Keyword: niobium
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MOPMB003 Flux Expulsion Lens: Concept and Measurements FEL, cavity, site, SRF 56
 
  • D.A. Turner
    European Organization for Nuclear Research (CERN), Geneva, Switzerland
  • A. Gallifa Terricabras, T. Koettig, A. Macpherson, G.J. Rosaz, N. Stapley
    CERN, Meyrin, Switzerland
  • I. González Díaz-Palacio
    University of Hamburg, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • M. Wenskat
    DESY, Hamburg, Germany
  
  A magnetic flux expulsion lens (MFEL) has been designed and built at CERN. This device uses closed topology conduction cooling of samples to quantify magnetic flux expulsion of superconductors, and allows for systematic measurements of the cooling dynamics and the magnetic response during the superconducting transition. Measurements for bulk Nb, cold worked Nb, sputtered Nb on Cu, and SIS multilayer structures are given. Preliminary results for both sample characterization of expulsion dynamics, and observation of an enhanced flux expulsion in SIS samples are also reported.  
poster icon Poster MOPMB003 [2.459 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB003  
About • Received ※ 27 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 14 July 2023
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MOPMB005 Muon Spin Rotation Studies of Bilayer Superconductors and Low Temperature Baked Niobium interface, experiment, cavity, polarization 62
 
  • M. Asaduzzaman, R.E. Laxdal, R.M.L. McFadden, E. Thoeng
    TRIUMF, Vancouver, Canada
  • M. Asaduzzaman, T. Junginger, R.M.L. McFadden
    UVIC, Victoria, Canada
  • E. Thoeng
    UBC & TRIUMF, Vancouver, British Columbia, Canada
  
  Funding: Financial support was provided by an Natural Sciences and Engineering Research Council of Canada (NSERC)
Muon spin rotation (muSR) results have shown that vortex penetration into Nb can be delayed up to the superheating field Hsh by a single layer of a material with larger London penetration depth. For low temperature baked (LTB) Nb an increase in the vortex penetration field Hvp has also been observed. While clearly exceeding the lower critical field Hc1, Hvp was found to remain significantly below Hsh for LTB niobium (Superconductor Science and Technology 30 (12), 125012). Further, magnetometry experiments suggested that there is no interface barrier in LTB Nb and that the apparent Hvp increase as observed by muSR was due to surface pinning (Scientific Reports 12 (1), 5522). By varying the implantation depth of ~4.1 MeV muons using moderating foils, new muSR measurements confirm that the apparent Hvp increase in LTB Nb is indeed due to surface pinning, while for a Nb₃Sn/Nb bilayer we find an interface barrier for flux penetration. These results confirm the potential of using superconducting bilayers to achieve a flux free Meissner state up to the superheating field of the substrate. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB005  
About • Received ※ 17 June 2023 — Revised ※ 21 June 2023 — Accepted ※ 25 June 2023 — Issue date ※ 21 July 2023
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MOPMB006 SIMS Characterization of Nitrogen Doping of LCLS-II-HE Production Cavities cavity, SRF, vacuum, controls 67
 
  • C.E. Reece, M.J. Kelley, E.M. Lechner
    JLab, Newport News, Virginia, USA
  • J.W. Angle
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Office of High Energy Physics grant DE-SC-0014475.
The thermal diffusion of nitrogen into the surface of niobium has been shown to yield superior low-loss SRF performance. An effective solution was identified and promptly employed in the production of cryomodules for LCLS-II. With added experience and R&D, a modified process was chosen for use in the upgrade for LCLS-II-HE. Largely motivated by this circumstance, supporting research has significantly refined the technique for making calibrated secondary ion mass spectrometry (SIMS) measurements of the N concentration depth profiles produced by production processes. Standardized reference samples were included with four HE production cavities in their N-doping furnace runs. We report the calibrated dynamic SIMS depth profiles of N, C, and O for these samples, together with the cryogenic acceptance test performance of the associated cavities. Interpretation and comparison with similar samples acquired in other furnaces highlights the importance of intentional process quality control of furnace conditions. 		 
poster icon Poster MOPMB006 [1.380 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB006  
About • Received ※ 16 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 18 July 2023
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MOPMB012 Investigation, Using Nb Foils to Characterise the Optimal Dimensions of Samples Measured by the Magnetic Field Penetration Facility cavity, SRF, experiment, ECR 88
 
  • L.G.P. Smith, D.A. Turner
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • G. Burt, O.B. Malyshev, D.A. Turner
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
  • T. Junginger
    TRIUMF, Vancouver, Canada
  • T. Junginger
    UVIC, Victoria, Canada
  • O.B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  SRF cavities made of bulk Nb are reaching their theoretical limits in the maximum accelerating gradient, Eacc, where Eacc is limited by the maximum magnetic field, Bmax, that can be applied on the surface of the accelerating cavity wall. To increase Eacc, Bmax, which can be applied to the surface, must also be increased. The A15 materials or multilayer structures are the potential solution to increase Bmax. Since coating and RF testing of full size RF cavities is both expensive and time consuming, one need to evaluate new ideas in superconducting thin films quickly and at low cost. A magnetic field penetration experiment has been designed and built at Daresbury Laboratory to test small superconducting samples. The facility produces a parallel DC magnetic field, which applied from one side of the sample to the other similar to that in an RF cavity. The facility applies an increasing magnetic field at a set temperature to determine the field of full flux penetration which can give an insight into the quality and structure of the superconducting structure. The facility has been characterised using both type I and II superconductors and is now producing results from novel materials.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB012  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 17 July 2023
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MOPMB013 Influence of the Coating Parameters on the Tc of Nb₃Sn Thin Films on Copper Deposited via DC Magnetron Sputtering site, cavity, SRF, cathode 92
 
  • D. Fonnesu, O. Azzolini, R. Caforio, E. Chyhyrynets, D. Ford, V.A. Garcia, G. Keppel, C. Pira, A. Salmaso, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  • G. Marconato
    Università degli Studi di Padova, Padova, Italy
  
  Funding: The I.FAST project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
The I.FAST collaboration aims at pushing the performance of particle accelerators by developing sustainable innovative technologies. Among its goals, the development of thin film-coated copper elliptical accelerating cavities covers both the optimization of the manufacturing of seamless substrates and the development of functional coatings able to conform to the 3D cavity geometry while delivering the needed performance. For the latter, the optimization of the deposition recipe is central to a successful outcome. The work presented here focuses on the deposition of Nb₃Sn films on flat, small copper samples. The films are deposited via DCMS from a planar stoichiometric Nb₃Sn commercial target. The results of the film characterization are presented here. The observed dependencies between the film properties and, in particular, Tc(90%-10%) = (17.9±0.1)K is reported for Nb₃Sn on sapphire and Tc(90%-10%) = (16.9±0.2)K for Nb₃Sn on copper with a 30 micron thick niobium buffer layer. 		 
poster icon Poster MOPMB013 [1.749 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB013  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 02 July 2023
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MOPMB016 Successful Al₂O₃ Coating of Superconducting Niobium Cavities by Thermal ALD cavity, SRF, HOM, experiment 104
 
  • G.K. Deyu, W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • R.H. Blick, I. González Díaz-Palacio, R. Zierold
    University of Hamburg, Hamburg, Germany
  
  Funding: This work is supported by the BMBF under the research Grant 05K19GUB.
Al₂O₃ is one of the potential insulator materials in the superconductor-insulator-superconductor (SIS) multilayer coatings of superconducting radio-frequency (SRF) cavities for pushing their performance limits. We report on the successful coating of two 1.3 GHz Tesla-shaped SRF cavities with 18 nm and 36 nm layers of Al₂O₃ deposited by thermal atomic layer deposition (ALD). The coating recipe was developed by thermal atomic layer deposition (ALD). The coating recipe was optimized with respect to different the applied process parameters such as exposure and purge times, substrate temperature and flow rates. After a proof-of-principle Al₂O₃ coating of a cavity, second the cavity maintained its maximum achievable accelerating field of more than 40 MV/m and no deterioration was observed [1]. On the contrary, an improvement of the surface resistance above 10 MV/m has been observed, which is now further under investigation.
[1].Wenskat, Marc, et al. "Successful Al₂O₃ coating of superconducting niobium cavities with thermal ALD." Superconductor Science and Technology 36.1 (2022): 015010. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB016  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
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MOPMB017 Development of a Thermal Conductance Instrument for Niobium at Cryogenic Temperatures cavity, ECR, cryogenics, operation 109
 
  • C. Saribal, C. Martens
    University of Hamburg, Hamburg, Germany
  • W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  Funding: University of Hamburg
Particle accelerators form an important tool in a variety of research fields. In an effort to reduce operation costs while maintaining high energies, their accelerating structures are steadily improved towards higher accelerating fields and lower RF losses. Stable operation of such a cavity generally requires Joule-heating, generated in its walls, to be conducted to an outer helium bath. Therefore, it is of interest to experimentally evaluate how present and future cavity treatments affect thermal characteristics. We present an instrument for measuring the thermal performance of SRF cavity materials at cryogenic temperatures. Pairs of niobium disks are placed inside of a liquid helium bath and a temperature gradient is generated across them to obtain total thermal resistance for temperatures below 2 Kelvin. To get an idea of the instruments sensitivity and how standard cavity treatments influence thermal resistance, samples are tested post fabrication, polishing and 800 °C baking. The first tests show the commissioning of our newly set up system and if it is feasible to observe relevant changes and evaluate new and promising cavity treatments such as SIS structures. 		 
poster icon Poster MOPMB017 [3.217 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB017  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023
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MOPMB020 A Comprehensive Picture of Hydride Formation and Dissipation cavity, site, superconductivity, SRF 119
 
  • N. Sitaraman, T. Arias
    Cornell University, Ithaca, New York, USA
  • A.V. Harbick, M.K. Transtrum
    Brigham Young University, Provo, USA
  • M. Liepe
    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 PHY-1549132, the Center for Bright Beams.
Research linking surface hydrides to Q-disease, and the subsequent development of methods to eliminate surface hydrides, is one of the great successes of SRF cavity R\&D. We use time-dependent Ginzburg-Landau to extend the theory of hydride dissipation to sub-surface hydrides. Just as surface hydrides cause Q-disease behavior, we show that sub-surface hydrides cause high-field Q-slope (HFQS) behavior. We find that the abrupt onset of HFQS is due to a transition from a vortex-free state to a vortex-penetration state. We show that controlling hydride size and depth through impurity doping can eliminate HFQS. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB020  
About • Received ※ 30 June 2023 — Revised ※ 18 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023
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MOPMB021 Correlating Lambda Shift Measurements with RF Performance in Mid-T Heat Treated Cavities cavity, SRF, radio-frequency, ECR 124
 
  • R. Ghanbari, G.K. Deyu, W. Hillert, R. Monroy-Villa, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • C. Bate, D. Reschke, L. Steder, J.C. Wolff
    DESY, Hamburg, Germany
  
