SRF2023 - List of Keywords (site)

Paper	Title	Other Keywords	Page
MOPMB001	Development and Testing of Split 6 GHz Cavities With Niobium Coatings	cavity, SRF, coupling, target	51
	N.L. Leicester, G. Burt, H.S. Marks Cockcroft Institute, Lancaster University, Lancaster, United Kingdom E. Chyhyrynets, C. Pira INFN/LNL, Legnaro (PD), Italy J.A. Conlon, O.B. Malyshev, B.S. Sian, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom D.J. Seal Lancaster University, Lancaster, United Kingdom
	Superconducting thin-films on a copper substrate are used in accelerator RF cavities as an alternative to bulk Nb due to the high thermal conductivity of copper and the lower production costs. Although thin-film coated RF cavities can match, or even exceed the performance of bulk Nb, there are some challenges around the deposition. The RF cavities are often produced as two half-cells with a weld across the centre where the RF surface current is highest, which could reduce cavity performance. To avoid this, a cavity can be produced in 2 longitudinally split halves, with the join parallel to the surface current. As the current doesn’t cross the join a simpler weld can be performed far from the fields, simplifying the manufacturing process, and potentially improving the cavities performance. This additionally allows for different deposition techniques and coating materials to be used, as well as easier post-deposition quality control. This paper discusses the development and testing of 6 GHz cavities that have been designed and coated at the Cockcroft Institute, using low temperature RF techniques to characterise cavities with different substrate preparations and coating techniques.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB001
About •	Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023
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MOPMB003	Flux Expulsion Lens: Concept and Measurements	FEL, cavity, niobium, 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 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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MOPMB011	Deposition and Characterisation of V₃Si films for SRF Applications	cavity, SRF, target, vacuum	84
	C. Benjamin, J.A. Conlon, O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G. Burt, O.B. Malyshev, D.J. Seal, R. Valizadeh Cockcroft Institute, Warrington, Cheshire, United Kingdom G. Burt, D.J. Seal Lancaster University, Lancaster, United Kingdom N.L. Leicester, H.S. Marks Cockcroft Institute, Lancaster University, Lancaster, United Kingdom L.G.P. Smith STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. A15 superconducting materials, like V₃Si and Nb₃Sn, are potential alternatives to Nb for next generation thin film SRF cavities when operated at 4 K. Their relatively high Tc and superconducting properties could allow for higher accelerating gradients and elevated operating temperatures. We present work on the deposition of V₃Si thin films on planar Cu substrates and an open structure 6 GHz cavity, using physical vapour deposition (PVD) and a V₃Si single target. The surface structure, composition and DC superconducting properties of two planar samples were characterised via secondary electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and in a magnetic field penetration facility. Furthermore, the first deposition using PVD of a V₃Si film on a 6 GHz split cavity and the RF performance is presented.
	Poster MOPMB011 [7.496 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB011
About •	Received ※ 16 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 19 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	niobium, 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 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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MOPMB020	A Comprehensive Picture of Hydride Formation and Dissipation	cavity, superconductivity, SRF, niobium	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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MOPMB033	Efforts to Suppress Field Emission in SRF Cavities at KEK	cavity, SRF, laser, acceleration	167
	M. Omet, H. Araki, T. Dohmae, H. Ito, R. Katayama, K. Umemori, Y. Yamamoto KEK, Ibaraki, Japan
	Our main objective is to achieve as high as possible quality factors Q₀ and maximal accelerating voltages E_acc within 1.3 GHz superconducting radio frequency (SRF) cavities. Beside an adequate surface treatment, key to achieve good performance is a proper assembly in the clean room prior cavity testing or operation. In this contribution we present the methods and results of our efforts to get a better understanding of our clean room environment and the particulate generation caused during the assembly work. Furthermore, we present the measures taken to suppress filed emission, followed by an analysis of vertical test results of the last six years.
