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SUPCAV002 Ex-Situ Investigation of the Effects of Heating Rate on the Recrystallization in Rolled Polycrystals of High-Purity Niobium 1
 
  • Z.L. Thune, N. Fleming, C. McKinney, E.M. Nicometo
    MSU, East Lansing, USA
  • S. Balachandran
    NHMFL, Tallahassee, Florida, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
 
  Funding: US Dept. of Energy award DE-SC0009960
The consistent production of high-purity niobium cavities for superconducting radiofrequency (SRF) applications is crucial for enabling improvements in accelerator performance. Recent work has shown that dislocations and grain boundaries trap magnetic flux which dissipates energy and degrades cavity performance. We hypothesize that the current heating rate used in production is too slow and therefore facilitates recovery rather than recrystallization. Recovery, unlike recrystallization, does not reduce the number of geometrically necessary dislocations (GNDs) that are strongly correlated to trapped magnetic flux. Using excess high-purity niobium saved from the production of a cavity, the material was divided into two groups and rolled to ~30% reduction with half rolled parallel to the original rolling direction, and the other half rolled perpendicular. To examine the effect of heating rate, samples were encapsulated in quartz tubes and placed into either a preheated furnace or a cold furnace to allow for heat treatments at different rates. Then using ex-situ electron backscatter diffraction (EBSD) mapping, the extent of recrystallization was determined.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV002  
About • Received ※ 22 June 2021 — Revised ※ 31 August 2021 — Accepted ※ 16 November 2021 — Issue date ※ 20 February 2022
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SUPCAV003 Dynamic Temperature Mapping of Nb3Sn Cavities 6
 
  • R.D. Porter, N. Banerjee, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Niobium-3 Tin (Nb3Sn) is the most promising alternative material to niobium for SRF accelerator cavities. The material promises nearly twice the potential accelerating gradients (~100 MV/m in TESLA elliptical cavities), increased quality factors, and 4.2 K operation. Current state of the art Nb3Sn cavities reach quality factors of 2 x 1010 at 4.2 K and have reached 24 MV/m. Determining the cause of the premature field limitation is the topic of ongoing research. Cornell University has recently developed a high-speed temperature mapping system that can examine cavity quench mechanisms in never before achieved ways. Here we present high-speed temperature map results of Nb3Sn cavities and examine the quench mechanism and dynamic heating. We show an initial multipacting quench and sudden temperature jumps at multiple locations on the cavity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV003  
About • Received ※ 09 July 2021 — Accepted ※ 12 August 2021 — Issue date; ※ 31 August 2021  
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SUPCAV005 Current Status of the ALPI Linac Upgrade for the SPES Facilities at INFN LNL 11
 
  • A. Tsymbaliuk, D. Bortolato, F. Chiurlotto, E. Chyhyrynets, G. Keppel, E. Munaron, C. Pira, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  • E. Chyhyrynets
    Università degli Studi di Padova, Padova, Italy
  • A. Tsymbaliuk
    UNIFE, Ferrara, Italy
 
  The SPES project is based at INFN LNL and covers basic research in nuclear physics, radionuclide production, materials science research, nuclear technology and medicine. The Radioactive Ion Beam (RIB) produced by SPES will be accelerated by ALPI, which is a linear accelerator, equipped with superconducting quarter wave resonators (QWRs) and operating at LNL since 1990. For RIB acceleration it is mandatory to perform an upgrade of ALPI which consists of the implementation of two additional cryostats, containing 4 accelerating cavities each, in the high-ß section. The QWRs production technology is well established. The production technology of Nb/Cu QWRs should be adjusted for high-ß cavities production. In the framework of the upgrade, several vacuum systems were refurbished, optimal parameters of the biased sputtering processes of copper QWR cavities and plates were defined. The process of mechanical and chemical preparation, sputtering and cryogenic measurement of the high-ß Nb/Cu QWR cavities were adjusted. Several QWR cavities were already produced and measured. Currently, the production of the Nb/Cu sputtered QWR cavities and plates is ongoing.  
poster icon Poster SUPCAV005 [0.938 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV005  
About • Received ※ 21 June 2021 — Revised ※ 07 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 29 April 2022
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SUPCAV006 Cavity Designs for the CH3 to CH11 of the Superconducting Heavy Ion Accelerator HELIAC 15
 
  • T. Conrad, M. Busch, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • K. Aulenbacher, J. List
    IKP, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, M. Basten, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
    HIM, Mainz, Germany
  • W.A. Barth, M. Heilmann, A. Rubin, A. Schnase, S. Yaramyshev
    GSI, Darmstadt, Germany
  • S. Lauber
    KPH, Mainz, Germany
 
  Funding: BMBF
In collaboration of GSI, HIM and IAP Frankfurt, the superconducting linear accelerator HELIAC is being built at GSI. The cw-mode operated linac with a final energy of 7.3 MeV/u at a mass-to-charge ratio of A/q=6 and a frequency of 216.816 MHz is intended for various experiments, especially with heavy ions at energies close to the Coulomb barrier for the research of SHE. The planned linac consists of 4 cryostats, 4 superconducting bunchers, 4 solenoids and 12 superconducting CH-cavities. After successful beam tests with CH0 and high frequency tests with CH1 and CH2, CH3 to CH11 will be designed. Based on previous experience and successful test results, individual optimizations of the cavity design will be performed. Attention has been paid to reducing production costs by designing as many components as possible, such as spokes or the tank caps with the same geometries. Despite this cost reduction, it was possible to improve the theoretical performance in the simulations. In addition, a test bench is being developed which will be used for the first-time investigation of the mechanical stability, possible material fatigue and the durability of the dynamic bellows tuners.
 
poster icon Poster SUPCAV006 [1.490 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV006  
About • Received ※ 21 June 2021 — Accepted ※ 21 October 2021 — Issue date; ※ 12 November 2021  
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SUPCAV007 Thick Film Morphology and SC Characterizations of 6 GHz Nb/Cu Cavities 18
 
  • V.A. Garcia Diaz, O. Azzolini, E. Chyhyrynets, G. Keppel, C. Pira, F. Stivanello, M. Zanierato
    INFN/LNL, Legnaro (PD), Italy
  • E. Chyhyrynets
    Università degli Studi di Padova, Padova, Italy
  • D. Fonnesu
    CERN, Meyrin, Switzerland
  • O. Kugeler, D.B. Tikhonov
    HZB, Berlin, Germany
  • R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • M. Vogel
    University Siegen, Siegen, Germany
 
  Funding: European Union’s H2020 Framework Programme under Grant Agreement no. 764879
Thick films deposited in long pulse DCMS mode onto 6 GHz copper cavities have demonstrated the mitigation of the Q-slope at low accelerating fields. The Nb thick films (~40 microns) show the possibility to reproduce the bulk niobium superconducting properties and morpholo-gy characterizations exhibited dense and void-free films that are encouraging for the scaling of the process to 1.3 GHz cavities. In this work a full characterization of thick films by DC magnetometry, computer tomography, SEM and RF characterizations are presented.
 
poster icon Poster SUPCAV007 [1.007 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV007  
About • Received ※ 21 June 2021 — Revised ※ 07 July 2021 — Accepted ※ 16 February 2022 — Issue date ※ 08 April 2022
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SUPCAV008 Design and Construction of Nb3Sn Vapor Diffusion Coating System at KEK 23
 
  • K. Takahashi, T. Okada
    Sokendai, Ibaraki, Japan
  • H. Ito, E. Kako, T. Konomi, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
 
  Vapor diffusion Nb3Sn coating system was developed at KEK. At most 1.3GHz 3-cell cavity can be coat with the coating system. The coating system consists of a coating chamber made of Nb, a vacuum furnace for heating the Nb chamber, and a heating device of Tin in the crucible. The Nb chamber vacuum and the furnace vacuum are isolated to prevent contamination from the furnace. There is a heating device for increasing Tin vapor pressure. In this presentation, the design and construction of the coating system are reported.  
poster icon Poster SUPCAV008 [0.981 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV008  
About • Received ※ 21 June 2021 — Accepted ※ 18 November 2021 — Issue date; ※ 11 April 2022  
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SUPCAV009 First Nb3Sn Coating and Cavity Performance Result at KEK 27
 
  • K. Takahashi, T. Okada
    Sokendai, Ibaraki, Japan
  • H. Ito, E. Kako, T. Konomi, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
 
  At KEK, Nb3Sn vapor diffusion R&D for High-Q has just started. We have performed Nb3Sn coating on niobium samples and characterized these samples. We optimized the cavity coating parameter from the result of characterized samples. After optimizing the parameter, we have performed Nb3Sn coating on a TESLA-like single-cell Nb cavity and measured cavity performance in vertical tests. This presentation presents the result of the cavity coating and performance results.  
poster icon Poster SUPCAV009 [1.477 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV009  
About • Received ※ 21 June 2021 — Accepted ※ 18 March 2022 — Issue date; ※ 16 May 2022  
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SUPCAV010 Design of Third-Harmonic Superconducting Cavity for Shen-Zhen Industry Synchrotyon Radiation Source7 32
 
  • N. Yuan, L. Lu, W. Ma
    Sun Yat-sen University, Zhuhai, Guangdong, People’s Republic of China
  • L.G. Liu
    SINAP, Shanghai, People’s Republic of China
  • L. Yang, Z. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Shenzhen industry synchrotron radiation source is the fourth generation of medium energy light source with beam energy of 3GeV. It has the characteristics of low emittance and high brightness. In the design, the beam lifetime is one of the most important parameters. The main factor that affects its beam lifetime is the scattering of electron collisions inside the beam. To solve this problem, a harmonic radio frequency system is used. The third harmonic superconducting elliptical cavity is de-signed to stretch beam length to improve beam quality and beam lifetime. The present work is mainly about the shape optimization of 1.5 GHz 2-cell third harmonic superconducting elliptical cavity. Firstly, the principle of harmonic cavity in dual high frequency system is introduced, and the resonant frequency and acceleration gradient of superconducting cavity are given. Then, CST, electromagnetic field simulation software is used to optimize the cavity parameters to obtain the high performance and high frequency parameters that meet the requirements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV010  
About • Received ※ 21 June 2021 — Revised ※ 21 November 2021 — Accepted ※ 18 February 2022 — Issue date ※ 03 May 2022
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SUPCAV011 Third Harmonic Superconductive Cavity for Bunch Lengthening and Beam Lifetime Increase of Sirius Synchrotron Light Source 37
 
  • I. Carvalho de Almeida, M. Hoffmann Wallner, A. Pontes Barbosa Lima
    CNPEM, Campinas, SP, Brazil
 