  Funding: This work was supported by the BMBF under the research grants 05K19GUB and 05H2021.
Heat treatment procedures have been identified as cru-cial for the performance of niobium SRF cavities, which are the key technology of modern accelerators. The so called "mid-T heat treatments", invert the dependence of losses on the applied accelerating field (anti-Q slope) and significantly reduce the absolute value of losses. The mechanism behind these improvements is still under investigation, and further research is needed to fully understand the principle processes involved. Anomalies in the frequency shift near the transition temperature (Tc), known as "dip" can provide insight into fundamental material properties and allow us to study the relation-ship of frequency response with surface treatments. Therefore, we have measured the frequency versus temperature of multiple mid-T heat treated cavities with different recipes and studied the correlation of SRF properties with frequency shift features. The maximum quality factor correlates with two such shift features, namely the dip magnitude per temperature width and the total frequency shift. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB021  
About • Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 15 August 2023
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MOPMB022 Recent mid-T Single-Cell Treatments R&D at DESY cavity, SRF, vacuum, controls 129
 
  • C. Bate, D. Reschke, J. Schaffran, L. Steder, L. Trelle, H. Weise
    DESY, Hamburg, Germany
  
  The challenge of improving the performance of SRF cavities is being faced worldwide. One approach is to modify the superconducting surface properties through certain baking procedures. Recently a niobium retort furnace placed directly under an ISO4 clean room has been refurbished at DESY. Thanks to an inter-vacuum chamber and cryopumps, with high purity values in the mass spectrum it is working in the UHV range of 2·10-8 mbar. The medium temperature (mid-T) heat treatments around 300°C are promising and successfully deliver reproducible very high Q₀ values of 2-5·1010 at medium field strengths of 16 MV/m. Since the first DESY and ZRI mid-T campaign yielded promising results, further results of 1.3 GHz single-cell cavities are presented here after several modified treatments of the mid-T recipe. In addition, samples were added to each treatment, the RRR value change was examined, and surface analyses were subsequently performed. The main focus of the sample study is the precise role of the changes in the concentration of impurities on the surface. In particular, the change in oxygen content due to diffusion processes is suspected to be the cause of enhancing the performance.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB022  
About • Received ※ 18 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023
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MOPMB024 Flux Expulsion Studies of Niobium Material of 650 MHz Cavities for PIP-II cavity, simulation, factory, radio-frequency 141
 
  • K.E. McGee
    FRIB, East Lansing, Michigan, USA
  • F. Furuta, M. Martinello, O.S. Melnychuk, A.V. Netepenko, G. Wu, Y. Xie
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Two different vendors supplied the niobium sheet material for PIP-II 5-cell 650 MHz cavities, which was characterized by multiple different ASTM sizes. Cavities subsequently fabricated from these sheets were heat-treated at various temperatures, then the cavities’ flux-expulsion performance was measured. Where the initial measurements of vendor O materials showed that nearly all flux remained trapped despite a high thermal gradient, 900C heat treatment subsequently improved the flux expulsion to an acceptable rate. Understanding and characterizing vendor O materials in this way is key for upcoming and future projects planning to employ niobium sheet from this supplier. 		 
poster icon Poster MOPMB024 [4.064 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB024  
About • Received ※ 26 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023
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MOPMB027 Successful Superheating Field Formulas from an Intuitive Model cavity, experiment, SRF, superconductivity 151
 
  • K. Saito, T. Konomi
    FRIB, East Lansing, Michigan, USA
  
  Funding: Work supported by the U.S. Department of Energy Office of Science DE-S0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511
To date, many theoretical formulas for superheating field on SRF cavity are already proposed based rather complicated calculations. This paper proposes the formulas by a very intuitive simple model: energy balance between RF magnetic energy and superconducting condensed one, and a condition of vanishing the mirror vortex line image. The penetration of a single vortex determines the superheating field for a type II superconductor. On the other hand, for type I superconductors, the surface flux penetration determines it. The formula fits very well quantitatively the results of niobium cavity and Nb₃Sn one. In addition, it gives a nice guideline for new material beyond niobium.
male, senior 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB027  
About • Received ※ 23 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 15 July 2023
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MOPMB030 Medium Temperature Furnace Baking of Low-beta 650 MHz Five-cell Cavities cavity, radio-frequency, SRF, multipactoring 158
 
  • G. Wu, S.K. Chandrasekaran, V. Chouhan, G.V. Eremeev, F. Furuta, K.E. McGee, A.A. Murthy, A.V. Netepenko, J.P. Ozelis, H. Park, S. Posen
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Medium Temperature baking of low beta 650 MHz cavities was conducted in a UHV furnace. A systematic study of cavity surface resistance components, residual and BCS, was conducted, including analyzing surface resistance due to trapped magnetic flux. Cavities showed an average 4.5 nano-ohm surface resistance at 17 MV/m under 2 K, which meets PIP-II specifications with a 40% margin. The results provided helpful information for the PIP-II project to optimize the cavity processing recipe for cryomodule application. The results were compared to the 1.3 GHz cavity that received a similar furnace baking. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB030  
About • Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
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MOPMB032 The Collaborative Effects of Intrinsic and Extrinsic Impurities in Low RRR SRF Cavities cavity, SRF, radio-frequency, accelerating-gradient 162
 
  • K. Howard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The SRF community has shown that introducing certain impurities into high-purity niobium can improve quality factors and accelerating gradients. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium coupons with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of impurity-based improvements can be better understood and improved upon. The combination of RF testing and material analysis reveals a microscopic picture of why low RRR cavities experience low BCS resistance behavior more prominently than their high RRR counterparts. We performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of oxygen and nitrogen to the RF layer further improves performance through changes in the mean free path and impurity profile. The results of this study have the potential to unlock a new understanding on SRF materials and enable the next generation of high Q/high gradient surface treatments. 		 
poster icon Poster MOPMB032 [1.444 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB032  
About • Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 23 July 2023
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MOPMB036 Magnetic Field Mapping of a Large-Grain 1.3 GHz Single-Cell Cavity cavity, radio-frequency, SRF, cryogenics 172
 
  • I.P. Parajuli, J.R. Delayen, A.V. Gurevich
    ODU, Norfolk, Virginia, USA
  • G. Ciovati
    JLab, Newport News, Virginia, USA
  
  Funding: This work was supported by the National Science Foundation under Grant No. PHY 100614-010. G.C. is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
A new magnetic field mapping system for 1.3 GHz single-cell cavities was developed in order to reveal the impact of ambient magnetic field and temperature gradients during cool-down on the flux trapping phenomenon. Measurements were done at 2 K for different cool-down conditions of a large-grain cavity before and after 120 °C bake. The fraction of applied magnetic field trapped in the cavity walls was ~ 50% after slow cool-down and ~20% after fast cool-down. The results showed a weak correlation between between trapped flux locations and hot-spots causing the high-field Q-slope. The results also showed an increase of the trapped flux at the quench location, after quenching, and a local redistribution of trapped flux with increasing RF field. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB036  
About • Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 05 July 2023
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MOPMB037 Exploration of Parameters that Affect High Field Q-Slope cavity, accelerating-gradient, SRF, radio-frequency 178
 
  • K. Howard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The onset of high field Q-slope (HFQS) around 25 MV/m prevents cavities in electropolished (EP) condition from reaching high quality factors at high gradients due to the precipitation of niobium hydrides during cooldown. These hydrides are non-superconducting at 2 K, and contribute to losses such as Q disease and HFQS. We are interested in exploring the parameters that affect the behavior of HFQS. We study a high RRR cavity that received an 800 C by 3 hour bake and EP treatment to observe HFQS. First, we explore the effect of trapped magnetic flux. The cavity is tested after cooling slowly through Tc while applying various levels of ambient field. We observe the onset of the HFQS and correlate this behavior with the amount of trapped flux. Next, we investigate the effect of the size/concentration of hydrides. The cavity is tested after holding the temperature at 100 K for 12 hours during the cooldown to promote the growth of hydrides. We can correlate the behavior of the HFQS with the increased hydride concentration. Our results will help further the understanding of the mechanism of HFQS. 		 
poster icon Poster MOPMB037 [1.648 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB037  
About • Received ※ 12 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 19 August 2023
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MOPMB040 Comparing the Effectiveness of Low Temperature Bake in EP and BCP Cavities cavity, SRF, radio-frequency, factory 187
 
  • H. Hu, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Electropolishing (EP) and buffered chemical polishing (BCP) are conventional surface preparation techniques for superconducting radiofrequency (SRF) cavities. Both EP and BCP treated SRF cavities display high field Q-slope (HFQS) which degrades performance at high gradients. While high gradient performance in EP cavities can be improved by introducing oxygen via a low temperature bake (LTB) of 120°C by 48 hours, LTB does not consistently remove HFQS in BCP cavities. There is no consensus as to why LTB is not effective on BCP prepared cavities. We examine quench in EP, BCP, EP+LTB, and BCP+LTB treated 1.3 GHz single-cell Nb cavities by studying the heating behavior with field using a temperature mapping system. Cavity performance is correlated to characterizations of surface impurity profile obtained via time of flight secondary ion mass spectrometry studies. We observe a difference in near surface hydrogen concentration following BCP compared to EP that may suggest that the causes of quench in EP and BCP cavities are different. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB040  
About • Received ※ 14 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB041 Microstructure Development in a Cold Worked SRF Niobium Sheet After Heat Treatments cavity, ECR, SRF, radio-frequency 191
 
  • S. Balachandran, P. Dhakal, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  • S. Chetri, P.J. Lee
    NHMFL, Tallahassee, Florida, USA
  • Z.L. Thune
    MSU, East Lansing, USA
  
  Funding: Jefferson Science Associates, LLC under U.S. DOE Grant DEAC05-06OR23177, U.S. DOE, Office of HEP under Grant DE-SC0009960, and NHMFL through NSF Grant DMR-1644779 and the State of Florida.
Bulk Nb for TESLA shaped SRF cavities is a mature technology. Significant advances are in order to push Q0’s to 1010-11(T= 2K), and involve modifications to the sub-surface Nb layers by impurity doping. In order to achieve the lowest surface resistance any trapped flux needs to be expelled for cavities to reach high Q0’s. There is clear evidence that cavities fabricated from polycrystalline sheets meeting current specifications require higher temperatures beyond 800 °C leads to better flux expulsion, and hence improves Q0. Recently, cavities fabricated with a non-traditional Nb sheet with initial cold work due to cold rolling expelled flux better after 800 °C/3h heat treatment than cavities fabricated using fine-grain poly-crystalline Nb sheets. Here, we analyze the microstructure development in Nb from the vendor supplied cold work non- annealed sheet that was fabricated into an SRF cavity as a function of heat treatment building upon the methodology development to analyze microstructure being developed by the FSU-MSU-UT, Austin-JLAB collaboration. The results indicate correlation between full recrystallization and better flux expulsion. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB041  
About • Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB042 Evaluation of Flux Expulsion and Flux Trapping Sensitivity of SRF Cavities Fabricated from Cold Work Nb Sheet with Successive Heat Treatment cavity, SRF, ECR, radio-frequency 197
 
  • B.D. Khanal
    ODU, Norfolk, Virginia, USA
  • P. Dhakal
    JLab, Newport News, Virginia, USA
  
