Keyword: HOM
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MOPB028 Preservation of Very High Quality Factors of 1.3 GHz Nine Cell Cavities From Bare Vertical Test to Dressed Horizontal Test cavity, cryomodule, factory, shielding 149
 
  • A. Grassellino, S. Aderhold, M. Checchin, A.C. Crawford, C.J. Grimm, A. Hocker, M. Martinello, O.S. Melnychuk, J.P. Ozelis, S. Posen, A.M. Rowe, D.A. Sergatskov, N. Solyak, R.P. Stanek, G. Wu
    Fermilab, Batavia, Illinois, USA
  • D. Gonnella
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.M. Köszegi
    HZB, Berlin, Germany
  • M. Liepe
    Cornell University, Ithaca, New York, USA
  
  In this contribution we will report quality factor evolution of several different nine cell N doped cavities with very high Q. The evolution of the quality factor will be reported from bare to dressed in vertical test to dressed in horizontal test with unity coupling to dressed in horizontal test and CM-like environment/configuration (with RF ancillaries). Cooling studies and optimal cooling regimes will be discussed for both vertical and horizontal tests and comparisons will be drawn also for different styles titanium vessels. Studies of sensitivities to magnetic field in final horizontal configuration have been performed by applying a field around the dressed cavity and varying the cooling; parameters required for a very good flux expulsion will be presented.  
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MOPB040 Performance of Dressed Cavities for the Jefferson Laboratory LCLS-II Prototype Cryomodule - With Comparison to the Pre-Dressed Performance cavity, cryomodule, hardware, linac 178
 
  • A.D. Palczewski, G.K. Davis
    JLab, Newport News, Virginia, USA
  • F. Furuta, G.M. Ge, D. Gonnella, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 with supplemental funding from the LCLS-II Project U.S. DOE Contract No. DE-AC02-76SF00515.
Initial vertical RF test results and quench studies for six of the eight undressed 9 cell cavities slated for use in the Jefferson laboratory LCLS-II prototype cryomodule were presented at IPAC2015*. For the final string 2 more cavities AES029 and AES030 (work done at Cornell) are being processed and tested for qualification before helium vessel welding. In addition, AES034 (initial R&D treatment) is being reworked with the current production protocol after a surface reset to improve the overall performance. After final qualification all 8 cavities will be welded into helium vessels and equipped with HOM couplers. In this paper we will present the final undressed and dressed vertical RF data comparing the changes in the surface resistance before their installation in the cryomodule string.
*A.D. Palczewski et al. Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for use in the LCLS-II Prototype Cryo-module at Jefferson Laboratory, Proc. IPAC2015, WEPWI019, 2015. 		 
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MOPB041 Cryomodule Testing of Nitrogen-Doped Cavities cavity, cryomodule, SRF, linac 182
 
  • D. Gonnella, B. Clasby, R.G. Eichhorn, B. Elmore, F. Furuta, G.M. Ge, D.L. Hall, Y. He, G.H. Hoffstaetter, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco, T.I. O'Connell, P. Quigley, D.M. Sabol, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A. Grassellino, C.J. Grimm, J.P. Holzbauer, O.S. Melnychuk, Y.M. Pischalnikov, A. Romanenko, W. Schappert, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
  
  Funding: DOE and the LCLS-II High Q Project
The Linac Coherent Light Source-II (LCLS-II) is a new FEL x-ray source that is planned to be constructed in the existing SLAC tunnel. In order to meet the required high Q0 specification of 2.7x1010 at 2 K and 16 MV/m, nitrogen-doping has been proposed as a preparation method for the SRF cavities in the linac. In order to test the feasibility of these goals, four nitrogen-doped cavities have been tested at Cornell in the Horizontal Test Cryomodule (HTC) in five separate tests. The first three tests consisted of cavities assembled in the HTC with high Q input coupler. The fourth test used the same cavity as the third but with the prototype high power LCLS-II coupler installed. Finally, the fifth test used a high power LCLS-II coupler, cavity tuner, and HOM antennas. Here we report on the results from these tests along with a systematic analysis of change in performance due to the various steps in preparing and assembling LCLS-II cavities for cryomodule operation. These results represent one of the final steps to demonstrate readiness for full prototype cryomodule assembly for LCLS-II. 		 
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MOPB069 Superconducting Linac Upgrade Plan for the Second Target Station Project at SNS cryomodule, cavity, linac, accelerating-gradient 268
 
  • S.-H. Kim, M. Doleans, J. Galambos, M.P. Howell
    ORNL, Oak Ridge, Tennessee, USA
  • J.D. Mammosser
    ORNL RAD, Oak Ridge, Tennessee, USA
  
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The beam power of the Linac for the Second Target Station (STS) at the Spallation Neutron Source (SNS) will be doubled to 2.8 MW. For the energy upgrade seven additional cryomodules will be installed in the reserved space at the end of the linac tunnel to produce the linac output energy of 1.3 GeV. The cryomodules for STS will have some changes that do not require changes of overall layout based on the lessons learned from operational experience over the last 10 years and the high beta spare cryomodule developed in house. The average macro-pulse beam current for the STS will be 38 mA that is about 40 % increase from that for the present 1.4 MW operation. Plans for the existing cryomodules to support higher beam current for the STS is also presented in this paper. 		 
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MOPB070 Preliminary Conceptual Design of the CEPC SRF System cavity, SRF, collider, booster 272
 
  • J.Y. Zhai, J. Gao, T.M. Huang, Z.C. Liu, Z.H. Mi, P. Sha, Y. Sun, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  • S.A. Belomestnykh
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh
    Stony Brook University, Stony Brook, USA
  • C. Pagani
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  CEPC is a circular electron positron collider operating at 240 GeV center-of-mass energy as a Higgs factory, recently proposed by the Chinese high energy physics community. The CEPC study group, together with the FCC and ILC community, will contribute to the development of future high energy colliders and experiments which will ensure that the elementary particle physics remain a vibrant and exciting field of fundamental investigation for decades to come. Superconducting RF (SRF) system is one of the most important technical systems of CEPC and is a key to achieving its design energy and luminosity. It will dominate, with the associated RF power source and cryogenic system, the overall machine cost, efficiency and performance. The CEPC SRF system will be one of the largest and most powerful SRF accelerator installations in the world. The preliminary conceptual design of the CEPC SRF system is summarized in this paper, including the machine layout, key parameter choices and some critical issues such as HOM damping, emphasizing the new technology requirement and R&D focuses.  
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MOPB076 Horizontal RF Test of a Fully Equipped 3.9 GHz Cavity for the European XFEL in the DESY AMTF cavity, operation, cryomodule, controls 301
 