  A passive third harmonic superconducting cavity is to be installed at Sirius’ 4th generation synchrotron light source in order to lengthen the bunches and improve beam lifetime, which is dominated by Touschek scattering. A study of optimal bunch lengthening is carried on by enforcing a flat potential well around the synchronous electron and the results are compared to the passive operation case for several shunt impedances and unloaded quality factors based on known operating cavities. To determine the new bunch shape due to beam loading and its length, a full consistent approach is followed by setting the harmonic voltage amplitude equal to the optimum value and calculating the required detune, harmonic phase and synchronous phase for an initial complex form factor, allowing the new distribution to be obtained by an iterative process. For each case analyzed, energy acceptance is obtained through the separatrix in the phase plane and the corresponding lifetime increase ratio is calculated. Input power required after the addition of the harmonic cavity is then estimated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV011  
About • Received ※ 20 June 2021 — Accepted ※ 15 November 2021 — Issue date; ※ 21 March 2022  
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SUPCAV013 Multipacting Analysis of the Quadripolar Resonator (QPR) at HZB 42
 
  • S. Bira, D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • Y. Kalboussi
    CEA-IRFU, Gif-sur-Yvette, France
  • S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • Th. Proslier
    CEA-DRF-IRFU, France
 
  Multipacting (MP) is a resonating electron discharge, often plaguing radio-frequency (RF) structures, produced by the synchronization of emitted electrons with the RF fields and the electron multiplication at the impact point with the surface structure. The electron multiplication can take place only if the secondary emission yield (SEY, i.e. the number of electrons emitted due to the impact of one incoming electron), , is higher than 1. The SEY value depends strongly on the material and the surface contamination. Multipacting simulations are crucial in high-frenquency (HF) vacuum structures to localize and potentially improve the geometry. In this work, multipacting simulations were carried out on the geometry of the Quadrupole Resonator (QPR) in operation at HZB using the Spark 3D module in Microwave Studio suite (CST). These simulations helped to understand a particular behavior observed during the QPR tests, and furthermore made it possible to suggest enhancement ways in order to limit this phenomenon and facilitate its operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV013  
About • Received ※ 09 July 2021 — Revised ※ 09 July 2021 — Accepted ※ 09 April 2022 — Issue date ※ 07 May 2022
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SUPCAV014 Design and Simulation of 500 MHz Single Cell Superconducting Cavity 46
 
  • Y.B. Sun, W. Ma
    Sun Yat-sen University, Zhuhai, Guangdong, People’s Republic of China
  • L.G. Liu
    SSRF, Shanghai, People’s Republic of China
  • L. Lu, L. Yang, Z. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Funding: Work supported by Shenzhen Development and Reform Commis-sion
The Shenzhen Industrial Synchrotron Radiation Light Source is a fourth-generation medium-energy light source with a 3GeV storage ring electron energy and an emit-tance less than 100 pm·rad. In order to ensure the long-term stable and efficient operation of the light source, a new type of 500 MHz single-cell superconducting cavity was designed in this study to be used as a pre-research superconducting cavity for the Light Source. The 500 MHz superconducting cavity has a large beam aperture and low high order modes (HOMs) impedance, which can be used in accelerators with larger currents. In this design, we simply adopted the same design scheme as the KEKB-type and CESR-type superconducting cavity. Using CST electromagnetic field simulation software to calculate and simulate the characteristics of the cavity, the results show that the designed 500 MHz single-cell cavity can meet the requirements of a high acceleration gradient, a high r/Q value, and a low peak surface field.
 
poster icon Poster SUPCAV014 [0.420 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV014  
About • Received ※ 21 June 2021 — Revised ※ 07 July 2021 — Accepted ※ 12 August 2021 — Issue date ※ 05 May 2022
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SUPCAV016 Studies on the Fundamental Mechanisms of Niobium Electropolishing 50
 
  • E.A.S. Viklund, D.N. Seidman
    NU, Evanston, Illinois, USA
  • L. Grassellino, S. Posen, T.J. Ring
    Fermilab, Batavia, Illinois, USA
 
  To improve the superconducting performance of niobium SRF cavities, electropolishing (EP) with a sulfuric and hydroflouric acid mixture is used. The chemistry of this reaction is complex due to the interactions between diffusion mechanisms, surface oxide structure, and multiple chemical species. Past studies on the EP process have produced a certain set of optimum parameters that have been used successfully for a long time. However, two recent developments have called the efficacy of the existing EP process into question. Since the introduction of nitrogen doping the surface quality of some cavities has been very poor. Also, EP performed at colder than standard temperatures leads to an increase in the cavity performance. To understand these questions, we perform a multivariate study on the EP process using niobium test samples electropolished at different temperatures and potentials. We find that electropolishing at lower potentials leads to rough surface features such as pitting and grain etching. Some of the surface features show similarities to features seen in niobium cavities. The effect of electropolishing temperature is not clear based on the results of this study.  
poster icon Poster SUPCAV016 [2.447 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV016  
About • Received ※ 22 June 2021 — Revised ※ 21 August 2021 — Accepted ※ 29 September 2021 — Issue date ※ 15 November 2021
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SUPCAV018 First N-Doping and Mid-T Baking of Medium-ß 644 MHz 5-Cell Elliptical Superconducting RF Cavities for Michigan State University’s Facility for Rare Isotope Beams 53
 
  • K.E. McGee, S.H. Kim, P.N. Ostroumov, A. Taylor
    FRIB, East Lansing, Michigan, USA
  • G.V. Eremeev, M. Martinello, A.V. Netepenko
    Fermilab, Batavia, Illinois, USA
  • M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
 
  Funding: Work supported by the 2020 US DoE, Office of Science Graduate Student Research award (SCGSR), and US DoE, Office of Science, High Energy Physics under Cooperative Agreement award number DE-SC0018362
Two hadron linacs currently under development in the US, the PIP-II linac at Fermi National Accelerator Laboratory (FNAL) and the upgrade for Michigan State University’s Facility For Rare Isotope Beams (FRIB), will employ 650 and 644 MHz ß-0.6 elliptical superconducting cavities respectively to meet their design energy requirements. The desired CW operation modes of these two linacs sets Q-factor requirements well above any previously achieved for cavities at this operating frequency and velocity, driving the need to explore new high-Q treatments. The N-doping technique developed at FNAL and employed at an industrial scale to the LCLS-II cryomodules is a strong candidate for high-Q treatments, but work is needed to refine the treatment to the lower operating frequency and velocity regime. We present the first results of the first N-doping tests and a "mid-T" bake test in the FRIB 644 MHz 5-cell elliptical cavities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV018  
About • Received ※ 23 June 2021 — Revised ※ 16 November 2021 — Accepted ※ 08 May 2022 — Issue date ※ 08 May 2022
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MOPCAV001 Cavity Production and Testing of the First C75 Cryomodule for CEBAF 250
 
  • G. Ciovati, G. Cheng, E. Daly, G.K. Davis, M.A. Drury, J.F. Fischer, D. Forehand, K. Macha, F. Marhauser, E.A. McEwen, A.L.A. Mitchell, A.V. Reilly, R.A. Rimmer, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refurbished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into ’cavity pairs’ and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8·109. The performance limitations were field emission and multipacting.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV001  
About • Received ※ 17 June 2021 — Accepted ※ 21 February 2022 — Issue date; ※ 10 April 2022  
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MOPCAV002 Shape Evolution of C75 Large-Grain Niobium Half-Cells During Cavity Fabrication 255
 
  • G. Ciovati
    JLab, Newport News, Virginia, USA
 
  Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The largely anisotropic deformation of large-grain Nb discs during deep drawing into half-cells poses a challenge for achieving a desired shape accuracy. Two 5-cell cavities for the C75 CEBAF cryomodule rework program have been fabricated at Jefferson Lab from large-grain Nb discs directly sliced from an ingot. The shape of the inner surface of eight half-cells has been inspected using a FARO Edge laser scanner during the fabrication process and compared to the reference shape. On average, approximately 63% of the half-cell inner surface was found to be within 0.1 mm of the reference shape and ~90% to be within 0.2 mm, after the final equator machining. Several 5-cell C75 cavities have also been fabricated at Research Instruments, Germany, and measurements of the shape accuracy using a Zeiss 3D coordinate measuring machine gave similar results. One half-cell was measured both at Research Instruments and Jefferson Lab for comparison.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV002  
About • Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 11 February 2022  
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MOPCAV004 Mechanical Properties of Directly Sliced Medium Grain Niobium for 1.3 GHz SRF Cavity 259
 
  • A. Kumar, K. Abe, T. Dohmae, S. Michizono, T. Saeki, Y. Watanabe, A. Yamamoto, M. Yamanaka
    KEK, Ibaraki, Japan
  • A. Fajardo, N. Lannoy
    ATI, Albany, Oregon, USA
  • G.R. Myneni
    JLab, Newport News, Virginia, USA
  • G.R. Myneni
    BSCE, Yorktown, Virginia, USA
 
  At KEK, research is being conducted to manufacture cost-effective 1.3 GHz superconducting radio frequency cavities based on the fine grain (FG) and large grain (LG) Niobium (Nb) materials. Medium grain (MG) Nb has been proposed and developed as an alternative to the FG and LG Nb, being expected to have better mechanical stability with a cost-effective and clean manufacturing approach. MG Nb has an average grain size of 200 - 300 µm, which is approximately 100 times smaller than the LG Nb, however, there are occasional grains as large as 1-2 mm. As such, it is expected to have isotropic properties rather than the anisotropic properties of LG Nb. In this paper, we will outline the mechanical properties of the directly sliced high RRR MG Nb material (manufactured by ATI), and a comparative study will be presented with respect to FG and LG Nb. Moreover, the viability of MG Nb for the global high-pressure regulation for 1.3 GHz SRF cavity will be presented.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV004  
About • Received ※ 21 June 2021 — Revised ※ 11 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 25 March 2022
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MOPCAV005 Status of SNS Proton Power Upgrade SRF Cavities Production Qualification 265
 
  • P. Dhakal, E. Daly, G.K. Davis, J.F. Fischer, D. Forehand, N.A. Huque, A.L.A. Mitchell, P.D. Owen
    JLab, Newport News, Virginia, USA
  • M.P. Howell, S.-H. Kim, J.D. Mammosser
    ORNL, Oak Ridge, Tennessee, USA
 
