MC7: Accelerator Technology
T07 Superconducting RF
Paper Title Page
MOYPLM2 SRF Operation at XFEL: Lessons Learned After More Than One Year 12
 
  • D. Kostin, V. Ayvazyan, J. Branlard, W. Decking, L. Lilje, M. Omet, T. Schnautz, E. Vogel, N. Walker
    DESY, Hamburg, Germany
 
  The European XFEL is the largest high-field SRF installation in the world and has now been in operation more than a year. It serves as a "prototype" for other facilities being constructed or in the planning stages. Performance of the operation of the SRF system over this period of time and the lessons learned will be discussed.  
slides icon Slides MOYPLM2 [4.351 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOYPLM2  
About • paper received ※ 10 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUXPLM1
Superconducting RF for the Future: Is Nb3Sn Ready for Next-generation Accelerators?  
 
  • M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Nb3Sn has long held the promise to significantly improve the performance of superconducting RF cavities in terms of power dissipation and achievable field. However, measurements in the 1980’s and 1990’s proved very disappointing and it was believed that practical limits due to grain boundaries prevented Nb3Sn from achieving its full potential. Only recently (around 2013) has use of the material for accelerator applications been re-visited. Significant progress has been made in the last several years with demonstrated performance reaching levels where implementing Nb3Sn in accelerator applications should be considered. The talk discusses the performance limits and potential applications of Nb3Sn.  
slides icon Slides TUXPLM1 [16.100 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUXXPLM1
Flux Expulsion in SRF Cavities: Discovery of Influencing Parameters and Implementation in LCLS-II Cryomodule Production  
 
  • S. Posen, A. Grassellino, E.R. Harms, O.S. Melnychuk, T.J. Peterson, D.A. Sergatskov, N. Solyak, G. Wu
    Fermilab, Batavia, Illinois, USA
  • D. Gonnella
    SLAC, Menlo Park, California, USA
  • A.D. Palczewski
    JLab, Newport News, Virginia, USA
 
  For decades, magnetic flux trapping in superconducting RF cavities has been poorly understood, with various reports of all ambient flux being trapped in the superconductor during cooldown or unreproducible behavior. This recently changed, when an R&D study at Fermilab showed that thermal gradients over the surface of the cavity can expel flux from the superconducting material. Further R&D studies showed that the expulsion behavior also depended strongly on the high temperature heat treatment of the cavity. These studies were timely for LCLS-II cryomodule production, in which stringent requirements on the quality factor make trapped flux a significant problem. To minimize degradation due to trapped flux, the recommendations from the R&D program were applied to cryomodule production. This is the first implementation of several new paradigms to minimize trapped flux: fast cooldown, high temperature heat treatment to minimize flux pinning centers, and magnetic hygiene controls. In this contribution, we review the R&D studies and the implementation of the lessons learned in cryomodules for LCLS-II. We present performance statistics from cryomodules as a function of heat treatment temperature and helium mass flow during cooldown. We show that with these modifications, LCLS-II production cryomodules are now achieving an unprecedented Q0 of ~3x1010 or higher, approximately 3x higher than the state-of-the-art 5 years ago.  
slides icon Slides TUXXPLM1 [20.003 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUXXPLM2 SRF Cavity Fault Classification Using Machine Learning at CEBAF 1167
 
  • A.D. Solopova, A. Carpenter, T. Powers, Y. Roblin, C. Tennant
    JLab, Newport News, Virginia, USA
  • K.M. Iftekharuddin, L. Vidyaratne
    ODU, Norfolk, Virginia, USA
 
  The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is the first large high power CW recirculating electron accelerator which makes use of SRF accelerating structures configured in two antiparallel linacs. Each linac consists of twenty C20/C50 cryomodules each containing eight 5-cell cavities and five C100 upgrade cryomodules each containing eight 7-cell cavities. Accurately classifying the source of cavity faults is critical for improving accelerator performance. In addition to archived signals sampled at 10 Hz, a cavity fault triggers a waveform acquisition process where 16 waveform records sampled at 5 kHz are recorded for each of the 8 cavities in the effected cryomodule. The waveform record length is sufficiently long for transient microphonic effects to be observable. Significant time is required by a subject matter expert to analyze and identify the intra-cavity signatures of imminent faults. This paper describes a path forward that utilizes machine learning for automatic fault classification. Post-training identification of the physical origins of faults are discussed, as are potential machine-trained model-free implementations of trip avoidance procedures. These methods should provide new insights into cavity fault mechanisms and facilitate intelligent optimization of cryomodule performance  
slides icon Slides TUXXPLM2 [4.404 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUXXPLM2  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTS118 LASA Activities on Surface Treatment of Low-beta Elliptical Cavities 2207
 
  • M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • D. Rizzetto, M. Rizzi
    Ettore Zanon S.p.A., Schio, Italy
  • L. Sagliano
    ESS, Lund, Sweden
 
  This paper describes the efforts made by LASA on the development of surface treatments for low-beta elliptical cavities, for the current series production of ESS and the foreseen series production of PIP-II. The traditional techniques of buffered chemical polishing and electropolishing are here discussed taking into account the industrial environment, the practical issues due to the size and geometry of such cavities and according to the required qualification values for quality factor and accelerating gradient.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS118  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTS119 Status of the ESS Medium Beta Cavities at INFN - LASA 2211
 
  • P. Michelato, M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • S. Aurnia, O. Leonardi, A. Miraglia, G. Vecchio
    INFN/LNS, Catania, Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • L. Sagliano
    ESS, Lund, Sweden
 