  Funding: The work is partially supported by DOE HEP under Awards No. DE-SC 0009960. This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The main source of RF losses leading to lower quality factor of superconducting radio-frequency cavities is due to the residual magnetic flux trapped during cool-down. The loss due to flux trapping is more pronounced for cavities subjected to impurities doping. The flux trapping and its sensitivity to rf losses are related to several intrinsic and extrinsic phenomena. To elucidate the effect of re-crystallization by high temperature heat treatment on the flux trapping sensitivity, we have fabricated two 1.3 GHz single cell cavities from cold-worked Nb sheets and compared with cavities made from standard fine-grain Nb. Flux expulsion ratio and flux trapping sensitivity were measured after successive high temperature heat treatments. The cavity made from cold worked Nb showed better flux expulsion after 800 C/3h heat treatment and similar behavior when heat treated with additional 900 C/3h and 1000 C/3h. In this contribution, we present the summary of flux expulsion, trapping sensitivity, and RF results. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB042  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 25 June 2023 — Issue date ※ 04 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB043 Characterization of Dissipative Regions of an N-Doped SRF Cavity cavity, radio-frequency, electron, experiment 202
 
  • E.M. Lechner, G. Ciovati
    JLab, Newport News, Virginia, USA
  • G. Ciovati, A.V. Gurevich, J. Makita
    ODU, Norfolk, Virginia, USA
  • M. Iavarone, E.M. Lechner, B.D. Oli
    Temple University, Philadelphia, USA
  
  Funding: DE-AC05-06OR23177 NSF Award No. 1734075 W911NF-16-2-0189
We report scanning tunneling microscopy measurements on N-doped cavity hot and cold spot cutouts. Analysis of the electron tunneling spectra using a proximity effect theory shows that hot spots have a reduced superconducting gap and a wider distribution of the contact resistance. Alone, these degraded superconducting properties account for a much weaker excess dissipation as compared with the vortex contribution. Based on the correlation between the quasiparticle density of states and temperature mapping, we suggest that degraded superconducting properties may facilitate vortex nucleation or settling of trapped flux during cooling the cavity through the critical temperature. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB043  
About • Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB044 Topographic Evolution of Nitrogen Doped Nb Subjected to Electropolishing SRF, cavity, vacuum, ECR 207
 
  • E.M. Lechner, C.G. Baxley, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • J.W. Angle, M.J. Kelley
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  
  Funding: DE-AC05-06OR23177 DE-SC-0014475
Surface quality is paramount in facilitating high perfor-mance SRF cavity operation. Here, we investigate the topographic evolution of samples subjected to N-doping and 600 °C vacuum anneal. We show that in N-doped Nb, niobium nitrides may grow continuously along grain boundaries. Upon electropolishing high slope angle grooves are revealed which sets up a condition that may facilitate a supression of the superheating field. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB044  
About • Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 17 July 2023
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MOPMB045 Quench Detection in a Superconducting Radio Frequency Cavity with Combined Temperature and Magnetic Field Mapping cavity, radio-frequency, SRF, ECR 211
 
  • B.D. Khanal, G. Ciovati
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, P. Dhakal
    JLab, Newport News, Virginia, USA
  
  Funding: This is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Local dissipation of rf power in SRF cavities create so called ’hot-spots’, primary precursors of cavity quench driven by either thermal or magnetic instability. These hot spots are may be detected by a temperature mapping system, and a large increase in temperature on the outer surface is detected during cavity quench events. Here, we have used combined magnetic and temperature mapping systems using anisotropic magneto-resistance sensors and carbon resisters to locate the hot spots and areas with high trapped flux on a 3 GHz single-cell Nb cavity during the rf tests at 2 K. The effect of global and localized flux trapping on the rf performance will be presented. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB045  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 12 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB047 Commissioning of Dedicated Furnace for Nb₃Sn Coatings of 2.6 GHz Single Cell Cavities cavity, SRF, MMI, factory 216
 
  • P.A. Kulyavtsev, G.V. Eremeev, S. Posen, B. Tennis
    Fermilab, Batavia, Illinois, USA
  • J. Zasadzinski
    IIT, Chicago, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
We present the results of commissioning a dedicated furnace for Nb₃Sn coatings of 2.6GHz single cell cavities. Nb₃Sn is a desired coating due to its high critical temperature and smaller surface resistance compared to bulk Nb. Usage of Nb₃Sn coated cavities will greatly reduce operating costs due to its higher operating temperature providing decreased cooling costs. Tin is deposited in the bulk Nb cavity by use of a tin chloride nucleation agent and tin vapor diffusion. Analysis of the resultant coating was performed using SEM/EDS to verify successful formation of desired Nb:Sn phase. Witness samples located in line of sight of the source were analyzed in order to understand the coating efficacy. The cavity’s performance was assessed in the Vertical Test Stand (VTS) at Fermilab. 		 
poster icon Poster MOPMB047 [4.858 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB047  
About • Received ※ 26 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 08 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB050 Thermal Feedback in Coaxial SRF Cavities cavity, feedback, SRF, ECR 224
 
  • M.W. McMullin, P. Kolb, R.E. Laxdal, Z.Y. Yao
    TRIUMF, Vancouver, Canada
  • T. Junginger
    UVIC, Victoria, Canada
  
  Funding: Natural Sciences and Engineering Research Council of Canada
The phenomenon of Q-slope in SRF cavities is caused by a combination of thermal feedback and field-dependent surface resistance. There is currently no commonly accepted model of field-dependent surface resistance, and studies of Q-slope generally treat thermal feedback as a correction to whichever surface resistance model is being used. In the present study, we treat thermal feedback as a distinct physical effect whose effect on Q-slope is calculated using a novel finite-element code. We performed direct measurements of liquid helium pool boiling from niobium surfaces to obtain input parameters for the finite-element code. This code was used to analyze data from TRIUMF’s coaxial test cavity program, which has provided a rich dataset of Q-curves at temperatures between 1.7 K and 4.4 K at five different frequencies. Preliminary results show that thermal feedback makes only a small contribution to Q-slope at temperatures near 4.2 K, but has stronger effects as the bath temperature is lowered. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB050  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB053 Theoretical Study of Thin Noble-Metal Films on the Niobium Surface interface, lattice, electron, experiment 230
 
  • C.A. Méndez, T. Arias, M. Liepe, N. Sitaraman
    Cornell University, Ithaca, New York, USA
  
  Funding: The Center for Bright Beams, Supported by National Science Foundation award No. PHY-1549132
Recent experiments suggest that noble-metal deposition on niobium metal surfaces can remove the surface oxide and ultimately improve superconducting radio-frequency (SRF) cavities performance. In this preliminary study, we use density-functional theory to investigate the potential for noble-metal passivation of realistic, polycrystalline niobium surfaces for SRF. Specifically, we investigate the stability of gold and palladium monolayers on niobium surfaces with different crystal orientations and evaluate the impact of these impurities on superconducting properties. In particular, our results suggest that gold can grow in thin layers on the niobium surface, whereas palladium rather tends to dissolve into the niobium cavity. These results will help inform ongoing experimental efforts to passivate niobium surfaces of SRF cavities. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB053  
About • Received ※ 22 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023
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MOPMB062 Optimisation of Niobium Thin Film Deposition Parameters for SRF Cavities cavity, SRF, site, target 253
 
  • D.J. Seal, O.B. Malyshev, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • J.A. Conlon, O.B. Malyshev, K.T. Morrow, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  In order to accelerate the progression of thin film (TF) development for future SRF cavities, it is desirable to optimise material properties on small flat samples. Most importantly, this requires the ability to measure their superconducting properties. At Daresbury Laboratory, it has been possible for many years to characterise these films under DC conditions; however, it is not yet fully understood whether this correlates with RF measurements. Recently, a high-throughput RF facility was commissioned that uses a novel 7.8 GHz choke cavity. The facility is able to evaluate the RF performance of planar-coated TF samples at low peak magnetic fields with a high throughput rate of 2-3 samples per week. Using this facility, an optimisation study of the deposition parameters of TF Nb samples deposited by HiPIMS has begun. The ultimate aim is to optimise TF Nb as a base layer for multilayer studies and replicate planar magnetron depositions on split 6 GHz cavities. The initial focus of this study was to investigate the effect of substrate temperature during deposition. A review of the RF facility used and results of this study will be presented.  
poster icon Poster MOPMB062 [2.395 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB062  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 24 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB076 Surface Characterization Studies of Gold-Plated Niobium cavity, controls, site, radio-frequency 290
 
  • S.G. Seddon-Stettler, M. Liepe, T.E. Oseroff, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • N. Sitaraman
    Cornell University, Ithaca, New York, USA
  
  Funding: The National Science Foundation, Grant No. PHY-1549132
The native niobium oxide layer present on niobium has been shown to affect the performace of superconducting RF cavities. Extremely thin layers of gold on the surface of niobium have the potential to suppress surface oxidation and improve cavity performance. However, depositing uniform layers of gold at the desired thickness (sub-nm) is difficult, and different deposition methods may have different effects on the gold surface, on the niobium surface, and on the interface between the two. In particular, the question of whether gold deposition actually passivates the niobium oxide is extremely relevant for assessing the potential of gold deposition to improve RF performance. This work builds on previous research studying the RF performance of gold/niobium bilayers with different gold layer thicknesses. We here consider alternative methods to characterize the composition and chemical properties of gold/niobium bilayers to supplement the previous RF study. 		 
poster icon Poster MOPMB076 [1.536 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB076  
About • Received ※ 25 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
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MOPMB083 Investigation of the Multilayer Shielding Effect through NbTiN-AlN Coated Bulk Niobium site, cavity, SRF, shielding 311
 
  • I.H. Senevirathne, J.R. Delayen, A.V. Gurevich
    ODU, Norfolk, Virginia, USA
  • D.R. Beverstock, J.R. Delayen, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • D.R. Beverstock
    The College of William and Mary, Williamsburg, Virginia, USA
  
  We report measurements of the dc field onset Bp of magnetic flux penetration through NbTiN-AlN coating on bulk niobium using the Hall probe experimental setup. The measurements of Bp reveal the multilayer shielding effect on bulk niobium under high magnetic fields at cryogenic temperatures. We observed a significant enhancement in Bp for the NbTiN-AlN coated Nb samples as compared to bare Nb samples. The observed dependence of Bp on the coating thickness is consistent with theoretical predictions.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB083  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 12 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMB093 Optimizing Growth of Niobium-3 Tin Through Pre-nucleation Chemical Treatments site, cavity, SRF, controls 337
 
  • S.G. Arnold, G. Gaitan, M. Liepe, L. Shpani, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, N. Sitaraman
    Cornell University, Ithaca, New York, USA
  
  Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
Nb₃Sn is a promising alternative material for SRF cavities that is close to reaching practical applications. To date, one of the most effective growth methods for this material is vapor diffusion, yet further improvement is needed for Nb₃Sn to reach its full potential. The major issues faced by vapor diffusion are tin depleted regions and surface roughness, both of which lead to impaired performance. Literature has shown that the niobium surface oxide plays an important role in the binding of tin to niobium. In this study, we performed various chemical treatments on niobium samples pre-nucleation to enhance tin nucleation. We quantify the effect that these various treatments had through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). These methods reveal information on tin nucleation density and uniformity, and a thin tin film present on most samples, even in the absence of nucleation sites. We present our findings from these surface characterization methods and introduce a framework for quantitatively comparing the samples. We plan to apply the most effective treatment to a cavity and conduct an RF test soon. 		 
poster icon Poster MOPMB093 [1.118 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB093  
About • Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 July 2023
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TUIBA01 A Three-Fluid Model of Dissipation at Surfaces in Superconducting Radiofrequency Cavities scattering, cavity, electron, SRF 361
 