  The Proton Power Upgrade project at Oak Ridge National Lab’s Spallation Neutron Source (SNS PPU) currently being constructed will double the proton beam power from 1.4 to 2.8 MW by adding 7 additional cryomodules, each contains four six-cell high beta (\beta = 0.81) superconducting radio frequency cavities. The cavities were built by Research Instruments, Germany, with all the cavity processing done at the vendor site, including electropolishing as the final active chemistry step. All 28 cavities needed for 7 cryomodules were delivered to Jefferson Lab, ready to be tested. The cryogenic RF qualifications and helium vessel welding were done at Jefferson Lab. The performance largely exceed the requirements, and greatly exceeded the performance of the original SNS cavity production series. Here, we present the summary of RF test on production cavities to this date.
This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV005  
About • Received ※ 19 June 2021 — Revised ※ 10 July 2021 — Accepted ※ 12 March 2022 — Issue date ※ 06 April 2022
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MOPCAV006 High-Q/High-G R&D at KEK Using 9-Cell TESLA-Shaped Niobium Cavities 268
 
  • R. Katayama, A. Araki, H. Ito, E. Kako, T. Konomi, S. Michizono, M. Omet, K. Umemori
    KEK, Ibaraki, Japan
 
  We will report on the current progress of High-Q/High-G R&D using three 1.3 GHz 9-cell TESLA shape niobium superconducting cavities at the High Energy Accelerator Research Organization (KEK). These cavities are made of bulk niobium of fine grain material with RRR >300 and have been annealed at 900 degrees for 3 hours. The cavity performances were evaluated at the Superconducting RF Test Facility at KEK (KEK-STF) after 2-step bake (70-75°C 4 h + 120°C 48 h), electropolishing at low temperature, and fast cooling procedure were applied to these cavities. In this study, obtained results will be compared with the baseline measurement for the standard recipe at KEK.  
poster icon Poster MOPCAV006 [1.876 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV006  
About • Received ※ 22 June 2021 — Revised ※ 14 January 2022 — Accepted ※ 22 February 2022 — Issue date ※ 28 February 2022
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MOPCAV008 CiADS and HIAF Superconducting Cavity Development Status and the Transition to Production Stage 273
 
  • M. Xu, H. Guo, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, C.L. Li, L.B. Liu, S.H. Liu, T. Liu, S.M. Shanab, T. Tan, Y. Tao, Y.Q. Wan, F.F. Wang, R.X. Wang, Z.J. Wang, P.R. Xiong, J.C. Yang, Z.Q. Yang, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
  • E.Z. Zaplatin
    FZJ, Jülich, Germany
 
  Funding: Work supported by Large Research Infrastructures "China initiative Accelerator Driven System’(Grant No.2017-000052-75-01-000590 )
Two accelerators facilities, China initiative Accelerator Driven Sub-critical System (CiADS) and High Intensity heavy-ion Accelerator Facility (HIAF), co-funded by the China central and local government, is being designed and constructed at Huizhou city, Guangdong Province. The Institute of Modern Physics(IMP), Chinese Academy of Science is responded for constructing and operating the facility. CiADS’s mission is to demonstrate the principle and technical of employing high power protons to transit fission nuclear plant wastes. HIAF is defined as a nuclear structure research facility. The two linacs contains six types , totally 233 superconducting cavities, will be constructed in recent three years. Stable production rate and reliable surface processing will be the main challenges. This paper reports the cavity design, prototype status and massive production plan and status.
 
poster icon Poster MOPCAV008 [2.254 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV008  
About • Received ※ 22 June 2021 — Revised ※ 10 December 2021 — Accepted ※ 04 February 2022 — Issue date ※ 10 April 2022
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MOPCAV009 A New Process for Nitrogen Doping of Niobium Cavities 276
 
  • M. Cavellier
    Omega Physics, St Gildas de Rhuys, France
 
  Nitrogen-doping of Niobium cavities is now well known and industrialization of this process is emerging. However, the current process, based on thermal treatment in Nitrogen atmosphere leads to various inaccuracies (what is the concentration of Nitrogen in the Nb material? Penetration depth, created phases, …) and some post-treatment like chemical-mechanical polishing of the inner surface. This work presents a new and more accurate patented process based on nitrogen ion beam implantation into the inner surface of Nb cavities. Ion implantation is a well-known, controlled, accurate and reproducible process that does not require post-treatment. For these reasons, the industrialization of Nitrogen-doping Nb cavities will be improved through ion implantation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV009  
About • Received ※ 19 June 2021 — Revised ※ 10 July 2021 — Accepted ※ 19 November 2021 — Issue date ※ 06 April 2022
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MOPCAV010 Design of a HOM-Damped 166.6 MHz Compact Quarter-Wave β=1 Superconducting Cavity for High Energy Photon Source 278
 
  • X.Y. Zhang, J. Dai, L. Guo, T.M. Huang, Z.Q. Li, Q. Ma, F. Meng, Z.H. Mi, P. Zhang, H.J. Zheng
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China.
Superconducting cavities with low RF frequencies and heavy damping of higher order modes (HOM) are desired for the main accelerator of High Energy Photon Source (HEPS), a 6 GeV synchrotron light source promising ultralow emittance currently under construction in Beijing. A compact 166.6 MHz superconducting cavity was proposed adopting a quarter-wave β=1 geometry. Based on the successful development of a proof-of-principle cavity, a HOM-damped 166.6 MHz compact superconducting cavity was subsequently designed. Ferrite damper was installed on the beam pipe to reduce HOM impedance below stringent threshold of coupled-bunch instabilities. Being compact, RF field heating on the cavity vacuum seal was carefully examined against quenching the NbTi flange. The cavity was later dressed with helium vessel and the tuning mechanism was also realized. Excellent RF and mechanical properties were eventually achieved. Finally, the two-cavity string was designed to ensure smooth transitions among components and proper shielding of synchrotron light. This paper presents a complete design of a fully dressed HOM-damped low-frequency β=1 superconducting cavity for HEPS.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV010  
About • Received ※ 20 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 14 April 2022  
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MOPCAV011 Fabrication Process of Single Spoke Resonator Type-2 (SSR2) for RISP 283
 
  • M.O. Hyun, J. Joo, H.C. Jung, Y. Kim
    IBS, Daejeon, Republic of Korea
 
  Funding: This paper was supported by the Rare Isotope Science Project (RISP), which is funded by the Ministry of Science and ICT (MSIT) and National Research Foundation (NRF) of the Republic of Korea.
Rare Isotope Science Project (RISP) in the Institute of Basic Science (IBS), South Korea, is now constructing superconducting linear accelerator 3 (SCL3) for low-energy beam experiment and also making prototypes of superconducting cavity, RF power coupler, tuner, and cryomodule of superconducting (SC) linear accelerator 2 (SCL2) for high-energy beam experiment. Single spoke resonator type-1 (SSR1) and type-2 (SSR2) superconducting cavities are now on the prototyping stage. This paper explains about SSR2 fabrication process from press-forming to electron beam welding (EBW) with RRR300 niobium sheets.
 
poster icon Poster MOPCAV011 [1.949 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV011  
About • Received ※ 22 June 2021 — Revised ※ 26 August 2021 — Accepted ※ 26 August 2021 — Issue date ※ 22 April 2022
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MOPCAV012 Fabrication of 1.3 GHz SRF Cavities Using Medium Grain Niobium Discs Directly Sliced from Forged Ingot 287
 
  • T. Dohmae, K. Abe, H. Inoue, A. Kumar, S. Michizono, T. Saeki, K. Umemori, Y. Watanabe, A. Yamamoto, M. Yamanaka, K. Yoshida
    KEK, Ibaraki, Japan
  • A. Fajardo, N. Lannoy
    ATI, Albany, Oregon, USA
  • G.R. Myneni
    JLab, Newport News, USA
 
  Medium grain (MG) niobium disc which is directly sliced from forged ingot is newly investigated for the cavity material. An effective cost reduction can be achieved using MG niobium since rolling process which is necessary for typical niobium sheet can be skipped during MG niobium production. Grain size of MD niobium is 200-300 um which is much smaller than large grain (LG) niobium directly sliced from melted niobium ingot. Hence, the formability of MG niobium is expected to be much better than LG niobium. KEK has started fabrication of cavity using MG niobium. In this talk, characteristic of MG niobium during fabrication will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV012  
About • Received ※ 20 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 17 September 2021
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MOPCAV013 LCLS-II-HE Vertical Acceptance Testing Plans 291
 
  • J.T. Maniscalco, S. Aderhold, J.D. Fuerst, D. Gonnella
    SLAC, Menlo Park, California, USA
  • T.T. Arkan, M. Checchin, J.A. Kaluzny, S. Posen
    Fermilab, Batavia, Illinois, USA
  • J. Hogan, A.D. Palczewski, C.E. Reece, K.M. Wilson
    JLab, Newport News, Virginia, USA
 
  LCLS-II-HE has performance requirements similar to but generally more demanding than those of LCLS-II, with an operating gradient of 21 MV/m (up from 16 MV/m in LCLS-II) and tighter restrictions on field emission and multipacting. In this paper, we outline the requirements for the 1.3 GHz cavities and the plans for qualification of these cavities by vertical test. We discuss lessons learned from LCLS-II and highlight the changes implemented in the vertical test procedure for the new project.  
poster icon Poster MOPCAV013 [0.413 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV013  
About • Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 02 May 2022
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MOPCAV014 The Development of a Prototype Fundamental Power Coupler for CiADS and HIAF Half Wave Resonators 295
 
  • T.C. Jiang, F. Bai, Y. He, Z.Q. Lin, Y.Q. Wan, R.X. Wang, Z.J. Wang, M. Xu, S.H. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  More than 100 Half-wave resonators (HWR) will be adopted for China Initiative Accelerator Driven Sys-tem (CiADS) and High Intensity heavy-ion Accelerator Facility (HIAF) at IMP. Each HWR cavity equips with one variable coupling, dual-warm-ceramic fundamen-tal power coupler (FPC). The FPC should be able to transmit up to 30 kW in CW mode. This paper will give an overview of the RF design of the 162.5 MHz CW power coupler. The coupler employs two warm ceram-ics in a 50 Ω coaxial line to ensure operation relia-bility. The results of thermal and thermomechanical will also be reported. Two prototype couplers have been fabricated and the RF measurements with low RF power were carried out.  
poster icon Poster MOPCAV014 [1.123 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV014  
About • Received ※ 21 June 2021 — Accepted ※ 01 April 2022 — Issue date; ※ 07 April 2022  
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MOPCAV015 Development of QWRS for the Future Upgrade of JAEA Tandem Superconducting Booster 299
 