  INFN-LASA contributes in-kind to the European Spallation Source ERIC with 36 6-cell cavities for the Medium Beta section of the Superconducting Linac. After having developed the electromagnetic and mechanical models, few prototypes have been produced and tested. Based on this experience, we are now supervisioning the cavity production at the industry, the resonators test at DESY and the delivery to CEA at Saclay. In this paper, we report on the status of the overall INFN-LASA contribution including also document handling, interface data exchange and QA/QC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS119  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPTS120 Status of the PIP-II Activities at INFN-LASA 2215
 
  • R. Paparella, M. Bertucci, A. Bignami, A. Bosotti, M. Chiodini, A. D’Ambros, P. Michelato, L. Monaco, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • J.F. Chen
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • L. Sagliano
    ESS, Lund, Sweden
 
  INFN-LASA joined the international effort for the PIP-II project in Fermilab and it is expected to build the 650 MHz superconducting cavities required by the low-beta section of the 800 MeV front-end proton linac, as recently signed by US DOE and Italian MIUR. After developing the electro-magnetic and mechanical design, INFN-Milano started the prototyping phase by producing five single-cells and two complete 5-cells cavities. In a joint effort with Fermilab the road for the optimal surface treatment for such low-beta resonators has started in order to approach the existing state-of-the-art performances of beta 1 cavities. This paper reports the status of PIP-II activities at INFN-LASA summarizing manufacturing experience and preliminary experimental results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS120  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB003 Parametric Pumped Oscillation by Lorentz Force in Superconducting Rf Cavity 2798
 
  • K. Fong, R. Leewe
    TRIUMF, Vancouver, Canada
 
  Mechanical instabilities have been observed in superconducting RF cavities, when multiple cavities are driven by a single klystron and these cavities are regulated by vector-summing the outputs from these cavities. A nonlinear theory has been developed to study the source of this mechanical instability, which is due to the coupling between Lorentz force detuning and mechanical oscillation by parametric pumping. Analytical and numerical analysis of this model show regions of stability, limit cycles and instabilities. These results are in agreement with the observed oscillations by TRIUMF eLinac Acceleration Module.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB003  
About • paper received ※ 13 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB009 Validation of the Series Power Couplers of the LIPAc SRF Linac 2811
 
  • H. Jenhani, N. Bazin, C. Boulch, S. Chel, G. Devanz, G. Disset, C. Servouin
    CEA-IRFU, Gif-sur-Yvette, France
  • I. Kirpitchev, J. Mollá, P. Méndez, D. Regidor, C. de la Morena
    CIEMAT, Madrid, Spain
 
  In the framework of the IFMIF/EVEDA project, the cryomodule of the Linear IFMIF Prototype Accelerator (LIPAc) will be assembled then tested at Rokkasho in 2019. Eight Series Power Couplers (PC) operating at 175 MHz were manufactured under a CEA contract, in order to equip this Cryomodule. They were all successfully RF conditioned up to 100 kW CW in TW and SW configurations. All the high RF power tests were performed under CIEMAT responsibility in BTESA Company premises, according to the CEA requirements. In order to fix difficulties encountered during the fab process, manufacturing and quality control have been analyzed in depth. Thanks to the corrective actions implemented, every PC reached the performances targeted for qualification. This paper will give details about this manufacturing phase and provide an overview of the obtained RF test results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB009  
About • paper received ※ 09 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB011 PVD Depostion of Nb3Sn Thin Film on Copper Substrate from an Alloy Nb3Sn Target 2818
 
  • R. Valizadeh, S. Aliasghari, A.N. Hannah, O.B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • K. Dawson, V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • G.B.G. Stenning
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • D. Turner
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Turner
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  In this study we report on the PVD deposition of Nb3Sn on Cu substrates with and without a thick Nb interlayer to produce Cu/Nb/Nb3Sn and Cu/Nb3Sn multilayer structures. The Nb3Sn was sputtered directly from an alloy target at room and elevated temperatures. The dependence of the superconducting properties of the total structure on deposition parameters has been determined. The films have been characterized via SEM, XRD, EDX and SQUID magnetometer measurements. Analysis showed that the composition at both room and elevated temperature was within the desired stoichiometry of 24’25 at%. However, superconductivity was only observed for deposition at elevated temperature or post annealing at 650 °C. The critical temperature was determined to be in the range of 16.8 to 17.4 K. In the case of bilayer deposition, copper segregation from the interface all the way to the surface was observed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB011  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB012 Overview on SC CH-Cavity Development 2822
 
  • M. Busch, M. Basten, T. Conrad, P. Müller, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • W.A. Barth, F.D. Dziuba, M. Miski-Oglu
    GSI, Darmstadt, Germany
  • W.A. Barth, F.D. Dziuba, M. Miski-Oglu
    HIM, Mainz, Germany
  • W.A. Barth
    MEPhI, Moscow, Russia
  • F.D. Dziuba
    IKP, Mainz, Germany
 
  Funding: Work supported by GSI, HIC for FAIR, BMBF Contr. No. 05P18RFRB1
During the last decades an enermous effort has been put into the development of low beta structures for hadron acceleration worldwide. Since hadrons exhibit a very inert velocity gain due to their high mass this change in speed has to be taken into account when utilizing low beta cavities. At the Institute of Applied Physics (IAP), Frankfurt, Germany, five multi-cell CH-cavities (Crossbar H-Mode) have been developed and tested for different kind of applications so far. In addition to the successfully tested original 360 MHz prototype further structures envisaged for beam operation have been fabricated and tested. Overview, status and outlook of this cavity technology is topic of this contribution.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB012  
About • paper received ※ 08 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB014 Further RF Measurements on the Superconducting 217 MHz CH Demonstrator Cavity for a CW Linac at GSI 2826
 