  • C.G. Maiano, C. Albrecht, R. Bospflug, J. Branlard, L. Butkowski, T. Delfs, J. Eschke, A. Gössel, F. Hoffmann, M. Hüning, K. Jensch, R. Jonas, R. Klos, D. Kostin, W. Maschmann, A. Matheisen, U. Mavrič, W.-D. Möller, C. Müller, K. Mueller, B. Petersen, P. Pierini, J. Rothenburg, O. Sawlanski, M. Schmökel, A.A. Sulimov, E. Vogel
    DESY, Hamburg, Germany
  • A. Bosotti, M. Moretti, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • E.R. Harms
    Fermilab, Batavia, Illinois, USA
  • C.R. Montiel
    ANL, Argonne, Illinois, USA
  • S. Pivovarov
    BINP SB RAS, Novosibirsk, Russia
  
  In order to validate the cavity package concept before the module preparation for the European XFEL Injector, one 3.9 GHz cavity, complete with magnetic shielding, power coupler and frequency tuner was tested in a specially designed single cavity cryomodule in one of the caves of the DESY Accelerator Module Test Facility (AMTF). The cavity was tested in high power pulsed operation up to the quench limit of 24 MV/m, above the vertical test qualifications and all subsystems under test (coupler, tuner, waveguide tuners, LLRF system) were qualified to design performances.  
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MOPB077 Vertical Tests of XFEL 3rd Harmonic Cavities cavity, vacuum, operation, instrumentation 306
 
  • D. Sertore, M. Bertucci, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, M. Moretti, R. Paparella, P. Pierini
    INFN/LASA, Segrate (MI), Italy
  • A. Matheisen, M. Schmökel
    DESY, Hamburg, Germany
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  The 10 cavities of the EXFEL 3rd Harmonic Cryomodule have been tested and qualified, before integration in the He-tank, in our upgraded Vertical Test stand. In this paper, we report the measured RF performance of these cavities together with the main features of the test facility.  
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MOPB078 Mode Sensitivity Analysis of 704.4 MHz Superconducting RF Cavities cavity, operation, linac, dipole 311
 
  • K. Papke, F. Gerigk, S. Horvath-Mikulas, S. Papadopoulos, E. Pilicer, F. Pillon
    CERN, Geneva, Switzerland
  • U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  
  Due to the large variety of beam patterns considered for the superconducting proton linac (SPL) at CERN it is likely that the frequencies of some HOMs are close to machine lines during operation. Hence, in the interest of developing a method to shift HOM frequencies away from machine lines, we study the influence of cavity detuning and re-tuning (e.g. by Lorentz forces, field flatness tuning, frequency tuning during operation) on HOMs. The sensitivity of HOMs with respect to the fundamental mode was studied for a mono-cell and for 5-cell high-beta SPL cavities operating at 704.4 MHz. First, the variation of the HOMs during the flat-field tuning was measured. In this process, several detuning and re-tuning cycles were made to estimate the range of possible HOM frequency shifts. Secondly the effect of the frequency tuner on the HOMs is presented and finally the frequency shifts of all modes due to the cool down.  
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MOPB084 Performance of Nitrogen-Doped 9-Cell SRF Cavities in Vertical Tests at Cornell University cavity, SRF, superconducting-RF, linac 328
 
  • G.M. Ge, R.G. Eichhorn, B. Elmore, F. Furuta, D. Gonnella, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connell, J. Sears, E.N. Smith
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Cornell University treated five LCLS-II 9-cell cavities by nitrogen-doping recipe. In this paper, we reported the performance of these 9-cell cavities. In the treatments, the nitrogen recipes are slightly different. The cavities have been firstly doped under high nitrogen pressure; after the vertical tests some of the cavities has been reset the surface and re-doped under light nitrogen pressure. The detail of the cavity preparation and test results will be shown. The comparison of the different recipes will be discussed.  
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MOPB087 Integrated High-Power Tests of Dressed N-doped 1.3 GHz SRF Cavities for LCLS-II cavity, cryomodule, resonance, vacuum 342
 
  • N. Solyak, T.T. Arkan, B.E. Chase, A.C. Crawford, E. Cullerton, I.V. Gonin, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, J.P. Ozelis, T.J. Peterson, Y.M. Pischalnikov, K.S. Premo, A. Romanenko, A.M. Rowe, W. Schappert, D.A. Sergatskov, R.P. Stanek, G. Wu
    Fermilab, Batavia, Illinois, USA
  
  New auxiliary components have been designed and fabricated for the 1.3 GHz SRF cavities comprising the LCLS-II linac. In particular, the LCLS-II cavity’s helium vessel, high-power input coupler, higher-order mode (HOM) feedthroughs, magnetic shielding, and cavity tuning system were all designed to meet LCLS-II specifications. Integrated tests of the cavity and these components were done at Fermilab’s Horizontal Test Stand (HTS) using several kilowatts of continuous-wave (CW) RF power. The results of the tests are summarized here.  
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MOPB088 HOM Measurements on the ARIEL eLINAC Cryomodules cavity, simulation, cryomodule, linac 347
 
  • P. Kolb, R.E. Laxdal, Y. Ma, Z.Y. Yao, V. Zvyagintsev
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  The ARIEL eLINAC is a 50 MeV, 10 mA electron LINAC designed for the creation of rare isotopes via photo-fission. Future upgrade plans include the addition of a recirculating beam line to allow for either further energy increase of the beam beyond 50 MeV or to operate a free electron laser in an energy recovery mode. For both recirculating LINAC and ERL the higher order modes (HOM) have to be sufficiently suppressed to prevent beam-break-up. The design of the 1.3 GHz nine-cell cavity incorporated this requirement by including beam line absorbers on both ends of each cavity and an asymmetric beam pipe configuration on the cavity to allow trapped modes to propagate to the beam line absorbers. Measurements of the higher order modes on the completed injector cryomodule and the first cavity in the accelerating cryomodules will be shown and compared to simulations.  
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MOPB112 SRF Quality Assurance Studies and Their Application to Cryomodule Repairs at SNS cryomodule, cavity, vacuum, hardware 428
 