  • Y. Kondo, H. Kabumoto, M. Matsuda
    JAEA, Ibaraki-ken, Japan
  • T. Dohmae, E. Kako, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
  • H. Harada, J. Kamiya, K. Moriya, J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  The Japan Atomic Energy Agency (JAEA) tandem booster is one of the pioneering superconducting heavy ion linac in the world. It consists of 40 QWRs with an operation frequency of 130 MHz and βopt=0.1, and has potential to accelerate various ions up to Au to 10 MeV/u. The user operation was started in 1994, however, it has been suspended since the Great East Japan Earthquake in 2011. Recently, we started activities to investigate and improve the performance of the QWR cavities towards the restart of the tandem booster. In addition, design work of new lower beta cavities to improve the acceleration efficiency of heavier ions such as Uranium has been launched. Now we are surveying some operation frequencies and types of cavities including multi-gap QWR with use of electro-magnetic simulation of the cavities. In this work, the current status of the R&D program for the JAEA tandem facility is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV015  
About • Received ※ 20 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 01 October 2021  
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MOPCAV016 HOM Couplers and RF Antennas for HL-LHC Crab Cavities: Developments for Manufacturing 303
 
  • S. Barrière, S. Atieh, B. Bulat, R. Calaga, S.J. Calvo, O. Capatina, T. Demazière, G. Favre, A. Gallifa Terricabras, M. Garlasché, J.-M. Geisser, J.A. Mitchell, E. Montesinos, F. Motschmann, P. Naisson, R. Ninet, L. Prever-Loiri, L.R.A. Renaglia, K. Scibor, N. Villanti
    CERN, Geneva, Switzerland
 
  Superconducting RF crab cavities are being manufactured as part of the HL-LHC upgrade at CERN. Amongst its related ancillaries, radiofrequency HOM (High Order Modes) suppressors and field antennas are essential for reaching nominal performance during operation with high energy beams, as they monitor and control the electromagnetic fields in the cavities. Several concepts of such equipment have been engineered and manufactured, for both design validation and RF performance assessment. The following paper highlights manufacturing process definition, its challenges and the assembly strategies focusing on the ongoing RFD prototypes for the SPS beam tests. Specific tooling development and test campaigns are also described.  
poster icon Poster MOPCAV016 [1.452 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPCAV016  
About • Received ※ 21 June 2021 — Revised ※ 10 July 2021 — Accepted ※ 11 November 2021 — Issue date ※ 18 November 2021
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TUPCAV001 Vertical Electro-Polishing of 704 MHz Resonators Using Ninja Cathode: First Results 431
 
  • F. Éozénou, M. Baudrier, E. Cenni, E. Fayette, L. Maurice, C. Servouin
    CEA-DRF-IRFU, France
  • V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, H. Ito, S. Kato, T. Kubo, H. Monjushiro, T. Saeki
    KEK, Ibaraki, Japan
  • G. Jullien
    CEA-IRFU, Gif-sur-Yvette, France
 
  Vertical Electro-Polishing (VEP) of elliptical cavities using rotating Ninja cathodes (Marui Company patented technology) has continually been improved since 2012 and successfully applied for 1300MHz multicell ILC-type resonators. The goal of the presented study is to apply this technology to 704 MHz ESS-type resonators with both better Q0 and accelerating gradients in mind. We intend to demonstrate the superiority of VEP compared to standard Buffer Chemical Polishing (BCP), for possible applications such as MYRRHA accelerator. We describe here the promising results achieved on β=0.86 single-cell cavity after 200 µm uniform removal. The cavity quenched at 27 MV/m without any heat treatment. The surface resistance achieved was less than 5nΩ at 1.8K. Substantial performance improvement is expected after heat treatment of the cavity and additional 20 µm VEP sequence. A cathode for 5-Cell ESS cavity is concomitantly under design stage.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV001  
About • Received ※ 21 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 23 August 2021 — Issue date ※ 17 March 2022
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TUPCAV002 HOM Excitation in Spoke Resonator for SRF Studies 435
 
  • D. Longuevergne, N. Bippus, F. Chatelet, V. Delpech, N. Hu, C. Joly, T. Pépin-Donat, F. Rabehasy, L. Renard
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • M. Baudrier
    CEA-DRF-IRFU, France
  • E. Cenni, L. Maurice
    CEA-IRFU, Gif-sur-Yvette, France
 
  The excitation of Higher Order Modes (HOM) or Lower Order Modes (LOM) has been performed for years on multi-cell superconducting accelerating cavities as a mean to coarsely locate a quench, a defective area or ignite a plasma for surface cleaning. Moreover, such multi-mode testing is very useful to understand more accurately the frequency dependence of the surface resistance in a wide range of surface magnetic fields (0<B<150mT). In that sense, several type of dedicated non-accelerating resonators like Quadrupole Resonator (QPR), Half- or Quarter- Wave resonators have been built to specifically study new superconducting materials or new surface or heat treatments. What is proposed in this paper is to perform such multi-mode analysis (352 MHz, 720 MHz and 1300 MHz) in an existing accelerating cavity, in particular a Spoke Resonator. Baseline results will be presented and perspectives of such technique will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV002  
About • Received ※ 22 June 2021 — Revised ※ 19 July 2021 — Accepted ※ 23 August 2021 — Issue date ※ 15 April 2022
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TUPCAV003 1.3 GHz Seamless Copper Cavities via CNC Spinning Technique 440
 
  • F. Sciarrabba, O. Azzolini, G. Keppel, C. Pira
    INFN/LNL, Legnaro (PD), Italy
  • I. Calliari, R. Guggia, L. Pezzato, M. Pigato
    UNIPD, Padova, Italy
 
  The spinning process is an established technology for the production of seamless resonant cavities. The main drawback is that, so far, a manual process is adopted, so the quality of the product is subject to the worker’s skills. The Compute Numerical Controlled (CNC) applied to the spinning process can be used to limit this problem and increase the reproducibility and geometrical accuracy of the cavities obtained. This work reports the first 1.3 GHz SRF seamless copper cavities produced by CNC spinning at the Laboratori Nazionali di Legnaro of INFN. For this purpose, metrological analysis were conducted to verify the geometrical accuracy of the cavities after different steps of forming and thermal treatments; axial profile and wall thickness measurements were carried out, investigating different zones of the cavity profile. The cavities were also characterized through mechanical and microstructural analysis, to identify the effect of the automatic forming process applied to the production process of the 1.3 GHz SRF seamless copper cavities.  
poster icon Poster TUPCAV003 [1.025 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV003  
About • Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 23 August 2021 — Issue date ※ 24 December 2021
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TUPCAV004 Deflecting Cavities for Proton Beam Spreader in CiADS Project 445
 
  • Y.L. Huang, Y. He, H. Jia, Y.S. Qin, Z.J. Wang, Z.L. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Funding: Large Research Infrastructures "China initiative Accelerator Driven System’(Grant No.2017-000052-75-01-000590 ) and National Natural Science Foundation of China (Grant NO. 11805249)
Chinese initiative Accelerator Driven Subcritical System (CiADS) is supposed to accelerate continuous 162.5 MHz, 10 mA (or higher) proton beam to 500 MeV (or higher energy) with a superconducting driver linac. More application scenarios based on this high power intensity proton linac are now under considerations. Beam spreader system based on deflecting cavities for multiple users simultaneous operation are discussed in this paper, as well as the RF structure options for the equal eight- and nigh- beam-line split schemes.
#huangyulu@impcas.ac.cn
 
poster icon Poster TUPCAV004 [1.074 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV004  
About • Received ※ 21 June 2021 — Revised ※ 16 August 2021 — Accepted ※ 23 August 2021 — Issue date ※ 13 May 2022
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TUPCAV005 Toward Qualifications of HB and LB 650MHz Cavities for the Prototype Cryomodules for the PIP-II Project 448
 
  • M. Martinello, D.J. Bice, C. Boffo, S.K. Chandrasekaran, G.V. Eremeev, F. Furuta, T.N. Khabiboulline, K.E. McGee, A.V. Netepenko, J.P. Ozelis, A.I. Sukhanov, G. Wu
    Fermilab, Batavia, Illinois, USA
  • M. Bagre, V. Jain, A. Puntambekar, S. Raghvendra, P. Shrivastava
    RRCAT, Indore (M.P.), India
  • M. Bertucci, A. Bosotti, C. Pagani, R. Paparella
    INFN/LASA, Segrate (MI), Italy
  • P. Bhattacharyya, S. Ghosh, S. Ghosh, A. Mandal, S. Seth, S. Som
    VECC, Kolkata, India
  • M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
  • S.H. Kim, K.E. McGee, P.N. Ostroumov
    FRIB, East Lansing, Michigan, USA
  • K.K. Mistri, P.N. Prakash
    IUAC, New Delhi, India
 
  High-beta (HB) and low-beta (LB) 650 MHz cryomodules are key components of the Proton Improvement Plan II (PIP-II) project. In this contribution we present the results of several 5-cell HB650 cavities that have been processed and tested with the purpose of qualifying them for the prototype cryomodule assembly, which will take place later this year. We also present the first results obtained in LB650 single-cell cavities process optimization. Taking advantage of their very similar geometry, we are also analyzing the effect of different surface treatments in FRIB’s 5-cell medium-beta 644MHz cavities. Cavities processed with N-doping and mid-T baking showed very promising results in term of both Q-factors and accelerating gradient for these low-beta structures.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV005  
About • Received ※ 01 July 2021 — Accepted ※ 02 November 2021 — Issue date; ※ 16 May 2022  
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TUPCAV006 Nb3Sn Films Depositions from Targets Synthesized via Liquid Tin Diffusion 452
 
  • M. Zanierato, O. Azzolini, E. Chyhyrynets, V.A. Garcia Diaz, G. Keppel, C. Pira, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
 
  The deposition of Nb3Sn on copper cavities is inter-esting for the higher thermal conductivity of copper compared to common Nb substrates. The better heat exchange would allow the use of cryocoolers reducing cryogenic costs and the risk of thermal quench [1]. Magnetron sputtering technology allows the deposi-tion of Nb3Sn on substrates different than Nb, however the coating of substrates with complex geometry (such as elliptical cavities) may require targets with non-planar shape, difficult to realize with classic powder sintering techniques. In this work, the possibility of using the Liquid Tin Diffusion (LTD) technique to produce sputtering targets is explored. The LTD tech-nique is a wire fabrication technology, already devel-oped in the past at LNL for SRF applications [2], that allows the deposition of very thick and uniform coat-ing on Nb substrates even with complex geometry [3]. Improvements in LTD process, proof of concept of a single use LTD target production, and characterization of the Nb3Sn film coated by DC magnetron sputtering with these innovative targets are reported in this work.  
poster icon Poster TUPCAV006 [5.032 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV006  
About • Received ※ 21 June 2021 — Revised ※ 12 July 2021 — Accepted ※ 23 August 2021 — Issue date ※ 02 September 2021
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TUPCAV009 AMR Sensors Studies and Development for Cavities Tests Magnetometry at CEA 457
 
