit. At low frequencies Ri(H) increases smoothly with the field amplitude at small H and levels off at higher fields. The mean free path dependency of viscosity and pinning strength can result in a nonmonotonic mean free path dependence of Ri, which decreases with li at higher fields and weak pinning strength.

Poster SUPFDV003 [1.344 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV003

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Received ※ 20 June 2021 — Accepted ※ 19 December 2021 — Issue date ※ 09 April 2022

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SUPFDV006

Investigation of SIS Multilayer Films at HZB

SRF, cavity, superconductivity, quadrupole

72

D.B. Tikhonov, S. Keckert, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
E. Chyhyrynets, C. Pira
INFN/LNL, Legnaro (PD), Italy
J. Knobloch
University of Siegen, Siegen, Germany
S.B. Leith, M. Vogel
University Siegen, Siegen, Germany

Funding: The manufacture of the QPR samples received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871
The systematic study of multilayer SIS films (Superconductor-Insulator-Superconductor) is being conducted in Helmholtz-Zentrum Berlin. Such films theoretically should boost the performance of superconducting cavities, and reduce some problems related to bulk Nb such as magnetic flux trapping. Up to now such films have been presented in theory, but the RF performance of those structures have not been widely studied. In this contribution we present the results of the latest tests of AlN-NbN films, deposited on micrometers-thick Nb layers on copper. It has, also, been shown previously at HZB that such SIS films may show some unexpected behavior in surface resistance versus temperature parameter space. In this contribution we continue to investigate those effects with the variation of different parameters of films (such as insulator thickness) and production recipes.

Poster SUPFDV006 [2.234 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV006

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Received ※ 21 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 21 December 2021

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

SUPFDV009

Thermal Annealing of Sputtered Nb₃Sn and V₃Si Thin Films for Superconducting RF Cavities

SRF, cavity, ECR, target

82

K. Howard, M. Liepe, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams and Cornell Center for Materials Research Shared Facilities supported through the NSF MRSEC program (DMR-1719875)
Nb₃Sn and V₃Si thin films are alternative material candidates for the next-generation of superconducting radio frequency (SRF) cavities. However, past sputtered films suffer from stoichiometry and strain issues during deposition and post annealing. As such, we aim to explore the structural and chemical effects of thermal annealing, both in-situ and post-sputtering, on DC-sputtered Nb₃Sn and V₃Si with varying thickness on Nb or Cu substrates. We successfully enabled recrystallization of 100 nm thin Nb₃Sn films with stoichiometric and strain-free grains at 950 C annealing. For 2 um films, we observed removal of strain and slight increase in grain size with increasing temperature. A phase transformation from unstable to stable structure appeared on thick V₃Si samples, while we observed significant Sn loss in thick Nb₃Sn films at high temperature anneals. For films on Cu substrates, we observed similar Sn and Si loss during annealing likely due to Cu-Sn and Cu-Si phase generation and subsequent Sn and Si evaporation. These results encourage us to refine our process to obtain high quality films for SRF use.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV009

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Received ※ 22 June 2021 — Revised ※ 06 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 17 March 2022

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SUPTEV010

Electrical and Thermal Properties of Cold-Sprayed Bulk Copper and Copper-Tungsten Samples at Cryogenic Temperatures

cavity, site, SRF, vacuum

142

H. Pokhrel
ODU, Norfolk, Virginia, USA
G. Ciovati, P. Dhakal, J.K. Spradlin
JLab, Newport News, Virginia, USA
C.-J. Jing, A. Kanareykin
Euclid TechLabs, Solon, Ohio, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, SBIR grant DE-SC00195589
The development of high thermal conductivity coatings with pure copper or copper-tungsten alloy could be beneficial to improve the heat transfer of bulk Nb cavities for conduction cooling applications and to increase the stiffness of bulk Nb cavities cooled by liquid helium. Cold-spray is an additive manufacturing technique suitable to grow thick coatings of either Cu or CuW on a Nb substrate. Bulk (~5 mm thick) coatings of Cu and CuW were deposited on standard 3 mm thick, high-purity Nb samples and smaller samples with 2 mm x 2 mm cross section were cut for measuring the thermal conductivity and the residual resistivity ratio. The samples were subjected to annealing at different temperatures and a maximum RRR of ~130 and ~40 were measured for the Cu samples and CuW samples, respectively.