  • M.M. Kelley, T. Arias, S. Deyo, D. Liarte, J.P. Sethna, N. Sitaraman
    Cornell University, Ithaca, New York, USA
  • M. Liepe, T.E. Oseroff
    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 PHY-1549132, the Center for Bright Beams.
Experiments on superconducting cavities have found that under large RF fields the quality factor can improve with increasing field amplitude, a so-called anti-Q slope. We numerically solve the Bogoliubov-de Gennes equations at a superconducting surface in a parallel magnetic field, finding at large fields there are surface quasiparticle states with energies below the bulk superconducting gap that emerge and disappear as the field cycles. Modifying the standard two-fluid model, we introduce a ‘‘three’’-fluid model where we partition the normal fluid to consider continuum and surface quasiparticle states separately. We compute dissipation in a semi-classical theory of conductivity, where we provide physical estimates of elastic scattering times of Bogoliubov quasiparticles with point-like impurities having potential strengths informed from complementary ab initio calculations of impurities in bulk niobium. We show, in this simple yet effective framework, how the relative scattering rates of surface and continuum quasiparticle states can play a role in producing an anti-Q slope while demonstrating how this model naturally includes a mechanism for turning the anti-Q slope on and off.
S. Deyo, M. Kelley et al. Phys. Rev. B 106, 104502 (2022) 		 
slides icon Slides TUIBA01 [2.019 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUIBA01  
About • Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 08 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUCBA01 Measurements of the Amplitude-Dependent Microwave Surface Resistance of a Proximity-Coupled Au/Nb Bilayer cavity, factory, SRF, extraction 369
 
  • T.E. Oseroff, M. Liepe, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  A sample host cavity is used to measure the surface resistance of a niobium substrate with a gold film deposited in place of its surface oxide. This talk will report about this measurement result. The film thickness of the gold layer was increased from 0.1 nm to 2.0 nm in five steps to study the impact of the normal layer thickness. The 0.1 nm film was found to reduce the surface resistance below its value with the surface oxide present and to enhance the quench field. The magnitude of the surface resistance increased substantially with gold film thickness. The surface resistance field-dependence appeared to be independent from the normal layer thickness. The observations reported in this work have profound implications for both low-field and high-field S.C. microwave devices. By controlling or eliminating the niobium oxide using a gold layer to passivate the niobium surface, it may be possible to improve the performance of SRF cavities used for particle acceleration. This method to reduce surface oxidation while maintaining low surface resistance could also be relevant for minimizing dissipation due to two-level systems observed in low-field low-temperature devices.  
slides icon Slides TUCBA01 [2.292 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCBA01  
About • Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 26 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUIXA04 First Results from beta-SRF- Testing SRF Samples at High Parallel Field SRF, polarization, experiment, ISAC 374
 
  • E. Thoeng, R. Kiefl, W.A. MacFarlane, J.O. Ticknor
    UBC & TRIUMF, Vancouver, British Columbia, Canada
  • M. Asaduzzaman, S.R. Dunsiger, D. Fujimoto, T. Junginger, V.L. Karner, P. Kolb, R.E. Laxdal, R. Li, R.M.L. McFadden, G. Morris, M. Stachura
    TRIUMF, Vancouver, Canada
  • T. Junginger, R.M.L. McFadden
    UVIC, Victoria, Canada
  
  The new ¿-SRF facility at TRIUMF has recently been commissioned. A new 1 m extension has been added to an existing ¿-NMR beamline with a large Helmholtz coil to produce fields up to 200 mT parallel to sample surfaces. The ¿-NMR technique allows depth dependent characterization of the local magnetic field in the first 100 nm of the sample surface making the probe ideal for studying Meissner screen- ing in heat treated Niobium or layered SRF materials. First measurements of Meissner screening at fields up to 200 mT have been analyzed. The results show clear differences in the Meissner screening of baseline treatments compared to mid-T baked (O-doped) Niobium.  
slides icon Slides TUIXA04 [1.644 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUIXA04  
About • Received ※ 24 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 06 July 2023 — Issue date ※ 09 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUCXA01 Study of the Dynamics of Flux Trapping in Different SRF Materials experiment, cavity, ECR, controls 380
 
  • F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  • T. Kubo
    KEK, Ibaraki, Japan
  
  A dedicated experimental setup to measure magnetic flux dynamics and trapped flux in samples is used to precisely map out how trapped flux is influenced by different parameters. The setup allows for rapid thermal cycling of the sample so that effects of cooldown parameters can be investigated in detail. We show how temperature gradient, cooldown rate, and the magnitude of external field influence trapped flux in large grain, fine grain and coated niobium samples. The detailed measurements show unexpected results, namely that too fast cooldowns increase trapped flux, large grain material traps flux only when the external field is larger than a temperature gradient dependent threshold field, and the measured dependence of trapped flux on temperature gradient does not agree with an existing model. Therefore, a new model is presented which agrees better with the measured results.  
slides icon Slides TUCXA01 [3.180 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUCXA01  
About • Received ※ 17 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 June 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB001 Demonstration of Niobium Tin in 218 MHz Low-Beta Quarter Wave Accelerator Cavity cavity, multipactoring, SRF, vacuum 388
 
  • T.B. Petersen, G. Chen, B.M. Guilfoyle, M. Kedzie, M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
  • G.V. Eremeev, S. Posen, B. Tennis
    Fermilab, Batavia, Illinois, USA
  
  A 218 MHz quarter wave niobium cavity has been fabricated for the purpose of demonstrating Nb₃Sn technology on a low-beta accelerator cavity. Niobium-tin has been established as a promising next generation SRF material, but development has focused primarily in high-beta elliptical cell cavities. This material has a significantly higher TC than niobium, allowing for design of higher frequency quarter wave cavities (that are subsequently smaller) as well as for significantly lowered cooling requirements (possibly leading to cryocooler based de-signs). The fabrication, initial cold testing, and Nb₃Sn coating are discussed as well as test plans and details of future applications.  
poster icon Poster TUPTB001 [0.653 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB001  
About • Received ※ 16 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 08 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB002 Modelling Trapped Flux in Niobium ECR, experiment, cavity, controls 393
 
  • F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  • T. Kubo
    KEK, Ibaraki, Japan
  
  Detailed measurements of magnetic flux dynamics and trapped magnetic flux in niobium samples were conducted with a new experimental setup that permits precise control of the cooldown parameters. With this setup the dependency of trapped flux on the temperature gradient, external magnetic field, and cooldown rate can be mapped out in more detail compared to cavity measurements. We have obtained unexpected results, and an existing model describing trapped flux in dependence of temperature gradient does not agree with the measured data. Therefore, a new model is developed which describes the magnitude of trapped flux in dependence of the temperature gradient across the sample during cooldown. The model describes the amount of trapped flux lines with help of a density distribution function of the pinning forces of pinning centers and the thermal force which can de-pin flux lines from pinning centers. The model shows good agreement with the measured data and correctly predicts trapped flux at different external flux densities.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB002  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB004 Progress on Zirconium-Doped Niobium Surfaces ECR, vacuum, electron, superconductivity 398
 
  • N. Sitaraman, T. Arias, Z. Baraissov, D.A. Muller
    Cornell University, Ithaca, New York, USA
  • G. Gaitan, M. Liepe, T.E. Oseroff, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: This work was supported by the NSF under Award PHY-1549132, the Center for Bright Beams, and in part by CNF (NSF Grant NNCI-2025233), and in part by CCMR (DMR-1719875).
The first experimental studies of zirconium-doped surfaces verified that zirconium can enhance the critical temperature of the surface, resulting in a lower BCS resistance than standard-recipe niobium. However, they also produced a disordered oxide layer, resulting in a higher residual resistance than standard-recipe niobium. Here, we show that zirconium-doped surfaces can grow well-behaved thin oxide layers, with a very thin ternary suboxide capped by a passivating ZrO2 surface. The elimination of niobium pentoxide may allow zirconium-doped surfaces to achieve low residual resistance. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB004  
About • Received ※ 30 June 2023 — Revised ※ 26 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 22 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB006 Materials Design for Superconducting RF Cavities: Electroplating Sn, Zr, and Au onto Nb and and Chemical Vapor Deposition cavity, SRF, plasma, controls 401
 
  • Z. Sun, M. Liepe, T.E. Oseroff
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • Z. Baraissov, D.A. Muller, M.O. Thompson
    Cornell University, Ithaca, New York, USA
  
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Materials scientists seek to contribute to the development of next-generation superconducting radio-frequency (SRF) accelerating cavities. Here, we summarize our achievements and learnings in designing advanced SRF materials and surfaces, including Nb₃Sn [1¿3], ZrNb(CO) [4, 5], and Au/Nb surface design [6,7]. Our efforts involve electrochemical synthesis, phase transformation, and surface chemistry, which are closely coupled with superconducting properties, SRF performance, and engineering considerations. We develop electrochemical processes for Sn, Zr, and Au on the Nb surface, an essential step in our investigation for producing high-quality Nb₃Sn, ZrNb(CO), and Au/Nb structures. Additionally, we design a custom chemical vapor deposition system to offer additional growth options. Notably, we find the second-phase NbC formation in ZrNb(CO) and in ultra-high-vacuum baked or nitrogen-processed Nb. We also identify low-dielectric-loss ZrO2 on Nb and NbZr(CO) surfaces. These advancements provide materials science approaches dealing with fundamental and technical challenges to build high-performance, multi-scale, robust SRF cavities for particle accelerators and quantum applications. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB006  
About • Received ※ 30 June 2023 — Revised ※ 11 August 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023
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TUPTB010 Preservation of the High Quality Factor and Accelerating Gradient of Nb₃Sn-Coated Cavity During Pair Assembly cavity, SRF, accelerating-gradient, cryomodule 405
 
  • G.V. Eremeev, S. Cheban, S. Posen, B. Tennis
    Fermilab, Batavia, Illinois, USA
  • J.F. Fischer, D. Forehand, U. Pudasaini, A.V. Reilly, R.A. Rimmer
    JLab, Newport News, Virginia, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Two CEBAF 5-cell accelerator cavities have been coated with Nb₃Sn film using the vapor diffusion technique. One cavity was coated in the Jefferson Lab Nb₃Sn cavity coating system, and the other in the Fermilab Nb₃Sn coating system. Both cavities were measured at 4 K and 2 K in the vertical dewar test in each lab and then assembled into a cavity pair at Jefferson Lab. Previous attempts to assemble Nb₃Sn cavities into a cavity pair degraded the superconducting properties of Nb₃Sn-coated cavities. This contribution discusses the efforts to identify and mitigate the pair assembly challenges and will present the results of the vertical tests before and after pair assembly. Notably, one of the cavities reached the highest gradient above 80 mT in the vertical test after the pair assembly. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB010  
About • Received ※ 23 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 02 July 2023 — Issue date ※ 09 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB013 Commissioning of a New Sample Test Cavity for Rapid RF Characterization of SRF Materials cavity, MMI, SRF, operation 410
 