  • F.D. Dziuba, K. Aulenbacher, W.A. Barth, C. Burandt, V. Gettmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu
    HIM, Mainz, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, C. Burandt, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, J. Salvatore, A. Schnase, S. Yaramyshev
    GSI, Darmstadt, Germany
  • M. Basten, M. Busch, T. Conrad, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • S. Lauber, J. List
    KPH, Mainz, Germany
 
  Funding: Work supported by GSI, HIM, BMBF Contr. No. 05P18UMRB2
Recently, the first section of the superconducting (sc) continuous wave (cw) Linac has been extensively tested with heavy ion beam from the GSI High Charge State Injector (HLI). During this testing phase, the reliable operability of 217 MHz multi gap crossbar-H-mode (CH) cavities has been successfully demonstrated. The sc 217 MHz CH cavity (CH0) of the demonstrator setup accelerated heavy ions up to the design beam energy and even beyond at high beam intensities and full transmission. This worldwide first beam test with a sc CH cavity is a major milestone on the way realizing the entire sc cw Linac project. In this contribution further RF measurements on the cavity are presented providing full characterization of the RF structure.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB014  
About • paper received ※ 26 April 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB015 Cleanroom Installations for SRF Cavities at the Helmholtz-Institut Mainz 2830
 
  • T. Kürzeder, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, R.G. Heine, S. Lauber, J. List, M. Miski-Oglu
    HIM, Mainz, Germany
  • K. Aulenbacher, F.D. Dziuba
    IKP, Mainz, Germany
  • W.A. Barth, C. Burandt, V. Gettmann, M. Miski-Oglu, S. Yaramyshev
    GSI, Darmstadt, Germany
  • J. Conrad
    TU Darmstadt, Darmstadt, Germany
  • R.G. Heine, F. Hug, T. Stengler
    KPH, Mainz, Germany
 
  At the Helmholtz-Institut Mainz (HIM) a cleanroom has been equipped with new tools and installations for the planned treatment of different superconducting RF-cavities. At first TESLA/XFEL type 9-cell cavities for the Mainz Energy-Recovering Superconducting Accelerator (MESA) project or 217 MHz multigap Crossbar H-mode cavities for the HElmholtz LInear ACcelerator (HELIAC) under development by HIM and GSI will be treated. The cleanroom installations, including the greyroom, cover an area of about 155 sqm. In its ISO-class 6 area a large ultrasonic and a conductance rinsing bath has been installed recently. A high pressure rinsing cabinet (HPR) has been implemented between the ISO-class 6 and 4 cleanroom. A RF-cavity can be loaded and unloaded from both sides. HPR treatments are possible for cavities of up to 1.4 m length and about 0.7 m diameter. For drying the ISO-class 4 clean room is equipped with a 160 C vacuum oven. New cleanroom lifters allow the handling of up to 200 kg heavy objects. A rail system in the cleanroom floor is installed to move out the entire cold string of the cleanroom after assembly and leak testing. First operational experiences with this facility will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB015  
About • paper received ※ 29 April 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB016 Simulation of Quench Detection Algorithms for Helmholtz Zentrum Berlin SRF Cavities 2834
 
  • P. Echevarria, A. Neumann, A. Ushakov
    HZB, Berlin, Germany
  • B. Garcia
    UPV-EHU, Leioa, Spain
  • J. Jugo
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
 
  The Helmholtz Zentrum Berlin is carrying out two accelerator projects which make use of high gradient SRF cavities: BERLinPro* and BESSY-VSR**. In both projects, a prompt detection of a quench is crucial to avoid damages in the cryomodules and cavities themselves. In this paper, the response of real time estimation of the cavity parameters*** using the transmitted and forward RF signals is simulated, in order to perform the quench detection. The time response of the estimated half bandwidth is compared with the dissipated power in the cavity walls for the different type of SRF cavities used in both projects, i.e., BERLinPro’s photoinjector, booster and linac, and BESSY-VSR 1.5 GHz and 1.75 GHz cavities. As an intermediate step prior to the implementation in an mTCA.4 system together with the LLRF control and test with a real cavity, the algorithm has been implemented using a National Instruments FPGA board to check the its proper behavior.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB016  
About • paper received ※ 16 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB017 Operational Experiences with X-Ray Tomography for SRF Cavity Shape and Surface Control 2838
 
  • H.-W. Glock, J. Knobloch, A. Neumann, Y. Tamashevich
    HZB, Berlin, Germany
  • M. Böhnel, N. Reims
    Fraunhofer IIS EZRT, Fürth, Germany
  • J. Kinzinger
    X-RAY LAB, Sachsenheim, Germany
 