  • J. Plouin, E. Cenni, L. Maurice
    CEA-DRF-IRFU, France
 
  Studying flux expulsion during superconducting cavities test increases the need for exhaustive magnetometric cartography. The use of Anistropic Magneto Resistance (AMR) sensors, much cheaper than commercial fluxgates, allows the use of tens of sensors simultaneously. Such sensors are developed and sold for room temperature application but are resistant to cryogenic temperatures. However, they need proper calibration, which is more difficult at cryogenic temperature. Actually, this calibration uses the flip of the magnetization of the anisotropic ferromagnetic element, which coercitive field is increased at low temperature. We will present the development of method and software carried out at CEA for the use of such sensors, as well as the preliminary design of a rotating magnetometric device destined to elliptical cavities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV009  
About • Received ※ 22 June 2021 — Revised ※ 13 January 2022 — Accepted ※ 22 February 2022 — Issue date ※ 22 February 2022
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TUPCAV010 Application of the ASME Boiler and Pressure Vessel Code in the Design of SRF Cavities at Fermilab 460
 
  • C.S. Narug, M. Parise, D. Passarelli
    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.
Jacketed Superconducting Radio Frequency (SRF) cavities structurally comprise of an inner niobium vessel surrounded by a liquid helium containment vessels. The pressure of the helium bath and/or its volume might be such that a jacketed SRF cavity shall be considered a system of pressure vessels. Thus, methods described in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) should be used to analyze the structural soundness of jacketed SRF cavities. This paper will report the use of the set of rules developed at Fermilab for the design of SRF cavities, such as jacketed 1.3 GHz cavities for LCLS-II HE and jacketed Single Spoke Resonator type~2 (SSR2) for PIP-II, to ensure a similar level of safety as prescribed by the ASME BPVC.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV010  
About • Received ※ 22 June 2021 — Accepted ※ 23 August 2021 — Issue date; ※ 12 December 2021  
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TUPCAV013 STC Qualification Tests of PIP-II HB650 Cavities 465
 
  • A.I. Sukhanov, S.K. Chandrasekaran, G.V. Eremeev, F. Furuta, S. Kazakov, T.N. Khabiboulline, T.H. Nicol, Y.M. Pischalnikov, O.V. Prokofiev, V. Roger, G. Wu, V.P. Yakovlev, J.C. Yun
    Fermilab, Batavia, Illinois, USA
  • C. Contreras-Martinez
    FRIB, East Lansing, Michigan, USA
 
  Design of the high beta 650 MHz prototype cryomodule for PIP-II is currently undergoing at Fermilab. The cryomodule includes six 5-cell elliptical SRF cavities with accelerating voltage up to 20 MV and low heat dissipation (Q0 > 3.3 · 10zEhNZeHn). Characterization of performance of fully integrated jacketed cavities with high power coupler and tuner is crucial for the project. Such a characterization of jacketed cavity requires a horizontal test cryostat. The Fermilab Spoke Test Cryostat (STC) has been upgraded to accommodate testing of 650 MHz cavities. Commissioning of upgraded STC has been reported at SRF’19 conference. In this paper we present results of testing of the prototype HB650 cavity in upgraded STC facility. We characterize cavity performance and qualify it for the prototype HB650 cryomodule assembly.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV013  
About • Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date; ※ 04 October 2021  
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TUPCAV014 Design of a Third Harmonic Cavity With Low R/Q for the ESR in BNL EIC 469
 
  • B.P. Xiao
    BNL, Upton, New York, USA
 
  Funding: The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
For the electron Storage Ring (ESR) of Brookhaven National Lab Electron Ion Collider (BNL EIC), beam loading is a great concern due to the high beam current together with abortion gap, especially for harmonic cavities due to higher operational frequency. There were attempts to use feedback/feedforward control, using multiple cavities with counter-phasing. A straightforward way to lower beam loading effect is to design a cavity with low R/Q. In this paper, we show such a design for the 3rd harmonic cavity for BNL EIC ESR.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV014  
About • Received ※ 22 June 2021 — Revised ※ 12 November 2021 — Accepted ※ 11 February 2022 — Issue date ※ 22 February 2022
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TUPCAV015 Performance of a Low Frequency QWR-Based SRF Gun 472
 
  • G. Chen, M.V. Fisher, M. Kedzie, M.P. Kelly, T.B. Petersen, T. Reid
    ANL, Lemont, Illinois, USA
  • X. Lu, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
 
  Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
Superconducting radio-frequency (SRF) electron guns are generally considered to be an effective way of producing beams with high brightness and high repetition rates (or continuous wave). In this work, the 199.6 MHz quarter wave resonator (QWR)-based Wisconsin Free Electron Laser (WiFEL) superconducting electron gun was recently refurbished and tested at Argonne (ANL). The field performance of the e-gun was fully characterized. During this time, multipacting (MP) conditioning was performed for over 20 hours to overcome the hard MP barrier observed in the accelerating voltage range of 8 to 40 kV; the presence of multipacting is expected to operationally important for future e-guns. Here we simulated and studied the effect using CST* Microwave Studio and Particle Studio and compare with the measured data.
* CST Studio Suite, version 2020, https://www.cst.com.
 
poster icon Poster TUPCAV015 [4.870 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPCAV015  
About • Received ※ 21 June 2021 — Revised ※ 20 December 2021 — Accepted ※ 22 February 2022 — Issue date ※ 23 March 2022
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WEPCAV001 Study of the Niobium Oxide Structure and Microscopic Effect of Plasma Processing on the Niobium Surface 585
 
  • B. Giaccone, M. Martinello
    Fermilab, Batavia, Illinois, USA
  • B. Giaccone, J. Zasadzinski
    IIT, Chicago, Illinois, USA
 
  A study of the niobium oxide structure is presented here, with particular focus on the niobium suboxides. Multiple steps of argon sputtering and XPS measurements were carried out until the metal surface was exposed. The sample was then exposed to air and the oxide regrowth was studied. In addition, three Nb samples prepared with different surface treatments were studied before and after being subjected to plasma processing. The scope is investigating the microscopic effect that the reactive oxygen contained in the glow discharge may have on the niobium surface. This study suggests that the Nb2O5 thickness may increase, although no negative change in the cavity performance is measured since the pentoxide is a dielectric.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV001  
About • Received ※ 22 June 2021 — Revised ※ 13 September 2021 — Accepted ※ 13 January 2022 — Issue date ※ 16 May 2022
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WEPCAV002 Improvement of Chemical Etching Capabilities (BCP) for SRF Spoke Resonators at IJCLab 590
 
  • J. Demercastel-Soulier, P. Duchesne, D. Longuevergne, G. Olry, T. Pépin-Donat, F. Rabehasy, D. Reynet, S. Roset, L.M. Vogt
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
 
  Buffered chemical polishing (BPC) is the reference surface polishing adopted for ESS and MYRRHA SRF spoke resonators at IJCLab. This chemical treatment, in addition to improving the RF performance, fits into the frequency adjustment strategy of the jacketed cavity during its preparation phase. In the framework of the collaboration with Fermilab for PIP-II project, IJCLab has developed a new setup to perform rotational BCP. The implementation of a rotation during chemical etching improves significantly the homogeneity and quality of surface polishing. In this paper, we present the numerical analysis based on a fluid dynamics model. The goal is to estimate the acid flow characteristics inside the cavity, determine the influence of several parameters as mass flow rate and rotation speed and propose the best configuration for the new experimental setup  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV002  
About • Received ※ 23 June 2021 — Revised ※ 18 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 14 January 2022
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WEPCAV006 650 MHz Elliptical Cavities in IMP for CiADS Project 594
 
  • Y.L. Huang, H. Guo, Y. He, C.L. Li, R.X. Wang, Z.J. Wang, M. Xu, Z.Q. Yang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Funding: Large Research Infrastructures "China initiative Accelerator Driven System"(Grant No.2017-000052-75-01-000590 ) and National Natural Science Foundation of China (Grant NO. 11805249)
650MHz multi-cell superconducting elliptical cavities with optimum beta equal to 0.62 and 0.82 were adopted in the driver linac of Chinese initiative Accelerator Driven Subcritical System (CiADS) to accelerate the 10 mA proton beam from 175 MeV up to 500 MeV, with the possibility to upgrade the energy to 1 GeV and higher. Mechanical design and optimization of the niobium cavity-titanium helium vessel assembly will be summarized in this paper. Vertical test results of three single cell prototype cavities will also be discussed, with comparisons with the simulation values.
*Work supported by Large Research Infrastructures "China initiative Accelerator Driven System’(Grant No.2017-000052-75-01-000590 ) and National Natural Science Foundation of China (Grant NO. 11805249)
 
poster icon Poster WEPCAV006 [1.389 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV006  
About • Received ※ 21 June 2021 — Revised ※ 10 December 2021 — Accepted ※ 05 February 2022 — Issue date ※ 07 April 2022
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WEPCAV007 Status and First Tests of the Reduced-Beta Capture Cavity for the S-DALINAC 597
 
  • S. Weih, M. Arnold, M. Dutine, J. Enders, R. Grewe, L.E. Jürgensen, N. Pietralla, F. Schließmann, M. Steinhorst
    TU Darmstadt, Darmstadt, Germany
 
  Funding: work supported by German research council (DFG) through GRK 2128 ’AccelencE’ and the state of Hesse through the LOEWE research project Nuclear Photonics and the Collaborative Research Cluster ELEMENTS
The superconducting part of the injector section of the superconducting Darmstadt electron linear accelerator (S-DALINAC) [1] consisted of one five-cell capture cavity and two 20-cell cavities at 3 GHz resonance frequency. All of them were geometrically adapted to electron velocities with a beta of 1, while the thermionic gun provides electrons with a beta of 0.74. This mismatch resulted in an insufficient capture process for optimum beam quality. For this reason, a new six-cell capture cavity with a beta of 0.86 has been designed and built. Field flatness tuning, a test in the vertical bath cryostat, and a UHV furnace treatment have been carried out in-house to finalize the cavity processing. The cryostat module was adapted to house the new cavity, which has been recently installed. Following the module assembly, a first RF test run was conducted at the S-DALINAC. We report on these latest advancements towards the implementation of the injector upgrade.
* N. Pietralla, Nuclear Physics News, Vol. 28, No. 2, 4 (2018).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV007  
About • Received ※ 20 June 2021 — Revised ※ 22 December 2021 — Accepted ※ 27 February 2022 — Issue date ※ 01 March 2022
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WEPCAV008 A Fast Mechanical Tuner for SRF Cavities 600
 