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reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV010

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Received ※ 21 June 2021 — Revised ※ 13 August 2021 — Accepted ※ 15 November 2021 — Issue date ※ 21 March 2022

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MOPTEV017

Development and Operation of PIP-II Injector Test, SSR1 Cryomodule, 325 MHz Amplifiers

cavity, rf-amplifier, operation, cryomodule

245

J. Steimel, V.M. Grzelak, D.W. Peterson
Fermilab, Batavia, Illinois, USA
V.R. Bala, S.K. Bharade, G. Joshi, R. Keshwani, J.K. Mishra, M.M. Pande, S. Shrotriya, H. Shukla, S. Singh, C.I. Sujo
BARC, Mumbai, India
D. Balakrishna, N. Chikte, S. Dubey, C. G, V. Gollapalli, J. K Chandra, V. Kumar, M. M, A. Maheshwari, S.N. Nagaratnam, G. Poornima, T.V.S. Thalluri
ECIL, Hyderabad, India

Funding: 1Fermilab, U.S.Department of Energy 2 Bhabha Atomic Research Centre, Department of Atomic Energy, Government of India 3 Electronic Corporation of India, Department of Atomic Energy, Government of India
The PIP-II Injector Test (PIP2IT) has successfully accelerated ionized hydrogen up to 17MeV through a superconducting, single spoke resonator (SSR1) cryomodule at Fermi National Accelerator Laboratory (FNAL). Each of the SSR1 cavities is tuned to 325MHz and requires up to 6 kW of RF power to accelerate 2mA of ionized hydrogen at the design gradients. RF power amplifiers, specialized for SRF cavity beam operations, were designed by Bhabha Atomic Research Center (BARC) and constructed in a collaboration between the BARC in Mumbai, India and the Electronics Corporation of India Limited (ECIL) in Hyderabad, India. The RF amplifiers meet the specifications and requirements mutually approved between BARC and FNAL. They operate at 325 MHz with a linear power output of 7 kW in both CW and pulse mode. The amplifiers are compatible with the FNAL accelerator personnel safety system and the cavity protection interlocks. Access to controls and internal diagnostic instrumentation are compatible with EPICS control standards. This paper gives details about RF power amplifier development within the Department of Atomic Energy (DAE), India and the operational details with PIP2IT at FNAL.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPTEV017

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Received ※ 28 June 2021 — Revised ※ 08 September 2021 — Accepted ※ 18 November 2021 — Issue date ※ 14 May 2022

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TUPFAV006

The Superconducting Radio Frequency System of Shenzhen Industrial Synchrotron Radiation Source FacilityRIAL SYNCHROTRON RADIATION SOURCE FACILITY

cavity, radiation, synchrotron, storage-ring

392

W. Ma, Y.B. Sun, N. Yuan
Sun Yat-sen University, Zhuhai, Guangdong, People’s Republic of China
G.M. Liu
SSRF, Shanghai, People’s Republic of China
L. Lu, L. Yang, Z.L. Zhang
IMP/CAS, Lanzhou, People’s Republic of China

Shenzhen industrial synchrotron radiation source is a 3 GeV synchrotron radiation diffraction-limited source. It consists of three parts, linear accelerator, booster, and storage ring. As a basic part of the storage ring, the superconducting radio frequency system provides energy for the beam to supplement the beam power loss caused by synchrotron radiation and higher-order modes, and provide the longitudinal bunch for the electron beam. The superconducting radio frequency cavity of the storage ring consists of two 500 MHz single-cell cavities and a third harmonic 1500 MHz double-cell cavity. This paper will introduce the superconducting cavity, radio frequency amplifier, and low-level radio frequency system in the Shenzhen industrial synchrotron radiation source facility.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFAV006

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Received ※ 20 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 26 November 2021