	Poster MOPMB033 [1.532 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB033
About •	Received ※ 14 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023
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MOPMB062	Optimisation of Niobium Thin Film Deposition Parameters for SRF Cavities	cavity, SRF, target, niobium	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 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
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MOPMB076	Surface Characterization Studies of Gold-Plated Niobium	niobium, cavity, controls, 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 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	cavity, SRF, niobium, 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 B_p 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 B_p 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
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MOPMB093	Optimizing Growth of Niobium-3 Tin Through Pre-nucleation Chemical Treatments	niobium, 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 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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TUPTB019	First Results from Nb₃Sn Coatings of 2.6 GHz Nb SRF Cavities Using DC Cylindrical Magnetron Sputtering System	cavity, SRF, vacuum, MMI	429
	M.S. Shakel, H. Elsayed-Ali ODU, Norfolk, Virginia, USA G.V. Eremeev Fermilab, Batavia, Illinois, USA U. Pudasaini, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: Supported by DOE, Office of Accelerator R&D and Production, Contact No. DE-SC0022284, with partial support by DOE, Office of Nuclear Physics DE-AC05-06OR23177, Early Career Award to G. Eremeev. A DC cylindrical magnetron sputtering system has been commissioned and operated to deposit Nb₃Sn onto 2.6 GHz Nb SRF cavities. After optimizing the deposition conditions in a mock-up cavity, Nb-Sn films are deposited first on flat samples by multilayer sequential sputtering of Nb and Sn, and later annealed at 950 °C for 3 hours. X-ray diffraction of the films showed multiple peaks for the Nb₃Sn phase and Nb (substrate). No peaks from any Nb-Sn compound other than Nb₃Sn were detected. Later three 2.6 GHz Nb SRF cavities are coated with ~1 µm thick Nb₃Sn. The first Nb₃Sn coated cavity reached close to E_acc = 8 MV/m, demonstrating a quality factor Q₀ of 3.2 × 10⁸ at Tbath = 4.4 K and E_acc = 5 MV/m, about a factor of three higher than that of Nb at this temperature. Q₀ was close to 1.1 × 10⁹, dominated by the residual resistance, at 2 K and E_acc = 5 MV/m. The Nb₃Sn coated cavities demonstrated Tc in the range of 17.9 ¿ 18 K. Here we present the commissioning experience, system optimization, and the first results from the Nb₃Sn fabrication on flat samples and SRF cavities.
	Poster TUPTB019 [1.216 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB019
About •	Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 10 July 2023
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TUPTB039	Simulation of High Pressure Rinse in Superconducting Radio Frequency Cavities	cavity, simulation, SRF, radio-frequency	496
	B.E. Gower, K. Elliott, E.S. Metzgar, T. Xu FRIB, East Lansing, Michigan, USA
	Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Resources of the Facility for Rare Isotope Beams, a DOE Office of Science User Facility, under Award Number DE-SC0000661. The finish of radio frequency (RF) surfaces inside superconducting RF (SRF) cavities is of utmost importance as it dictates ultimate cavity performance. After the cavity surfaces have undergone chemical etching, polishing, and hydrogen degassing, the final step in surface preparation involves cleaning using a high pressure rinse (HPR) with ultra-high purity water (UPW) to remove any residue from the previous chemical processes. The complex surface geometry of cavities poses difficulties in achieving effective and thorough HPR cleaning. This study introduces a versatile simulation tool created in MATLAB, which has the potential to be applied to various SRF cavities. The detail of the algorithm used and nozzle and motion setup will be described using an FRIB 0.53 half wave resonator (HWR) cavity as an example.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB039
About •	Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 07 July 2023
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TUPTB060	Reconstruction of Field Emission Pattern for PIP-II LB650 Cavity	cavity, electron, radiation, experiment	554
	E. Del Core, M. Bertucci, A. Bosotti, A.T. Grimaldi, L. Monaco, C. Pagani, R. Paparella, D. Sertore INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Field emission (FE) is a key limiting phenomenon in SRF cavities. An algorithm exploiting a self-consistent model of cavity FE has been developed. This method exploits experimental observables (such as Q value , X-ray endpoint, and dose rate) to reconstruct emitter position and size as well as the field enhancement factor. To demonstrate the model effectiveness, the algorithm has been applied to a data set of the PIP-II LB650 prototype cavity.