  • S.V. Kuzikov
    Euclid TechLabs, Solon, Ohio, USA
  • V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  There is a particular need for fast tuners and phase shifters for advanced superconducting accelerator RF systems. The tuners based on ferrite, ferroelectric and piezo materials are commonly used. However, those methods suffer from one or another issue of high power loss, slow response, and narrow tuning range. We propose a robust, fast (up to ~5 MHz/sec), high efficient mechanical tuner for SRF cavities operating at the frequency 50 MHz. We develop an external mechanical tuner that is strongly coupled to the cavity. The tuner design represents a trade-off of high efficiency (low RF losses and low heat flux) and frequency tunability range. Our approach solves this trade-off issue. We propose RF design which exploits two coupled resonators so that a main high-field cavity is controlled with a small tunable resonator with a flexible metallic wall operating in a relatively low RF field. Simulations, carried out for a 7.5 MV/m 50 MHz SRF Quarter Wave Resonator (QWR), show that frequency tunability at level 10-3 is obtainable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV008  
About • Received ※ 17 June 2021 — Revised ※ 06 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 04 February 2022
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WEPCAV009 Conceptual Design of Balloon Double Spoke Resonator 604
 
  • Z.Y. Yao, R.E. Laxdal
    TRIUMF, Vancouver, Canada
 
  Funding: TRIUMF receives funding via a contribution through the National Research Council Canada.
The balloon variant of the spoke resonator was proposed to eliminate the intensive multipacting (MP) barriers around the operating field level by modifying the local electro-magnetic (EM) fields. TRIUMF has previously reported the prototyping of a 325MHz β=0.3 single spoke resonator (SSR) that demonstrated the principle of the balloon concept. To extend the benefits of the balloon variant to multi-spoke resonators, this paper will report a conceptual design of a 325MHz β=0.5 balloon double spoke resonator (DSR). The consequences from the balloon SSR design, such as the relations between EM field distributions and the field levels of the MP barriers, were applied to the DSR design. Other particular geometry features were also added due to the characters of DSRs. The simulated MP barriers were significantly squeezed to the lower field level compared to a conventional DSR design. Simulation results and conceptual design will be reported.
 
poster icon Poster WEPCAV009 [2.260 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV009  
About • Received ※ 22 June 2021 — Revised ※ 20 December 2021 — Accepted ※ 01 March 2022 — Issue date ※ 18 April 2022
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WEPCAV010 Comparison of Electromagnetic Properties During Fabrication of Copper and Niobium Prototypes of 325 MHz Coaxial Half-Wave Resonator 609
 
  • D. Bychanok, V. Bayev, S. Huseu, S.A. Maksimenko, A.E. Sukhotski, E. Vasilevich
    INP BSU, Minsk, Belarus
  • A.V. Butenko, E. Syresin
    JINR, Dubna, Moscow Region, Russia
  • M. Gusarova, M.V. Lalayan, S.M. Polozov
    MEPhI, Moscow, Russia
  • V.S. Petrakovsky, A.I. Pokrovsky, A. Shvedov, S.V. Yurevich
    Physical-Technical Institute of the National Academy of Sciences of Belarus, Minsk, Belarus
  • Y. Tamashevich
    HZB, Berlin, Germany
 
  The main fabrication stages of niobium and copper prototypes of coaxial half-wave resonators (HWR) operating at frequency 325 MHz for the Nuclotron-based Ion Collider fAcility (NICA) injector are presented and discussed. Results of intermediate measurements and electromagnetic properties control for niobium and copper cavities of equivalent geometrical characteristics are compared and analyzed. The comparison of electromagnetic properties of Cu- and Nb-prototypes allows estimating specific features and differences of intermediate "warm" measurements of niobium and copper cavities. The presented results will be used for further development and production of superconductive niobium cavities with a similar design for the NICA-project.  
poster icon Poster WEPCAV010 [3.180 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV010  
About • Received ※ 21 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 27 December 2021 — Issue date ※ 05 May 2022
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WEPCAV011 Present Status of the Spoke Cavity Prototyping for the JAEA-ADS Linac 612
 
  • J. Tamura, Y. Kondo, F.M. Maekawa, S.I. Meigo, B. Yee-Rendón
    JAEA/J-PARC, Tokai-mura, Japan
  • T. Dohmae, E. Kako, H. Sakai, K. Umemori
    KEK, Ibaraki, Japan
 
  The Japan Atomic Energy Agency (JAEA) is proposing an accelerator-driven subcritical system (ADS) for efficient reduction of high-level radioactive waste generated in nuclear power plants. One of the challenging R¥&Ds for ADS is the reliability of the accelerator. In preparation for the full-scale design of the proton linac for the JAEA-ADS, we are now prototyping a single-spoke cavity for low-beta (around 0.2) beam acceleration. As there is no experience of manufacturing a superconducting spoke cavity in Japan, the cavity prototyping and performance testing are essential to ensure the feasibility of the JAEA-ADS linac. To proceed to an actual cavity fabrication, we have carefully reviewed the fabrication process. And then, we examined the electron-beam welding using niobium test pieces and investigated the welding condition for realizing the smooth underbead. We have finally started the press forming of niobium sheets and the machine work to shape the cavity parts. Now, we are parparing for the electron-beam welding of the shaped niobium parts.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV011  
About • Received ※ 02 July 2021 — Revised ※ 30 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 28 March 2022
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WEPCAV012 Research and Development of 650 MHz Cavities for CEPC 616
 
  • P. Sha, C. Dong, F.S. He, S. Jin, Z.Q. Li, B.Q. Liu, Z.H. Mi, W.M. Pan, J.Y. Zhai, X.Y. Zhang, H.J. Zheng
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work was supported by the National Key Programme for S&T Research and Development (No. 2016YFA0400400), the Platform of Advanced Photon Source Technology R&D.
650 MHz 2-cell superconducting cavities are proposed for the main ring of the Circular Electron Positron Collider (CEPC). The design, fabrication, surface treatment (buffered chemical polishing) and vertical tests of the cavities with HOM couplers were conducted. The performance of the cavity at 2 K is not affected by the HOM coupler. The maximum intrinsic quality factor of the cavity with the HOM coupler reached 3.1·1010 at 20 MV/m. The vertical test results showed that the fundamental mode external quality factor of all HOM couplers is an order of magnitude larger than quality factor of the cavity. The HOM damping results for the 650 MHz 2-cell cavity were also measured at cryogenic temperature and compared with the simulated and measured results at room temperature. Two 650 MHz 2-cell cavities jacketed have been integrated into a test cryomodule for CEPC. Another 650 MHz 2-cell cavity reached 6·1010 at 22 MV/m after nitrogen infusion. In addition, two 650 MHz 1-cell cavities reached 2.7·1010 at 35 MV/m (fine grain) and 3.6·1010 at 32 MV/m (large grain) after electro-polishing, respectively. In future, electro-polishing will be applied to 650 MHz 2-cell cavity soon.
 
poster icon Poster WEPCAV012 [1.956 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV012  
About • Received ※ 21 June 2021 — Accepted ※ 07 December 2021 — Issue date; ※ 02 May 2022  
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WEPCAV013 Occurring Dependency between Adjustable Coupling and Q0 - Finding and Solving a Problem during Vertical Cavity Testing at DESY 619
 
  • Y.F. Liu, C. Luo
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • D. Reschke, L. Steder, M. Wiencek
    DESY, Hamburg, Germany
 
  In the AMTF (Accelerator Module Test Facility) hall at DESY, various types of cavities have been tested for different accelerators and R&D projects during the last years. For R&D purposes, dedicated inserts with additional auxiliaries like a movable INPUT antenna can be used to perform accurate measurements at different temperatures between 1.4 K and 4 K. Since 2017 more than hundred vertical tests were conducted in these inserts without troubles besides rare expected occurrences of cold leaks or even rarer a loose antenna. However, in the last months, an unexpected dependency between the measured quality factor and the coupling coefficient ß has been observed. In order to understand the source of this measurement uncertainty, several different special checks have been performed. In a logical sequence of measurements with different cryostats, inserts and cavities the problem has been encircled and in the end was identified and solved. In this paper, the observed problem is described in detail as well as the entire path leading to its solution.  
poster icon Poster WEPCAV013 [1.073 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV013  
About • Received ※ 18 June 2021 — Revised ※ 18 October 2021 — Accepted ※ 18 October 2021 — Issue date ※ 22 November 2021
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WEPCAV014 HOM Damper Design for BNL EIC 197 MHz Crab Cavity 624
 
  • B.P. Xiao, Q. Wu
    BNL, Upton, New York, USA
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen, R.A. Rimmer
    JLab, Newport News, Virginia, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
  • S. Verdú-Andrés
    Brookhaven National Laboratory (BNL), Electron-Ion Collider, Upton, New York, USA
 
  Funding: The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The interaction region (IR) crab cavity system is a special RF system to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point (IP) for BNL EIC. There will be six crab cavities, with four 197 MHz crab cavities and two 394 MHz crab cavities, installed on each side of the IP in the proton/ion ring, and one 394 MHz crab cavity on each side of the IP in the electron ring. Both rings share identical 394 MHz crab cavity design to minimize the cost and risk in designing a new RF system, and it will be scaled from 197 MHz crab cavity. In this paper, the HOM damper design for 197 MHz crab cavity is introduced.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV014  
About • Received ※ 22 June 2021 — Revised ※ 17 October 2021 — Accepted ※ 17 December 2021 — Issue date ※ 07 April 2022
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WEPCAV015 Refurbishment and Testing of the WiFEL E-Gun at Argonne 627
 
  • T.B. Petersen, G. Chen, M.V. Fisher, M. Kedzie, M.P. Kelly, T. Reid
    ANL, Lemont, Illinois, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
 
