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Superconducting RF
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TU1AA01
Status and Challenges of Nb/Cu SRF Cavities for Superconducting Linac  
 
  • M. Xu, H. Guo, Y. He, S.C. Huang, T.C. Jiang, C.L. Li, L.B. Liu, T. Liu, Z.J. Wang, Z.Q. Yang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Funding: China initiative Accelerator Driven System Large Research Infrastructures China initiative Accelerator Driven System (2017-000052-75-01-000590)
The reactor of China initiative Accelerator Driven Sub-critical (CiADS) system has strict stability requirements to the driving superconducting Linac. From the previous operation experiences of intensity superconducting Linac at institute of modern physics (IMP), more than half of the beam trips were indicated to the SRF cavity phase unlock, which is related to the thin-walled low beta SRF cavity can not tolerate the helium pressure vibration and environment vibration. In recent years, IMP is developing low beta Nb/Cu cavities to provide high stability. The cavity was made from a thin layer of high purity niobium, then the outside of cavity was cast or coat of high purity copper layer. The Nb/Cu cavities have same SRF performance as bulk-Nb cavity and improved mechanical stability. The prototype cavities have been vertical tested couple times. A horizontally testing facility are under assembly for validating the integration performance of cavity, tuner, and coupler. The technical challenges to obtain high thermal conducting copper layer and high SRF performance niobium cavity will be report too.
 
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TU1AA02 Compact, Turn-Key SRF Accelerators 290
SUPCJO04   use link to see paper's listing under its alternate paper code  
 
  • N.A. Stilin, A.T. Holic, M. Liepe, T.I. O’Connell, J. Sears, V.D. Shemelin, J. Turco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The development of simpler, compact Superconducting RF (SRF) systems represents a new subject of research in accelerator science. These compact accelerators rely on advancements made to both Nb3Sn SRF cavities and commercial cryocoolers, which together allow for the removal of liquid cryogenics from the system. This approach to SRF cavity operation, based on novel conduction cooling schemes, has the potential to drastically extend the range of application of SRF technology. By offering robust, non-expert, turn-key operation, such systems enable the use of SRF accelerators for industrial, medical, and small-scale science applications. This presentation will provide an overview of the significant progress being made at Cornell, Jefferson Lab, and Fermilab (FNAL), including stable cavity operation at 10 MV/m. It will also introduce the primary challenges of this new field and their potential solutions, along with an overview of the various applications which could benefit the most from this technology.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TU1AA02  
About • Received ※ 29 August 2022 — Revised ※ 31 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 14 October 2022
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TU1AA03 R&D Towards High Gradient CW SRF Cavities 295
 
  • D. Bafia, P. Berrutti, B. Giaccone, A. Grassellino, D.V. Neuffer, S. Posen, A.S. Romanenko
    Fermilab, Batavia, Illinois, USA
 
  This talk will discuss Fermilab’s recent progress in the surface engineering of superconducting radio-frequency (SRF) cavities geared toward producing simultaneously high quality factors and high accelerating gradients in cryomodules. We investigate possible microscopic mechanisms that drive improved performance by carrying out sequential RF tests on cavities subjected to low temperature baking. We compare performance evolution to observations made with material science techniques and find correlations with material parameters. We also discuss other key advancements that enable high gradient operation in cryomodules.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TU1AA03  
About • Received ※ 20 August 2022 — Revised ※ 24 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 16 October 2022
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TU1AA04 SWELL and Other SRF Split Cavity Development 300
 
  • F. Peauger
    CERN, Meyrin, Switzerland
 
  An innovative superconducting cavity topology has been recently proposed at CERN and at Lancaster University. It integrates longitudinal slots crossing perpendicularly the RF surface. The RF current lines run along the slots, inducing no perturbation of the accelerating mode. Thanks to this approach, the cavity can be built using halves or quadrants, which is well appropriate to precise manufacturing techniques. This configuration allows direct access to the RF surface, thus facilitating the surface preparation and thin film deposition process in the case of cavities based on Nb/Cu technology. The contact faces between the cavity parts are moved to the slots’ ends where the electromagnetic fields are extremely low, thus relaxing the constraints on the quality of the assembly joints. This paper covers the latest development of a 600 MHz slotted elliptical cavity called SWELL, which has been proposed as an alternative option for the FCC-ee RF system as well as a simplified SWELL version of a single cell 1.3 GHz elliptical cavity and a new 6 GHz split resonator made of two halves for superconducting thin film characterization.
Acknowledgement of U. Van Rienen from Rostock University for the use of their GPU based workstations for RF simulations.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TU1AA04  
About • Received ※ 14 August 2022 — Revised ※ 24 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 02 September 2022
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TU1AA06 Next-Generation Nb3Sn Superconducting RF Cavities 305
SUPCJO08   use link to see paper's listing under its alternate paper code  
 
