SRF2021 - List of Keywords (site)

Paper	Title	Other Keywords	Page
SUPCAV003	Dynamic Temperature Mapping of Nb₃Sn Cavities	cavity, SRF, multipactoring, accelerating-gradient	6
	R.D. Porter, N. Banerjee, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Niobium-3 Tin (Nb₃Sn) is the most promising alternative material to niobium for SRF accelerator cavities. The material promises nearly twice the potential accelerating gradients (~100 MV/m in TESLA elliptical cavities), increased quality factors, and 4.2 K operation. Current state of the art Nb₃Sn cavities reach quality factors of 2 x 10¹⁰ at 4.2 K and have reached 24 MV/m. Determining the cause of the premature field limitation is the topic of ongoing research. Cornell University has recently developed a high-speed temperature mapping system that can examine cavity quench mechanisms in never before achieved ways. Here we present high-speed temperature map results of Nb₃Sn cavities and examine the quench mechanism and dynamic heating. We show an initial multipacting quench and sudden temperature jumps at multiple locations on the cavity.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV003
About •	Received ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 31 August 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPCAV007	Thick Film Morphology and SC Characterizations of 6 GHz Nb/Cu Cavities	cavity, niobium, SRF, superconductivity	18
	V.A. Garcia Diaz, O. Azzolini, E. Chyhyrynets, G. Keppel, C. Pira, F. Stivanello, M. Zanierato INFN/LNL, Legnaro (PD), Italy E. Chyhyrynets Università degli Studi di Padova, Padova, Italy D. Fonnesu CERN, Meyrin, Switzerland O. Kugeler, D.B. Tikhonov HZB, Berlin, Germany R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom M. Vogel University Siegen, Siegen, Germany
	Funding: European Union’s H2020 Framework Programme under Grant Agreement no. 764879 Thick films deposited in long pulse DCMS mode onto 6 GHz copper cavities have demonstrated the mitigation of the Q-slope at low accelerating fields. The Nb thick films (~40 microns) show the possibility to reproduce the bulk niobium superconducting properties and morpholo-gy characterizations exhibited dense and void-free films that are encouraging for the scaling of the process to 1.3 GHz cavities. In this work a full characterization of thick films by DC magnetometry, computer tomography, SEM and RF characterizations are presented.
	Poster SUPCAV007 [1.012 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV007
About •	Received ※ 21 June 2021 — Revised ※ 07 July 2021 — Accepted ※ 16 February 2022 — Issue date ※ 08 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPFDV002	Ab Initio Theory of the Impact of Grain Boundaries on the Superconducting Properties of Nb₃Sn	cavity, SRF, electron, niobium	62
	M.M. Kelley, T. Arias, N. Sitaraman Cornell University, Ithaca, New York, USA
	Funding: This work was supported by the US National Science Foundation under award PHY-1549132, the Center for Bright Beams. For over 50 years experiments have repeatedly demonstrated that the superconducting performance of Nb₃Sn is profoundly sensitive to grain boundaries (GBs), but only recently has a microscopic theory emerged. Here we present the first comprehensive, ab initio study of GBs in Nb₃Sn. While most conventional superconductors, such as Nb, are not significantly impacted by GBs, Nb₃Sn is much more sensitive to defects and disorder owing to its short coherence length of ~3 nm. Indeed, experiments suggest a link between GB stoichiometry and the performance of Nb₃Sn superconducting radio frequency (SRF) cavities, and mesoscopic simulations point to GBs as a candidate mechanism that lowers the vortex-entry field in Nb₃Sn SRF cavities. Our density-functional theory (DFT) calculations on tilt and twist GBs provide direct insight into antisite defect formation near GBs and how local electronic properties are impacted by clean GBs and by GBs with added point defects. Ultimately, we will show how GB composition affects the local Tc around GBs in Nb₃Sn to elucidate recent SRF experiments and provide insight on promising modifications to the growth procedure of Nb₃Sn to optimize its SRF performance. [] Michelle M Kelley et al 2021 Supercond. Sci. Technol. 34 015015
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV002
About •	Received ※ 01 July 2021 — Accepted ※ 02 December 2021 — Issue date ※ 09 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPFDV007	Magnetic Field Penetration of Niobium Thin Films Produced by the ARIES Collaboration	cavity, dipole, SRF, controls	77
	D.A. Turner Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G. Burt, K.D. Dumbell, O.B. Malyshev, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom G. Burt Lancaster University, Lancaster, United Kingdom E. Chyhyrynets, C. Pira INFN/LNL, Legnaro (PD), Italy T. Junginger TRIUMF, Vancouver, Canada T. Junginger UVIC, Victoria, Canada S.B. Leith, M. Vogel University Siegen, Siegen, Germany O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom A. Medvids, P. Onufrijevs Riga Technical University, Riga, Latvia R. Ries Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic E. Seiler IEE, Bratislava, Slovak Republic A. Sublet CERN, Meyrin, Switzerland J.T.G. Wilson STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	Superconducting (SC) thin film coatings on Cu substrates are already widely used as an alternative to bulk Nb SRF structures. Using Cu allows improved thermal stability compared to Nb due to having a greater thermal conductivity. Niobium thin film coatings also reduce the amount of Nb required to produce a cavity. The performance of thin film Nb cavities is not as good as bulk Nb cavities. The H2020 ARIES WP15 collaboration studied the impact of substrate polishing and the effect produced on Nb thin film depositions. Multiple samples were produced from Cu and polished with various techniques. The polished Cu substrates were then coated with a Nb film at partner institutions. These samples were characterised with surface characterisation techniques for film morphology and structure. The SC properties were studied with 2 DC techniques, a vibrating sample magnetometer (VSM) and a magnetic field penetration (MFP) facility. The results conclude that both chemical polishing and electropolishing produce the best DC properties in the MFP facility. A comparison between the VSM and the MFP facility can be made for 10 micron thick samples, but not for 3 micron thick samples.
	Poster SUPFDV007 [1.064 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV007
About •	Received ※ 21 June 2021 — Accepted ※ 28 October 2021 — Issue date ※ 09 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPFDV012	The Development of HiPIMS Multilayer SIS Film Coatings on Copper for SRF Applications	cavity, SRF, lattice, shielding	86
	S.B. Leith, X. Jiang, A.O. Sezgin, M. Vogel University Siegen, Siegen, Germany B. Butz, Y. Li, J. Müller MNaF, Siegen, Germany S. Keckert, J. Knobloch, O. Kugeler, D.B. Tikhonov HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany R. Ries, E. Seiler Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
	Funding: Authors acknowledge both the EASITrain, Marie Sklodowska-Curie Action (MSCA) Innovative Training Network (ITN), Grant Agreement no. 764879 and the ARIES collaboration, Grant Agreement no. 730871 In recent years, the use of alternatives to bulk Nb in the fabrication of SRF cavities, including novel materials and/or fabrication techniques, have been extensively explored by the SRF community. One of these new methodologies is the use of a superconductor-insulator-superconductor (SIS) multilayer structure. Typically, these have been envisaged for use with bulk Nb cavities. However, it is conceivable to combine the benefits of SIS structures with the benefits of coated Cu cavities. It is also clear that the use of energetic deposition techniques such as high power impulse magnetron sputtering (HiPIMS), provide significant benefits over typical DC magnetron sputtering (MS) coatings, in terms of SRF performance. In light of this, two series of multilayer SIS film coatings, with a Nb-AlN-NbN structure, were deposited onto electropolished OFHC Cu samples, with the use of HiPIMS, in order to determine the efficacy of this approach. This contribution details the development of these coatings and the required optimization of the coating parameters of the separate material systems, through the use of multiple material and superconducting characterization techniques.