  We report on the refurbishment and testing of the Wisconsin Free Electron Laser (WiFEL) superconducting radiofrequency electron gun with application as an electron injector for DOE accelerators and as a possible future stand-alone tool for electron microscopy. Initial testing at ANL showed the cavity had a very low quality factor, ~107, later determined to be due to contamination some-time since the initial assembly. Following ultrasonic cleaning, high-pressure water rinsing, reassembly, and cold testing, the e-gun has largely recovered with Q~109 and surface electric fields ~15 MV/m. We intend that WiFEL be available as a testbed for future high brightness sources and, in particular, for testing an SRF gun photocathode loader design; an essential, and as yet, not sufficiently proven technology. We report here on many operationally important properties of a quarter-wave SRF cavity for application as an e-gun, including microphonics, pressure sensitivity, and mechanical tuning. New electromagnetic simulations show that the WiFEL cavity shape and design can be optimized in several respects.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEPCAV015  
About • Received ※ 21 June 2021 — Revised ※ 23 October 2021 — Accepted ※ 07 April 2022 — Issue date ※ 07 April 2022
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WEOCAV01
High-Performance Large-Grain Cavities for the ILC  
 
  • K. Umemori
    KEK, Ibaraki, Japan
 
  Large-grain SRF cavities might offer performance and cost benefits for the ILC and other future accelerators. On the other hand, ununiformity of grains might sometimes give difficulties on fabrication. Varication of mechanical strength is also another issues related to high pressure gas safety. This contribution will present an overview of recent worldwide activities related to large grain cavities. Materials, fabrications and cavity performances will be discussed.  
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WEOCAV02
Development and Vertical Tests of a 166.6-MHz Proof-of-Principle Superconduting β = 1 Quarter-Wave Cavity for HEPS  
 
  • P. Zhang, J. Dai, L. Guo, T.M. Huang, Z.Q. Li, H.Y. Lin, Q. Ma, F. Meng, Z.H. Mi, Q.Y. Wang, X.Y. Zhang
    IHEP, Beijing, People’s Republic of China
 
  Funding: This work was supported by the High Energy Photon Source - Test Facility (HEPS-TF) project, HEPS project and Chinese Academy of Sciences.
Low-frequency superconducting cavities are needed in main accelerators for storage ring light sources with ultralow emittance. Therefore, a compact 166.6-MHz superconducting proof-of-principle cavity was designed for the High Energy Photon Source (HEPS) in China by adopting a quarter-wave geometry with β=1*. The cavity is compact in size yet possessing a low resonant frequency. The nearest higher order mode is significantly separated from the fundamental mode, making the cavity attractive for high-current accelerators such as HEPS. The achieved accelerating voltage of 3.0 MV is well beyond the designed 1.5 MV and high surface electromagnetic fields were reached with excellent RF and mechanical performances. Multipacting barriers were easily processed. This constitutes the first demonstration of a compact low-frequency β=1 superconducting cavity for HEPS. The design, fabrication, surface preparation, and cryogenic tests of the cavity will be presented.
* P. Zhang, et al., Review of Scientific Instruments 90, 084705 (2019).
 
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WEOCAV03 RF Dipole Crab Cavity Testing for HL-LHC 687
 
  • N. Valverde Alonso, R. Calaga, S.J. Calvo, O. Capatina, O. Capatina, A. Castilla, M. Chiodini, C. Duval, L.M.A. Ferreira, M. Gourragne, P.J. Kohler, T. Mikkola, J.A. Mitchell, E. Montesinos, C. Pasquino, G. Pechaud, N. Stapley, M. Therasse, K. Turaj, J.D. Walker
    CERN, Geneva 23, Switzerland
  • A. Castilla
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • A. Castilla
    Lancaster University, Lancaster, United Kingdom
 
  RF Crab Cavities are an essential element of the High Luminosity LHC (HL-LHC) upgrade at CERN. Two RF dipole crab cavity used for the compensation of the horizontal crossing angle were recently manufactured and integrated into Titanium Helium tank and RF ancillaries necessary for the beam operation. The two cavities will be integrated into a cryomodule in collaboration with UK-STFC and tested with proton beams in the SPS in 2023. This paper will highlight the RF measurements during the important manufacturing steps, surface preparation and cavity performance at 2K.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOCAV03  
About • Received ※ 18 June 2021 — Revised ※ 07 September 2021 — Accepted ※ 16 September 2021 — Issue date ※ 22 November 2021
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WEOCAV04 Optimization of a Traveling Wave Superconducting Radiofrequency Cavity for Upgrading the International Linear Collider 694
 
  • V.D. Shemelin
    Valery D Shemelin, Freeville, USA
  • H. Padamsee
    Cornell University, Ithaca, New York, USA
  • H. Padamsee, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  The Standing Wave TESLA Niobium-based structure is limited to a gradient of about 50 MV/m by the critical RF magnetic field. To break through this barrier, we explore the option of Niobium-based traveling wave (TW) structures. Optimization of TW structures was done taking into account experimentally known limiting electric and magnetic fields. It is shown that a TW structure can have an accelerating gradient above 70 MeV/m that is about 1.5 times higher than contemporary standing wave structures with the same critical magnetic field. The other benefit of TW structures shown is R/Q about 2 times higher than TESLA structure that reduces 2 times the dynamic heat load. A method is proposed how to make TW structures multipactor-free. Some design proposals can be realized to facilitate fabrication. Further increase of the real-estate gradient (equivalent to 80 MV/m active gradient) is also possible by increasing the length of the accelerating structure because of higher group velocity and cell-to-cell coupling. Realization of this work opens paths to ILC energy upgrades beyond 1 TeV to 3 TeV in competition with CLIC. The paper will discuss corresponding opportunities and challenges.  
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slides icon Slides WEOCAV04 [3.667 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOCAV04  
About • Received ※ 15 June 2021 — Accepted ※ 24 October 2021 — Issue date; ※ 16 May 2022  
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WEOCAV06 Saraf-Phase 2 Low-Beta and High-Beta Superconducting Cavities Qualification 703
 
  • G. Ferrand, G. Jullien, S. Ladegaillerie, N. Misiara, N. Pichoff, C. Servouin
    CEA-IRFU, Gif-sur-Yvette, France
  • M. Baudrier, E. Fayette, L. Maurice
    CEA-DRF-IRFU, France
  • A. Navitski, L. Zweibaeumer
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
 
  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 consists in four cryomodules. The first two identical cryomodules host 6 half-wave resonator (HWR) low beta cavities (β= 0.09) at 176 MHz. The last two identical cryomodules will host 7 HWR high-beta cavities (β = 0.18) at 176 MHz. The low-beta prototypes was qualified in 2019. Low-beta series manufacturing is on-going. The high-beta prototype was first tested in 2019 but failed. A new prototype was tested in the end of 2020. This contribution will present the results of the tests for low- and high-beta SARAF cavities, series and prototypes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-WEOCAV06  
About • Received ※ 21 June 2021 — Revised ※ 17 October 2021 — Accepted ※ 20 December 2021 — Issue date ※ 17 May 2022
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WEOCAV07
Damage Recovery for SRF Photoinjector Cavities  
 
  • Y. Tamashevich, A. Frahm, F. Göbel, S. Heling, A. Hellwig, K. Janke, S. Klauke, J. Knobloch, A.N. Matveenko, A. Neumann, H. Plötz, A.L. Prudnikava, S. Rotterdam, M. Schuster, J. Ullrich
    HZB, Berlin, Germany
 
  Two niobium elliptical 1.3 GHz SRF electron photoinjector cavities were successfully recovered after mechanical inner surface damage. Both injector cavities had deep imprints in critical high surface electric field area around the photoelectric cathode position. The repairing procedure, consisting of surface inspection, mechanical polishing and light chemical etching is described in detail. Subsequent cold RF tests demonstrate complete performance recovery.  
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THPCAV001 Modal Analysis and Vibration Test of Single Spoke Resonator Type-1 (SSR1) for RISP 776
 
  • M.O. Hyun, Y.W. Jo, H.C. Jung, Y. Kim, M. Lee
    IBS, Daejeon, Republic of Korea
 
  Funding: This paper was supported by the Rare Isotope Science Project (RISP), which is funded by the Ministry of Science and ICT (MSIT) and National Research Foundation (NRF) of the Republic of Korea.
Rare Isotope Science Project (RISP) is developing the single spoke resonator type-1 (SSR1) and type-2 (SSR2) for making superconducting linear accelerator 2 (SCL2). For optimizing of SSR1 and SSR2, we should research every aspects of superconducting cavity including RF performances and mechanical properties. This paper explains about modal analysis of SSR1 using FEM (finite element method) applying material properties of RRR300 niobium for bare cavity and STS316L for liquid helium jacket. Also, this paper shows the vibration test results with modal analysis.
 
poster icon Poster THPCAV001 [1.636 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV001  
About • Received ※ 22 June 2021 — Accepted ※ 06 September 2021 — Issue date; ※ 15 May 2022  
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THPCAV002 Low Temperature Heat Treatment on the HWR Cavity 779
 
  • Y. Jung, H. Jang, H. Kim, H. Kim, J.W. Kim, M.S. Kim, J. Lee, M. Lee
    IBS, Daejeon, Republic of Korea
  • S. Jeon
    Kyungpook National University, Daegu, Republic of Korea
 
  Institute for Basic Science have been constructing Superconducting LINAC composed of quarter wave resonator (QWR) and half wave resonator (HWR). All QWR cavities have been completely fabricated and successfully tested to be assembled in QWR cryomodules. For now, we have been testing HWR cavities over 50%. For the testing period, the success rate experienced up and downs like we went through during the QWR tests. In many cases, we observed that some cavities did not reach requirement performance 2K although they showed high performance at 4K. We increased the temperature of heat treatment to cure the rapid Q drop at the high gradient and observed most cavities passed the test after heat treatment.  
poster icon Poster THPCAV002 [1.975 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV002  
About • Received ※ 21 June 2021 — Revised ※ 25 August 2021 — Accepted ※ 22 November 2021 — Issue date ※ 23 February 2022
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THPCAV003 Impact of Vertical Electropolishing with Flipping System on Removal Uniformity and Surface State: Study with 9-Cell Niobium Coupon Cavity 783
 
  • K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
    MGH, Hyogo-ken, Japan
  • H. Hayano, S. Kato, H. Monjushiro, T. Saeki
    KEK, Ibaraki, Japan
 
  We have been developing a vertical electropolishing (VEP) method for niobium superconducting RF cavities using a novel setup that allows periodic flipping of the cavity to put it upside down in the VEP process. The purpose of using the novel setup named as flipping system is to achieve uniform removal and smooth surface of the cavity. Previously, we have already introduced the VEP system and showed the preliminary results of VEP performed with the flipping system. In this article, we report VEP results obtained with a nine-cell coupon cavity. The results include detail on coupon currents with I-V curves for coupons, and impact of the cavity flipping on removal uniformity and surface morphology of the cavity.  
poster icon Poster THPCAV003 [1.261 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV003  
About • Received ※ 19 June 2021 — Revised ※ 10 August 2021 — Accepted ※ 22 October 2021 — Issue date ※ 23 November 2021
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THPCAV005 Status of the INFN-LASA Contribution to the PIP-II Linac 787
 