  • N.M. Verboncoeur, G. Gaitan, M. Liepe, R.D. Porter, L. Shpani, N.A. Stilin, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Nb3Sn currently is the most promising alternative material for next-generation, higher-performance SRF cavities. Significant recent progress has been made in further increasing efficiency, maximum field, and demonstrating readiness for first applications in actual accelerators. This paper will present an overview of worldwide recent progress in making this material a viable option for further accelerators.  
slides icon Slides TU1AA06 [6.559 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TU1AA06  
About • Received ※ 31 August 2022 — Revised ※ 01 September 2022 — Accepted ※ 04 September 2022 — Issue date ※ 09 September 2022
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TH1AA02 Developments Towards FRIB Upgrade to 400 MeV/u for Heaviest Uranium Ions 653
 
  • K.E. McGee, K. Elliott, A. Ganshyn, W. Hartung, S.H. Kim, P.N. Ostroumov, J.T. Popielarski, L. Popielarski, A. Taylor, T. Xu
    FRIB, East Lansing, Michigan, USA
  • G.V. Eremeev, F. Furuta, M. Martinello, O.S. Melnychuk, A.V. Netepenko
    Fermilab, Batavia, Illinois, USA
  • B.M. Guilfoyle, M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
 
  High-Q0 medium-velocity (beta opt = 0.6) 5-cell elliptical cavities for superconducting linacs are critical technology for advancing current and future projects such as the Proton Improvement Plan II linac and the proposed energy upgrade of Michigan State University’s Facility For Rare Isotope Beams linac, FRIB400. Previous work established the validity of the novel geometry of the FRIB400 prototype 644 MHz 5-cell elliptical β = 0.65 cavities for future high Q0 development. In collaboration with FNAL, two leading-edge high-Q0 recipes, N-doping and Mid-T baking, were tested in the 5-cell format. 2/0 N-doping + cold electropolishing was successful at achieving FRIB400 and PIP-II Q0 requirements, achieving an unprecedented 3.8 x 1010 at 17.5 MV/m, satisfying the FRIB400 Q0 requirements by 1.75 times in a low-gauss environment. Mid-T baking exceeded FRIB400 Q0 requirements by 1.4 times, and benefitted from decreased residual resistance compared to the N-doped cavity test. Systematic ultrasonic thickness measurements in single-cell revealed bulk (150 microns) EP with the modified EP tool is consistent across the inner surfaces of the cavity walls.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TH1AA02  
About • Received ※ 11 August 2022 — Revised ※ 22 August 2022 — Accepted ※ 23 September 2022 — Issue date ※ 14 October 2022
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THPOGE01 Study on the Multipactor Barriers of the SARAF-Phase 2 Low-Beta and High-Beta Superconducting Cavities 802
 
  • G. Ferrand, L. Maurice
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Baudrier, N. Pichoff
    CEA-DRF-IRFU, France
 
  CEA is committed to delivering a Medium Energy Beam Transfer line and a superconducting linac (SCL) for SARAF accelerator in order to accelerate 5 mA beam of either protons from 1.3 MeV to 35 MeV or deuterons from 2.6 MeV to 40 MeV. The SCL contains 13 half-wave resonator (HWR) low beta cavities (β= 0.09) at 176 MHz and 14 HWR high-beta cavities (β = 0.18) at 176 MHz. The low-beta and high-beta series were qualified in 2021 and 2022 respectively. This contribution will focus on the observation of the multipactor barriers for all cavi-ties. It will present series of data obtained during the conditioning of these cavities  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE01  
About • Received ※ 27 July 2022 — Revised ※ 23 August 2022 — Accepted ※ 07 September 2022 — Issue date ※ 15 September 2022
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THPOGE02 Investigation of HiPIMS-Coated S(I)S Structures for SRF Cavities 805
SUPCPA02   use link to see paper's listing under its alternate paper code  
 