  • J.D. Mammosser, R. Afanador, D.L. Barnhart, B. DeGraff, B.S. Hannah, J. Saunders, P.V. Tyagi
    ORNL RAD, Oak Ridge, Tennessee, USA
  • C.M. Campbell
    Omega Technical Services, Oak Ridge, Tennessee, USA
  • M. Doleans, D.K. Hensley, S.-H. Kim
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Many of the SRF activities involve interactions to cavities which presents risk for particulate contamination to RF surfaces. In order to understand and reduce contamination in cavities during cleaning, vacuum pumping and purging, and in-situ cryomodule repairs, a Quality Assurance (QA) studies were initiated to evaluate these activities and improve them where possible. This paper covers the results of investigations on the effectiveness of the SNS ultrasonic cleaning systems, particulate control during pumping and purging, procedure development for in-situ cryomodule repairs, the application of these studies to the repair of a linac cryomodule, and discussion of further improvement in these areas. 		 
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TUAA03 BESSY VSR: A Novel Application of SRF for Synchrotron Light Sources cavity, damping, SRF, storage-ring 462
 
  • A.V. Vélez, H.-W. Glock, P. Goslawski, A. Jankowiak, J. Knobloch, A. Neumann, M. Ries, G. Wüstefeld
    HZB, Berlin, Germany
  
  CW SRF Cavities have been used very successfully in the past in synchrotron light sources to provide high power acceleration. Here we present a novel application of higher harmonic systems of two frequencies (1.5 GHz and 1.75 GHz) to generate a beating of accelerating voltage. With such a system it is possible to store "standard" (some 10 ps long) and "short" (ps and sub-ps long) pulses simultaneously in the light source. This opens up brand new possibilities for light source users to perform dynamic and high-resolution experiments at the same facility. The demands on the SRF system and RF control are substantial and a new design, based on waveguide damping, is currently being developed. This system will be used for a major upgrade of the BESSY-II facility to the BESSY Variable Pulse Storage Ring (BESSY-VSR) for a next-generation storage-ring light source. We will discuss the concept, challenges and designs for BESSY-VSR.  
slides icon Slides TUAA03 [2.103 MB]  
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TUPB017 1.3 GHz SRF Technology R&D Progress of IHEP cavity, cryomodule, vacuum, cryogenics 581
 
  • J.Y. Zhai, Y.L. Chi, J.P. Dai, X.W. Dai, J. Gao, R. Ge, D.Y. He, T.M. Huang, X. Huang, S. Jin, S.P. Li, H.Y. Lin, B. Liu, Z.C. Liu, Q. Ma, Z.H. Mi, W.M. Pan, X.H. Peng, L.R. Sun, Y. Sun, Z. Xue, S.W. Zhang, Z. Zhang, H. Zhao, T.X. Zhao, H.J. Zheng, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
  
  IHEP started the 1.3GHz SRF technology R&D in 2006 and recently enters the stage of integration and industrialization. After successfully making several single cell and 9-cell cavities of different shape and material, we designed and assembled a short cryomodule containing one large grain low loss shape 9-cell cavity with an input coupler and a tuner etc. This module will perform horizontal test in 2016 with the newly commissioned 1.3GHz 5MW klystron and the 2K cryogenic system. Beam test with a DC photocathode gun is also foreseen in the near future. We report here the problems, key findings and improvements in cavity dressing, clean room assembly, cryomodule assembly and the liquid nitrogen cool down test. A fine grain TESLA 9-cell cavity is also under fabrication in a company as the industrialization study.  
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TUPB018 Preparation of the 3.9 GHz System for the European XFEL Injector Commissioning cavity, operation, alignment, vacuum 584
 
  • P. Pierini, M. Bertucci, M. Bonezzi, A. Bosotti, J.F. Chen, M. Chiodini, P. Michelato, L. Monaco, M. Moretti, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C. Albrecht, N. Baboi, S. Barbanotti, J. Branlard, Th. Buettner, L. Butkowski, T. Delfs, H. Hintz, F. Hoffmann, M. Hüning, K. Jensch, R. Jonas, R. Klos, D. Kostin, L. Lilje, C.G. Maiano, W. Maschmann, A. Matheisen, U. Mavrič, W.-D. Möller, C. Müller, P. Pierini, J. Prenting, J. Rothenburg, O. Sawlanski, M. Schlösser, M. Schmökel, A.A. Sulimov, E. Vogel
    DESY, Hamburg, Germany
  • E.R. Harms
    Fermilab, Batavia, Illinois, USA
  • C.R. Montiel
    ANL, Argonne, Illinois, USA
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  The 3.9 GHz cryomodule and RF system for the XFEL Injector is being assembled and delivered to the underground building in summer 2015, for the injector commissioning in Fall 2015. This contribution outlines the status of the activity and reports the preparation stages of the technical commissioning of the system.  
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TUPB078 Developments on a Cold Bead-Pull Test Stand for SRF Cavities cavity, SRF, factory, operation 770
 
  • A.V. Vélez, A. Frahm, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  
  Final tuning and field profile characterization of SRF cavities always takes place at room temperature. However, important questions remains as to what happens when the cavity is cooled to LHe temperature, in particular with multi cell systems. To enable the characterization of cavities in the cold, we have designed and commissioned a "cold bead-pull" test stand at HZB. The present test stand is designed to be integrated in HoBiCaT (Horizontal bi-cavity testing facility) with the ability to provide electric field profile measurements under realistic superconducting conditions (T=1.8K). In this paper mechanical and operational details of the apparatus will be described as well as future plans for the development and usage of this facility.  
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TUPB079 Second Sound Quench Detection of Dressed TESLA-Shape SRF Cavities cavity, detector, simulation, SRF 774
 