  X-ray tomography has established as a non-destructive three-dimensional analysis tool, commercially offered by industrial vendors. Typical applications cover shape control and failure detection (voids, cracks) deep inside of complicated bulk pieces like engine blocks, bearings, turbine blades etc. We evaluated the applicability of the process for superconducting radio frequency cavities, in particular the 1.4-cell 1.3 GHz BERLinPro electron gun cavity and the 1.5 GHz single-cell VSR cavity prototype. The former experienced severe shape modifications during its tuning process and features a complicated internal stiffening construction. Thus it is a demanding challenge to measure its actual internal cavity surface shape after the complete preparation process with a resolution, sufficiently high (better than 0.2 mm) to serve as input for meaningful comparative field simulations. First tests with a vendor’s on-site X-ray source, operating at X-ray energies up to 590 keV revealed an insufficient resolution of the inner surface, attributed to the unfavorable X-ray damping characteristics of niobium. This was overcome with the aid of an accelerator-based source (X-ray spectrum up to 9 MeV), operated by Fraunhofer IIS, Fürth, Germany. Results both show significant, while understood, shape changes and indicate partial inner surface modifications of the gun cavity. Further the data evaluation process, which was needed to provide input for field simulations, raised issues because of the data set size and complexity, which are discussed in the paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB017  
About • paper received ※ 17 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB023 Vertical Test of ESS Medium Beta Cavities 2852
 
  • A. Bosotti, M. Bertucci, A. Bignami, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • D. Reschke, A.A. Sulimov, M. Wiencek
    DESY, Hamburg, Germany
 
  The Medium beta (β=0.67) section of the European Spallation Source (ESS) Linac is composed of 36 six-cell elliptical superconducting (SC) cavities. As a part to the in kind contribution of Italy to the ESS project, INFN-LASA is in charge of the development and of the industrial production of the whole set of 36 resonators plus two spares. The production activity is now ongoing at ZANON. To qualify the cavities power tests in vertical cryostat has been committed to DESY. During the qualification tests, where the cavities provided with He tanks are pushed to their electromagnetic limits, recording their main electromagnetics parameters such as quality factor Q0 vs Eacc. In this paper we report about the qualification tests performed on the first part of the quality production.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB023  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB025 High Density Mapping for Superconducting Cavities 2860
 
  • Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • Y. Fuwa
    Kyoto University, Research Reactor Institute, Osaka, Japan
  • R.L. Geng
    JLab, Newport News, Virginia, USA
  • H. Hayano
    KEK, Ibaraki, Japan
 
  High density mapping system for superconducting cavities are under development. Testing on the stiffener X-ray mapping system at JLAB showed consistent results in comparison with simultaneously taken GM tube or ion chamber output signals. The system provides better visi-bility as shown by data briefly reported here. In addition to the temperature and the X-ray mapping, a sensitive magnetic field mapping system with high spatial density is also under development. The magnetic field sensor is AF755B, whose operations at cryogenic temperatures are already reported by other group. Our development status using the magnetic field sensor will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB025  
About • paper received ※ 19 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB028 Electromagnetic Design of the Low Beta Cavities for the JAEA ADS 2870
 
  • B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  The Japan Atomic Energy Agency (JAEA) is designing a superconducting CW proton linear accelerator for the ADS project. The superconducting region will use five types of radio frequency cavities. In the region from 2 to 180 MeV the acceleration will be done using Half Wave Resonator (HWR) and Single Spokes (SS) cavities. HWR cavities will accelerate the beam from 2 to 10 MeV with a geometrical beta of 0.08 and the SS ones will do from 10 to 180 MeV using two cavity families with geometrical betas of 0.16 and 0.43. The results of electromagnetic model design are presented and the comparison with similar cavities from other projects are included.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB028  
About • paper received ※ 19 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB029 Design of the Elliptical Superconducting Cavities for the JAEA ADS 2873
 
  • B. Yee-Rendón, Y. Kondo, F.M. Maekawa, S.I. Meigo, J. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
 
  The superconducting CW proton linear accelerator for an Accelerator Driven Subcritical System (ADS) proposed by Japan Atomic Energy Agency (JAEA) employs elliptical cavities for the final acceleration of 180 MeV to 1.5 GeV. Since this energy region implies a change of beta from 0.55 to 1, two cavity models were developed using the geometrical betas of 0.68 and 0.89 to improve the acceleration efficiency. The study of the electromagnetic design was simulated using SUPERFISH (SF) code and python program to do variable scan, the results were benchmarked with CST Microwave Studio program (CST).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB029  
About • paper received ※ 18 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB031 SRF Trip Caused by the Tuner in BEPCII 2880
 
  • J.P. Dai, Z.H. Mi, P. Sha, Y. Sun, Q.Y. Wang, L.G. Xiao
    IHEP, Beijing, People’s Republic of China
 
  Funding: Work support by Natural Science Foundation of China (11575216)
The stability and reliability of the Superconducting RF system (SRF) is generally a key issue in a large scale accelerator such as Beijing Electron Positron Collider II (BEPCII). In the past several years, SRF is one of the main factors limiting the availability of BEPCII, and many efforts have been made to fix the SCRF troubles. This paper focuses on the details of the SCRF trip caused by the tuner, which is one of the most persistent troubles and figured out till the summer of 2018.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB031  
About • paper received ※ 08 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB032 Superconducting Elliptical Cavities Developed in IMP for the CiADS 2883
 
  • Y.L. Huang, Y. He, R. Huang, T.C. Jiang, L.B. Liu, S.H. Liu, T. Tan, R.X. Wang, Z.J. Wang, S.H. Zhang, S.X. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  Multicell superconducting radio frequency (SRF) ellip-tical cavities are proposed for efficient acceleration of proton beam in the Chinese initiative Accelerator Driven Subcritical System (CiADS). Two families of such cavities will be used in the driver SRF Linac, the first family corresponding to βopt=0.62 cavities that will be used to accelerate the H+ beam from 175 MeV to 377 MeV and the second family corresponding to βopt=0.82 cavities that will accelerate the H+ beam from 377 MeV to 500 MeV, with the possibility to upgrade to 1 GeV and higher. The electromagnetic optimization of the cavities with the HOM, wakefield and multipacting analysis will be dis-cussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB032  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB037 Development of EP System at IHEP 2890
 