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TUPFDV007

Surface Impedance of Nb₃Sn and YBa₂Cu₃O_7-δ in High Magnetic Fields

impedance, cavity, framework, collider

416

N. Pompeo, A. Alimenti, E. Silva, K. Torokhtii
Università degli Studi Roma III, Roma, Italy
G. Celentano, V. Pinto, F. Rizzo
ENEA C.R. Frascati, Frascati (Roma), Italy
R. Flükiger
UNIGE, Geneva, Switzerland
T. Spina
Fermilab, Batavia, Illinois, USA

Funding: This work has been partially carried out within the framework of the EUROfusion consortium, funding from the Euratom research and training programme 2014-18 and 2019-20 under grant agreement No 633053
New potential rf applications of superconductors emerged with the need to operate in high dc magnetic fields (up to 16 T) where vortex motion dictates the response: the beam screen coating of the Future Circular Collider (FCC) [1] and haloscopes, i.e. rf cavities for the axions detection [2]. However, very few data are available in the required regimes. We present in this work measurements of the surface impedance Z up to 12 T on bulk Nb₃Sn and YBCO thin films grown by different techniques. The measurements are performed with a dielectric loaded resonator operating at 15 GHz. We obtained the vortex motion resistivity and extracted the high frequency vortex motion parameters [3]: the depinning frequency, the flux-flow resistivity and the pinning constant, as well as their temperature and field dependences. Substantial differences are highlighted in the high frequency pinning properties of the studied materials, providing useful information on possible improvements in view of applications. A comparison with the results obtained in the microwave frequency range at lower fields (up to 1 T) is given.
[1] S. Calatroni, IEEE Trans. Appl. Supercond., vol. 26 p. 3500204, 2016.
[2] D. Alesini et al., Phys. Rev. D, vol. 99, p. 101101, 2019.
[3] J.I. Gittleman and B. Rosenblum, Phys. Rev. Lett., vol. 16, p.734, 1966.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV007

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Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date ※ 02 January 2022

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TUPTEV003

Progress of MgB₂ Deposition Technique for SRF Cavities at LANL

cavity, SRF, experiment, superconductivity

482

P. Pizzol, L. Civale, D.N. Kelly, I. Nekrashevich, A. Poudel, H.R. Salazar, R.K. Schulze, T. Tajima
LANL, Los Alamos, New Mexico, USA

Since its discovery in 2001, Magnesium Diboride (MgB₂) has had the potential to become a material for cavity manufacturing. Having a transition temperature (Tc) at ~39 K, there is a potential to operate the cavity at ~20 K with cryocoolers. This will open up a variety of applications that benefit from compact high-efficiency superconducting accelerators. We have found a 2-step deposition technique as a viable technique for cavity coating, i.e., coating of a pure boron layer with chemical vapor deposition using a diborane gas in the first step and react it with Mg vapor in the second step. In this paper, we will show some recent results with up to Tc ~38 K using a small furnace and describe a new coating system under construction with a new 3-zone furnace to coat a 1.3-GHz single-cell cavity.

Poster TUPTEV003 [0.456 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPTEV003

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Received ※ 21 June 2021 — Accepted ※ 16 October 2021 — Issue date ※ 02 May 2022

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WEPFDV008

Thermal Conductivity of Electroplated Copper Onto Bulk Niobium at Cryogenic Temperatures

cavity, SRF, niobium, site

576

G. Ciovati, P. Dhakal
JLab, Newport News, Virginia, USA
I.P. Parajuli, M.R.P. Walive Pathiranage
ODU, Norfolk, Virginia, USA
T. Saeki
KEK, Ibaraki, Japan

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Superconducting radio-frequency (SRF) cavities made of high-purity bulk niobium are widely used in modern particle accelerators. The development of metallic outer coatings with high thermal conductivity would have a beneficial impact in terms of improved thermal stability, reduced material cost and for the development of conduction-cooled, cryogenic-free SRF cavities. Several high-purity, fine-grain Nb samples have been coated with 2’4 mm thick copper by electroplating. Measurements of the thermal conductivity of the bimetallic Nb/Cu samples in the range 2’7 K showed values of the order of 1 kW/(m K) at 4.3 K. Very good adhesion between copper and niobium was achieved by depositing a thin Cu layer by cold spray on the niobium, prior to electroplating the bulk Cu layer.