  • S. Keckert, J. Knobloch, F. Kramer, O. Kugeler
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  
  RaSTA, the Rapid Superconductor Test Apparatus, is a new sample test cavity that is currently being commissioned at HZB. It uses the established QPR sample geometry but with a much smaller cylindrical cavity operating in the TM020 mode at 4.8 GHz. Its compact design allows for smaller cryogenic test stands and reduced turnaround time, enabling iterative measurement campaigns for thin film R&D. Using the same calorimetric measurement technique as known from the QPR allows direct measurements of the residual resistance. We report first prototype results obtained from a niobium sample that demonstrate the capabilities of the system.  
poster icon Poster TUPTB013 [0.464 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB013  
About • Received ※ 16 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB037 Refurbishment and Reactivation of a Niobium Retort Furnace at DESY cavity, vacuum, controls, target 485
 
  • L. Trelle, C. Bate, H. Remde, D. Reschke, J. Schaffran, L. Steder, H. Weise
    DESY, Hamburg, Germany
  
  Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
For research in the field of heat treatments of supercon-ducting cavities, a niobium ultra-high vacuum furnace built in 1992 - originally used for the titanization of 1.3 GHz nine-cell cavities - and later shut down was recently refurbished and reactivated. A significant upgrade is the ability to run the furnace in partial pressure mode with nitrogen. The furnace is connected directly to the ISO4 area of the clean room for cavity handling. At room temperature vacuum values of around 3×10-8 mbar are achieved. The revision included the replacement of the complete control system and a partial renewal of the pump technology. The internal mounting structures are optimized for single-cell operation including tandem operation (two single-cell cavities at once) and corresponding accessories such as witness-samples and caps for the cavities. The installation of additional thermocouples for a detailed monitoring of the temperature curves is also possible at the mounting structure. Due to the furnace design, its location and the strict routines in handling, very high purity levels are achieved in comparison to similar setups and hence provide a mighty tool for SRF cavity R&D at DESY. 		 
poster icon Poster TUPTB037 [0.404 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB037  
About • Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB040 Mechanical Design and Analysis of SRF Gun Cavity Using ASME BPVC Section Viii, Division-2, Design by Analysis Requirement cavity, SRF, gun, vacuum 501
 
  • M.S. Patil, C. Compton, S.H. Kim, S.J. Miller, T. Xu
    FRIB, East Lansing, Michigan, USA
  
  Funding: Work supported by the Department of Energy Contract DE-AC02- 76SF00515
A prototype SRF gun is currently being designed at FRIB, MSU for the Low Emittance Injector of the Linac Coherent Light Source high energy upgrade at SLAC. This employs a 185.7 MHz superconducting quarter-wave resonator (QWR). The mechanical design of this cavity has been optimized for performance and to comply with ASME Section VIII, Div 2, Design by analysis requirements. This paper presents the various design by analysis procedures and how they have been adopted for the SRF gun cavity design. 		 
poster icon Poster TUPTB040 [1.235 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB040  
About • Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB041 Visual, Optical and Replica Inspections: Surface Preparation of 650 MHz Nb Cavity for PIP-II Linac cavity, SRF, linac, embedded 507
 
  • V. Chouhan, D.J. Bice, D.A. Burk, M.K. Ng, G. Wu
    Fermilab, Batavia, Illinois, USA
  
  Surface preparation of niobium superconducting RF cavities is a critical step for achieving good RF performance under the superconducting state. Surface defect, roughness, and contamination affect the accelerating gradient and quality factor of the cavities. We report surface inspection methods used to control the surface processing of 650 MHz cavities that will be used in the pre-production cryomodule for PIP-II linac. The cavity surface was routinely inspected visually, with an optical camera, and by microscopic scanning of surface replicas. This article covers details on the surface inspection methods and surface polishing process used to repair the surface.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB041  
About • Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 12 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB042 Latest Development of Electropolishing Optimization for 650 MHz Cavity cavity, cathode, SRF, polarization 512
 
  • V. Chouhan, D.J. Bice, D.A. Burk, S.K. Chandrasekaran, A.T. Cravatta, P.F. Dubiel, G.V. Eremeev, F. Furuta, O.S. Melnychuk, A.V. Netepenko, M.K. Ng, J.P. Ozelis, H. Park, T.J. Ring, G. Wu
    Fermilab, Batavia, Illinois, USA
  • B.M. Guilfoyle, M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
  
  Electropolishing (EP) of 1.3 GHz niobium (Nb) superconducting RF cavities is conducted to achieve a desired smooth and contaminant-free surface that yields good RF performance. Achieving a smooth surface of a large-sized elliptical cavity with the standard EP conditions was found to be challenging. This work aimed to conduct a systematic parametric EP study to understand the effects of various EP parameters on the surface of 650 MHz cavities used in PIP-II linac. Parameters optimized in this study provided a smooth surface of the cavities. The electropolished cavities met the baseline requirement of field gradient and qualified for further surface treatment to improve the cavity quality factor.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB042  
About • Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 06 July 2023
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TUPTB045 PIP-II SSR2 Cavities Fabrication and Processing Experience cavity, SRF, linac, target 526
 
  • M. Parise, P. Berrutti, D. Passarelli
    Fermilab, Batavia, Illinois, USA
  • P. Duchesne, D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  
  The Proton Improvement Plan-II (PIP-II) linac will include 35 Single Spoke Resonators type 2 (SSR2). A pre-production SSR2 cryomodule will contain 5 jacketed cavities. Several units are already manufactured and prepared for cold testing. In this work, data collected from the fabrication, processing and preparation of the cavities will be presented and the improvements implemented after the completion of the first unit will be highlighted.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB045  
About • Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 08 July 2023
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TUPTB046 Development and Performance of RFD Crab Cavity Prototypes for HL-LHC AUP cavity, HOM, impedance, higher-order-mode 531
 
  • L. Ristori, P. Berrutti, M. Narduzzi
    Fermilab, Batavia, Illinois, USA
  • A. Castilla
    JLAB, Newport News, USA
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • N.A. Huque
    JLab, Newport News, Virginia, USA
  • Z. Li, A. Ratti
    SLAC, Menlo Park, California, USA
  
  Funding: Operated by Fermi Research Alliance, LLC, under Contract DE-AC02-07CH11359 with the U.S. DOE
The US will be contributing to the HL-LHC upgrade at CERN with the fabrication and qualification of RFD crabbing cavities in the framework of the HL-LHC Accelerator Upgrade Project (AUP) managed by Fermilab. AUP received Critical Decision 3 (CD-3) approval by DOE in December 2020 launching the project into the production phase. The electro-magnetic design of the cavity was inherited from the LHC Accelerator Research Program (LARP) but needed to be revised to meet new project requirements and to prevent issues encountered during beam tests performed at CERN in the R&D phase. Two prototype cavities were manufactured in industry and cold tested. Challenges specific to the RFD cavity were the stringent interface tolerances, the pole symmetry and the higher-order-mode impedance spectrum. Chemical processing and heat treatments were performed initially at FNAL/ANL and are now being transferred to industry for the production phase. HOM dampers are manufactured and validated by JLAB. A summary of cold test results with and without HOM dampers is presented. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB046  
About • Received ※ 20 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 11 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB047 The Evaluation of Mechanical Properties of LB650 Cavities cavity, controls, cryomodule, SRF 536
 
  • G. Wu, S.D. Adams, D.J. Bice, S.K. Chandrasekaran, I.V. Gonin, C.J. Grimm, J.P. Holzbauer, T.N. Khabiboulline, C.S. Narug, J.P. Ozelis, H. Park, G.V. Romanov, R. Thiede, R. Treece, A.D. Wixson
    Fermilab, Batavia, Illinois, USA
  • K.E. McGee
    FRIB, East Lansing, Michigan, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The 650 MHz cavities have a stronger requirement of niobium mechanical properties because of the geometric shape of the cavity due to reduced beta. The mechanical property of the niobium half-cell was measured following various heat treatments. The 5-cell cavities were tested in a controlled drop test fashion and the real-world road test. The result showed that the 900C heat treatment was compatible with cavity handling and transportation during production. The test provides the bases of the transportation specification and shipping container design guidelines. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB047  
About • Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 14 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB052 A Novel Manufacture of Niobium SRF Cavities by Cold Spray cavity, SRF, radio-frequency, experiment 545
 
  • M. Yamanaka
    KEK, Ibaraki, Japan
  • K. Shimada
    Nihon University, College of Engineering, Koriyama, Japan
  
  Cold spray is a lower-temperature solid-state thermal spray process that deposits metal powder using a heated inert gas through a supersonic nozzle. When the material hits at supersonic speed and reaches the critical speed, the particles themselves are plastically deformed to form a film. The material of the superconducting cavity is niobium, a very expensive rare metal. To reduce the amount of niobium and the cost, we propose a novel manufacturing method of forming a thick niobium film on the surface of a mandrel by cold spray using niobium powder and removing the mandrel to finish a hollow shape. We confirmed the feasibility of the proposed method using a model similar to a 3.9 GHz one-cell cavity. Also, the RRR measurement of the niobium specimen made by cold spray was carried out and the measured value of 11 was obtained. We report on these results.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB052  
About • Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 10 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB062 RF Measurements of the 3rd Harmonic Superconducting Cavity for a Bunch Lengthening cavity, target, superconducting-cavity, MMI 565
 
  • J.Y. Yoon, J.H. Han, H.S. Park, Y.D. Yoon
    Kiswire Advanced Technology Ltd., Daejeon, Republic of Korea
  • E. Kako
    KEK, Ibaraki, Japan
  • E.-S. Kim
    Korea University Sejong Campus, Sejong, Republic of Korea
  
  The brightness can be increased by minimizing the emittance in the light source, but the reduced emittance also increases the number of collisions of electrons in the beam bunch. Therefore, the bunch lengthening by using the 3rd harmonic cavity reduces the collisions of electrons and increases the Touschek lifetime. Since the resonant frequency of the main RF cavity is 500 MHz, the resonant frequency of 3rd harmonic cavity is selected as 1500 MHz. The prototype cavity is a passive type in which a power coupler is not used, and power is supplied from the beam. The operating temperature is 4.5 K, which is a superconducting cavity. The elliptical double-cell geometry was selected to increase the accelerating voltage of the cavity and reduce power losses. Based on this design, three niobium cavities are fabricated and tested. In this paper, we present the RF measurement results of the 3rd harmonic cavity at room temperature.
*3rd harmonic cavity
*4th generation storage ring 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB062  
About • Received ※ 12 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB063 Fabrication Efforts Toward a Superconducting Rf Photo-Infector Quarter-Wave Cavity for Use in Low Emittance Injector Applications cavity, SRF, cryomodule, gun 568
 