	Poster TUPTB060 [0.956 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB060
About •	Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023
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WEIAA03	Surface Roughness Reduction and Performance of Vapor-Diffusion Coating of Nb₃Sn Film for SRF Application	cavity, SRF, accelerating-gradient, factory	593
	U. Pudasaini, M.J. Kelley, E.M. Lechner, C.E. Reece, O. Trofimova, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	Funding: This work is authored by Jefferson Science Associates LLC under U.S. DOE Contract No. DE-AC05- 06OR23177. Nb₃Sn offers the prospect of better RF performance (Q and E_acc) than niobium at any given temperature because of its superior superconducting properties. Nb₃Sn-coated SRF cavities are routinely produced by growing a few microns thick Nb₃Sn film on Nb cavities via tin vapor diffusion. It has been observed that a clean and smooth surface can enhance the performance of the Nb₃Sn-coated cavity, typically, the attainable acceleration gradient. The reduction of surface roughness is often linked with a correlative reduction in average coating thickness and grain size. Besides Sn supply’s careful tuning, the temperature profiles were varied to reduce the surface roughness as low as ~40 nm in 20 µm × 20 µm AFM scans, one-third that of the typical coating. Samples were systematically coated inside a mock single-cell cavity and examined using different material characterization techniques. A few sets of coating parameters were used to coat 1.3 GHz single-cell cavities to understand the effects of roughness variation on the RF performance. This presentation will discuss ways to reduce surface roughness with results from a systematic analysis of the samples and Nb₃Sn-coated single-cell cavities.
	Slides WEIAA03 [7.231 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIAA03
About •	Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023
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WEIAA04	Development of High-performance Niobium-3 Tin Cavities at Cornell University	cavity, niobium, SRF, 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 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
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WEIBA01	Surface Engineering by ALD for Superconducting RF Cavities	cavity, niobium, vacuum, SRF	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 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
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WEPWB001	Preparation and Characterization of Nb Films Deposited in SRF Cavity via HiPIMS	cavity, SRF, niobium, 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 (E_acc) 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
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WEPWB084	The Interaction among Interstitial C/N/O/H and Vacancy in Niobium via First-Principles Calculation	niobium, lattice, electron, 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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WEPWB135	A Novel Twin Drive Tuner Mechanism for 1.3 GHz ILC Cavity	cavity, SRF, FEL, operation	914
	M. Yamanaka KEK, Ibaraki, Japan
	A tuner is a device that adjusts the resonant frequency of a cavity. Here we propose a new tuner mechanism for the 1.3 GHz ILC cavity. A bellow is provided in the central portion of the helium tank in the longitudinal direction, and flanges are provided on both sides of the bellows. A linear motion actuator is fixed to the flange on one side, and the frequency is changed by pushing and pulling the flange on the opposite side. Significantly, two linear motion actuators are placed in circumference and working simultaneously. It is named a twin-drive tuner. According to the ILC specification, the cavity has a spring constant of 3 KN/mm, requiring a stroke of 2 mm to adjust the 600 kHz range. A loading force of 6 kN is required. This is shared by two linear motion actuators. We developed a prototype actuator with a loading force of 4 kN per unit. It consists of a stepping motor and a sliding screw with a plastic nut. An experimental device was constructed using this actuator and a 1.3 GHz cavity with a helium tank, and the frequency tuning was evaluated. The displacement between the flanges and the frequency are proportional, both have good linearity, and the slope is 296 kHz/mm.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB135
About •	Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 17 July 2023
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Paper