  • Y. Tamashevich
    University of Hamburg, Hamburg, Germany
  • E. Elsen, A. Navitski
    DESY, Hamburg, Germany
  
  A compact detector and numerical algorithm for second sound measurements has been developed. The detector allows precise 3D quench localisation within a single unit and can be used even for cavities with mounted helium tank. The compact device is easily mounted and requires minimum space. It can be used as a part of the standard cold test of cavities. The results obtained with the new detector and a 3D algorithm have been cross-checked by optical inspection and resistor-based temperature mapping. The resolution of the detector is seen to be limited by the sampling rate and the lateral extent of the quench induced heated area on the Nb superconductor.  
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TUPB109 Assembly and Cool-Down Tests of STF2 Cryomodule at KEK cavity, cryomodule, vacuum, network 888
 
  • T. Shishido, K. Hara, E. Kako, Y. Kojima, H. Nakai, Y. Yamamoto
    KEK, Ibaraki, Japan
  
  As the next step of the quantum beam project, the STF2 project is in progress at KEK. Eight 9-cell SC cavities and one superconducting quardrapole magnet were assembled into the cryomodule called CM1. Four 9-cell SC cavities were assembled into the cryomodule called CM2a. These two cryomodules were connected as one unit, and the examination of completion by a prefectural government was carried out. The target value of beam energy in the STF2 accelerator is 400 MeV with a beam current of 6 mA. The first cool down test for low power level RF measurements was performed in autumn of 2014. In this paper, the assembly procedure of the STF2 cryomodules and the results of the low-power measurement are reported.  
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TUPB118 Improvements of the RF Test Procedures for European XFEL Cryomodule Testing cryomodule, cavity, cryogenics, LLRF 914
 
  • M. Wiencek, K. Kasprzak, D. Konwisorz, S. Myalski, K. Turaj, A. Zwozniak
    IFJ-PAN, Kraków, Poland
  
  The testing of the 100 SRF cryomodules for E-XFEL is currently ongoing at the AMTF Hall, located at DESY, Hamburg. Cold tests for the cryomodules have been developed based on TTF (Tesla Test Facility) experience. However, to be able to test the cryomodules with required test rate of one a week, some improvements to the measurements had to be made. The goal of these improvements was to reduce the time needed for testing without losing any of the important data for the cryomodule. Currently, after testing more than 30% of the cryomodules, gathered experience is now allowing us to skip or combine some of the measurements. This paper describes changes in the cold test procedures which have been made since the testing of the first serial cryomodules delivered by IRFU.  
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WEA2A02 High Gradient Testing of the Five-Cell Superconducting RF Module With a PBG Coupler Cell cavity, niobium, dipole, factory 948
 
  • S. Arsenyev
    MIT/PSFC, Cambridge, Massachusetts, USA
  • C.H. Boulware, T.L. Grimm, A. Rogacki
    Niowave, Inc., Lansing, Michigan, USA
  • W.B. Haynes, D.Y. Shchegolkov, E.I. Simakov, T. Tajima
    LANL, Los Alamos, New Mexico, USA
  
  Funding: DOE Office of Science/Office of High Energy Physics
Superconducting radio-frequency (SRF) accelerating structures allow high-gradient operation in continuous-wave mode. These machines can be limited by beam-breakup instability at high currents because higher-order modes with very high Q factors are easily excited by the beam. Photonic band gap (PBG) structures provide a way to strongly damp higher-order modes without compromising the performance of the structure in the fundamental mode. We first address the design of the structure and issues that arise from incorporating a complex PBG cell into an SRF module. In particular, the module was tuned to have uneven accelerating gradient profile in order to provide equal peak surface magnetic field in every cell. We then cover the fabrication steps and surface treatment of the five-cell niobium structure and report results of the high gradient tests at temperatures of 4 K and 2 K. 		 
slides icon Slides WEA2A02 [7.023 MB]  
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WEBA02 RF Measurements for Quality Assurance During SC Cavity Mass Production cavity, controls, GUI, linac 955
 
  • A.A. Sulimov
    DESY, Hamburg, Germany
  
  The publication will describe the comprehensive program and results of RF measurements taken during the mass production of superconducting cavities for the European XFEL.  
slides icon Slides WEBA02 [2.305 MB]  
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WEBA07 Beam Commissioning of the 56 MHz QW Cavity in RHIC cavity, operation, damping, SRF 982
 
  • Q. Wu, S.A. Belomestnykh, I. Ben-Zvi, M. Blaskiewicz, T. Hayes, K. Mernick, F. Severino, K.S. Smith, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh, I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 56 MHz superconducting RF cavity has been designed, fabricated and installed in the Relativistic Heavy Ion Collider (RHIC). The cavity operates at 4.4 K with a “quiet helium source” to isolate the cavity from environmental acoustic noise. The cavity is a beam driven quarter wave resonator. It is detuned and damped during injection and acceleration cycles and is brought to operation only at store energy. We have observed clear luminosity increase and bunch length reduction in the first operation of the cavity with Au + Au and Au + He3 collisions. The cavity voltage was limited by quenching in the Higher Order Mode coupler. This paper also discusses the cavity beam experiments with no higher order mode coupler in p + p and p + Au RHIC operation. 		 
slides icon Slides WEBA07 [2.522 MB]  
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THAA01 Recent Developments in Superconducting Deflecting-Mode Cavities cavity, dipole, simulation, luminosity 987
 
  • J.R. Delayen
    ODU, Norfolk, Virginia, USA
  
  In the last few years there has been a growing interest in compact superconducting cavities operating in a deflecting mode to be used either in rf separators or crabbing systems. This talk will give an overview of recent progress in global activities towards SRF deflecting mode cavities.  
slides icon Slides THAA01 [4.729 MB]  
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THBA04 Overview of Recent HOM Coupler Development cavity, damping, SRF, operation 1031
 