  • C. Compton
    NSCL, East Lansing, Michigan, USA
  • K. Elliott, W. Hartung, J.D. Hulbert, S.H. Kim, T. Konomi, S.J. Miller, M.S. Patil, J.T. Popielarski, L. Popielarski, K. Saito, K. Witgen, T. Xu
    FRIB, East Lansing, Michigan, USA
  • M. Kedzie, M.P. Kelly, T.B. Petersen
    ANL, Lemont, Illinois, USA
  • J.W. Lewellen, J. Smedley
    SLAC, Menlo Park, California, USA
  
  Funding: * Work supported by the Department of Energy Contract DE-AC02- 76SF00515
The Facility for Rare Isotope Beams (FRIB), in collaboration with Argonne National Laboratory (ANL) and Helmholtz-Zentrum Dresden-Rossendorf (HDZR), is working on the design and fabrication of a photo-injector cryomodule; suitable for operation as part of accelerator systems at SLAC National Accelerator Laboratory. Project scope requires the fabrication of two 185.7 MHz superconducting, quarter-wave resonators (QWR) based, injector cavities. Cavity fabrication will be completed at FRIB with contracted vendors supporting subcomponent fabrication and electron-beam welding. Fabrication will use poly-crystalline and large grain RRR niobium materials. The current status of cavity fabrication will be presented including material procurement, prototype forming, and electron-beam welding development. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB063  
About • Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 21 August 2023 — Issue date ※ 21 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTB067 Fabrication and Surface Treatment of Superconducting Rf Single Spoke Cavities for the Myrrha Project cavity, simulation, MMI, linac 578
 
  • M. Moretti, Y.N. Hoerstensmeyer, A. Navitski
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • F. Marhauser
    SCK•CEN, Mol, Belgium
  
  The MYRRHA project, based at SCK•CEN (Belgium), aims at coupling a 600 MeV proton accelerator to a subcritical fission core with a maximal output of 100 MWth. The first phase of the project, MINERVA, includes the design, construction, and commissioning of a 100 MeV superconducting RF linac in order to demonstrate the machine requirements in terms of reliability and fault tolerance. The MINERVA linac comprises several cryomodules, each containing two Single Spoke 352.2 MHz cavities made out of high RRR niobium and operating at 2K. The fabrication and surface treatment of the Single Spoke RF Cavities is currently ongoing and completely carried out by RI Research Instruments GmbH (Germany); the first pre-series cavities were completed and delivered for cold testing. Main highlights of the fabrication include the deep-drawing of complex shapes, such as central spokes and outer caps of the cavity, which was successfully accomplished. As for the surface treatment, RI has commissioned, tested, and effectively started utilizing a new rotational buffered chemical polishing facility; this is required to polish the cavity inner surface, while ensuring an almost uniform material removal.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB067  
About • Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIAA04 Development of High-performance Niobium-3 Tin Cavities at Cornell University cavity, SRF, site, accelerating-gradient 600
 
  • L. Shpani, S.G. Arnold, G. Gaitan, M. Liepe, T.E. Oseroff, R.D. Porter, N.A. Stilin, Z. Sun, N.M. Verboncoeur
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • N. Sitaraman
    Cornell University, Ithaca, New York, USA
  
  Funding: Work supported by the National Science Foundation under Grant No. PHY-1549132, the Center for Bright Beam and U.S. DOE grant No. DE-SC0008431.
Niobium-3 tin is a promising material for next-generation superconducting RF cavities due to its high critical temperature and high theoretical field limit. There is currently significant worldwide effort aiming to improve Nb₃Sn growth to push this material to its ultimate performance limits. This talk will present an overview of Nb₃Sn cavity development at Cornell University. One approach we are pursuing is to further advance the vapor diffusion process through optimized nucleation and film thickness. Additionally, we are exploring alternative Nb₃Sn growth methods, such as the development of a plasma-enhanced chemical vapor deposition (CVD) system, as well as Nb₃Sn growth via electrochemical synthesis. 		 
slides icon Slides WEIAA04 [5.260 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIAA04  
About • Received ※ 29 June 2023 — Revised ※ 11 August 2023 — Accepted ※ 21 August 2023 — Issue date ※ 22 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WECAA01 Progress in European Thin Film Activities cavity, SRF, target, laser 607
 
  • C. Pira, O. Azzolini, R. Caforio, E. Chyhyrynets, D. Fonnesu, D. Ford, V.A. Garcia, G. Keppel, G. Marconato, A. Salmaso, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  • C.Z. Antoine, Y. Kalboussi, Th. Proslier
    CEA-IRFU, Gif-sur-Yvette, France
  • C. Benjamin, O.B. Malyshev, N. Marks, B.S. Sian, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • C. Benjamin, J.W. Bradley, G. Burt, O.B. Malyshev, N. Marks, D.J. Seal, B.S. Sian, S. Simon, D.A. Turner, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • S. Berry
    CEA-DRF-IRFU, France
  • R. Berton, D. Piccoli, F. Piccoli, G. Squizzato, F. Telatin
    Piccoli, Noale (VE), Italy
  • M. Bertucci, R. Paparella
    INFN/LASA, Segrate (MI), Italy
  • M. Bonesso, S. Candela, V. Candela, R. Dima, G. Favero, A. Pepato, P. Rebesan, M. Romanato
    INFN- Sez. di Padova, Padova, Italy
  • J.W. Bradley, S. Simon
    The University of Liverpool, Liverpool, United Kingdom
  • G. Burt, D.J. Seal, D.A. Turner
    Lancaster University, Lancaster, United Kingdom
  • O. Hryhorenko, D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • X. Jiang, T. Staedler, A.O. Zubtsovskii
    University Siegen, Siegen, Germany
  • S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  • N.L. Leicester
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Medvids, A. Mychko, P. Onufrijevs
    Riga Technical University, Riga, Latvia
  • S. Prucnal, S. Zhou
    HZDR, Dresden, Germany
  • R. Ries
    Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
  • E. Seiler
    IEE, Bratislava, Slovak Republic
  • L.G.P. Smith
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  
  Funding: This project has received funding from the European Union s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730.
Thin-film cavities with higher Tc superconductors (SC) than Nb promise to move the operating temperature from 2 to 4.5 K with savings 3 orders of magnitude in cryogenic power consumption. Several European labs are coordinating their efforts to obtain a first 1.3 GHz cavity prototype through the I.FAST collaboration and other informal collaborations with CERN and DESY. R&D covers the entire production chain. In particular, new production techniques of seamless Copper and Niobium elliptical cavities via additive manufacturing are studied and evaluated. New acid-free polishing techniques to reduce surface roughness in a more sustainable way such as plasma electropolishing and metallographic polishing have been tested. Optimization of coating parameters of higher Tc SC than Nb (Nb₃Sn, V₃Si, NbTiN) via PVD and multilayer via ALD are on the way. Finally, rapid heat treatments such as Flash Lamp Annealing and Laser Annealing are used to avoid or reduce Cu diffusion in the SC film. The development and characterization of SC coatings is done on planar samples, 6 GHz cavities, choke cavities, QPR and 1.3 GHz cavities. This work presents the progress status of these coordinated efforts. 		 
slides icon Slides WECAA01 [15.846 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WECAA01  
About • Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIBA01 Surface Engineering by ALD for Superconducting RF Cavities cavity, vacuum, SRF, site 615
 
  • Y. Kalboussi, C.Z. Antoine, M. Baudrier, Q. Bertrand, C. Boulch, B. Delatte, G. Jullien, L. Maurice, Th. Proslier, P. Sahuquet, T.V. Vacher
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Asaduzzaman, T. Junginger
    UVIC, Victoria, Canada
  • M. Asaduzzaman
    TRIUMF, Vancouver, Canada
  • D. Dragoe
    ICMMO, Orsay, France
  • F. Éozénou
    CEA-DRF-IRFU, France
  • N. Lochet
    CEA, DES, Université Paris-Saclay, Gif-sur-Yvette, France
  • D. Longuevergne, T. Pépin-Donat
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • F. Miserque
    CEA, LECA, Université Paris-Saclay, Gif-sur-Yvette, France
  
  Atomic Layer Deposition is a synthesis method that enable a unique control of thin films chemical composition and thickness over complex shape objects such as SRF cavities. This level of control opens the way to new surface treatments and to study their effect on RF cavity performances. We will present coupon and, in some cases, preliminary cavity results, from various surface engineering routes based on the deposition of thin oxides and nitrides films combined with post annealing treatments and study their interactions with the niobium. Three main research directions will be presented: 1/ replacing the niobium oxides by other surface layers (Al₂O₃, Y2O3, MgO) and probe their effect on the low and high field performances, 2/ doping with N and combine approaches 1/ and 2/ and finally 3/ optimize the superconducting properties of NbTiN multilayers on Nb and Sapphire.  
slides icon Slides WEIBA01 [13.613 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIBA01  
About • Received ※ 06 July 2023 — Revised ※ 12 August 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIXA02 Results of the R&D RF Testing Campaign of 1.3 GHz Nb/Cu Cavities cavity, SRF, operation, cryogenics 621
 
  • L. Vega Cid, S. Atieh, G. Bellini, A. Bianchi, L.M.A. Ferreira, C. Pereira Carlos, G.J. Rosaz, W. Venturini Delsolaro
    CERN, Meyrin, Switzerland
  • S.B. Leith
    European Organization for Nuclear Research (CERN), Geneva, Switzerland
  
  In the context of the R&D program on Nb/Cu carried out at CERN, a total of 25 tests have been performed since 2021. This talk will present these results. Three different manufacturing techniques have been used to produce the copper substrates, in order to investigate which is the most suitable in terms of quality and economy of scale. On one hand, the focus has been on optimizing the surface resistance at 4.2K, as this will be the operating temperature of FCC. The results at this temperature are encouraging, showing repeatable and optimized RF performance. On the other hand, RF tests have been done at 1.85 K too aiming at deepening the knowledge of the mechanisms behind the Q slope. This is key to work on the mitigation of this phenomenon and ultimately to extend the application of this technology to high energy, high gradient accelerators. The influence of the thermal cycles has been thoroughly investigated. A systematic improvement has been observed of both the Q slope and the residual resistance with slow thermal cycles.  
slides icon Slides WEIXA02 [5.385 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA02  
About • Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 02 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIXA03 Optimizing the Manufacture of High-Purity Niobium SRF Cavities Using the Forming Limit Diagram: A Case Study of the HL-LHC Crab Cavities RFD Pole cavity, simulation, SRF, luminosity 627
 
  • A. Gallifa Terricabras, I. Aviles Santillana, S. Barrière, M. Garlasché, L. Prever-Loiri, J.S. Swieszek
    CERN, Meyrin, Switzerland
  • E. Cano-Pleite
    UC3M, Leganes, Spain
  • M. Narduzzi
    Fermilab, Batavia, Illinois, USA
  • S. Pfeiffer
    European Organization for Nuclear Research (CERN), Geneva, Switzerland
  
