SUPFDV —  Sunday Student Poster Fundamental Development and Research   (27-Jun-21   08:00—09:30)
Paper Title Page
SUPFDV001 Update on Nitrogen Infusion Sample R&D at DESY 57
 
  • C. Bate, A. Dangwal Pandey, A. Ermakov, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, H. Weise, M. Wenskat
    DESY, Hamburg, Germany
  • B. Foster
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Many accelerator projects such as the European XFEL cw upgrade or the ILC, would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. The approach shown here is based on R\&D using small samples, with the goal of identifying all key parameters of the process and establishing a stable, reproducible recipe. To understand the underlying processes of the surface evolution that give improved cavity performance, advanced surface-analysis techniques (e.g. SEM/EDX, TEM, XPS, TOF-SIMS) are utilized and several kinds of samples are analyzed. Furthermore, parameters such as RRR and the surface critical magnetic field denoted as Hc3 have been investigated. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Results of these analyses and their implications for the R\&D on cavities are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV001  
About • Received ※ 22 June 2021 — Accepted ※ 03 January 2022 — Issue date; ※ 27 April 2022  
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SUPFDV002 Ab Initio Theory of the Impact of Grain Boundaries on the Superconducting Properties of Nb₃Sn 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 ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV002  
About • Received ※ 01 July 2021 — Accepted ※ 02 December 2021 — Issue date; ※ 09 April 2022  
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SUPFDV003 Effect of Mean Free Path on Nonlinear Losses of Trapped Vortices Driven by a RF Field Field 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 icon Poster SUPFDV003 [1.339 MB]  
DOI • reference for this paper ※ https://doi.org/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 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 icon Poster SUPFDV006 [2.229 MB]  
DOI • reference for this paper ※ https://doi.org/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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SUPFDV007 Magnetic Field Penetration of Niobium Thin Films Produced by the ARIES Collaboration 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
    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 icon Poster SUPFDV007 [1.059 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV007  
About • Received ※ 21 June 2021 — Accepted ※ 28 October 2021 — Issue date; ※ 09 April 2022  
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SUPFDV009 Thermal Annealing of Sputtered Nb₃Sn and V₃Si Thin Films for Superconducting RF Cavities 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 ※ https://doi.org/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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SUPFDV012 The Development of HiPIMS Multilayer SIS Film Coatings on Copper for SRF Applications 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 icon Poster SUPFDV012 [2.056 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV012  
About • Received ※ 20 June 2021 — Accepted ※ 21 December 2021 — Issue date; ※ 27 April 2022  
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SUPFDV013 HiPIMS NbN Thin Film Development for Use in Multilayer SIS Films 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 icon Poster SUPFDV013 [0.918 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV013  
About • Received ※ 20 June 2021 — Revised ※ 08 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 25 October 2021
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SUPFDV015 Preliminary Results from Magnetic Field Scanning System for a Single-Cell Niobium Cavity 96
 
  • I.P. Parajuli, G. Ciovati, J.R. Delayen, A.V. Gurevich
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, J.R. Delayen
    JLab, Newport News, Virginia, USA
 
  One of the building blocks of modern particle accelerators is superconducting radiofrequency (SRF) cavities. Niobium is the material of choice to build such cavities, which operate at liquid helium temperature (2 - 4 K) and have some of the highest quality factors found in Nature. There are several sources of residual losses, one of them is trapped magnetic flux, which limits the quality factor in SRF cavities. The flux trapping mechanism depends on different niobium surface preparations and cool-down conditions. Suitable diagnostic tools are not yet available to study the effects of such conditions on magnetic flux trapping. A magnetic field scanning system (MFSS) for SRF cavities using Hall probes and Fluxgate magnetometer has been designed, built, and is commissioned to measure the local magnetic field trapped in 1.3 GHz single-cell SRF cavities at 4 K. In this contribution, we will present the preliminary results from MFSS for a single cell niobium cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV015  
About • Received ※ 21 June 2021 — Revised ※ 13 August 2021 — Accepted ※ 08 November 2021 — Issue date ※ 27 April 2022
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SUPFDV016 A Low Power Test Facility for SRF Thin Film Testing with High Sample Throughput Rate 100
 
  • D.J. Seal
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • G. Burt, P. Goudket, O.B. Malyshev, B.S. Sian, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt, B.S. Sian
    Lancaster University, Lancaster, United Kingdom
  • J.A. Conlon, P. Goudket, O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  A low-power SRF test facility is being upgraded at Daresbury Laboratory as part of the superconducting thin film testing programme. The facility consists of a bulk niobium test cavity operating at 7.8 GHz, surrounded by RF chokes, and can be run with input RF powers up to 1 W. It is housed within a liquid helium free cryostat and is able to test thin film planar samples up to 100 mm in diameter with a thickness between 1 and 20 mm. The RF chokes allow the cavity to be physically and thermally isolated from the sample, thus reducing the need for complicated sample mounting, whilst minimising field leakage out of the cavity. This allows for a fast turnaround time of two to three days per sample. Initial tests using a newly designed sample holder have shown that an RF-DC compensation method can be used successfully to calculate the surface resistance of samples down to 4 K. Potential upgrades include a pick-up antenna for direct measurements of stored energy and the addition of a self-excited loop to mitigate the effects of microphonics. Details of this facility and preliminary results are described in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV016  
About • Received ※ 21 June 2021 — Accepted ※ 12 August 2021 — Issue date; ※ 18 December 2021  
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SUPFDV018 CERN Based T_{c} Measurement Station for Thin-Film Coated Copper Samples and Results on Related Studies 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 (Tc) 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 icon Poster SUPFDV018 [1.611 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV018  
About • Received ※ 21 June 2021 — Revised ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 01 May 2022
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SUPFDV020 ALD-Based NbIiN Studies for SIS R&D 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 Tc by 87.5% after thermal annealing and a maximum Tc 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 ※ https://doi.org/10.18429/JACoW-SRF2021-SUPFDV020  
About • Received ※ 22 June 2021 — Revised ※ 17 August 2021 — Accepted ※ 17 August 2021 — Issue date ※ 19 January 2022
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