  • B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work partly supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE， by the US LARP, and by EU FP7 HiLumi LHC - Grant Agreement 284404.
HOM damping is important for SRF applications, especially for high intensity machines. A good HOM damping design will help to reduce power load to the cryogenic system and to reduce the risk of beam breakup. The design of HOM damping, including antenna/loop HOM couplers, beam pipe HOM absorbers and waveguide HOM couplers, is to solve a multi-physics problem that involves RF, thermal, mechanical, and beam-cavity interaction issues. In this talk, the author provides an overview on the latest advances of the HOM couplers for high intensity SRF applications. 		 
slides icon Slides THBA04 [2.619 MB]  
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THBA05 Higher Order Mode Absorbers for High Current SRF Applications cavity, higher-order-mode, linac, operation 1036
 
  • R.G. Eichhorn, J.V. Conway, T. Gruber, Y. He, G.H. Hoffstaetter, Y. Li, M. Liepe, T.I. O'Connell, P. Quigley, J. Sears, V.D. Shemelin, E.N. Smith, M. Tigner
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Efficient damping of the higher-order modes (HOMs) of the superconducting cavities is essential for any high current operation. The talk will provide an overview on the latest advances of HOM absorber development for high intensity SRF applications. As the ideal absorber does not exist, the different conceptual approaches will be presented and the associated issues are outlined. Design examples from various labs will be given that help explain the issues and resolutions. Some focus will be given to the Cornell HOM beamline absorber that was design for high current, short bunch operation with up to 400 W heating. The design will be reviewed and testing results will be reported.  
slides icon Slides THBA05 [4.022 MB]  
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THPB002 Second Harmonic Cavity Design for Synchrotron Radiation Energy Compensator in eRHIC Project cavity, impedance, linac, radiation 1052
 
  • C. Xu, S.A. Belomestnykh, I. Ben-Zvi, W. Xu
    BNL, Upton, Long Island, New York, USA
  
  Funding: DOE
eRHIC project requires construction of a FFAG ring to accelerate electrons and connect to the existing ion ring of Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This new ring will have the same radius as the RHIC ring. Synchrotron radiation lost in the electron ring should be compensated by a CW superconducting radio frequency (SRF) cavity. Here we propose an 845 MHz single cell harmonic cavity. This cavity will experience a high average current (∼0.7 A) passing through it. With this consideration, this cavity design requires optimization to reduce higher order mode power. On the other hand, the cavity will operate at relatively high gradient up to 18 MV/m. Current design requires fundamental couplers to handle 400 kW forward RF power and HOM couplers to extract 2.5 kW HOM power.
This work is supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
 		 
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THPB003 Calculations for RF Cavities with Dissipative Material cavity, SRF, dipole, damping 1056
 
  • F. Marhauser
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
3D simulations have been performed for a variety of SRF cavities which incorporate Higher Order Mode dampers, either in form of coaxial couplers or waveguide dampers. Instead of utilizing the rather standard approach of matching the output port of the dampers with a broadband coaxial or waveguide port, dissipative materials are modelled for RF field absorption. This for instance not only avoids the otherwise required definition of the number of modes considered for damping, which has an impact on the computational time, but also allows tailoring the load material to conform with experimental data of e.g. non-perfect absorbers. The new calculation scheme is presented. Findings are partially compared with those achieved with the standard waveguide port approach by means of external quality factors. CPU speeds are briefly discussed for both approaches. 		 
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THPB004 HOM Calculations for Different Cavities and Beam Induced HOM Power Analysis of ESS cavity, sextupole, dipole, quadrupole 1061
 
  • H.J. Zheng, J. Gao
    IHEP, Beijing, People's Republic of China
  • J.F. Chen
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  For different design of ESS superconducting cavities, the higher order modes (HOM's) of monopoles, dipoles, quadrupoles and sextupoles are found. Their R/Q values are also calculated. Main HOM related issues are the beam instabilities and the HOM induced power especially from TM monopoles. The analysis for the beam induced HOM voltage and power in this paper showed that, if the HOM frequency is a few kHz away from the beam spectrum, it is not a problem. In order to understand the effects of the beam structure, analytic expressions are developed. With these expressions, the induced HOM voltage and power were calculated by assuming external Q for each HOM. Our analysis confirm that, with thebeam structure of ESS and a good cavity design, no special tight tolerances are required for cavity fabrication and no HOM couplers in the cavity beam pipes are planned.  
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THPB006 Improvements of Buildcavity Code cavity, interface, simulation, coupling 1070
 
  • J.F. Chen, M. Moretti, C. Pagani, P. Pierini
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  Recentely, we improve the BuildCavity code, which is a graphics interface to SUPERFISH for the study of superconducting cavities of elliptical shape. Now it works with latest SUPERFISH 7 and can be installed also on newer Windows system such as Win 7 and 8. Several improvements have been done in the code. As an example, a design of ESS median-beta cavity with BuildCavity will also be presented.  
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THPB007 A Study of Resonant Excitation of Longitudinal HOMs in the Cryomodules of LCLS-II cavity, factory, resonance, impedance 1073
 
  • K.L.F. Bane, C. Adolphsen, A. Chao, Z. Li
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515
The Linac Coherent Light Source (LCLS) at SLAC, the world's first hard X-ray FEL, is being upgraded to the LCLS-II. The major new feature will be the installation of 35 cryomodules (CMs) of TESLA-type, superconducting accelerating structures. It is envisioned that LCLS-II will eventually be able to deliver 300 pC, 1 kA pulses of beam at a rate of 1 MHz. At a cavity temperature of 2K, any heat generated (even on the level of a few watts) is expensive to remove. In the last linac of LCLS-II, L3–-where the peak current is highest–-the power radiated by the bunch in the CMs is estimated at 14 W (charge 300 pC option, rep rate 1 MHz). But this calculation ignores resonances that can be excited between the bunch frequency and higher order mode (HOM) frequencies in the CMs, which in principle can greatly increase this number. In this report we develop a theory of resonant build up. Then, using 500 numerically obtained modes over the frequency range 3–5 GHz, we estimate the probability of significant resonant build up in L3 of LCLS-II. The effects of small random bunch phase and charge errors will also be addressed. 		 
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THPB008 RF Simulations for an LCLS-II 3rd Harmonic Cavity Cyromodule cavity, damping, cryomodule, dipole 1078
 