  • S. Jin, J.P. Dai, J. Dai, H.F.S. Feisi, J. Gao, D.J. Gong, Z.Q. Li, Z.C. Liu, W.M. Pan, P. Sha, Y. Sun, J.Y. Zhai, P. Zhang
    IHEP, Beijing, People’s Republic of China
 
  Electropolishing (EP) is a necessary technology for high quality cavities including both high accelerating gradient and high quality factor cavities, which will be used for several future large projects such as CEPC, Shanghai hard X-ray FEL, ILC, and so on. An EP system was development at IHEP, CAS. In last years, we finished all the engineering design and fabrication including functional circulation loops design, system parameters choices, key equipment choice or design, components test and fabrication. According to the functions of various components, the whole system were divided into three main units: electrolyte mixing, acid solution and mechanical platform, and several key components such as rotation sleeves, DC power supply and so on. Since the system is designed for both R&D and mass production, several characteristics comparing with those in other labs in the world can be realized, including dozens of solution circulations, electrolyte mixing, new and old acid separation, cavity outside water cooling, cathode vertical assembly, and compatible for several types of cavities. We will report them in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB037  
About • paper received ※ 21 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB044 Microphonics Simulation and Parameters Design of the SRF Cavities for CiADS 2903
SUSPFO066   use link to see paper's listing under its alternate paper code  
 
  • J.Y. Ma, G. Huang
    IMP/CAS, Lanzhou, People’s Republic of China
 
  The CiADS (China initiative Accelerator Driven System) proton Linac is designed to accelerate CW beams of up to 500 MeV and 5mA, which is delivered to the spallation target. Since the beam power will eventually reach 2.5 MW, the beam loss should be restricted, which is sensitive to the SC cavity stability. On CW operating mode, the main perturbation to the cavity is microphonics. This paper will describe a set of tools developed to simulate performance of the cavity and its LLRF control system in order to ensure proper cavity operation under microphonics. The simulation tools describe a relationship between microphonics and the RF parameters. The microphonics effect to the cavity is simulated. The tolerated intensity of microphonics is determined by simulation, in order to satisfy the stability of amplitude and phase with 0.1% and 0.1 degree respectively.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB044  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB049 HOM Analysis of the 4-cell Superconducting Cavity on CTFEL Facility 2918
 
  • X. Luo, T.H. He, C.L. Lao, L.J. Shan, X.M. Shen, D. Wu, K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
  • F. Wang
    PKU, Beijing, People’s Republic of China
 
  The higher order modes (HOMs) of the 1.3GHz 4-cell cavity on CTFEL facility is analyzed in this paper. The passbands of the HOMs in the 4-cell cavity were simulat-ed, and the most harmful modes were determined. The power of the wakefields was estimated. By microwave test at room temperature, the frequencies of the HOMs were measured, as well as the external Q’s of the HOM cou-plers. Besides, a frequency distribution measurement system was built. The HOM signal excited by beam at 2 K temperature is measured, and some preliminary results are obtained. The measurement techniques and results of the HOM damping performance are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB049  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB056 Design Study of 325MHz RF Power Coupler for Superconducting Cavity 2937
SUSPFO088   use link to see paper's listing under its alternate paper code  
 
  • J.Y. Yoon, H.J. Cha, S.W. Jang, E.-S. Kim, K.R. Kim, C.S. Park, S. H. Park
    KUS, Sejong, Republic of Korea
  • J. Bahng
    Korea University Sejong Campus, Sejong, Republic of Korea
  • K.R. Kim
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  We present the design study of the RF input power coupler for 325 MHz superconducting cavities. The power coupler, based on a conventional coaxial transmission line, provides RF powers to the cavity up to 12kW in CW mode. The thermal interceptors are considered as 4.5 K and 40 K or 4.5 K and 77 K corresponding to the usage of liquid Helium only or both liquid Helium and Nitrogen for cryogenic temperature to reduce the thermal load. The transition box (T-box), which is assembled with power coupler, is designed and applied for impedance matching and inner conductor cooling.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB056  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB061 The Integration and RF Conditioning of the ESS Double-Spoke Prototype Cryomodule at FREIA 2952
 
  • H. Li, K. Fransson, K.J. Gajewski, L. Hermansson, A. Miyazaki, R.J.M.Y. Ruber, R. Santiago Kern
    Uppsala University, Uppsala, Sweden
 
  ESS, the European Spallation Source, will adopt a single family of double-spoke cavities for accelerating the proton beam from the normal conducting section to the first family of the elliptical superconducting cavities. They will be the first double-spoke cavities in the world to be commissioned for a high power proton accelerator. The first double-spoke cavity cryomodule for the ESS project is under high power test at Uppsala University. This paper presents the integration, RF conditioning and experience of this prototype cryomodule.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB061  
About • paper received ※ 26 April 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB065 Multi-physics Computation and Deformation Testing of a Shell-type 1.5-GHz Cavity 2968
 
  • M.-C. Lin, C.H. Lo
    NSRRC, Hsinchu, Taiwan
  • M. -R. Lu, M.-K. Yeh
    NTHU, Hsinchu, Taiwan
 