  Funding: CERN HL-LHC
The Crab Cavities are key components of the High Luminosity Large Hadron Collider (HL-LHC) project at CERN, which aims to increase the integrated luminosity of the LHC, the world’s largest particle accelerator, by a factor of ten. This paper explores the application of the Forming Limit Diagram (FLD) to enhance the manufacturing process of complex-shape Nb-based cavities, with a focus on the formability challenges experienced with the pole of the Radio Frequency Dipole (RFD) Crab Cavities. The study includes the material characterization of ultra-high-purity niobium (Nb RRR300) sheets, namely mechanical tests and microstructural analysis; it also contains large-deformation Finite Element simulations of the pole deep drawing process, and the translation of the resulting strains in a FLD diagram, together with several suggestions on how to improve the manufacturing process of such deep drawn parts. The results of this study can provide valuable insights into improving the design and fabrication of complex-shaped superconducting radio-frequency cavities made by large-deformation metal-sheet forming processes. 		 
slides icon Slides WEIXA03 [15.991 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA03  
About • Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 27 June 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIXA04 Development of the Directly-Sliced Niobium Material for High Performance SRF Cavities cavity, SRF, collider, linear-collider 634
 
  • A. Kumar, H. Araki, T. Dohmae, H. Ito, T. Saeki, K. Umemori, A. Yamamoto, M. Yamanaka
    KEK, Ibaraki, Japan
  • A. Yamamoto
    CERN, Meyrin, Switzerland
  
  For the purpose of cost reduction for the ILC, KEK has been conducting R&D on direct sliced Nb materials such as large grain and medium grain Nb. Single-cell, 3-cell, and 9-cell cavities have been manufactured, and each has demonstrated a high-performance accelerating gradient exceeding 35 MV/m. The results of applying high-Q/high-G recipes, such as two-step baking and furnace baking to these cavities are also shown. Moreover, mechanical tests have been carried out for the beforementioned materials to evaluate their strength for application to the High-Pressure Gas Safety Law. The status of development of these large grain and Medium grain Nb will be presented.  
slides icon Slides WEIXA04 [3.773 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA04  
About • Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 12 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIXA05 Electropolishing Study on Nitrogen-Doped Niobium Surface cavity, SRF, cathode, radio-frequency 641
 
  • V. Chouhan, T.J. Ring, G. Wu
    Fermilab, Batavia, Illinois, USA
  • E.A.S. Viklund
    NU, Evanston, Illinois, USA
  
  The nitrogen doping (N-doping) process is applied to niobium (Nb) superconducting cavities to enhance their quality factors. The N-doping is followed by an electropolishing process that provides the final surface of the cavities. A controlled EP process is necessary to get the benefit of N-doping and achieve a high accelerating gradient. We have performed electropolishing of N-doped Nb surface under various conditions to understand their impact on the surface. A modified EP process was developed to obtain a smooth pit-free surface.  
slides icon Slides WEIXA05 [17.622 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA05  
About • Received ※ 19 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEIXA06 Recent Advances in Metallographic Polishing for SRF Application cavity, SRF, laser, framework 646
 
  • O. Hryhorenko
    JLab, Newport News, Virginia, USA
  • C.Z. Antoine, F. Éozénou, Th. Proslier
    Université Paris-Saclay, CEA, Gif-sur-Yvette, France
  • T. Dohmae
    KEK, Ibaraki, Japan
  • S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  
  Funding: ENSAR-2 under grant agreement N° 654002. IFAST under Grant Agreement No 101004730. The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
This talk is an overview of the metallographic polishing R&D program covering Niobium and Copper substrates treatment for thin film coating as an alternative fabrication pathway for 1.3 GHz elliptical cavities. The presented research is the result of a collaborative effort between IJCLab, CEA/Irfu, HZB, and KEK in order to develop innovative surface processing and cavity fabrication protocols capable of meeting stringent requirements for SRF surfaces, including the reduction of safety risks and ecological footprint, enhancing reliability, improving the surface roughness, and potentially allowing cost reduction. The research findings will be disclosed. 		 
slides icon Slides WEIXA06 [7.469 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIXA06  
About • Received ※ 16 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 14 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB001 Preparation and Characterization of Nb Films Deposited in SRF Cavity via HiPIMS cavity, SRF, site, lattice 651
 
  • P. He, J. Dai, H.C. Duan, J.W. Kan, Y. Ma, T. Xin, Y.C. Yang, P. Zhang
    IHEP, Beijing, People’s Republic of China
  
  The RF performance of the niobium superconducting cavity has been continuously improved in recent 50 years. Since the maximum acceleration field (Eacc) has approached its theoretical limit, developing a more efficient and low-cost SRF cavity is one of the key challenges of the next generation particle accelerators. Niobium coated copper cavities are promising solutions because the SRF phenomenon occurrs within several hundred nanometers under the cavity surface. In literatures, the Nb coated Cu cavity prepared by direct current magnetron sputtering (DCMS) has serious Q-slope problem, which may be related to the low energy deposition. High power impulse magnetron sputtering (HiPIMS) can produce a high peak power and high ionization rate which may improve the thin film quality. Therefore, we prepared Nb coated Cu samples via HiPIMS on the 1.3 GHz dummy cavity at IHEP.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB001  
About • Received ※ 15 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB043 Nb3Sn Vapor Diffusion Coating System at SARI: Design, Construction, and Commissioning cavity, vacuum, MMI, superconducting-cavity 655
 
  • Q.X. Chen, Y. Zong
    SINAP, Shanghai, People’s Republic of China
  • J.F. Chen, S. Xing
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • J. Rong
    SSRF, Shanghai, People’s Republic of China
  
  This paper describes the design of a coating system for the preparation of a superconducting radio-frequency cavity with Nb3Sn thin films. The device consists of a coating chamber made of pure niobium, a vacuum furnace for heating the coating chamber, a superconducting cavity bracket and two crucible heaters. The chamber is vacuum isolated from the furnace body to protect the superconducting cavity from contamination during the coating process. The device has been built and commissioned, which could be used for Nb₃Sn coating of a 1.3 GHz single-cell superconducting cavity in future.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB043  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 08 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB045 The Oxidizing Responses of Baked Niobium Exposed to Various Gases via In-situ NAXPS cavity, experiment, SRF, vacuum 662
 
  • Z.T. Yang, J.K. Hao, K.X. Liu, S.W. Quan
    PKU, Beijing, People’s Republic of China
  
  We carried out in-situ NAXPS (Near-atmospheric X-ray Photoelectron Spectroscopy) on SRF-cavity class niobium to observe its oxidizing responses when exposed to various gases. The niobium samples were baked at 800°C until the peaks of niobium oxides disappeared in the spectrum. Then the revealed pure niobium samples were exposed to the air-proportion mixture of nitrogen and oxygen, pure oxygen, and pure water vapor respectively. And for the pure oxygen and water vapor group, we also carried out TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectroscopy) measurements before and after the baking and oxidation experiments. We found that pure oxygen and water vapor could oxidize niobium at similar rate which was faster than the N2/O2 mixture. After re-oxidized by pure oxygen and water vapor, the niobium sample presented a significant increase of interstitial carbon and a moderate increase of interstitial oxygen in the magnetic penetration depth, while it showed a mild decrease of interstitial hydrogen.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB045  
About • Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 25 June 2023 — Issue date ※ 31 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB050 Exploring Innovative Pathway for SRF Cavity Fabrication cavity, SRF, laser, electron 680
 
  • O. Hryhorenko
    JLab, Newport News, Virginia, USA
  • C.Z. Antoine
    Université Paris-Saclay, CEA, Gif-sur-Yvette, France
  • T. Dohmae
    KEK, Ibaraki, Japan
  • D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Funding: ENSAR-2 under grant agreement N° 654002. The U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
This article shows a study on an alternative pathway for the fabrication of a complete 1.3 GHz SRF cavity, aiming at improving production reliability, reducing the use of chemical polishing (EP or BCP) which is a costly and safety-critical step, and preserving surface quality after forming. Unlike the conventional pathway, the fabrication process is performed after polishing. This point is crucial as the used polishing technology could be applied only to flat geometries. The performed investigation demonstrates that damages during the fabrication process are considered minor, localized, and limited to the near-surface. Moreover, these studies confirm that the damaged layer (100-200 µm) is mainly caused by the rolling process, and not by the subsequent fabrication steps. A laser confocal microscope and SEM-EBSD technique were used to compare samples before and after forming. The preliminary results are discussed and presented in this paper. 		 
poster icon Poster WEPWB050 [2.263 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB050  
About • Received ※ 20 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 01 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB051 Development of a Prototype 197 MHz Crab Cavity for the Electron-Ion Collider at JLab cavity, GUI, HOM, electron 685
 
  • N.A. Huque, E.F. Daly, E. Drachuk, J. Henry, M. Marchlik
    JLab, Newport News, Virginia, USA
  • A. Castilla
    JLAB, Newport News, USA
  • S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • B.P. Xiao
    BNL, Upton, New York, USA
  
  Thomas Jefferson National Accelerator Facility (JLab) is currently developing a prototype 197 MHz Radio-Frequency Dipole (RFD) crab cavity as part of the Electron-Ion Collider (EIC) to be built at Brookhaven National Laboratory (BNL). Cryomodules containing these cavities will be part of Hadron Storage Ring (HSR) of the EIC. The prototype cavity is constructed primarily of formed niobium sheets of thickness 4.17 mm, with machined niobium parts used as interfaces where tight tolerancing is required. The cavity¿s large size and complex features present a number of challenges in fabrication, tuning, and RF testing. Structural and forming analyses have been carried out to optimize the design and fabricated processes. An overview of the design phase and the current state of fabrication are presented in this paper.
Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB051  
About • Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 16 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB052 Temperature, RF Field, and Frequency Dependence Performance Evaluation of Superconducting Niobium Half-Wave Coaxial Cavity cavity, SRF, radio-frequency, experiment 691
 
  • N.K. Raut, G. Ciovati, P. Dhakal
    JLab, Newport News, Virginia, USA
  • S.U. De Silva, J.R. Delayen, B.D. Khanal, J.K. Tiskumara
    ODU, Norfolk, Virginia, USA
  
  Funding: This is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177
Recent advancement in superconducting radio frequency cavity processing techniques, with diffusion of impurities within the RF penetration depth, resulted in high quality factor with increase in quality factor with increasing accelerating gradient. The increase in quality factor is the result of a decrease in the surface resistance as a result of nonmagnetic impurities doping and change in electronic density of states. The fundamental understanding of the dependence of surface resistance on frequency and surface preparation is still an active area of research. Here, we present the result of RF measurements of the TEM modes in a coaxial half-wave niobium cavity resonating at frequencies between 0.3 - 1.3 GHz. The temperature dependence of the surface resistance was measured between 4.2 K and 1.6 K. The field dependence of the surface resistance was measured at 2.0 K. The baseline measurements were made after standard surface preparation by buffered chemical polishing. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB052  
About • Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 20 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB057 Refurbishment of an Elbe-Type Cryomodule for Coated HOM-Antenna Tests for MESA HOM, cavity, cryomodule, electron 709
 