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Other Keywords

Page

MOPMB001

Development and Testing of Split 6 GHz Cavities With Niobium Coatings

cavity, SRF, coupling, target

51

N.L. Leicester, G. Burt, H.S. Marks
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
E. Chyhyrynets, C. Pira
INFN/LNL, Legnaro (PD), Italy
J.A. Conlon, O.B. Malyshev, B.S. Sian, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D.J. Seal
Lancaster University, Lancaster, United Kingdom

Superconducting thin-films on a copper substrate are used in accelerator RF cavities as an alternative to bulk Nb due to the high thermal conductivity of copper and the lower production costs. Although thin-film coated RF cavities can match, or even exceed the performance of bulk Nb, there are some challenges around the deposition. The RF cavities are often produced as two half-cells with a weld across the centre where the RF surface current is highest, which could reduce cavity performance. To avoid this, a cavity can be produced in 2 longitudinally split halves, with the join parallel to the surface current. As the current doesn’t cross the join a simpler weld can be performed far from the fields, simplifying the manufacturing process, and potentially improving the cavities performance. This additionally allows for different deposition techniques and coating materials to be used, as well as easier post-deposition quality control. This paper discusses the development and testing of 6 GHz cavities that have been designed and coated at the Cockcroft Institute, using low temperature RF techniques to characterise cavities with different substrate preparations and coating techniques.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB001

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Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 July 2023

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MOPMB003

Flux Expulsion Lens: Concept and Measurements

FEL, cavity, niobium, 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 MOPMB003 [2.459 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB003

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Received ※ 27 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 30 June 2023 — Issue date ※ 14 July 2023

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MOPMB011

Deposition and Characterisation of V₃Si films for SRF Applications

cavity, SRF, target, vacuum

84

C. Benjamin, J.A. Conlon, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G. Burt, O.B. Malyshev, D.J. Seal, R. Valizadeh
Cockcroft Institute, Warrington, Cheshire, United Kingdom
G. Burt, D.J. Seal
Lancaster University, Lancaster, United Kingdom
N.L. Leicester, H.S. Marks
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
L.G.P. Smith
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730.
A15 superconducting materials, like V₃Si and Nb₃Sn, are potential alternatives to Nb for next generation thin film SRF cavities when operated at 4 K. Their relatively high Tc and superconducting properties could allow for higher accelerating gradients and elevated operating temperatures. We present work on the deposition of V₃Si thin films on planar Cu substrates and an open structure 6 GHz cavity, using physical vapour deposition (PVD) and a V₃Si single target. The surface structure, composition and DC superconducting properties of two planar samples were characterised via secondary electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and in a magnetic field penetration facility. Furthermore, the first deposition using PVD of a V₃Si film on a 6 GHz split cavity and the RF performance is presented.

Poster MOPMB011 [7.496 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB011

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Received ※ 16 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 19 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

niobium, 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 MOPMB013 [1.749 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB013

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Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 02 July 2023

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MOPMB020

A Comprehensive Picture of Hydride Formation and Dissipation

cavity, superconductivity, SRF, niobium

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

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Received ※ 30 June 2023 — Revised ※ 18 July 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023

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MOPMB033

Efforts to Suppress Field Emission in SRF Cavities at KEK

cavity, SRF, laser, acceleration

167

M. Omet, H. Araki, T. Dohmae, H. Ito, R. Katayama, K. Umemori, Y. Yamamoto
KEK, Ibaraki, Japan

Our main objective is to achieve as high as possible quality factors Q₀ and maximal accelerating voltages E_acc within 1.3 GHz superconducting radio frequency (SRF) cavities. Beside an adequate surface treatment, key to achieve good performance is a proper assembly in the clean room prior cavity testing or operation. In this contribution we present the methods and results of our efforts to get a better understanding of our clean room environment and the particulate generation caused during the assembly work. Furthermore, we present the measures taken to suppress filed emission, followed by an analysis of vertical test results of the last six years.