  Funding: Work supported by the Ministry of Science and Technology, R. O. C. (Taiwan) under grant NSC-100-2628-E-213-001-MY3.
A copper prototype of a 1.5-GHz cavity was manufac-tured to simulate a superconducting radio-frequency cavity for technique development. Frequency tuning with longitudinal compression of this prototype and cryogenic cooling with liquid nitrogen were performed to examine the numerical results from finite-element models, mainly the corresponding shifts of the fundamental resonant frequency. An appropriate element option improved the accuracy of the resonant frequency and the distribution of the magnetic field. Effects of geometry distortion of an uneven length on the frequency shift of this shell-type cavity as loaded on longitudinal compression are also examined and discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB065  
About • paper received ※ 25 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB070 Facile Deposition of Superconducting MgB2 Thin Films on Substrates: A Comparative Investigation of Electrochemical Deposition and Magnetron Sputtering Techniques 2984
 
  • N. Misra, A.N. Hannah, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: Authors acknowledge the funding received under the Rutherford International Postdoctoral Fellowship Programme
Coating of Copper cavities with a superconducting layer of MgB2 thin film is an attractive alternative to bulk Nb cavities. In this work, we investigate the application of two approaches-electrochemical deposition and magnetron sputtering of MgB2, to fabricate MgB2 films with potential accelerator applications. In the first approach, MgB2 powder dispersed in acetone was used as an electrolytic medium. Application of a DC voltage of 400 V between a graphite anode and a Copper film (serving as cathode), with the electrode distance maintained at ~2cm, resulted in the electrochemical deposition of MgB2 on the Cu surface. In an alternate approach, MgB2 in powder form was used directly for sputtering based deposition. The powder was initially compacted to form a thin layer that served as the magnetron target. Application of a pulsed DC power of 25W for 4 hours yielded MgB2 thin film on Si substrates. Samples were characterized by XPS analysis to ascertain their elemental composition, which confirmed the presence of Mg and B, in addition to traces of C and O as impurities. Surface morphology was determined using SEM characterization technique. Further work to determine the superconducting properties of the samples and fine tune the deposition processes for large scale MgB2 deposition inside actual RF cavities is in progress.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB070  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB076 Analysis of Higher Order Multipoles of the 952.6 Mhz RF-Dipole Crabbing Cavity for the Jefferson Lab Electron-Ion Collider 2996
 
  • S.U. De Silva, J.R. Delayen, S. Sosa
    ODU, Norfolk, Virginia, USA
  • V.S. Morozov, H. Park
    JLab, Newport News, Virginia, USA
 
  The crabbing system is a key feature in the Jefferson Lab Electron-Ion Collider (JLEIC) required to increase the luminosity of the colliding bunches. A local crabbing system will be installed with superconducting rf-dipole crabbing cavities operating at 952.6 MHz. The field non-uniformity across the beam aperture in the crabbing cavities produces higher order multipole components, similar to that which are present in magnets. Knowledge of higher order mode multipole field effects is important for accurate beam dynamics study for the crabbing system. In this paper, we quantify the multipole components and analyse their effects on the beam dynamics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB076  
About • paper received ※ 20 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB077 Simulation and Measurements of HOM Filter of the LARP Prototype RF-Dipole Crabbing Cavity Using an RF Test Box 2999
 
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
 
  The RF-Dipole Crabbing Cavity designed for the LHC High Luminosity Upgrade includes two higher order mode (HOM) couplers. One of the HOM couplers is an rf filter, which is a high pass filter designed to couple to the horizontal dipole modes and accelerating modes up to 2 GHz, while rejecting the fundamental operating mode at 400 MHz. The coupler consists of a high pass filter circuit where the rejection of the operating mode and transmission of HOMs are sensitive to dimensional deviations. An rf test box has been designed to measure the transmission of the rf filter in order to qualify the fabricated HOM coupler and to tune the coupler. This paper presents the measurements of the HOM coupler with the rf test box.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB077  
About • paper received ※ 20 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB078 RF Commissioning and Performance in the CBETA ERL 3003
 
  • N. Banerjee, K.E. Deitrick, J. Dobbins, G.H. Hoffstaetter, R.P.K. Kaplan, M. Liepe, C.W. Miller, P. Quigley, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the New York State Energy Research and Development Authority, Contract No. DE-SC0012704 with the U.S. Department of Energy and NSF award DMR-0807731.
The Cornell-BNL ERL Test Accelerator (CBETA) is a new multi-turn energy recovery linac currently being commissioned at Cornell University. It uses a superconducting main linac to accelerate electrons by 36 MeV and recover their energy. The energy recovery process is sensitive to fluctuations in the accelerating field of all cavities. In this paper, we outline our semi-automated RF commissioning procedure, which starts from automatic coarse tuning of the cavity all the way to adjusting the field control loops. We show some results of using these tools and describe the recent performance of the RF system during our ongoing commissioning phase.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB078  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB087 High-gradient SRF Cavity R&D at Cornell University 3017
 