  • A.Ö. Sezgin, X. Jiang, M. Vogel
    University Siegen, Siegen, Germany
  • C.Z. Antoine
    CEA-IRFU, Gif-sur-Yvette, France
  • S. Keckert, J. Knobloch, O. Kugeler, D.B. Tikhonov
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  • O.B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Ries, E. Seiler
    Slovak Academy of Sciences, Institute of Electrical Engineering, Bratislava, Slovak Republic
  • L.G.P. Smith
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
 
  The sustainable next generation particle accelerators require innovative solutions to overcome the current technological challenges set by existing bulk niobium superconducting radio-frequency (SRF) cavities. Thin film-based multilayer structures in the form of superconductor-insulator-superconductor (SIS) may be the long-sought-after breakthrough for higher performance SRF cavities by enhancing both accelerating gradients and quality factors. In order to understand better the underlying mechanisms of SIS structures to be coated onto (S)RF cavities, we study various material properties with the resultant superconducting properties of high-power im-pulse magnetron sputtering (HiPIMS)-coated S(I)S structures of Nb-(AlN)-NbN with different thicknesses which are designed to be coated mainly on OFHC copper (Cu) samples for more efficient SRF cavities. This contribution presents materials properties of the aforementioned HiPIMS-coated S(I)S structures as well as the superconducting and RF behaviours of these multilayers which are assessed comparatively via DC and AC magnetization techniques.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE02  
About • Received ※ 25 August 2022 — Revised ※ 30 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 02 September 2022
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THPOGE03 Design & Multiphysics Analysis of Three-cell, 1.3 GHz Superconducting RF Cavity for Electron Beam Accelerator to Treat Wastewater 809
SUPCGE04   use link to see paper's listing under its alternate paper code  
 
  • P. Kumar, A. Pathak, R. Varma
    IIT Mumbai, Mumbai, India
 
  To treat industrial effluents including contaminants of emerging concern (CECs), Irradiation treatment by electron beam accelerator has shown promising results. Our aim is to design and develop a superconducting linear electron accelerator. A 1.3 GHz, three cell conduction cooled, TM class superconducting cavity has been proposed to accelerate a 100 mA electron beam from 100 keV to 4.5 MeV. The main aim of the design is to optimize the cavity for low heat loss and high accelerating gradient. The optimized ratio of peak surface electric and magnetic field to accelerating field for cavity are Epk/Eacc= 2.72 and Hpk/Eacc= 4.11 mT/(MV/m). The optimized Geometry factor (G) and R/Q values for this cavity are 246.7 and 306.4 ohms respectively. Here we also addressed other multiphysics issues such as Lorentz force detuning (LFD), Higher order modes (HOMs) and Multipacting. The multiphysics analysis helps to estimate the degree of these challenges. The final Lorentz detuning factor of the cavity has been reduced to 0.12 Hz/(MV/m)2, HOMs of 2.18 and 2.9 GHz modes are dominating except the main mode and Multipacting phenomena is not found at 15 MV/m of accelerating gradient.  
poster icon Poster THPOGE03 [1.121 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE03  
About • Received ※ 22 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 14 October 2022
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THPOGE05 Some Interesting Observations During Vertical Test on ESS-HB-704 SRF Cavities 812
 
  • K.D. Dumbell, A.E.T. Akintola, R.K. Buckley, M.J. Ellis, S. Hitchen, P.C. Hornickel, C.R. Jenkins, J. Lewis, A.J. May, P.A. McIntosh, K.J. Middleman, A.J. Moss, S.M. Pattalwar, M.D. Pendleton, P.A. Smith, A.E. Wheelhouse, S. Wilde
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • M.D. Hancock, J. Hathaway, C. Hodgkinson, G. Jones, M. Lowe, D.A. Mason, G. Miller, J. Mutch, A. Oates, J.T.G. Wilson
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
 