Poster MOPMB033 [1.532 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB033

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Received ※ 14 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 02 September 2023 — Issue date ※ 02 September 2023

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MOPMB062

Optimisation of Niobium Thin Film Deposition Parameters for SRF Cavities

cavity, SRF, target, niobium

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 MOPMB062 [2.395 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB062

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Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 24 July 2023

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MOPMB076

Surface Characterization Studies of Gold-Plated Niobium

niobium, cavity, controls, 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 MOPMB076 [1.536 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB076

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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

cavity, SRF, niobium, 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 B_p 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 B_p on the coating thickness is consistent with theoretical predictions.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB083

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Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 12 August 2023

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MOPMB093

Optimizing Growth of Niobium-3 Tin Through Pre-nucleation Chemical Treatments

niobium, 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 MOPMB093 [1.118 MB]

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reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB093

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Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 July 2023

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TUPTB019

First Results from Nb₃Sn Coatings of 2.6 GHz Nb SRF Cavities Using DC Cylindrical Magnetron Sputtering System

cavity, SRF, vacuum, MMI

429

M.S. Shakel, H. Elsayed-Ali
ODU, Norfolk, Virginia, USA
G.V. Eremeev
Fermilab, Batavia, Illinois, USA
U. Pudasaini, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: Supported by DOE, Office of Accelerator R&D and Production, Contact No. DE-SC0022284, with partial support by DOE, Office of Nuclear Physics DE-AC05-06OR23177, Early Career Award to G. Eremeev.
A DC cylindrical magnetron sputtering system has been commissioned and operated to deposit Nb₃Sn onto 2.6 GHz Nb SRF cavities. After optimizing the deposition conditions in a mock-up cavity, Nb-Sn films are deposited first on flat samples by multilayer sequential sputtering of Nb and Sn, and later annealed at 950 °C for 3 hours. X-ray diffraction of the films showed multiple peaks for the Nb₃Sn phase and Nb (substrate). No peaks from any Nb-Sn compound other than Nb₃Sn were detected. Later three 2.6 GHz Nb SRF cavities are coated with ~1 µm thick Nb₃Sn. The first Nb₃Sn coated cavity reached close to E_acc = 8 MV/m, demonstrating a quality factor Q₀ of 3.2 × 10⁸ at Tbath = 4.4 K and E_acc = 5 MV/m, about a factor of three higher than that of Nb at this temperature. Q₀ was close to 1.1 × 10⁹, dominated by the residual resistance, at 2 K and E_acc = 5 MV/m. The Nb₃Sn coated cavities demonstrated Tc in the range of 17.9 ¿ 18 K. Here we present the commissioning experience, system optimization, and the first results from the Nb₃Sn fabrication on flat samples and SRF cavities.

Poster TUPTB019 [1.216 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB019

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Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 10 July 2023

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TUPTB039

Simulation of High Pressure Rinse in Superconducting Radio Frequency Cavities

cavity, simulation, SRF, radio-frequency

496

B.E. Gower, K. Elliott, E.S. Metzgar, T. Xu
FRIB, East Lansing, Michigan, USA

Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics. Resources of the Facility for Rare Isotope Beams, a DOE Office of Science User Facility, under Award Number DE-SC0000661.
The finish of radio frequency (RF) surfaces inside superconducting RF (SRF) cavities is of utmost importance as it dictates ultimate cavity performance. After the cavity surfaces have undergone chemical etching, polishing, and hydrogen degassing, the final step in surface preparation involves cleaning using a high pressure rinse (HPR) with ultra-high purity water (UPW) to remove any residue from the previous chemical processes. The complex surface geometry of cavities poses difficulties in achieving effective and thorough HPR cleaning. This study introduces a versatile simulation tool created in MATLAB, which has the potential to be applied to various SRF cavities. The detail of the algorithm used and nozzle and motion setup will be described using an FRIB 0.53 half wave resonator (HWR) cavity as an example.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB039

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Received ※ 18 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 07 July 2023

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TUPTB060

Reconstruction of Field Emission Pattern for PIP-II LB650 Cavity

cavity, electron, radiation, experiment

554

E. Del Core, M. Bertucci, A. Bosotti, A.T. Grimaldi, L. Monaco, C. Pagani, R. Paparella, D. Sertore
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Field emission (FE) is a key limiting phenomenon in SRF cavities. An algorithm exploiting a self-consistent model of cavity FE has been developed. This method exploits experimental observables (such as Q value , X-ray endpoint, and dose rate) to reconstruct emitter position and size as well as the field enhancement factor. To demonstrate the model effectiveness, the algorithm has been applied to a data set of the PIP-II LB650 prototype cavity.