  • M. Ge, T. Gruber, J.J. Kaufman, P.N. Koufalis, G. Kulina, M. Liepe, J.T. Maniscalco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Achieving high accelerating field is a critical R&D topic for superconducting RF cavities for future accelerators including the International Linear collider (ILC). The ILC requires an average accelerating field of 35MV/m with a Q0 of at least 8.9·109 at 2K. In this paper, we report the latest results from high-gradient research at Cornell, which focusses on 75C vacuum baking to improve maximum (quench) fields. We demonstrate that such low temperature bakes can significantly improve quench fields in certain cases by mitigating localized defects. We further report on high-pulsed power results of these cavities before and after baking.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB087  
About • paper received ※ 23 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB089 Theoretical Analysis of Quasiparticle Overheating, Positive Q-Slope, and Vortex Losses in SRF Cavities 3020
SUSPFO131   use link to see paper's listing under its alternate paper code  
 
  • J.T. Maniscalco, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, D. Liarte, J.P. Sethna, N. Sitaraman
    Cornell University, Ithaca, New York, USA
 
  The surface resistance of an SRF cavity is an important measure of its performance and utility: lower resistance leads directly to lower cryogenic losses and power consumption. This surface resistance comprises two components, namely the ‘‘BCS resistance’’, which depends strongly on the quasiparticle temperature, and a temperature-independent ‘‘residual resistance’’, which is often dominated by losses due to trapped magnetic vortices. Both components are generally dependent on the RF field strength. Here we present a summary of recent theoretical advances in understanding the microscopic mechanisms of the surface resistance, in particular addressing niobium hydride formation and quasiparticle overheating (using the tools of density functional theory) and discussing issues with existing models of the positive Q-slope, a field-dependent decrease in the BCS resistance, and possible paths for improvement of these models. We also discuss trapped flux losses using ideas from collective weak pinning theory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB089  
About • paper received ※ 20 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB090 The Design of Parallel-Feed SC RF Accelerator Structure 3024
 
  • M.H. Nasr, Z. Li, S.G. Tantawi, P.B. Welander
    SLAC, Menlo Park, California, USA
 
  Funding: Research funded by a SLAC Laboratory-Directed Research and Development award, supported by the U.S. Department of Energy, contract number DE-AC02-76SF00515
Development of superconducting RF (SRF) accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed normal-conducting RF structure at SLAC has served as a proof-of-concept. Instead of coupled elliptical cells, the structure employs isolated re-entrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Applied to SRF, simulations suggest such a structure could nearly double the achievable gradient, while reducing cryogenic RF loss by more than half. We are experimentally verifying the concept using an X-band SRF design to be tested at SLAC.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB090  
About • paper received ※ 24 May 2019       paper accepted ※ 27 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB093 Design of a Proof-of-principle Crabbing Cavity for the Jefferson Lab Electron-ion Collider 3027
 
  • H. Park, S.U. De Silva, J.R. Delayen, S.I. Sosa Guitron
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen, H. Park
    JLab, Newport News, Virginia, USA
 
  The Jefferson Lab design for an electron-ion collider (JLEIC) requires crabbing of the electron and ion beams in order to achieve the design luminosity. A number of options for the crabbing cavities have been explored, and the one which has been selected for the proof-of-principle is a 952 MHz, 2-cell rf-dipole (RFD) cavity. This paper summarizes the electromagnetic design of the cavity and its HOM characteristics.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB093  
About • paper received ※ 22 May 2019       paper accepted ※ 24 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB094 Measurements of the Electrical Axes of the CeC PoP RF Cavities 3031
 
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • Y.C. Jing, V. Litvinenko, J. Ma, I. Pinayev, K. Shih, G. Wang
    BNL, Upton, Long Island, New York, USA
  • V. Litvinenko
    Stony Brook University, Stony Brook, USA
  • K. Shih
    SBU, Stony Brook, New York, USA
 
  It is common knowledge that every mode in an SRF cavity has a so-called electrical axis, and only in an ideal cavity would this axis align exactly with the geometrical axis of the device. The misalignment of the electrical axis creates an additional undesirable transverse kick to the beam, which has to be corrected to achieve the designed beam parameters. In this paper we present the two methods which have been used in order to determine the electrical axes in the RF cavities of the Coherent electron Cooling (CeC) Proof of Principle (PoP) accelerator. The electron accelerator for the CeC PoP consists of the three main RF components: the 113 MHz SRF gun, the two normal-conducting 500 MHz bunching cavities, and the 704 MHz SRF 5-cell elliptical cavity. We discuss, in detail, the specifics of the measurement for each cavity and provide the corresponding results. In addition, we describe the influence of the field asymmetry in the 500 MHz bunchers on the beam dynamics, which was observed experimentally and confirmed by simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB094  
About • paper received ※ 14 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB097 Understanding and Mitigation of Field Emission in CEBAF SRF Linacs 3039
 
  • R.L. Geng, A. Freyberger, R.A. Rimmer
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
We will present current understanding of field emission in two 1.1 GeV CW SRF linacs at CEBAF and its mitigation for improved CEBAF energy reach and operation reliability. This contribution will provide a review of CEBAF gradient evolution since 2014, the impact of field emission, the effort in understanding the root cause of field emission in operational SRF cavities including the recently installed C100 cavities. We will evaluate the effect of initial mitigations implemented since 2016, aimed at reducing generation and transportation of new field emitting particulates. Effects of cavity thermal cycling aimed at abating activation of settled field emitting particulates will be evaluated as well. Remaining issues toward predictable control of field emission in operational SRF cavities will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB097  
About • paper received ※ 19 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB098 Cryogenic RF Performance of Double-Quarter Wave Cavities Equipped with HOM Filters 3043
 