  • P.S. Plattner, F. Hug, T. Stengler
    KPH, Mainz, Germany
  
  Funding: The work received funding by BMBF through 05H21UMRB1.
The Mainz Energy-Recovering Superconducting Accelerator (MESA), an energy-recovering (ER) LINAC, is currently under construction at the university Mainz. In the ER mode a continues wave (CW) beam is accelerated from 5 MeV up to 105 MeV with a beam current of up to 1 mA. This current is accelerated and decelerated twice within a cavity. For future experiments, the beam current limit has to be pushed up to 10 mA. An analysis of the MESA cavities has shown that the HOM antennas quench at such high beam currents due to the extensive power deposition and the resulting heating of the HOM coupler. To avoid quenching it is necessary to use superconducting materials with higher critical temperature. For this purpose, the HOM antennas will be coated with NbTiN and Nb3SN and their properties will be investigated. For use in the accelerator, the HOM antennas will be installed in the cavities of a former ALICE cryomodule, kindly provided by STFC Daresburry. This paper will show both the status of the refurbishment of the ALICE module to suit MESA, and the coating of the HOM antennas.
The authors would like to express their sincere gratitude to STFC Daresbury for the donation of the ALICE module, which strongly supports SRF research in Mainz. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB057  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 09 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB065 Impact of Medium Temperature Heat Treatments on the Magnetic Flux Expulsion Behavior of SRF Cavities cavity, SRF, controls, experiment 731
 
  • J.C. Wolff, J. Eschke, A. Gössel, K. Kasprzak, D. Reschke, L. Steder, L. Trelle, M. Wiencek
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Medium temperature (mid-T) heat treatments at 300 °C are used to enhance the intrinsic quality factor of superconducting radio frequency (SRF) cavities. Unfortunately, such treatments potentially increase the sensitivity to trapped magnetic flux and consequently the surface resistance of the cavity. For this reason, it is crucial to maximize the expulsion of magnetic flux during the cool down. The flux expulsion behavior is next to the heat treatment mainly determined by the geometry, the niobium grain size and the grain orientation. However, it is also affected by parameters of the cavity performance tests like the cool down velocity, the spatial temperature gradient along the cavity surface and the magnetic flux density during the transition of the critical temperature. To improve the flux expulsion behavior and hence the efficiency of future accelerator facilities, the impact of these adjustable parameters as well as the mid-T heat treatment on 1.3 GHz TESLA-Type single-cell cavities is investigated by a new approach of a magnetometric mapping system. In this contribution first performance test results of cavities before- and after mid-T heat treatment are presented. 		 
poster icon Poster WEPWB065 [3.077 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB065  
About • Received ※ 21 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPWB084 The Interaction among Interstitial C/N/O/H and Vacancy in Niobium via First-Principles Calculation lattice, electron, site, cavity 778
 
  • H. Liu, J.K. Hao, Z.T. Yang
    PKU, Beijing, People’s Republic of China
  
  We calculate the interaction among zero dimensional defects in niobium lattice through first-principles calculation. And we compare the trapping effect of hydrogen among carbon, nitrogen, and oxygen as well as the trapping effect of interstitial atoms by vacancy. We find that the interstitial C/N/O have similar effect of trapping interstitial hydrogen in niobium lattice, and the vacancy can trap interstitial C/N/O/H in adjacent protocells and strengthen their chemical bond with Nb. These calculations give some explanation for improving superconducting performance of niobium cavities through medium temperature baking.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB084  
About • Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
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WEPWB111 A New Ultra-High Vacuum Furnace for SRF R&D cavity, vacuum, operation, SRF 855
 
  • M. Wenskat, C. Bate
    DESY, Hamburg, Germany
  • C. Bate, C. Martens
    University of Hamburg, Hamburg, Germany
  • R. Ghanbari, W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  Funding: This work was supported by the BMBF under the research grants 05K19GUB and 05H2021.
A new vacuum furnace has been designed and purchased by the University of Hamburg and is operating in an ISO5 cleanroom. This furnace can anneal single-cell TESLA cavities at temperatures up to 1000°C and with a pressure of less than 10-7mbar or in a nitrogen atmosphere of up to 10-2mbar. We will lay out the underlying design ideas, based on the gained experience from our previous annealing research, and present the commissioning of the furnace itself. Additionally, we will show for the first time the results of sample and cavity tests after annealing in the furnace. This will be accompanied by an overview of the intended R&D process and scientific questions to be addressed. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB111  
About • Received ※ 21 June 2023 — Revised ※ 15 July 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023
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WEPWB116 The Influence of Sample Preparation, Soak Time, and Heating Rate on Measured Recrystallization of Deformed Polycrystalline Niobium cavity, ECR, SRF, electron 863
 
  • Z.L. Thune
    MSU, East Lansing, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  
  Funding: DOE/OHEP (Grant Number: DE-SC0009960)
Improving accelerator performance relies on consistent production of high-purity niobium superconducting radiofrequency (SRF) cavities. Current production uses an 800 °C 3 hr heat treatment, but 900-1000 °C can improve cavity performance via recrystallization (Rx) and grain growth. As Rx is thermally activated, increasing the temperature and/or the heating rate could facilitate a reduction in geometrically necessary dislocation (GND) density that is associated with the degradation of cavity performance via trapped magnetic flux. Recent work shows that increasing the annealing temperature increased the Rx fraction in cold-rolled polycrystalline niobium. However, the influence of heating rate on the extent of Rx was minimal with a 3 hr soak time. To further assess the influence of heating rate on measured Rx, as well as the effects of sample preparation, electron backscatter diffraction (EBSD) was used to quantify the extent of Rx on samples annealed at a single temperature with different soak times. Comparing samples with different surface preparation shows that pinned grain boundaries on the free surface reveal a much smaller grain size than below the surface.
* Z.L. Thune et al., "The Influence of Strain Path and Heat Treatment Variations on Recrystallization in Cold-Rolled High-Purity Niobium Polycrystals," doi: 10.1109/TASC.2023.3248533. 		 
poster icon Poster WEPWB116 [1.312 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB116  
About • Received ※ 23 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 21 August 2023
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WEPWB118 Study and Improvements of Liquid Tin Diffusion Process to Synthesize Nb₃Sn Cylindrical Targets target, simulation, experiment, cavity 868
 
  • D. Ford, E. Chyhyrynets, D. Fonnesu, G. Keppel, G. Marconato, C. Pira, A. Salmaso
    INFN/LNL, Legnaro (PD), Italy
  
  Funding: This project has received funding from the European Union¿s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
Nb₃Sn thin films on bulk Nb cavities exhibit comparable performance to bulk Nb at lower temperatures, and using Cu as a substrate material can further improve performance and reduce costs. However, coating substrates with curved geometries like elliptical cavities can be challenging due to the brittleness of Nb₃Sn targets produced by a classical sintering technique. This work explores the use of the Liquid Tin Diffusion (LTD) technique to produce sputtering targets for 6 GHz elliptical cavities, which allows for the deposition of thick and uniform coatings on Nb substrate, even for complex geometries. The study includes improvements in the LTD process and the production of a single-use LTD target, as well as the characterization of Nb₃Sn films coated by DC magnetron sputtering using these innovative targets. 		 
poster icon Poster WEPWB118 [5.462 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB118  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 August 2023
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WEPWB119 Additive Manufacturing of Pure Niobium and Copper Using Laser Powder Bed Fusion for Particle Accelerator Applications cavity, laser, SRF, plasma 872
 
  • D. Ford, R. Caforio, E. Chyhyrynets, G. Keppel, C. Pira
    INFN/LNL, Legnaro (PD), Italy
  • M. Bonesso, S. Candela, V. Candela, R. Dima, G. Favero, A. Pepato, P. Rebesan, M. Romanato
    INFN- Sez. di Padova, Padova, Italy
  • M. Pozzi
    Rösler Italiana s.r.l., Concorezzo, Italy
  
  Funding: This project has received funding from the European Union¿s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
In this study, Metal Additive Manufacturing (MAM) was evaluated as a viable method for producing seamless 6 GHz pure copper and niobium prototypes without the use of internal supports. Preliminary tests were performed to evaluate printability, leading to further investigations into surface treatments to reduce surface roughness from 35 µm to less than 1 µm. Additional prototypes were printed using different powders and machines, exploring various printing parameters and innovative contactless supporting structures to improve the quality of downward-facing surfaces with small inclination angles. These structures enabled the fabrication of seamless SRF cavities with a relative density greater than 99.8%. Quality testing was conducted using techniques such as tomography, leak testing, resonant frequency assessment, and internal inspection. The results of this study are presented herein. 		 
poster icon Poster WEPWB119 [9.235 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB119  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
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WEPWB120 Flux Expulsion Testing for LCLS-II-HE Cavity Production cavity, cryomodule, SRF, ECR 876
 
  • J.T. Maniscalco, S. Aderhold, M. Checchin, D. Gonnella, R.D. Porter
    SLAC, Menlo Park, California, USA
  • T.T. Arkan, D. Bafia, J.A. Kaluzny, S. Posen
    Fermilab, Batavia, Illinois, USA
  • M.E. Bevins, A.J. Grabowski, J. Hogan, C.E. Reece, D. Savransky, H. Vennekate
    JLab, Newport News, Virginia, USA
  
  Nitrogen-doped niobium SRF cavities are sensitive to trapped magnetic flux, which decreases the cavity intrinsic Q₀. Prior experimental results have shown that heat treatments to 900°C and higher can result in stronger flux expulsion during cooldown; the precise temperature required tends to vary by vendor lot/ingot of the niobium material used in the cavity cells. For LCLS-II-HE, to ensure sufficient flux expulsion in all cavities, we built and tested single-cell cavities to determine this required temperature for each vendor lot of niobium material to be used in cavity cells. In this report, we present the results of the single-cell flux expulsion testing and the Q₀ of the nine-cell cavities built using the characterized vendor lots. We discuss mixing material from different vendor lots, examine the lessons learned, and finally present an outlook on possible refinements to the single-cell technique.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB120  
About • Received ※ 15 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 03 July 2023 — Issue date ※ 13 July 2023
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WEPWB121 Niobium Chronicles: Surface Quality Investigation and Recovery During Material Procurement for the PIP-II High Beta 650 MHz Cavities cavity, controls, factory, synchrotron 880
 
  • A.D. Shabalina
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The surface quality of high-purity niobium for superconducting radiofrequency cavities experienced a sudden and significant decline in 2021. The recovery process and root cause analysis were challenging due to a variety of factors such as COVID-19 travel restrictions, cultural differences, and bureaucratic processes. Effective open communication was crucial to resolving the issue, especially with direct vendor oversight being impossible.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB121  
About • Received ※ 28 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 20 August 2023 — Issue date ※ 20 August 2023
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WEPWB125 Thermodynamic Properties of Srf Niobium cavity, SRF, radio-frequency, cryogenics 884
 
  • P. Dhakal
    JLab, Newport News, Virginia, USA
  
  Funding: This is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177.
Bulk and thin films of niobium are the materials of choice in fabricating superconducting radio frequency (SRF) cavities for modern particle accelerators and quantum computing applications. The thermodynamic properties of Nb are of particular interest in heat management in cryogenic environments. Here, we report the results of measurements of the thermodynamic properties of niobium used in the fabrication of superconducting radio frequency (SRF) cavities. The temperature and magnetic field dependence of thermal conductivity, Seebeck coefficient, and specific heat capacity was measured on bulk niobium samples. 		 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB125  
About • Received ※ 11 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023
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