	Poster SUPFDV012 [2.061 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV012
About •	Received ※ 20 June 2021 — Accepted ※ 21 December 2021 — Issue date ※ 27 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPFDV013	HiPIMS NbN Thin Film Development for Use in Multilayer SIS Films	cathode, lattice, ECR, cavity	91
	S.B. Leith, B. Bai, X. Jiang, M. Vogel University Siegen, Siegen, Germany R. Ries, E. Seiler Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
	Funding: Authors acknowledge both the EASITrain, Marie Sklodowska-Curie Action (MSCA) Innovative Training Network (ITN), Grant Agreement no. 764879 and the ARIES collaboration, Grant Agreement no. 730871 As part of efforts to improve the performance of SRF cavities, the use of alternative structures, such as superconductor-insulator-superconductor (SIS) film coatings have been extensively investigated. Initial efforts using DC magnetron sputtering (MS) deposited NbN films showed the efficacy of this approach. The use of energetic condensation methods, such as high power impulse magnetron sputtering (HiPIMS), have already improved the performance of Nb thin films for SRF cavities and have already been used for nitride film coatings in the tool industry. In this contribution, the results from the deposition of HiPIMS NbN thin films onto oxygen free high conductivity (OFHC) Cu substrates are presented. The effects of the different deposition parameters on the deposited films were elucidated through various characterisation methods, resulting in an optimum coating procedure. This allowed for further comparison between the HiPIMS NbN films and the previously presented DC MS NbN films. The results indicate the improvements offered by HiPIMS deposition, most notably, the significant increase in the entry field, and its applicability to the deposition of SIS films on Cu.
	Poster SUPFDV013 [0.923 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV013
About •	Received ※ 20 June 2021 — Revised ※ 08 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 25 October 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPFDV018	CERN Based T_c Measurement Station for Thin-Film Coated Copper Samples and Results on Related Studies	niobium, cavity, SRF, pick-up	105
	D. Fonnesu, J. Bremer, T. Koettig, L. Laín-Amador, C. Pereira Carlos, G.J. Rosaz, A.P.O. Vaaranta CERN, Meyrin, Switzerland
	Funding: EASITrain - European Advanced Superconductivity Innovation and Training. This MSCA ITN has received funding from the European Union’s H2020 Framework Programme under GA no. 764879. In the framework of The Future Circular Collider (FCC) Study, the development of thin-film coated superconducting radio-frequency (SRF) cavities capable of providing higher accelerating fields (10 to 20 MV/m against 5 MV/m of LHC) represents a major challenge. In this work, we present the development of a test stand commissioned at CERN for the inductive measurement of the critical temperature (T_c) of SC thin-film deposited on copper samples for SRF applications. Based on new studies for the production of Non Evaporable Getters (NEG) coated chambers [1], we also present the first results of an alternative forming method for seamless copper cavities with niobium layer integrated in the production process. [1] doi:10.1116/1.4999539
	Poster SUPFDV018 [1.616 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV018
About •	Received ※ 21 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 01 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPFDV020	ALD-Based NbIiN Studies for SIS R&D	cavity, plasma, vacuum, SRF	109
	I. González Díaz-Palacio, R.H. Blick, R. Zierold University of Hamburg, Hamburg, Germany W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Superconductor-Insulator-Superconductor multilayers improve the performance of SRF cavities providing magnetic screening of the bulk cavity and lower surface resistance. In this framework NbTiN mixtures stand as a potential material of interest. Atomic layer deposition (ALD) allows for uniform coating of complex geometries and enables tuning of the stoichiometry and precise thickness control in sub-nm range. In this talk, we report about NbTiN thin films deposited by plasma-enhanced ALD on insulating AlN buffer layer. The deposition process has been optimized by studying the superconducting electrical properties of the films. Post-deposition thermal annealing studies with varying temperatures, annealing times, and gas atmospheres have been performed to further improve the thin film quality and the superconducting properties. Our experimental studies show an increase in T_c by 87.5% after thermal annealing and a maximum T_c of 13.9 K has been achieved for NbTiN of 23 nm thickness. Future steps include lattice characterization, using XRR/XRD/EBSD/PALS, and SRF measurements to obtain Hc1 and the superconducting gap.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV020
About •	Received ※ 22 June 2021 — Revised ※ 17 August 2021 — Accepted ※ 17 August 2021 — Issue date ※ 19 January 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPTEV001	Magnetic Field Penetration Technique to Study High Field Shielding of Multilayered Superconductors	cavity, SRF, niobium, accelerating-gradient	112
	I.H. Senevirathne, J.R. Delayen, A.V. Gurevich ODU, Norfolk, Virginia, USA J.R. Delayen, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399 The SIS structure which consists of alternative thin layers of superconductors and insulators on a bulk niobium has been proposed to shield niobium cavity surface from high magnetic field and hence increase the accelerating gradient. The study of the behavior of multilayer super-conductors in an external magnetic field is essential to optimize their SRF performance. In this work we report the development of a simple and efficient technique to measure penetration of magnetic field into bulk, thin film and multilayer superconductors. Experimental setup contains a small superconducting solenoid which can produce a parallel surface magnetic field up to 0.5 T and Hall probes to detect penetrated magnetic field across the superconducting sample. This system was calibrated and used to study the effect of niobium sample thickness on the field of full magnetic flux penetration. We determined the optimum thickness of the niobium substrate to fabricate the multilayer structure for the measurements in our setup. This technique was used to measure penetration fields of Nb₃Sn thin films and Nb₃Sn/Al₂O₃ multi-layers deposited on Al₂O₃ wafers.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV001
About •	Received ※ 22 June 2021 — Revised ※ 15 August 2021 — Accepted ※ 20 September 2021 — Issue date ※ 28 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPTEV010	Electrical and Thermal Properties of Cold-Sprayed Bulk Copper and Copper-Tungsten Samples at Cryogenic Temperatures	cavity, SRF, vacuum, radio-frequency	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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPTEV016	Samples for 3rd Harmonic Magnetometry Assessment of NbTiN-Based SIS Structures	SRF, cavity, interface, FEL	164