  • L. Xiao, C. Adolphsen, Z. Li, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  
  The FNAL designed 3.9 GHz third harmonic cavity for XFEL will be used in LCLS-II for linearizing the longitudinal beam profile. The 3.9 GHz SRF cavity is scaled down from the 1.3 GHz TESLA cavity shape, but has a disproportionately large beampipe radius for better higher-order mode (HOM) damping. The HOM and fundamental power (FPC) couplers will generate asymmetric field in the beam region, and thereby dilute the beam emittance. Meanwhile, due to the large beampipe, all but a few of the HOMs are above the beampipe cutoff. Thus the HOM damping analyses need to be performed in a full cryomodule, rather than in an individual cavity. The HOM damping in a 4-cavity cryomodule was investigated to determine possible trapped modes using the parallel electromagnetic code suite ACE3P developed at SLAC. The coupler RF kicks induced by the HOM and FPC couplers in the 3.9 GHz cavity were evaluated. A possible cavity-to-cavity arrangement is proposed which could provide effective cancellation of these RF kicks. In this paper we present and discuss the RF simulation results in the 3.9 GHz third harmonic cavity cryomodule.
Work supported by Department of Energy under contract Number DE-AC02-76SF00515. 		 
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THPB013 A Novel Design and Development of 650 MHz, β=0.61, 5-Cell SRF Cavity for High Intensity Proton Linac cavity, niobium, electron, impedance 1088
 
  • S.S. Som, P. Bhattacharyya, A. Dutta Gupta, S. Ghosh, A. Mandal, S. Seth
    VECC, Kolkata, India
  
  Funding: DAE, Govt. of India
DAE laboratories in India are involved in R&D activities on SRF cavity technology for the proposed high intensity proton linacs for ISNS/IADS and also FERMILAB PIP-II program under IIFC. VECC is responsible for design, analysis and development of a 650 MHz, β=0.61, 5-cell elliptical cavity. This paper describes the novel design of the cavity, with different aperture and wall angle, having better field flatness and mechanical stability, reliable surface processing facility and less beam loss. The cavity geometry has been optimized to get acceptable values of field enhancement factors, R/Q, Geometric factor, cell-to-cell coupling etc. The effective impedance of transverse and longitudinal HOMs are low enough to get rid of HOM damper for low beam current. 2-D analysis shows no possibility of multipacting. However, 3-D analysis using CST Particle Studio code confirms its presence and it can be suppressed by introducing a small convexity in the equator region. Two niobium half cells and beam pipes for the single cell cavity have been fabricated. Measurement and RF characterisation of half cells, prototype 1-cell and 5-cell and also 1-cell niobium cavities have been carried out.
email:ssom@vecc.gov.in 		 
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THPB017 A Higher Harmonic Cavity at 800 MHz for HL-LHC cavity, polarization, cryomodule, simulation 1100
 
  • T. Roggen, P. Baudrenghien, R. Calaga
    CERN, Geneva, Switzerland
  
  Funding: Marie Curie action: Grant agreement PCOFUND-GA-2010-267194
A superconducting 800 MHz second harmonic system is proposed for HL-LHC. It serves as a cure for beam instabilities with high beam currents by improving Landau damping and will allow for bunch profile manipulation. This can potentially help to reduce intra-beam-scattering, beam induced heating and e-cloud effects, pile-up density in the detectors and beam losses. An overview of the 800 MHz cavity design and RF power requirements is given. In particular the design parameters of the cavity shape and HOM couplers are described. Some other aspects such as RF power requirements and cryomodule layout are also addressed. 		 
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THPB026 Update on SRF Cavity Design, Production and Testing for BERLinPro cavity, gun, linac, booster 1127
 
  • A. Neumann, W. Anders, A. Burrill, A. Frahm, H.-W. Glock, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • K. Brackebusch, T. Galek, J. Heller, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • G. Ciovati, W.A. Clemens, C. Dreyfuss, D. Forehand, T. Harris, P. Kneisel, R.B. Overton, L. Turlington
    JLab, Newport News, Virginia, USA
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association.
The BERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the accelerator physics of operating a high current, 100 mA, 50 MeV low emittance ERL utilizing all SRF cavity technology. For this machine three different types of SRF cavities are being developed. For the injector section, consisting of an SRF photoinjector and a three two cell booster cavity module, fabrication is completed. The cavities were designed at HZB and manufactured, processed and vertically tested at Jefferson Laboratory. In this paper we will review the design and production process of the two structures and show the latest horizontal acceptance tests at HZB prior to installation into the newly designed cryo-module. For the Linac cavity the latest cavity and module design studies are being shown. 		 
poster icon Poster THPB026 [1.535 MB]  
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THPB028 ESS Medium Beta Cavity Prototypes Manufacturing cavity, linac, coupling, cryomodule 1136
 
  • E. Cenni, C. Arcambal
    CEA/IRFU, Gif-sur-Yvette, France
  • P. Bosland, G. Devanz, X. Hanus, P. Hardy, V.M. Hennion, F. Leseigneur, F. Peauger, J. Plouin, D. Roudier
    CEA/DSM/IRFU, France
  • G. Costanza
    Lund University, Lund, Sweden
  • C. Darve
    ESS, Lund, Sweden
  
  The ESS elliptical superconducting linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity linac) up to the full energy at 2 GeV. The last linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. We describe here the procedures and numerical analysis leading from half-cells to a complete medium cavity assembly, which take into account not only the frequency of the fundamental accelerating mode but also the higher order modes near the machine line. The half cell selection process to form dumb bells will be described, as well as the reshaping and trimming procedure.  
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THPB031 Operation Experience with Half Cell Measurement Machine and Cavity Tuning Machine in 3 Years of European XFEL Cavity Series Production cavity, operation, controls, SRF 1149
 
  • J.H. Thie, A. Gössel, J. Iversen, D. Klinke, C. Müller, A.A. Sulimov, D. Tischhauser
    DESY, Hamburg, Germany
  