Poster TUPTB060 [0.956 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB060

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Received ※ 17 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 28 June 2023

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WEIAA03

Surface Roughness Reduction and Performance of Vapor-Diffusion Coating of Nb₃Sn Film for SRF Application

cavity, SRF, accelerating-gradient, factory

593

U. Pudasaini, M.J. Kelley, E.M. Lechner, C.E. Reece, O. Trofimova, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

Funding: This work is authored by Jefferson Science Associates LLC under U.S. DOE Contract No. DE-AC05- 06OR23177.
Nb₃Sn offers the prospect of better RF performance (Q and E_acc) than niobium at any given temperature because of its superior superconducting properties. Nb₃Sn-coated SRF cavities are routinely produced by growing a few microns thick Nb₃Sn film on Nb cavities via tin vapor diffusion. It has been observed that a clean and smooth surface can enhance the performance of the Nb₃Sn-coated cavity, typically, the attainable acceleration gradient. The reduction of surface roughness is often linked with a correlative reduction in average coating thickness and grain size. Besides Sn supply’s careful tuning, the temperature profiles were varied to reduce the surface roughness as low as ~40 nm in 20 µm × 20 µm AFM scans, one-third that of the typical coating. Samples were systematically coated inside a mock single-cell cavity and examined using different material characterization techniques. A few sets of coating parameters were used to coat 1.3 GHz single-cell cavities to understand the effects of roughness variation on the RF performance. This presentation will discuss ways to reduce surface roughness with results from a systematic analysis of the samples and Nb₃Sn-coated single-cell cavities.

Slides WEIAA03 [7.231 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIAA03

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Received ※ 19 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 21 August 2023

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WEIAA04

Development of High-performance Niobium-3 Tin Cavities at Cornell University

cavity, niobium, SRF, 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 WEIAA04 [5.260 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIAA04

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Received ※ 29 June 2023 — Revised ※ 11 August 2023 — Accepted ※ 21 August 2023 — Issue date ※ 22 August 2023

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WEIBA01

Surface Engineering by ALD for Superconducting RF Cavities

cavity, niobium, vacuum, SRF

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 WEIBA01 [13.613 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEIBA01

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Received ※ 06 July 2023 — Revised ※ 12 August 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023

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WEPWB001

Preparation and Characterization of Nb Films Deposited in SRF Cavity via HiPIMS

cavity, SRF, niobium, 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 (E_acc) 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

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Received ※ 15 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 20 August 2023

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WEPWB084

The Interaction among Interstitial C/N/O/H and Vacancy in Niobium via First-Principles Calculation

niobium, lattice, electron, 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

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Received ※ 15 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023

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WEPWB135

A Novel Twin Drive Tuner Mechanism for 1.3 GHz ILC Cavity

cavity, SRF, FEL, operation

914

M. Yamanaka
KEK, Ibaraki, Japan

A tuner is a device that adjusts the resonant frequency of a cavity. Here we propose a new tuner mechanism for the 1.3 GHz ILC cavity. A bellow is provided in the central portion of the helium tank in the longitudinal direction, and flanges are provided on both sides of the bellows. A linear motion actuator is fixed to the flange on one side, and the frequency is changed by pushing and pulling the flange on the opposite side. Significantly, two linear motion actuators are placed in circumference and working simultaneously. It is named a twin-drive tuner. According to the ILC specification, the cavity has a spring constant of 3 KN/mm, requiring a stroke of 2 mm to adjust the 600 kHz range. A loading force of 6 kN is required. This is shared by two linear motion actuators. We developed a prototype actuator with a loading force of 4 kN per unit. It consists of a stepping motor and a sliding screw with a plastic nut. An experimental device was constructed using this actuator and a 1.3 GHz cavity with a helium tank, and the frequency tuning was evaluated. The displacement between the flanges and the frequency are proportional, both have good linearity, and the slope is 296 kHz/mm.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB135

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Received ※ 17 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 17 July 2023

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