	D.R. Beverstock, J.R. Delayen, I.H. Senevirathne, J.K. Spradlin, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA C.Z. Antoine CEA-IRFU, Gif-sur-Yvette, France J.R. Delayen, I.H. Senevirathne ODU, Norfolk, Virginia, USA D. Manos The College of William and Mary, Williamsburg, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399. In the quest for alternative superconducting materials to bring accelerator cavity performance beyond the bulk niobium (Nb) intrinsic limits, a promising concept uses superconductor-insulator-superconductor (SIS) thin film structures that allows magnetic flux shielding in accelerator cavities to higher fields [1]. Candidate materials for such structures are NbTiN as the superconductor and AlN as the insulator. We have demonstrated high quality NbTiN and AlN deposited by reactive DC magnetron sputtering (DCMS), both for individual layers and multilayers. Interface quality has been assessed for bilayer stacks with 250 nm NbTiN layers and AlN thicknesses from 30 nm down to1 nm. These SIS structures show continued sharp interfaces with total average roughness under 2 nm. The Hfp enhancement of the films will be examined with a 3rd harmonic magnetometry. The system is being designed and built in a continuing collaboration with CEA Saclay. It can measure 25 to 50 mm samples on a temperature controlled stage. This contribution presents an overview of the design of the 3rd harmonic magnetometer and the material properties assessment of standalone films and multilayer nanostructures. [1] A. Gurevich, Applied Physics Letters, vol. 88, p. 012511, 2006.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV016
About •	Received ※ 22 June 2021 — Accepted ※ 10 November 2021 — Issue date ※ 16 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPCAV005	Status of SNS Proton Power Upgrade SRF Cavities Production Qualification	cavity, cryomodule, proton, neutron	265
	P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, D. Forehand, N.A. Huque, A.L.A. Mitchell, P.D. Owen JLab, Newport News, Virginia, USA M.P. Howell, S.-H. Kim, J.D. Mammosser ORNL, Oak Ridge, Tennessee, USA
	The Proton Power Upgrade project at Oak Ridge National Lab’s Spallation Neutron Source (SNS PPU) currently being constructed will double the proton beam power from 1.4 to 2.8 MW by adding 7 additional cryomodules, each contains four six-cell high beta (\beta = 0.81) superconducting radio frequency cavities. The cavities were built by Research Instruments, Germany, with all the cavity processing done at the vendor site, including electropolishing as the final active chemistry step. All 28 cavities needed for 7 cryomodules were delivered to Jefferson Lab, ready to be tested. The cryogenic RF qualifications and helium vessel welding were done at Jefferson Lab. The performance largely exceed the requirements, and greatly exceeded the performance of the original SNS cavity production series. Here, we present the summary of RF test on production cavities to this date. This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
	Poster MOPCAV005 [1.065 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPCAV005
About •	Received ※ 19 June 2021 — Revised ※ 10 July 2021 — Accepted ※ 12 March 2022 — Issue date ※ 06 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPFDV010	Microstructure Changes Observed in the Near-Surface Region of SRF Nb Cavities Cutouts upon Cooling/Heating Cycles Using GI-Synchrotron XRD	cavity, SRF, niobium, lattice	339
	A. Cano, D. Bafia, A. Grassellino, J. Lee, M. Martinello, A.S. Romanenko, T. Spina, Z-H. Sung Fermilab, Batavia, Illinois, USA E.A. Karapetrova ANL, Lemont, Illinois, USA
	We have mapped microstructural changes in the near-surface region of Nb from SRF cavity-cutouts upon thermal cycles in the range from 300 to 30 K using grazing incidence synchrotron X-Ray diffraction (GIXRD). Segregation of secondary phases was observed after the thermal cycle, and their nature has been clarified and discussed in view of previous studies on hydrides formation in SRF bulk Nb cavities. The temperature dependence of the relative population of these formed phases was obtained from GIXRD patterns profile fitting. Both, Nb bulk matrix and the new phases formed after cool-down show specific structural features as thermal contraction/expansion, structural transitions, and Nb lattice variation due to the induced strain by precipitates formation. The information derived from this structural study can explain some phenomena as the dissipation at high accelerating field (i.e. High Field Q Slope, HFQS) in the Nb SRF performance as well as new mechanisms never addressed in previous studies. A Romanenko, F Barkov, LD Cooley, A Grassellino, Proximity breakdown of hydrides in superconducting niobium cavities, Superconductor Science and Technology, 2013
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPFDV010
About •	Received ※ 28 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 23 September 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUOFDV05	Dynamics of RF Dissipation Probed via High-Speed Temperature Mapping	cavity, SRF, electron, data-acquisition	349
	R.D. Porter, N. Banerjee, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Recently, Cornell University has developed a new high-speed, high-resolution temperature mapping system that can resolve the time dynamics of RF dissipation, i.e., provide high-speed videos of the surface heating across the entire surface of the cavity. This new powerful tool allows to observe rapid changes in the local RF dissipation, as well as to resolve the dynamics of quenches, field emission processing, and other cavity events, giving new insights into these. This contribution presents the development of this new high-speed temperature mapping system, discusses its commissioning and extensive performance testing (e.g., demonstrating micro-Kelvin resolution), as well as show intriguing high-speed temperature mapping results from multiple Nb₃Sn cavities.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUOFDV05
About •	Received ※ 01 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 06 February 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPFDV010	New Recipes to Optimize the Niobium Oxide Surface From First-Principles Calculations	niobium, electron, cavity, SRF	426
	N. Sitaraman, T. Arias, Z. Baraissov, M.M. Kelley, D.A. Muller Cornell University, Ithaca, New York, USA M. Liepe, R.D. Porter, Z. Sun Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams The properties of niobium oxide are of critical importance for a wide range of topics, from the behavior of nitrogen during infusion treatments, to the nucleation of Nb₃Sn, to the superconducting properties of the surface. However, the modeling of the oxide is often much simplified, ignoring the variety of niobium oxide phases and the extremely different properties of these phases in the presence of impurities and defects. We use density functional theory (DFT) to investigate how electrochemical treatments and gas infusion procedures change the properties of niobium oxide, and to investigate how these properties could be optimized for Nb₃Sn nucleation and for niobium SRF performance.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV010
About •	Received ※ 01 July 2021 — Accepted ※ 18 November 2021 — Issue date ※ 22 February 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPCAV006	Nb₃Sn Films Depositions from Targets Synthesized via Liquid Tin Diffusion	target, niobium, cavity, controls	452
	M. Zanierato, O. Azzolini, E. Chyhyrynets, V.A. Garcia Diaz, G. Keppel, C. Pira, F. Stivanello INFN/LNL, Legnaro (PD), Italy
	The deposition of Nb₃Sn on copper cavities is inter-esting for the higher thermal conductivity of copper compared to common Nb substrates. The better heat exchange would allow the use of cryocoolers reducing cryogenic costs and the risk of thermal quench [1]. Magnetron sputtering technology allows the deposi-tion of Nb₃Sn on substrates different than Nb, however the coating of substrates with complex geometry (such as elliptical cavities) may require targets with non-planar shape, difficult to realize with classic powder sintering techniques. In this work, the possibility of using the Liquid Tin Diffusion (LTD) technique to produce sputtering targets is explored. The LTD tech-nique is a wire fabrication technology, already devel-oped in the past at LNL for SRF applications [2], that allows the deposition of very thick and uniform coat-ing on Nb substrates even with complex geometry [3]. Improvements in LTD process, proof of concept of a single use LTD target production, and characterization of the Nb₃Sn film coated by DC magnetron sputtering with these innovative targets are reported in this work.
	Poster TUPCAV006 [5.037 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPCAV006
About •	Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 23 August 2021 — Issue date ※ 02 September 2021