  For the European XFEL superconducting Cavity series production at both cavity vendors’ four manufacturing machines for production key functions, HAZEMEMA and CTM, are supplied by DESY. Among three years of cavity production in two companies a lot of experience is gathered about influence of surroundings and production quality on cycle times, machine drop outs, general stability time of machines and parts subject to wear. Significant factors on cycle time for tuning operation like temperature stability and drift during tuning and measurements, precision of cell trimming before welding and tuning and generally geometrical factors are shown. RF aspects of tuning and production quality control as additional measurements for TM011-mode to estimate quality of its damping is presented. Performed full Cavity RF measurements exceeds XFEL specifications gives a possibility for additional quality control on welding shrinkage stability and it’s homogeneously distribution. The use of HAZEMEMA and CTM to assess the impact of asymmetric trimming, including calculation of it’s influence on the higher-order modes, is shown.  
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THPB044 A Superconducting RF Deflecting Cavity for the ARIEL e-Linac Separator cavity, linac, electron, impedance 1187
 
  • D.W. Storey
    Victoria University, Victoria, B.C., Canada
  • R.E. Laxdal, L. Merminga, B.S. Waraich, Z.Y. Yao, V. Zvyagintsev
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  A 650 MHz SRF deflecting mode cavity has been designed for the ARIEL e-Linac to separate interleaved beams heading towards either Rare Ion Beam production or a recirculation loop for energy recovery, allowing the e-Linac to provide beam delivery to multiple users simultaneously. The cavity geometry has been optimized for the ARIEL specifications, resulting in a very compact cavity with high shunt impedance and low dissipated power. Analyses have been performed on the susceptibility to multipacting, input coupling considering beam loading and microphonics, and extensive studies into the damping of transverse and longitudinal higher order modes. The pressure sensitivity, frequency tuning, and thermal behaviour have also been studied using ANSYS. The cavity design resulting from these considerations will be discussed here.  
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THPB048 Design of a Compact Superconducting Crab-Cavity for LHC Using Nb-on-Cu-Coating Technique cavity, cathode, impedance, SRF 1205
 
  • A. Grudiev, S. Atieh, R. Calaga, S. Calatroni, O. Capatina, F. Carra, G. Favre, L.M.A. Ferreira, J.-F. Poncet, T. Richard, A. Sublet, C. Zanoni
    CERN, Geneva, Switzerland
  
  The design of a compact superconducting crab-cavity for LHC using Nb-on-Cu-coating technique is presented. The cavity shape is based on the ridged waveguide resonator with wide open apertures to provide access to the inner surface of the cavity for coating. It also provides natural damping for HOMs and rather low longitudinal and transverse impedances. The results of the cavity shape optimization taking into account RF performance, coating, and thermo-mechanical considerations as well as the design and fabrication plans of the first prototype for coating and cold tests are presented.  
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THPB050 Performance Evaluation of HL-LHC Crab Cavity Prototypes in a CERN Vertical Test Cryostat cavity, SRF, monitoring, electron 1210
 
  • K.G. Hernández-Chahín
    DCI-UG, León, Mexico
  • G. Burt
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C. Christophe, A. Macpherson, M. Navarro-Tapia, R. Torres-Sanchez
    CERN, Geneva, Switzerland
  • S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • A.R.J. Tutte
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • S. Verdú-Andrés
    BNL, Upton, Long Island, New York, USA
  
  Funding: My work is supported by the Mexican CONACYT(Consejo Nacional de Ciencia y Tecnologia) program through the Mexican national scholarship (Becas Nacionales y Becas Mixtas).
Three proof-of-principle compact crab cavity designs have been fabricated in bulk niobium and cold tested at their home labs, as a first validation step towards the High Luminosity LHC project. As a cross check, all three bare cavities have been retested at CERN, in order to cross check their performance, and cross-calibrate the CERN SRF cold test facilities. While achievable transverse deflecting voltage is the key performance indicator, secondary performance aspects derived from multiple cavity monitoring systems are also discussed. Temperature mapping profiles, quench detection, material properties, and trapped magnetic flux effects have been assessed, and the influence on performance discussed. The significant effort invested in developing expertise in preparation and testing of these crab cavities has already been fruitful for all partners, and more is to come within this ongoing program. 		 
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THPB052 Thermal Losses in Couplers and Ports of a SPS Double-Quarter Wave Crab Cavity cavity, pick-up, simulation, niobium 1219
 
  • S. Verdú-Andrés, S.A. Belomestnykh, Q. Wu, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh
    Stony Brook University, Stony Brook, USA
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
  • R. Calaga, O. Capatina, F. Carra, C. Zanoni
    CERN, Geneva, Switzerland
  • F. Carra
    Politecnico di Torino, Torino, Italy
  • T.J. Jones
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • Z. Li
    SLAC, Menlo Park, California, USA
  
  Funding: Supported by US DOE via US LARP, through BSA LLC under contract No. DE-AC02-98CH10886 and using NERSC resources under contract No. DE-AC02-05CH11231. Also supported by EU FP7 HiLumi LHC No.284404.
The Double-Quarter Wave Crab Cavity for beam tests at SPS will be equipped with a Fundamental Power Coupler (FPC), three HOM filters and one pickup. FPC and HOM couplers are located in high magnetic field region and have a hook shape. The FPC will be made in copper while HOM and pickup are in niobium. This paper explains the material choice for the FPC, HOM and pickup couplers given the calculated power dissipation for fundamental and selected high order modes. It also describes the envisaged cooling system and corresponding thermal distribution for each coupler. 		 
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THPB053 Electromagnetic Design of 400 MHz RF-Dipole Crabbing Cavity for LHC High Luminosity Upgrade cavity, dipole, luminosity, impedance 1222
 
  • S.U. De Silva, J.R. Delayen, H. Park
    ODU, Norfolk, Virginia, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
  
  The beam crabbing proposed for the LHC High Luminosity Upgrade requires two crabbing systems operating in both horizontal and vertical planes. In addition, the crabbing cavity design needs to meet strict dimensional constraints and functional specifications of the cavities. This paper presents the detailed electromagnetic design including em properties, multipole analysis, multipacting levels of the 400 MHz rf-dipole crabbing cavity.  
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THPB063 BNL 56 MHz HOM Damper Fabrication at JLab niobium, cavity, feedback, SRF 1262
 
  • N.A. Huque, W.A. Clemens, E. Daly
    JLab, Newport News, Virginia, USA
  • S. Bellavia, G.T. McIntyre, S.K. Seberg, Q. Wu
    BNL, Upton, Long Island, New York, USA
  