  The vertical test stand in use at Daresbury has three cavities loaded horizontally at different heights. The jacketed cavities are supplied with liquid helium from a header tank at the top of the configuration. A few cavities have been tested in different positions and the results have been analysed. The pressure of the helium inside the jacketed cavities is affected by the height of the liquid helium column above the jacket and using results from earlier analysis during cool-down enables the pressure of the cavity to be determined from the frequency of operation. Analysis of the effects may allow for corrections to the frequency to be made. In addition to the above observations there have also been some challenges in the operation at higher power as the phase of the self-excited loop driving the system, has been seen to change. This paper discusses some of the observation, analysis of those observations and challenges that are being addressed in the continuing use of this facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE05  
About • Received ※ 10 August 2022 — Revised ※ 13 August 2022 — Accepted ※ 31 August 2022 — Issue date ※ 15 September 2022
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THPOGE09 Split Thin Film SRF 6 GHz Cavities 814
 
  • B.S. Sian, G. Burt, D.J. Seal
    Lancaster University, Lancaster, United Kingdom
  • G. Burt, O.B. Malyshev, D.J. Seal, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • H.S. Marks
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  Many current accelerators use cavities that are manufactured as two half cells that are electron beam welded together, the weld is across the peak surface current of the cavity. This weld can lead to large increases in surface resistance and limit the performance of thin film coated cavities. Many problems with the coating process for thin film Superconducting Radio Frequency (SRF) cavities are also due to this weld. Thin film SRF cavities can perform as well as bulk niobium cavities if the cavity is manufactured seamlessly, without any weld, as they have a more uniform surface, however, they are much more difficult and expensive to manufacture. A cavity with a split longitudinally, parallel to the direction of the electric field, would not need to be welded. These seamless cavities are easier to manufacture and coat. This opens the possibilities to coat with new materials and multilayer coatings. These cavities may allow SRF cavities to operate at significantly better parameters (higher quality factor and maximum accelerating field) than current state of the art cavities. This work discusses development and testing of longitudinally split seamless cavities at Daresbury Laboratory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE09  
About • Received ※ 25 August 2022 — Revised ※ 28 August 2022 — Accepted ※ 12 September 2022 — Issue date ※ 15 October 2022
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THPOGE10 RF Characterisation of Bulk Niobium and Thin Film Coated Planar Samples at 7.8 GHz 818
SUPCPA04   use link to see paper's listing under its alternate paper code  
 
  • D.J. Seal, G. Burt, O.B. Malyshev, B.S. Sian, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt, D.J. Seal, B.S. Sian
    Lancaster University, Lancaster, United Kingdom
  • E. Chyhyrynets, C. Pira
    INFN/LNL, Legnaro (PD), Italy
  • O. Hryhorenko, D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • O.B. Malyshev, E.A. Marshall, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • H.S. Marks
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  Research is ongoing into the use of superconducting thin films to replace bulk niobium for future radio frequency (RF) cavities. A key part of this research requires measuring the RF properties of candidate films. However, coating and testing thin films on full-sized cavities is both costly and time-consuming. Instead, films are typically deposited on small, flat samples and characterised using a test cavity. A cost-effective facility for testing such samples has recently been built and commissioned at Daresbury Laboratory. The facility allows for low power surface resistance measurements at a resonant frequency of 7.8 GHz, temperatures down to 4 K and sample surface magnetic fields up to 1 mT. A brief overview of this facility as well as recent results from measurements of both bulk Nb and thin film coated samples will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE10  
About • Received ※ 11 August 2022 — Revised ※ 19 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 16 September 2022
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THPOGE13 Design of Production PIP-II SSR1 Cavities 822
 
  • C.S. Narug, J. Bernardini, M. Parise, D. Passarelli
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work supported by the Fermi National Accelerator Laboratory, managed and operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
The testing and manufacturing process of the PIP-II Single Spoke Resonators Type 1 (SSR1) prototype jacketed cavity presented opportunities for refinement of the production series. Experience from the prototype cavity and the design of other cavities at Fermilab were used. The mechanical design of the production jacketed cavity has been modified from the prototype design to allow for improvements in overall performance, structural behavior, and manufacturability of the weld joints.
 
poster icon Poster THPOGE13 [1.199 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE13  
About • Received ※ 14 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 02 September 2022
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THPOGE15 Measuring the Seebeck Coefficient at Cryogenic Temperatures for LCLS-II-HE Project 825
SUPCPA01   use link to see paper's listing under its alternate paper code  
 