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPFDV007	Main Highlights of ARIES WP15 Collaboration	SRF, cavity, laser, experiment	571
	O.B. Malyshev, P. Goudket, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C.Z. Antoine CEA-IRFU, Gif-sur-Yvette, France O. Azzolini, E. Chyhyrynets, G. Keppel, C. Pira, F. Stivanello INFN/LNL, Legnaro (PD), Italy G. Burt, D.J. Seal, D.A. Turner Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G. Burt, B.S. Sian Lancaster University, Lancaster, United Kingdom O. Kugeler, D.B. Tikhonov HZB, Berlin, Germany S.B. Leith, A.O. Sezgin, M. Vogel University Siegen, Siegen, Germany A. Medvids, P. Onufrijevs Riga Technical University, Riga, Latvia R. Ries, E. Seiler Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic B.S. Sian Cockcroft Institute, Warrington, Cheshire, United Kingdom A. Sublet, G. Vandoni, L. Vega Cid, W. Venturini Delsolaro, P. Vidal García CERN, Meyrin, Switzerland D.A. Turner STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: European Commission’s ARIES collaboration H2020 Research and Innovation Programme under Grant Agreement no. 730871 An international collaboration of research teams from CEA (France), CERN (Switzerland), INFN/LNL (Italy), HZB and USI (Germany), IEE (Slovakia), RTU (Latvia) and STFC/DL (UK), are working together on better understanding of how to improve the properties of superconducting thin films (ScTF) for RF cavities. The collaboration has been formed as WP15 in the H2020 ARIES project funded by EC. The systematic study of ScTF covers: Cu substrate polishing with different techniques (EP, SUBU, EP+SUBU, tumbling, laser), Nb, NbN, Nb₃Sn and SIS film deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application of all obtained knowledge on polishing, deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application to the QPR samples for testing the films at RF conditions. The preparation, deposition and characterisation of each sample involves 3-5 partners enhancing the capability of each other and resulting in a more complete analysis of each film. The talk will give an overview of the collaborative research and will be an introduction to the detailed talks given by the team members.
	Poster WEPFDV007 [2.013 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPFDV007
About •	Received ※ 19 June 2021 — Accepted ※ 12 February 2022 — Issue date ※ 10 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPFDV008	Thermal Conductivity of Electroplated Copper Onto Bulk Niobium at Cryogenic Temperatures	cavity, SRF, niobium, radio-frequency	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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPTEV012	Characterization of Atomic-Layer-Deposited NbTiN and NbTiN/AlN Films for SIS Multilayer Structures	interface, SRF, cavity, superconductivity	662
	Z. Sun, M. Liepe, T.E. Oseroff Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA X. Deng University of Virginia, Charlottesville, Virginia, USA
	SIS (superconductor-insulator-superconductor) mul-tilayer structures are proposed designs to repel early flux penetration and ease the impact of defects in SRF cavities. The demonstration of such device physics is strongly affected by the film qualities ’ material struc-ture and composition. Here, we characterized 100 nm NbTiN / 2 nm AlN / bulk Nb SIS structures and investigated the effect of the presence of the AlN layer on the NbTiN film properties. We find that the hcp-structured AlN layer results in a Nb composition gra-dient as a function of film depth, whereas the Nb con-centration remains constant in the NbTiN/Nb samples, which suggests that interface mismatch could induce significant change in NbTiN composition. The surface composition variation further leads to different oxide structures, which might impact the superconducting performance. Our observations indicate that the choice of the insulating layer in SIS structures is critical, and that interface mismatch together with internal strain could deteriorate the superconducting film.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV012
About •	Received ※ 08 July 2021 — Revised ※ 06 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 02 January 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPTEV014	Managing Procurements in the Time of Covid-19: SNS-PPU as a Case Study	operation, status, HOM, cryomodule	863
	K.M. Wilson, G. Cheng, E. Daly, N.A. Huque, T. Huratiak, M. Laney, K. Macha, D.J. Maddox, M. Marchlik, P.D. Owen, T. Peshehonoff, M. Torres, M. Wiseman JLab, Newport News, Virginia, USA
	Funding: Supported by the Dept of Energy, Office of Nuclear Physics under contract DE-AC05-06OR23177 (JSA); and by UT-B which manages Oak Ridge National Laboratory under contract DE-AC05-00OR22725. In early 2020, COVID-19 swept across the world. The accelerator industry, like many others, was impacted by disease, delays, shortages, and new working conditions. All Thomas Jefferson National Accelerator Facility (JLab) employees were sent home in mid-March 2020, with many still working remotely now. At the time, JLab was working on the Proton Power Upgrade (PPU) to the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). Procurements had been placed and were being managed, parts were being received and inspected. This paper details the JLab procurement plan for the SNS PPU project, and the mitigations that were developed to continue to support this project smoothly under the limitations imposed by COVID-19.
	Poster THPTEV014 [1.081 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV014
About •	Received ※ 15 June 2021 — Revised ※ 30 November 2021 — Accepted ※ 21 January 2022 — Issue date ※ 01 May 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPTEV015	Cylindrical Magnetron Development for Nb3sn Deposition via Magnetron Sputtering	cavity, SRF, target, radio-frequency	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
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FROFDV06	Synthesis of Nb and Alternative Superconducting Film to Nb for SRF Cavity as Single Layer	cavity, SRF, niobium, target	893
	R. Valizadeh, P. Goudket, A.N. Hannah, O.B. Malyshev STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C.Z. Antoine CEA-DRF-IRFU, France C.Z. Antoine CEA-IRFU, Gif-sur-Yvette, France E. Chyhyrynets, C. Pira INFN/LNL, Legnaro (PD), Italy P. Goudket, O.B. Malyshev, D.J. Seal, B.S. Sian, D.A. Turner Cockcroft Institute, Warrington, Cheshire, United Kingdom O. Kugeler, D.B. Tikhonov HZB, Berlin, Germany S.B. Leith, A.O. Sezgin, M. Vogel University Siegen, Siegen, Germany A. Medvids, P. Onufrijevs Riga Technical University, Riga, Latvia D.J. Seal, B.S. Sian, D.A. Turner Lancaster University, Lancaster, United Kingdom G.B.G. Stenning STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom A. Sublet, G. Vandoni, L. Vega Cid, W. Venturini Delsolaro, P. Vidal García CERN, Meyrin, Switzerland
	"Bulk niobium (Nb) has been the material of choice for superconducting RF (SRF) cavities but for further improvement in cavity RF performance, one may have to turn to films of Nb and to other superconducting materials deposited on copper as thermal and mechanical support. Other materials known as A15, such as Nb₃Sn or V₃Si and B1 such as NbTiN and NbN are much easier to synthesise in thin films rather than being made as bulk cavity. The potential benefits of using materials other than Nb would be a higher Tc, a potentially higher critical held Hc, leading to potentially significant cryogenics cost reduction if the cavity operation temperature is 4.2 K or higher. We report on optimising deposition parameters and effect of substrate treatment prior to deposition for successful synthesising of Nb and the alternative superconducting thin film with high superconducting properties (Tc and Hsh) on flat substrates and QPR samples in single layer. The DC and RF SC properties have been tested using PPMS and QPR measurements. This work is part of the H2020 ARIES collaboration. We further report on preparation of RF cavities employing these alternative material for future cavity production."
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2021-FROFDV06
About •	Received ※ 21 June 2021 — Accepted ※ 05 January 2022 — Issue date ※ 28 April 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