  • R. Paparella, M. Bertucci, M. Bonezzi, A. Bosotti, D. Cardelli, A. D’Ambros, G. Fornasier, A.T. Grimaldi, L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
 
  The international effort for the PIP-II project at Fermilab has been joined by INFN with its planned contribution to the PIP-II proton linac in the low-beta section. INFN-LASA is finalizing its commitment to deliver in kind the full set of the LB650 cavities, 36 plus spares resonators with 5-cell cavities at 650 MHz and geometrical beta 0.61. All cavities, designed by INFN-LASA, will be produced and surface treated in industry to reach the unprecedented performances required by PIP-II, qualified through vertical cold test at state-of-the art infrastructures and delivered as ready for the linac at the string assembly site. The status of INFN contribution to PIP-II, the development of infrastructures and prototypes as well as the ongoing activities toward the start of series production are summarized in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV005  
About • Received ※ 21 June 2021 — Accepted ※ 09 October 2021 — Issue date; ※ 08 May 2022  
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THPCAV006 Recent Activities Regarding 9-Cell TESLA-Type Cavities at KEK 792
 
  • M. Omet, R. Katayama, K. Umemori
    KEK, Ibaraki, Japan
 
  In this contribution we report on two topics regarding recent activities on 9-cell TESLA-type cavities at the High Energy Accelerator Research Organization (KEK). First, we give an overview of the inner surface treatments and vertical test (VT) results of four fine grain 9-cell TESLA-type cavities over the last one and a half years. Secondly, we report on the upgrade of the VT DAQ system at the Superconducting RF Test Facility (STF) at KEK. In this upgrade, most components of the VT system were integrated in an EPICS control system. Based on Control System Studio (CSS) and Python a new user interface was created, improving the workflow during and after VTs at STF.  
poster icon Poster THPCAV006 [1.748 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV006  
About • Received ※ 18 June 2021 — Revised ※ 26 August 2021 — Accepted ※ 23 November 2021 — Issue date ※ 04 March 2022
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THPCAV007 Thermal Mapping Studies on Nb/Su SRF Cavities 796
 
  • A. Bianchi, M. Chiodini, G. Vandoni, W. Venturini Delsolaro
    CERN, Meyrin, Switzerland
 
  A thermal mapping system is one of the most useful diagnostic tools to identify the mechanisms responsible of performance degradation in superconducting radio frequency (SRF) cavities. Unlike most of the thermal mapping systems currently in operation, we want to develop a system for mapping copper coated SRF cavities. This thermal mapping system, based on contact thermometry, will operate in both superfluid and normal liquid helium for the study of thin film cavities on copper built at CERN. This paper describes the R&D studies to design and develop the system. The characterisation of thermometers and the validation of their thermal contact are presented. Thanks to the use of some heaters with the aim of reproducing the presence of heat losses in a SRF cavity, temperature profiles on a copper surface will be shown at different conditions of the helium bath. In addition, preliminary results on magnetic field sensors, based on the anisotropic magnetoresistance effect, will be reported in view of their possible implementation in the thermal mapping system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV007  
About • Received ※ 18 June 2021 — Revised ※ 23 August 2021 — Accepted ※ 25 November 2021 — Issue date ※ 12 May 2022
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THPCAV008 Results From the Proton Power Upgrade Project Cavity Quality Assurance Plan 801
 
  • J.D. Mammosser, E. Robertson
    ORNL RAD, Oak Ridge, Tennessee, USA
  • R. Afanador, M.S. Champion, M.N. Greenwood, M.P. Howell, S.-H. Kim, S.E. Stewart, D.J. Vandygriff
    ORNL, Oak Ridge, Tennessee, USA
  • A. Bitter, K.B. Bolz, A. Navitski, L. Zweibaeumer
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  • E. Daly, G.K. Davis, P. Dhakal, D. Forehand, K. Macha, C.E. Reece, K.M. Wilson
    JLab, Newport News, Virginia, USA
 
  Funding: UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE)
The Proton Power Upgrade (PPU) Project at Oak Ridge National Lab’s Spallation Neutron Source (SNS) is currently under construction. The project will double the beam power from 1.4 to 2.8 MW. This is accomplished by increasing the beam current and adding seven new Superconducting Radio Frequency (SRF) cryomodules. Each new cryomodule will contain four six-cell, beta 0.81, PPU style cavities. A quality assurance plan was developed and implemented for the procurement of 32 PPU cavities. As part of this plan, reference cavities were qualified and sent to Research Instruments Co. for the development and verification of process steps. Here we present the results from this plan to date.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV008  
About • Received ※ 04 June 2021 — Accepted ※ 06 September 2021 — Issue date; ※ 16 May 2022  
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THPCAV009 Statistical Modeling of Peak Accelerating Gradients in LCLS-II and LCLS-II-HE 804
 
  • J.T. Maniscalco, S. Aderhold, J.D. Fuerst, D. Gonnella
    SLAC, Menlo Park, California, USA
  • T.T. Arkan, M. Checchin, J.A. Kaluzny, S. Posen
    Fermilab, Batavia, Illinois, USA
  • J. Hogan, A.D. Palczewski, C.E. Reece, K.M. Wilson
    JLab, Newport News, Virginia, USA
 
  In this report, we study the vertical test gradient performance and the gradient degradation between vertical test and cryomodule test for the 1.3 GHz LCLS-II cavities. We develop a model of peak gradient statistics, and use our understanding of the LCLS-II results and the changes implemented for LCLS-II-HE to estimate the expected gradient statistics for the new machine. Finally, we lay out a plan to ensure that the LCLS-II-HE cryomodule gradient specifications are met while minimizing cavity disqualification by introducing a variable acceptance threshold for the accelerating gradient.  
poster icon Poster THPCAV009 [1.306 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV009  
About • Received ※ 21 June 2021 — Revised ※ 14 September 2021 — Accepted ※ 02 November 2021 — Issue date ※ 23 November 2021
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THPCAV011 Operational Experience with the Mechanical Tuner Systems in the Superconducting Linac at IUAC 809
 
  • A. Pandey, R. Ahuja, G.K. Chaudhari, B.B. Chaudhary, R.N. Dutt, S. Ghosh, B. Karmakar, J. Karmakar, R. Kumar, D.S. Mathuria, P. Patra, P.N. Potukuchi, A. Rai, B.K. Sahu, S.K. Saini, A. Sharma, S.K. Sonti, S.K. Suman
    IUAC, New Delhi, India
 
  The phase locking of the QWRs by dynamic phase control method in the superconducting linac at IUAC is done in a faster time scale. The slow frequency drifts (few hundreds of ms) are corrected using a niobium bellows tuner attached at the open end of the cavity. Initially, the tuners in the cavities were operated using helium gas. This system had the limitation of non-linearity, hysteresis and slow response due to which the cavities could not be phase locked at higher fields. To address this, piezo based tuning system was implemented in the cavities of the 2nd and 3rd linac modules. But due to space constraints, the same could not be used in the 1st linac module and the buncher modules. For them, the helium gas based system was continued, albeit with suitable modifications. The old flow control valves which operated with DC voltages were replaced with valves operating in pulsed mode and controlled by varying the duty cycle of the input pulses. The above mentioned limitations were overcome by using this PWM based technique and this enabled phase locking at higher gradients. This paper presents our operational experience with all the different tuning systems and their comparison.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV011  
About • Received ※ 21 June 2021 — Revised ※ 11 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 27 October 2021
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THPCAV012 ESS Medium Beta Cavities at INFN LASA 815
 
  • D. Sertore, M. Bertucci, M. Bonezzi, A. Bosotti, D. Cardelli, A. D’Ambros, A.T. Grimaldi, L. Monaco, R. Paparella, G.M. Zaggia
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
 
  INFN Milano - LASA contributes in-kind to the ESS ERIC Superconducting Linac supplying 36 cavities for the Medium Beta section of the proton accelerator. All the cavities have been mechanical fabricated, BCP treated and, for most of them, also qualified with vertical test at cold at DESY. We present the result of the cavities already qualified and delivered to CEA, discussing the lessons learnt so far. For remaining cavities, we discuss the actions taken and the plans foreseen to recover them to full specifications.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV012  
About • Received ※ 21 June 2021 — Revised ※ 01 September 2021 — Accepted ※ 10 October 2021 — Issue date ※ 23 November 2021
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THPCAV014 Development of High-Q Treatments for PIP-II Prototype Cavities at LASA-INFN 820
 
  • M. Bertucci, A. Bosotti, A. D’Ambros, A.T. Grimaldi, P. Michelato, L. Monaco, C. Pagani, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • A. Gresele, A. Torri
    Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • M. Rizzi
    Ettore Zanon S.p.A., Schio, Italy
 
  INFN-LASA is currently involved in the production of PIP-II low-beta cavity prototypes. The main challenge of this activity is to develop a state-of-the art surface treatment recipe on such cavity geometry, to achieve the high-Q target required for cavity operation in the linac. This paper reports the status of cavity treatments development and the first cold test results of a single-cell cavity. This cavity has undergone a baseline treatment based on Electropolishing as bulk removal step. Being this test successful, a strategy for pushing the cavities towards higher performances is here proposed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-THPCAV014  
About • Received ※ 21 June 2021 — Accepted ※ 01 March 2022 — Issue date; ※ 01 May 2022  
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THOFDV01
Results and Analysis from Multi-mode Coaxial Cavity Tests  
 
  • P. Kolb, T. Junginger, R.E. Laxdal, Z.Y. Yao
    TRIUMF, Vancouver, Canada
  • T. Junginger
    UVIC, Victoria, Canada
 
  TRIUMF fabricated two coaxial test cavities (one QWR and one HWR) in order to investigate the characterization of TEM-mode cavities with standard and novel surface treatments. The cavities are intended as the TEM mode equivalent to the 1.3 GHz single cell cavity, which is the essential tool for high frequency cavity research. Given these coaxial structure, the cavities allow testing at the fundamental mode and higher harmonics, giving unique insight into the role of RF frequency on fundamental loss mechanisms from intrinsic and extrinsic sources. This talk will report the results related to the various heat treatments: 120OC bake, Mid-T bake, and Infusion. The characterization will be over a broad frequency range. In addition initial flux expulsion studies from built in Helmholtz coils will also be presented.  
slides icon Slides THOFDV01 [6.090 MB]  
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