  • S. Verdú-Andrés, I. Ben-Zvi, Q. Wu, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • G. Burt, J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • R. Calaga, O. Capatina
    CERN, Geneva, Switzerland
  • N.A. Huque, E.A. McEwen, H. Park, T. Powers
    JLab, Newport News, Virginia, USA
  • Z. Li, A. Ratti
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by US DOE through BSA LLC under contracts No. DE-AC02-98CH10886, No. DE-SC0012704, and the US LHC Accelerator Research Program (LARP) and by the EU HL-LHC Project.
Crab cavities are one of the several components included in the luminosity upgrade of the Large Hadron Collider (HL-LHC). The cavities have to provide a nominal deflecting kick of 3.4 MV per cavity while the cryogenic load per cavity stays below 5 W. Cold RF tests confirmed the required performances in bare cavities, with several cavities exceeding the required voltage by more than 50%. However, the first tests of a Double-Quarter Wave (DQW) cavity with one out of three HOM filters did not reach the required voltage. The present paper describes the studies and tests conducted on a DQW cavity with HOM filter to understand the limiting factor. The recipe to meet the performance specification and exceed the voltage requirement by more than 35% is discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB098  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB102 Correction of Crosstalk Effect in the LEReC Booster Cavity 3051
 
  • B. P. Xiao, K. Mernick, F. Severino, K.S. Smith, T. Xin, W. Xu
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Linac of Low Energy RHIC electron Cooler (LEReC) is designed to deliver a 1.6 MeV to 2.6 MeV electron beam, with peak-to-peak dp/p less than 7·10-4. The booster cavity is the major accelerating component in LEReC, which is a 0.4 cell cavity operating at 2 K, with a maximum energy gain of 2.2 MeV. It is modified from the Energy Recovery Linac (ERL) photocathode gun, with fundamental power coupler (FPC), pickup coupler (PU) and higher order mode (HOM) coupler close to each other. The direct coupling between FPC and PU induced crosstalk effect in this cavity. This effect is simulated and measured, and is further corrected using low level RF (LLRF) to meet the energy spread requirement.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB102  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB110 Recent Results from Nb3Sn-Coated Single-cell Cavities Combined with Sample Studies at Jefferson Lab 3066
SUSPFO133   use link to see paper's listing under its alternate paper code  
 
  • U. Pudasaini, M.J. Kelley
    The College of William and Mary, Williamsburg, Virginia, USA
  • G. Ciovati, G.V. Eremeev, M.J. Kelley, C.E. Reece
    JLab, Newport News, Virginia, USA
  • I.P. Parajuli
    ODU, Norfolk, Virginia, USA
 
  Funding: Partially authored by Jefferson Science Associates under contract no. DEAC0506OR23177. Supported by Office of High Energy Physics under grants DE-SC-0014475 and DE-SC-0018918.
The critical temperature (~ 18 K) and superheating field (~ 425 mT) of Nb3Sn are almost twice that of niobium, thereby promising the higher quality factor and accelerating gradient at any given temperature compared to traditional SRF cavities made of niobium. It can enable higher temperature for cavity operation (4 K Vs. 2 K), resulting in significant reduction in both capital and operating cost for the cryoplant. Several single-cell cavities along with witness samples were coated with Nb3Sn to explore, understand and improve the coating process for betterment of cavity performance. RF measurements of coated cavities combined with material characterization of witness samples were employed to update the coating process. Following some modifications to the existing coating process, we were able to produce Nb3Sn cavity with quality factor ≥ 2.1010 for accelerating gradient up to 15 MV/m at 4 K, without any significant Q-slope. In this article, we will discuss recent results from several Nb3Sn coated single-cell cavities combined with material studies of witness samples.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB110  
About • paper received ※ 15 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB111 Development of Nb3Sn Multicell Cavity Coatings 3070
 
  • G.V. Eremeev
    JLab, Newport News, Virginia, USA
  • U. Pudasaini
    The College of William and Mary, Williamsburg, Virginia, USA
 
  Funding: Co-Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.
Nb3Sn films have the potential to augment niobium in SRF cavities. Besides single-cell cavity efforts to improve Nb3Sn films, we are working to replicate single-cell results onto the practical 5-cell CEBAF cavities. High quality factors (1011 at 2.0K and 10zEhNZeHn at 4.3 K) have been measured, but the cavities are typically limited by strong low-field Q-slopes and early quenches. Two of the cavities were selected to be assembled into a ’mock-up’ cavity pair unit, the standard step before installation into a cryomodule. Comparison of test results between VTA and pair test offered the first glimpse into post-processing effects on the cavity performance.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB111  
About • paper received ※ 16 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPRB114 Understanding and Pushing the Limits of Nitrogen Doping 3078
SUSPFO030   use link to see paper's listing under its alternate paper code  
 
  • D. Bafia, M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, S. Posen, A.S. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • D. Bafia, J. Zasadzinski
    IIT, Chicago, Illinois, USA
  • D. Gonnella
    SLAC, Menlo Park, California, USA
  • A.D. Palczewski
    JLab, Newport News, Virginia, USA
 
  This work will describe Fermilab experiments that focus on the optimization of doping parameters to achieve low sensitivity to trapped magnetic flux while maintaining very high Q characteristic of nitrogen doped cavities and same or higher quench fields. Working partially in the context of LCLS-2 higher energy upgrade, new doping recipes are pursued and have been found to vary the mean free path of the resonator which is related to the sensitivity to trapped magnetic flux. Moreover, a correlation has been found between lighter doping and higher quench fields while maintaining sufficiently low surface resistance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB114  
About • paper received ※ 18 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)