SUPCAV003

Dynamic Temperature Mapping of Nb₃Sn Cavities

cavity, SRF, multipactoring, accelerating-gradient

6

R.D. Porter, N. Banerjee, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Niobium-3 Tin (Nb₃Sn) is the most promising alternative material to niobium for SRF accelerator cavities. The material promises nearly twice the potential accelerating gradients (~100 MV/m in TESLA elliptical cavities), increased quality factors, and 4.2 K operation. Current state of the art Nb₃Sn cavities reach quality factors of 2 x 10¹⁰ at 4.2 K and have reached 24 MV/m. Determining the cause of the premature field limitation is the topic of ongoing research. Cornell University has recently developed a high-speed temperature mapping system that can examine cavity quench mechanisms in never before achieved ways. Here we present high-speed temperature map results of Nb₃Sn cavities and examine the quench mechanism and dynamic heating. We show an initial multipacting quench and sudden temperature jumps at multiple locations on the cavity.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV003

About •

Received ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 31 August 2021

Cite •

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

SUPCAV007

Thick Film Morphology and SC Characterizations of 6 GHz Nb/Cu Cavities

cavity, niobium, SRF, superconductivity

18

V.A. Garcia Diaz, O. Azzolini, E. Chyhyrynets, G. Keppel, C. Pira, F. Stivanello, M. Zanierato
INFN/LNL, Legnaro (PD), Italy
E. Chyhyrynets
Università degli Studi di Padova, Padova, Italy
D. Fonnesu
CERN, Meyrin, Switzerland
O. Kugeler, D.B. Tikhonov
HZB, Berlin, Germany
R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
M. Vogel
University Siegen, Siegen, Germany

Funding: European Union’s H2020 Framework Programme under Grant Agreement no. 764879
Thick films deposited in long pulse DCMS mode onto 6 GHz copper cavities have demonstrated the mitigation of the Q-slope at low accelerating fields. The Nb thick films (~40 microns) show the possibility to reproduce the bulk niobium superconducting properties and morpholo-gy characterizations exhibited dense and void-free films that are encouraging for the scaling of the process to 1.3 GHz cavities. In this work a full characterization of thick films by DC magnetometry, computer tomography, SEM and RF characterizations are presented.

Poster SUPCAV007 [1.012 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV007

About •

Received ※ 21 June 2021 — Revised ※ 07 July 2021 — Accepted ※ 16 February 2022 — Issue date ※ 08 April 2022

Cite •

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

SUPFDV002

Ab Initio Theory of the Impact of Grain Boundaries on the Superconducting Properties of Nb₃Sn

cavity, SRF, electron, niobium

62

M.M. Kelley, T. Arias, N. Sitaraman
Cornell University, Ithaca, New York, USA

Funding: This work was supported by the US National Science Foundation under award PHY-1549132, the Center for Bright Beams.
For over 50 years experiments have repeatedly demonstrated that the superconducting performance of Nb₃Sn is profoundly sensitive to grain boundaries (GBs), but only recently has a microscopic theory emerged. Here we present the first comprehensive, ab initio study of GBs in Nb₃Sn*. While most conventional superconductors, such as Nb, are not significantly impacted by GBs, Nb₃Sn is much more sensitive to defects and disorder owing to its short coherence length of ~3 nm. Indeed, experiments suggest a link between GB stoichiometry and the performance of Nb₃Sn superconducting radio frequency (SRF) cavities, and mesoscopic simulations point to GBs as a candidate mechanism that lowers the vortex-entry field in Nb₃Sn SRF cavities. Our density-functional theory (DFT) calculations on tilt and twist GBs provide direct insight into antisite defect formation near GBs and how local electronic properties are impacted by clean GBs and by GBs with added point defects. Ultimately, we will show how GB composition affects the local Tc around GBs in Nb₃Sn to elucidate recent SRF experiments and provide insight on promising modifications to the growth procedure of Nb₃Sn to optimize its SRF performance.
[*] Michelle M Kelley et al 2021 Supercond. Sci. Technol. 34 015015

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV002

About •

Received ※ 01 July 2021 — Accepted ※ 02 December 2021 — Issue date ※ 09 April 2022

Cite •

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

SUPFDV007

Magnetic Field Penetration of Niobium Thin Films Produced by the ARIES Collaboration

cavity, dipole, SRF, controls

77

D.A. Turner
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt, K.D. Dumbell, O.B. Malyshev, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom
E. Chyhyrynets, C. Pira
INFN/LNL, Legnaro (PD), Italy
T. Junginger
TRIUMF, Vancouver, Canada
T. Junginger
UVIC, Victoria, Canada
S.B. Leith, M. Vogel
University Siegen, Siegen, Germany
O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
A. Medvids, P. Onufrijevs
Riga Technical University, Riga, Latvia
R. Ries
Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
E. Seiler
IEE, Bratislava, Slovak Republic
A. Sublet
CERN, Meyrin, Switzerland
J.T.G. Wilson
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Superconducting (SC) thin film coatings on Cu substrates are already widely used as an alternative to bulk Nb SRF structures. Using Cu allows improved thermal stability compared to Nb due to having a greater thermal conductivity. Niobium thin film coatings also reduce the amount of Nb required to produce a cavity. The performance of thin film Nb cavities is not as good as bulk Nb cavities. The H2020 ARIES WP15 collaboration studied the impact of substrate polishing and the effect produced on Nb thin film depositions. Multiple samples were produced from Cu and polished with various techniques. The polished Cu substrates were then coated with a Nb film at partner institutions. These samples were characterised with surface characterisation techniques for film morphology and structure. The SC properties were studied with 2 DC techniques, a vibrating sample magnetometer (VSM) and a magnetic field penetration (MFP) facility. The results conclude that both chemical polishing and electropolishing produce the best DC properties in the MFP facility. A comparison between the VSM and the MFP facility can be made for 10 micron thick samples, but not for 3 micron thick samples.

Poster SUPFDV007 [1.064 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV007

About •

Received ※ 21 June 2021 — Accepted ※ 28 October 2021 — Issue date ※ 09 April 2022

Cite •

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

SUPFDV012

The Development of HiPIMS Multilayer SIS Film Coatings on Copper for SRF Applications

cavity, SRF, lattice, shielding

86

S.B. Leith, X. Jiang, A.O. Sezgin, M. Vogel
University Siegen, Siegen, Germany
B. Butz, Y. Li, J. Müller
MNaF, Siegen, Germany
S. Keckert, J. Knobloch, O. Kugeler, D.B. Tikhonov
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
R. Ries, E. Seiler
Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic

Funding: Authors acknowledge both the EASITrain, Marie Sklodowska-Curie Action (MSCA) Innovative Training Network (ITN), Grant Agreement no. 764879 and the ARIES collaboration, Grant Agreement no. 730871
In recent years, the use of alternatives to bulk Nb in the fabrication of SRF cavities, including novel materials and/or fabrication techniques, have been extensively explored by the SRF community. One of these new methodologies is the use of a superconductor-insulator-superconductor (SIS) multilayer structure. Typically, these have been envisaged for use with bulk Nb cavities. However, it is conceivable to combine the benefits of SIS structures with the benefits of coated Cu cavities. It is also clear that the use of energetic deposition techniques such as high power impulse magnetron sputtering (HiPIMS), provide significant benefits over typical DC magnetron sputtering (MS) coatings, in terms of SRF performance. In light of this, two series of multilayer SIS film coatings, with a Nb-AlN-NbN structure, were deposited onto electropolished OFHC Cu samples, with the use of HiPIMS, in order to determine the efficacy of this approach. This contribution details the development of these coatings and the required optimization of the coating parameters of the separate material systems, through the use of multiple material and superconducting characterization techniques.