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reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPFDV008

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Received ※ 17 June 2021 — Accepted ※ 10 September 2021 — Issue date ※ 01 March 2022

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THPFDV003

SIMS Investigation of Furnace-Baked Nb

cavity, vacuum, niobium, SRF

761

E.M. Lechner, M.J. Kelley, A.D. Palczewski, C.E. Reece
JLab, Newport News, Virginia, USA
J.W. Angle, M.J. Kelley
Virginia Polytechnic Institute and State University, Blacksburg, USA
F.A. Stevie
NCSU AIF, Raleigh, North Carolina, USA

Funding: U.S. DOE Contract No. DE-AC05-06OR23177
Results recently published by Ito et al. showed that "furnace baking" Nb SRF cavities after electropolishing yields high quality factors and anti-Q-slopes resembling that of N doped cavities. Small Nb samples were prepared following the recipe outlined by Ito. These samples were measured by SIMS to examine impurity contributions to the RF penetration layer. These diffusion profiles are modeled, and their consequences on RF properties discussed.

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reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPFDV003

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Received ※ 22 June 2021 — Accepted ※ 24 November 2021 — Issue date ※ 15 May 2022

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THPTEV015

Cylindrical Magnetron Development for Nb3sn Deposition via Magnetron Sputtering

cavity, SRF, target, site

868

Md.N. Sayeed, H. Elsayed-Ali
ODU, Norfolk, Virginia, USA
C. Côté, M.A. Farzad, A. Sarkissian
PLASMIONIQUE Inc., Varennes, Québec, Canada
G.V. Eremeev
Fermilab, Batavia, Illinois, USA
A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177.
Due to its better superconducting properties (critical temperature Tc~ 18.3 K, superheating field Hsh~ 400 mT), Nb₃Sn is considered as a potential alternative to niobium (Tc~ 9.25 K, Hsh~ 200 mT) for superconducting radiofrequency (SRF) cavities for particle acceleration. Magnetron sputtering is an effective method to produce superconducting Nb₃Sn films. We deposited superconducting Nb₃Sn films on samples with magnetron sputtering using co-sputtering, sequential sputtering, and sputtering from a stoichiometric target. Nb₃Sn films produced by magnetron sputtering in our previous experiments have achieved DC superconducting critical temperature up to 17.93 K and RF superconducting transition at 17.2 K. A magnetron sputtering system with two identical cylindrical cathodes that can be used to sputter Nb₃Sn films on cavities has been designed and is under development now. We report on the design and the current progress on the development of the system.

Poster THPTEV015 [1.131 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV015

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Received ※ 22 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 27 September 2021

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THPTEV016

The Role of Oxygen Concentration in Enabling High Gradients in Niobium SRF Cavities

cavity, niobium, SRF, ECR

871

D. Bafia, A. Grassellino, A.S. Romanenko
Fermilab, Batavia, Illinois, USA

We studied the role of O concentration with depth in the performance of Nb SRF cavities. An ensemble of electropolished 1.3 GHz cavities, which initially showed high field Q-slope (HFQS), was subjected to sequential testing and treatment with in-situ low temperature baking at various temperatures. We find that increasing the bake duration causes (i) an increase in the onset of HFQS until it is absent up to quench (ii) a non-monotonic relationship with the quench field (iii) an evolution of the RBCS toward a non-equilibrium behavior that drives anti-Q slope. Our data is qualitatively explained by assuming an O diffusion model and suggests that the mitigation of HFQS that arises from 120°C in-situ LTB is mediated by the diffusion of O from the native oxide which prevents the precipitation of proximity-coupled Nb nano-hydrides, in turn enabling higher quench fields. The decrease in quench field for cavities in which O has been diffused >90 nm from the RF surface may be due to a reduction of the field limit in the SS bilayer structure. We also suggest that the evolution of the RBCS occurs due to the absence of proximity coupled inclusions, bringing about non-equilibrium effects.

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reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV016

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Received ※ 22 June 2021 — Revised ※ 13 September 2021 — Accepted ※ 13 October 2021 — Issue date ※ 23 November 2021

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