  • L. Shpani, M. Ge, A.T. Holic, M. Liepe, J. Sears, N.M. Verboncoeur
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work is supported by the DOE LCLS-II HE Project.
The Seebeck effect plays a crucial role during the cooldown procedure in SRF based accelerators, like LCLS-II at SLAC. The temperature-dependent Seebeck coefficient quantitatively measures the strength of electric potential induced by thermal gradients in metals. This effect is present in cryomodules and drives thermoelectric currents generating magnetic fields. These fields can get trapped in cavities and cause additional dissipation in RF fields. We have therefore designed and commissioned an experimental setup that does continuous measurements of the Seebeck coefficient for cryogenic temperatures ranging from 200K down to below 10K. We present results of the measurements of this coefficient for materials commonly used in cryomodules, such as niobium, titanium, niobium-titanium, silicon bronze, and stainless steel.
 
poster icon Poster THPOGE15 [0.959 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE15  
About • Received ※ 27 August 2022 — Revised ※ 04 September 2022 — Accepted ※ 26 September 2022 — Issue date ※ 29 September 2022
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THPOGE16 Evaluation of Single-Cell Cavities Made of Forged Ingot Niobium at Jefferson Lab 828
 
  • P. Dhakal, G. Ciovati, G.R. Myneni
    JLab, Newport News, Virginia, USA
  • G. Ciovati, B.D. Khanal
    ODU, Norfolk, Virginia, USA
  • G.R. Myneni
    BSCE, Yorktown, Virginia, USA
 
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Currently, fine grain niobium (Nb) (grain size ~ 50 um) and large grain Nb (grain size of a few cm) are being used for the fabrication of superconducting radio frequency (SRF) cavities. Medium grain forged ingot with grain size of a few hundred um may be beneficial for cost-effectiveness as well as providing better performance for future SRF-based accelerators. Forged ingot Nb with medium grain size is a novel production method to obtain Nb discs used for the fabrication of superconducting radio frequency cavities. We have fabricated two 1.5 GHz single cell cavities made from forged Nb ingot with a residual resistivity ratio of ~100. The cavities were chemically and mechanically polished and heat-treated in the temperature range of 650-1000 C before the rf test. One of the cavities reached an accelerating gradient of 34 MV/m with a quality factor Q > 1e10, while the second cavity was limited at 14 MV/m, likely due to a weld defect at the equator.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE16  
About • Received ※ 22 August 2022 — Revised ※ 29 August 2022 — Accepted ※ 03 September 2022 — Issue date ※ 15 September 2022
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THPOGE18 Design of a 1.3 GHz RF-Dipole Crabbing Cavity for International Linear Collider 832
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • R.A. Rimmer
    JLab, Newport News, Virginia, USA
 
  The International Liner Collider (ILC) requires crabbing systems to increase the luminosity of the colliding electron and positron bunches. There are several frequency options for the crabbing cavity. We have designed a 1.3 GHz compact 1-cell and 2-cell rf-dipole crabbing cavity to compensate for luminosity degradation due to large crossing angle. This paper presents the 1-cell and 2-cell cavities designed to meet the current specifications including the fundamental power coupler and higher order mode couplers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE18  
About • Received ※ 11 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 16 September 2022
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THPOGE19 Field Shielding of NbTiN Based Multilayer Structure for Accelerating Cavities 836
SUPCRI06   use link to see paper's listing under its alternate paper code  
 