Poster SUPFDV012 [2.061 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV012

About •

Received ※ 20 June 2021 — Accepted ※ 21 December 2021 — Issue date ※ 27 April 2022

Cite •

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

SUPFDV013

HiPIMS NbN Thin Film Development for Use in Multilayer SIS Films

cathode, lattice, ECR, cavity

91

S.B. Leith, B. Bai, X. Jiang, M. Vogel
University Siegen, Siegen, Germany
R. Ries, E. Seiler
Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic

Funding: Authors acknowledge both the EASITrain, Marie Sklodowska-Curie Action (MSCA) Innovative Training Network (ITN), Grant Agreement no. 764879 and the ARIES collaboration, Grant Agreement no. 730871
As part of efforts to improve the performance of SRF cavities, the use of alternative structures, such as superconductor-insulator-superconductor (SIS) film coatings have been extensively investigated. Initial efforts using DC magnetron sputtering (MS) deposited NbN films showed the efficacy of this approach. The use of energetic condensation methods, such as high power impulse magnetron sputtering (HiPIMS), have already improved the performance of Nb thin films for SRF cavities and have already been used for nitride film coatings in the tool industry. In this contribution, the results from the deposition of HiPIMS NbN thin films onto oxygen free high conductivity (OFHC) Cu substrates are presented. The effects of the different deposition parameters on the deposited films were elucidated through various characterisation methods, resulting in an optimum coating procedure. This allowed for further comparison between the HiPIMS NbN films and the previously presented DC MS NbN films. The results indicate the improvements offered by HiPIMS deposition, most notably, the significant increase in the entry field, and its applicability to the deposition of SIS films on Cu.

Poster SUPFDV013 [0.923 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV013

About •

Received ※ 20 June 2021 — Revised ※ 08 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 25 October 2021

Cite •

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

SUPFDV018

CERN Based T_c Measurement Station for Thin-Film Coated Copper Samples and Results on Related Studies

niobium, cavity, SRF, pick-up

105

D. Fonnesu, J. Bremer, T. Koettig, L. Laín-Amador, C. Pereira Carlos, G.J. Rosaz, A.P.O. Vaaranta
CERN, Meyrin, Switzerland

Funding: EASITrain - European Advanced Superconductivity Innovation and Training. This MSCA ITN has received funding from the European Union’s H2020 Framework Programme under GA no. 764879.
In the framework of The Future Circular Collider (FCC) Study, the development of thin-film coated superconducting radio-frequency (SRF) cavities capable of providing higher accelerating fields (10 to 20 MV/m against 5 MV/m of LHC) represents a major challenge. In this work, we present the development of a test stand commissioned at CERN for the inductive measurement of the critical temperature (T_c) of SC thin-film deposited on copper samples for SRF applications. Based on new studies for the production of Non Evaporable Getters (NEG) coated chambers [1], we also present the first results of an alternative forming method for seamless copper cavities with niobium layer integrated in the production process.
[1] doi:10.1116/1.4999539

Poster SUPFDV018 [1.616 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV018

About •

Received ※ 21 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 01 May 2022

Cite •

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

SUPFDV020

ALD-Based NbIiN Studies for SIS R&D

cavity, plasma, vacuum, SRF

109

I. González Díaz-Palacio, R.H. Blick, R. Zierold
University of Hamburg, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Superconductor-Insulator-Superconductor multilayers improve the performance of SRF cavities providing magnetic screening of the bulk cavity and lower surface resistance. In this framework NbTiN mixtures stand as a potential material of interest. Atomic layer deposition (ALD) allows for uniform coating of complex geometries and enables tuning of the stoichiometry and precise thickness control in sub-nm range. In this talk, we report about NbTiN thin films deposited by plasma-enhanced ALD on insulating AlN buffer layer. The deposition process has been optimized by studying the superconducting electrical properties of the films. Post-deposition thermal annealing studies with varying temperatures, annealing times, and gas atmospheres have been performed to further improve the thin film quality and the superconducting properties. Our experimental studies show an increase in T_c by 87.5% after thermal annealing and a maximum T_c of 13.9 K has been achieved for NbTiN of 23 nm thickness. Future steps include lattice characterization, using XRR/XRD/EBSD/PALS, and SRF measurements to obtain Hc1 and the superconducting gap.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPFDV020

About •

Received ※ 22 June 2021 — Revised ※ 17 August 2021 — Accepted ※ 17 August 2021 — Issue date ※ 19 January 2022

Cite •

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

SUPTEV001

Magnetic Field Penetration Technique to Study High Field Shielding of Multilayered Superconductors

cavity, SRF, niobium, accelerating-gradient

112

I.H. Senevirathne, J.R. Delayen, A.V. Gurevich
ODU, Norfolk, Virginia, USA
J.R. Delayen, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399
The SIS structure which consists of alternative thin layers of superconductors and insulators on a bulk niobium has been proposed to shield niobium cavity surface from high magnetic field and hence increase the accelerating gradient. The study of the behavior of multilayer super-conductors in an external magnetic field is essential to optimize their SRF performance. In this work we report the development of a simple and efficient technique to measure penetration of magnetic field into bulk, thin film and multilayer superconductors. Experimental setup contains a small superconducting solenoid which can produce a parallel surface magnetic field up to 0.5 T and Hall probes to detect penetrated magnetic field across the superconducting sample. This system was calibrated and used to study the effect of niobium sample thickness on the field of full magnetic flux penetration. We determined the optimum thickness of the niobium substrate to fabricate the multilayer structure for the measurements in our setup. This technique was used to measure penetration fields of Nb₃Sn thin films and Nb₃Sn/Al₂O₃ multi-layers deposited on Al₂O₃ wafers.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV001

About •

Received ※ 22 June 2021 — Revised ※ 15 August 2021 — Accepted ※ 20 September 2021 — Issue date ※ 28 April 2022

Cite •

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

SUPTEV010

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

cavity, SRF, vacuum, radio-frequency

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

Cite •

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

SUPTEV016

Samples for 3rd Harmonic Magnetometry Assessment of NbTiN-Based SIS Structures

SRF, cavity, interface, FEL

164

D.R. Beverstock, J.R. Delayen, I.H. Senevirathne, J.K. Spradlin, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA
C.Z. Antoine
CEA-IRFU, Gif-sur-Yvette, France
J.R. Delayen, I.H. Senevirathne
ODU, Norfolk, Virginia, USA
D. Manos
The College of William and Mary, Williamsburg, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399.
In the quest for alternative superconducting materials to bring accelerator cavity performance beyond the bulk niobium (Nb) intrinsic limits, a promising concept uses superconductor-insulator-superconductor (SIS) thin film structures that allows magnetic flux shielding in accelerator cavities to higher fields [1]. Candidate materials for such structures are NbTiN as the superconductor and AlN as the insulator. We have demonstrated high quality NbTiN and AlN deposited by reactive DC magnetron sputtering (DCMS), both for individual layers and multilayers. Interface quality has been assessed for bilayer stacks with 250 nm NbTiN layers and AlN thicknesses from 30 nm down to1 nm. These SIS structures show continued sharp interfaces with total average roughness under 2 nm. The Hfp enhancement of the films will be examined with a 3rd harmonic magnetometry. The system is being designed and built in a continuing collaboration with CEA Saclay. It can measure 25 to 50 mm samples on a temperature controlled stage. This contribution presents an overview of the design of the 3rd harmonic magnetometer and the material properties assessment of standalone films and multilayer nanostructures.
[1] A. Gurevich, Applied Physics Letters, vol. 88, p. 012511, 2006.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPTEV016

About •

Received ※ 22 June 2021 — Accepted ※ 10 November 2021 — Issue date ※ 16 May 2022

Cite •

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

MOPCAV005

Status of SNS Proton Power Upgrade SRF Cavities Production Qualification

cavity, cryomodule, proton, neutron

265

P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, D. Forehand, N.A. Huque, A.L.A. Mitchell, P.D. Owen
JLab, Newport News, Virginia, USA
M.P. Howell, S.-H. Kim, J.D. Mammosser
ORNL, Oak Ridge, Tennessee, USA

The Proton Power Upgrade project at Oak Ridge National Lab’s Spallation Neutron Source (SNS PPU) currently being constructed will double the proton beam power from 1.4 to 2.8 MW by adding 7 additional cryomodules, each contains four six-cell high beta (\beta = 0.81) superconducting radio frequency cavities. The cavities were built by Research Instruments, Germany, with all the cavity processing done at the vendor site, including electropolishing as the final active chemistry step. All 28 cavities needed for 7 cryomodules were delivered to Jefferson Lab, ready to be tested. The cryogenic RF qualifications and helium vessel welding were done at Jefferson Lab. The performance largely exceed the requirements, and greatly exceeded the performance of the original SNS cavity production series. Here, we present the summary of RF test on production cavities to this date.
This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.

Poster MOPCAV005 [1.065 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPCAV005

About •

Received ※ 19 June 2021 — Revised ※ 10 July 2021 — Accepted ※ 12 March 2022 — Issue date ※ 06 April 2022

Cite •

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

MOPFDV010

Microstructure Changes Observed in the Near-Surface Region of SRF Nb Cavities Cutouts upon Cooling/Heating Cycles Using GI-Synchrotron XRD

cavity, SRF, niobium, lattice

339

A. Cano, D. Bafia, A. Grassellino, J. Lee, M. Martinello, A.S. Romanenko, T. Spina, Z-H. Sung
Fermilab, Batavia, Illinois, USA
E.A. Karapetrova
ANL, Lemont, Illinois, USA

We have mapped microstructural changes in the near-surface region of Nb from SRF cavity-cutouts upon thermal cycles in the range from 300 to 30 K using grazing incidence synchrotron X-Ray diffraction (GIXRD). Segregation of secondary phases was observed after the thermal cycle, and their nature has been clarified and discussed in view of previous studies on hydrides formation in SRF bulk Nb cavities. The temperature dependence of the relative population of these formed phases was obtained from GIXRD patterns profile fitting. Both, Nb bulk matrix and the new phases formed after cool-down show specific structural features as thermal contraction/expansion, structural transitions, and Nb lattice variation due to the induced strain by precipitates formation. The information derived from this structural study can explain some phenomena as the dissipation at high accelerating field (i.e. High Field Q Slope, HFQS) in the Nb SRF performance as well as new mechanisms never addressed in previous studies.
A Romanenko, F Barkov, LD Cooley, A Grassellino, Proximity breakdown of hydrides in superconducting niobium cavities, Superconductor Science and Technology, 2013

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPFDV010

About •

Received ※ 28 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 23 September 2021

Cite •

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

TUOFDV05

Dynamics of RF Dissipation Probed via High-Speed Temperature Mapping

cavity, SRF, electron, data-acquisition

349

R.D. Porter, N. Banerjee, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Recently, Cornell University has developed a new high-speed, high-resolution temperature mapping system that can resolve the time dynamics of RF dissipation, i.e., provide high-speed videos of the surface heating across the entire surface of the cavity. This new powerful tool allows to observe rapid changes in the local RF dissipation, as well as to resolve the dynamics of quenches, field emission processing, and other cavity events, giving new insights into these. This contribution presents the development of this new high-speed temperature mapping system, discusses its commissioning and extensive performance testing (e.g., demonstrating micro-Kelvin resolution), as well as show intriguing high-speed temperature mapping results from multiple Nb₃Sn cavities.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUOFDV05

About •

Received ※ 01 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 06 February 2022

Cite •

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

TUPFDV010

New Recipes to Optimize the Niobium Oxide Surface From First-Principles Calculations

niobium, electron, cavity, SRF

426

N. Sitaraman, T. Arias, Z. Baraissov, M.M. Kelley, D.A. Muller
Cornell University, Ithaca, New York, USA
M. Liepe, R.D. Porter, Z. Sun
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams
The properties of niobium oxide are of critical importance for a wide range of topics, from the behavior of nitrogen during infusion treatments, to the nucleation of Nb₃Sn, to the superconducting properties of the surface. However, the modeling of the oxide is often much simplified, ignoring the variety of niobium oxide phases and the extremely different properties of these phases in the presence of impurities and defects. We use density functional theory (DFT) to investigate how electrochemical treatments and gas infusion procedures change the properties of niobium oxide, and to investigate how these properties could be optimized for Nb₃Sn nucleation and for niobium SRF performance.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV010

About •

Received ※ 01 July 2021 — Accepted ※ 18 November 2021 — Issue date ※ 22 February 2022

Cite •

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

TUPCAV006

Nb₃Sn Films Depositions from Targets Synthesized via Liquid Tin Diffusion

target, niobium, cavity, controls

452

M. Zanierato, O. Azzolini, E. Chyhyrynets, V.A. Garcia Diaz, G. Keppel, C. Pira, F. Stivanello
INFN/LNL, Legnaro (PD), Italy

The deposition of Nb₃Sn on copper cavities is inter-esting for the higher thermal conductivity of copper compared to common Nb substrates. The better heat exchange would allow the use of cryocoolers reducing cryogenic costs and the risk of thermal quench [1]. Magnetron sputtering technology allows the deposi-tion of Nb₃Sn on substrates different than Nb, however the coating of substrates with complex geometry (such as elliptical cavities) may require targets with non-planar shape, difficult to realize with classic powder sintering techniques. In this work, the possibility of using the Liquid Tin Diffusion (LTD) technique to produce sputtering targets is explored. The LTD tech-nique is a wire fabrication technology, already devel-oped in the past at LNL for SRF applications [2], that allows the deposition of very thick and uniform coat-ing on Nb substrates even with complex geometry [3]. Improvements in LTD process, proof of concept of a single use LTD target production, and characterization of the Nb₃Sn film coated by DC magnetron sputtering with these innovative targets are reported in this work.