  • I.H. Senevirathne, J.R. Delayen, A.V. Gurevich
    ODU, Norfolk, Virginia, USA
  • D.R. Beverstock
    The College of William and Mary, Williamsburg, Virginia, USA
  • D.R. Beverstock, J.R. Delayen, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Funding: NSF Grants PHY-1734075 and PHY-1416051, and DOE Awards DE-SC0010081 and DE-SC0019399
Over the past few decades, bulk niobium (Nb) has been the material of choice for superconducting radio frequen-cy (SRF) cavities used in particle accelerators to achieve higher accelerating gradients and lower RF losses. Multi-layer (SIS) structures consisting of alternating thin layers of superconductor(S) and insulator(I) deposited on a bulk Nb have been proposed to enhance the peak surface magnetic field and sustain a higher accelerating gradient. In this study, multilayers based NbTiN and AlN deposited on bulk Nb are used to test the proposed enhancement using the DC magnetic Hall probe technique. The tech-nique detects a penetrating magnetic field through the multilayer sample as it is placed under an external mag-netic field produced by a magnetic coil. This work re-ports the characterization and measurements of the mag-netic field of full flux penetration through single layers of NbTiN and bilayers of NbTiN/AlN on bulk Nb.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE19  
About • Received ※ 24 August 2022 — Revised ※ 01 September 2022 — Accepted ※ 08 September 2022 — Issue date ※ 15 September 2022
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THPOGE22 Medium Temperature Treatments of Superconducting Radio Frequency Cavities at DESY 840
THOPA07   use link to see paper's listing under its alternate paper code  
 
  • L. Steder, C. Bate, H. Remde, D. Reschke, J. Schaffran, L. Trelle, H. Weise, M. Wiencek
    DESY, Hamburg, Germany
  • M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Over the last years several different approaches to increase the performance of superconducting radio frequency (SRF) cavities by heat treatments have been developed and tested. At DESY, the R&D aims for cavities with enlarged quality factors while maintaining high accelerating gradients, since an envisaged upgrade of the European XFEL requires both. For this purpose, medium temperature (mid-T) treatments around 300 °C seem to be very promising. Lately, the furnace infrastructure at DESY was refurbished and now a niobium-retort furnace capable of carrying 1.3 GHz nine-cell cavities can be used for R&D studies. Vertical test results of single-cell cavities treated in this furnace at medium temperatures are presented and compared to four cavities treated similarly in a furnace at the company Zanon Research & Innovation Srl (Zanon). All mentioned cavities show enlarged quality factors but at the same time reduced gradients compared to their reference measurements before the mid-T treatment. The DESY treatments were accompanied by small niobium samples for surface analyses, which are also presented. Furthermore, the influence of post-treatment high pressure water rinsings is studied.  
slides icon Slides THPOGE22 [1.277 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE22  
About • Received ※ 19 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 27 August 2022 — Issue date ※ 15 September 2022
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THPOGE23 Vertical Electro-Polishing of 704 MHz Resonators Using Ninja Cathode: Gradients Over 40 MV/m Achieved on ESS Single-Cell Cavity 844
THOPA08   use link to see paper's listing under its alternate paper code  
 
  • F. Éozénou, M. Baudrier, E. Cenni, E. Fayette, L. Maurice, C. Servouin
    CEA-DRF-IRFU, France
  • H. Hayano, H. Ito, S. Kato, T. Kubo, H. Monjushiro, T. Saeki
    KEK, Ibaraki, Japan
  • Y.I. Ida, K. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • G. Jullien
    CEA-IRFU, Gif-sur-Yvette, France
 
  CEA, KEK and Marui Galvanizing Company have been collaborating to apply the Vertical Electropolishing (VEP) process of elliptical SRF cavities to a 704MHz single-cell ESS-type cavity, using a rotating so called and patented "Ninja" cathode. First presented results* were promising with a gradient of 27MV/m achieved, without any heat treatment applied. The performance has been pushed further since. The cavity has undergone a heat treatment at 650°C during 10h, followed by a final VEP sequence and a baking at 120°C during 48h hours. The achieved gradient at 2K was 44MV/m (power limitation), and the quality factor Q0 exceeding 5·1010 up to 10 MV/m. The superiority of VEP compared to standard "BCP" chemical treatment is demonstrated and we intend now to scale the process to 5-Cell β=0.86 ESS cavity. We also intend to push further the performance by applying "2-step baking" (75°C and 120°C) proposed by FNAL, which was successfully applied at CEA Saclay on 1300MHz single-cell resonators with gradients above 50MV/m achieved after VEP bulk treatment.
* TUPCAV001, SRF 2021
 
slides icon Slides THPOGE23 [0.868 MB]  
poster icon Poster THPOGE23 [0.918 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOGE23  
About • Received ※ 24 August 2022 — Revised ※ 01 September 2022 — Accepted ※ 09 September 2022 — Issue date ※ 16 September 2022
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