Poster TUPCAV006 [5.037 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPCAV006

About •

Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 23 August 2021 — Issue date ※ 02 September 2021

Cite •

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

WEPFDV007

Main Highlights of ARIES WP15 Collaboration

SRF, cavity, laser, experiment

571

O.B. Malyshev, P. Goudket, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.Z. Antoine
CEA-IRFU, Gif-sur-Yvette, France
O. Azzolini, E. Chyhyrynets, G. Keppel, C. Pira, F. Stivanello
INFN/LNL, Legnaro (PD), Italy
G. Burt, D.J. Seal, D.A. Turner
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt, B.S. Sian
Lancaster University, Lancaster, United Kingdom
O. Kugeler, D.B. Tikhonov
HZB, Berlin, Germany
S.B. Leith, A.O. Sezgin, M. Vogel
University Siegen, Siegen, Germany
A. Medvids, P. Onufrijevs
Riga Technical University, Riga, Latvia
R. Ries, E. Seiler
Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
B.S. Sian
Cockcroft Institute, Warrington, Cheshire, United Kingdom
A. Sublet, G. Vandoni, L. Vega Cid, W. Venturini Delsolaro, P. Vidal García
CERN, Meyrin, Switzerland
D.A. Turner
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: European Commission’s ARIES collaboration H2020 Research and Innovation Programme under Grant Agreement no. 730871
An international collaboration of research teams from CEA (France), CERN (Switzerland), INFN/LNL (Italy), HZB and USI (Germany), IEE (Slovakia), RTU (Latvia) and STFC/DL (UK), are working together on better understanding of how to improve the properties of superconducting thin films (ScTF) for RF cavities. The collaboration has been formed as WP15 in the H2020 ARIES project funded by EC. The systematic study of ScTF covers: Cu substrate polishing with different techniques (EP, SUBU, EP+SUBU, tumbling, laser), Nb, NbN, Nb₃Sn and SIS film deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application of all obtained knowledge on polishing, deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application to the QPR samples for testing the films at RF conditions. The preparation, deposition and characterisation of each sample involves 3-5 partners enhancing the capability of each other and resulting in a more complete analysis of each film. The talk will give an overview of the collaborative research and will be an introduction to the detailed talks given by the team members.

Poster WEPFDV007 [2.013 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPFDV007

About •

Received ※ 19 June 2021 — Accepted ※ 12 February 2022 — Issue date ※ 10 April 2022

Cite •

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

WEPFDV008

Thermal Conductivity of Electroplated Copper Onto Bulk Niobium at Cryogenic Temperatures

cavity, SRF, niobium, radio-frequency

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

Cite •

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

WEPTEV012

Characterization of Atomic-Layer-Deposited NbTiN and NbTiN/AlN Films for SIS Multilayer Structures

interface, SRF, cavity, superconductivity

662

Z. Sun, M. Liepe, T.E. Oseroff
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
X. Deng
University of Virginia, Charlottesville, Virginia, USA

SIS (superconductor-insulator-superconductor) mul-tilayer structures are proposed designs to repel early flux penetration and ease the impact of defects in SRF cavities. The demonstration of such device physics is strongly affected by the film qualities ’ material struc-ture and composition. Here, we characterized 100 nm NbTiN / 2 nm AlN / bulk Nb SIS structures and investigated the effect of the presence of the AlN layer on the NbTiN film properties. We find that the hcp-structured AlN layer results in a Nb composition gra-dient as a function of film depth, whereas the Nb con-centration remains constant in the NbTiN/Nb samples, which suggests that interface mismatch could induce significant change in NbTiN composition. The surface composition variation further leads to different oxide structures, which might impact the superconducting performance. Our observations indicate that the choice of the insulating layer in SIS structures is critical, and that interface mismatch together with internal strain could deteriorate the superconducting film.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPTEV012

About •

Received ※ 08 July 2021 — Revised ※ 06 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 02 January 2022

Cite •

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

THPTEV014

Managing Procurements in the Time of Covid-19: SNS-PPU as a Case Study

operation, status, HOM, cryomodule

863

K.M. Wilson, G. Cheng, E. Daly, N.A. Huque, T. Huratiak, M. Laney, K. Macha, D.J. Maddox, M. Marchlik, P.D. Owen, T. Peshehonoff, M. Torres, M. Wiseman
JLab, Newport News, Virginia, USA

Funding: Supported by the Dept of Energy, Office of Nuclear Physics under contract DE-AC05-06OR23177 (JSA); and by UT-B which manages Oak Ridge National Laboratory under contract DE-AC05-00OR22725.
In early 2020, COVID-19 swept across the world. The accelerator industry, like many others, was impacted by disease, delays, shortages, and new working conditions. All Thomas Jefferson National Accelerator Facility (JLab) employees were sent home in mid-March 2020, with many still working remotely now. At the time, JLab was working on the Proton Power Upgrade (PPU) to the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). Procurements had been placed and were being managed, parts were being received and inspected. This paper details the JLab procurement plan for the SNS PPU project, and the mitigations that were developed to continue to support this project smoothly under the limitations imposed by COVID-19.

Poster THPTEV014 [1.081 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-THPTEV014

About •

Received ※ 15 June 2021 — Revised ※ 30 November 2021 — Accepted ※ 21 January 2022 — Issue date ※ 01 May 2022

Cite •

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

THPTEV015

Cylindrical Magnetron Development for Nb3sn Deposition via Magnetron Sputtering

cavity, SRF, target, radio-frequency

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

Cite •

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

FROFDV06

Synthesis of Nb and Alternative Superconducting Film to Nb for SRF Cavity as Single Layer

cavity, SRF, niobium, target

893

R. Valizadeh, P. Goudket, A.N. Hannah, O.B. Malyshev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.Z. Antoine
CEA-DRF-IRFU, France
C.Z. Antoine
CEA-IRFU, Gif-sur-Yvette, France
E. Chyhyrynets, C. Pira
INFN/LNL, Legnaro (PD), Italy
P. Goudket, O.B. Malyshev, D.J. Seal, B.S. Sian, D.A. Turner
Cockcroft Institute, Warrington, Cheshire, United Kingdom
O. Kugeler, D.B. Tikhonov
HZB, Berlin, Germany
S.B. Leith, A.O. Sezgin, M. Vogel
University Siegen, Siegen, Germany
A. Medvids, P. Onufrijevs
Riga Technical University, Riga, Latvia
D.J. Seal, B.S. Sian, D.A. Turner
Lancaster University, Lancaster, United Kingdom
G.B.G. Stenning
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
A. Sublet, G. Vandoni, L. Vega Cid, W. Venturini Delsolaro, P. Vidal García
CERN, Meyrin, Switzerland

"Bulk niobium (Nb) has been the material of choice for superconducting RF (SRF) cavities but for further improvement in cavity RF performance, one may have to turn to films of Nb and to other superconducting materials deposited on copper as thermal and mechanical support. Other materials known as A15, such as Nb₃Sn or V₃Si and B1 such as NbTiN and NbN are much easier to synthesise in thin films rather than being made as bulk cavity. The potential benefits of using materials other than Nb would be a higher Tc, a potentially higher critical held Hc, leading to potentially significant cryogenics cost reduction if the cavity operation temperature is 4.2 K or higher. We report on optimising deposition parameters and effect of substrate treatment prior to deposition for successful synthesising of Nb and the alternative superconducting thin film with high superconducting properties (Tc and Hsh) on flat substrates and QPR samples in single layer. The DC and RF SC properties have been tested using PPMS and QPR measurements. This work is part of the H2020 ARIES collaboration. We further report on preparation of RF cavities employing these alternative material for future cavity production."

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2021-FROFDV06

About •

Received ※ 21 June 2021 — Accepted ※ 05 January 2022 — Issue date ※ 28 April 2022

Cite •

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