  The Higher-Order Mode (HOM) Dampers for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL) are currently being fabricated at JLab. The coaxial damper is primarily constructed with high RRR niobium, with a combination of niobium and sapphire rings as the filter assembly. Several design changes have been made with respect to the performance of a prototype damper – also fabricated at JLab – which was found to quench at low power. The production dampers are being tuned and tested in the JLab vertical test area (VTA) prior to delivery. Two HOM dampers will be delivered to BNL; they are to be used in the RHIC in November, 2015. This paper outlines the challenges faced in the fabrication and tuning process.  
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THPB066 RF Analysis of Equator Welding Stability for the European XFEL Cavities cavity, controls, linac, factory 1272
 
  • A.A. Sulimov
    DESY, Hamburg, Germany
  
  In order to guaranty a sufficient High Order Modes (HOM) damping in the European XFEL cavities, a detailed analysis of the mechanical cavity production was performed. The mechanical measurements are precise enough to control the shape of cavity parts, but cannot be used for a welded cavity. To estimate the shape deformation during equator welding, the eigenfrequencies of cavity cells are compared with frequencies of cavity parts. This simple RF analysis can indicate irregularity of 9 equator welds and was used in addition to control of mean values for longitudinal and transverse deformations.  
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THPB067 HOM Coupler Notch Filter Tuning for the European XFEL Cavities cavity, controls, resonance, database 1274
 
  • A.A. Sulimov
    DESY, Hamburg, Germany
  
  The notch filter (NF) tuning prevents the extraction of fundamental mode (1.3 GHz) RF power through Higher Order Modes (HOM) couplers. The procedure of NF tuning was optimized at the beginning of serial European XFEL cavities production. It allows keeping the filter more stable against temperature and pressure changes during cavity cool down. Some statistics of NF condition during cavities and modules cold tests is presented.  
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THPB068 Practical Aspects of HOM Suppression Improvement for TM011 damping, cavity, simulation, dipole 1277
 
  • A.A. Sulimov, A. Ermakov, J.H. Thie
    DESY, Hamburg, Germany
  • A. Gresele
    Ettore Zanon S.p.A., Nuclear Division, Schio, Italy
  
  Some Higher Order Modes (HOM) pass bands were controlled during cryo-tests at DESY for the European XFEL cavities. The second monopole mode (TM011) showed most instabilities and suppression degradation. The authors will explain this phenomenon on the example of cavity CAV00553 and present the practical method of TM011 damping improvement.  
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THPB069 Engineering Design and Prototype Fabrication of HOM Couplers for HL-LHC Crab Cavities niobium, cavity, luminosity, SRF 1279
 
  • C. Zanoni, S. Atieh, I. Aviles Santillana, R. Calaga, O. Capatina, T. Capelli, F. Carra, P. Freijedo Menendez, M. Garlaschè, J.-M. Geisser, R. Leuxe, L. Marques Antunes Ferreira, E. Rigutto
    CERN, Geneva, Switzerland
  • S.A. Belomestnykh, S. Verdú-Andrés, Q. Wu, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
  • S.U. De Silva, J.R. Delayen, R.G. Olave, H. Park
    ODU, Norfolk, Virginia, USA
  • T.J. Jones, N. Templeton
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • Z. Li
    SLAC, Menlo Park, California, USA
  • A.J. May, S.M. Pattalwar
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • T.H. Nicol
    Fermilab, Batavia, Illinois, USA
  • A. Ratti
    LBNL, Berkeley, California, USA
  
  The High-Luminosity upgrade for the LHC relies on a set of RF Crab Cavities for reaching its goals. Two parallel concepts, the Double Quarter Wave (DQW) and the RF Dipole (RFD), are going through a comprehensive design process along with preparation of fabrication in view of extensive tests with beam in SPS. High Order Modes (HOM) couplers are critical in providing damping in RF cavities for operation in accelerators. HOM prototyping and fabrication have recently started at CERN. In this paper, an overview of the final shape is provided along with an insight in the mechanical and thermal analyses performed to validate the design of these critical components. Emphasis is also given to test campaigns, material selection, prototyping and initial fabrication that are aimed at fulfilling the highly demanding tolerances of the couplers.  
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THPB071 Developments of SiC Damper for SuperKEKB Superconducting Cavity cavity, operation, factory, higher-order-mode 1289
 
  • M. Nishiwaki, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, Y. Morita
    KEK, Ibaraki, Japan
  
  Upgrade works for SuperKEKB is in the final stage and the commissioning operation will start in this JFY. Eight superconducting accelerating cavities were operated for more than ten years at KEKB electron ring and are to be used at SuperKEKB. The cavity operation at those high current accelerators requires sufficient absorption of the beam-induced HOM power. In KEKB, the absorbed HOM power of 16 kW in two ferrite dampers attached to each cavity was achieved at the beam current of 1.4 A. On the other hand, the expected HOM power at SuperKEKB is calculated to be 37 kW in the beam current of 2.6 A. To cope with the HOM power issue, we developed additional HOM dampers made of SiC to be installed to the downstream of the cavity module. From precise calculations, it was found that the additional dampers reduce the HOM power loads of the ferrite dampers more effectively than the large beam pipe model of cavity module, which is another option to reduce the HOM loads. New SiC dampers were fabricated and high power-tested. Those SiC dampers successfully absorbed the expected HOM power. In this report, we will describe the results of calculations and high-power RF tests of new SiC dampers.  
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THPB072 Higher Order Mode Damping in a Higher Harmonic Cavity for the Advanced Photon Source Upgrade cavity, impedance, dipole, simulation 1293
 
  • S.H. Kim, J. Carwardine, Z.A. Conway, G. Decker, M.P. Kelly, B. Mustapha, P.N. Ostroumov, G.J. Waldschmidt
    ANL, Argonne, Illinois, USA
  
  Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
A superconducting higher-harmonic cavity (HHC) is under development for the Advanced Photon Source Upgrade based on a Multi-Bend Achromat lattice. This cavity will be used to improve the Touschek lifetime and the single bunch current limit by lengthening the beam. A single-cell 1.4 GHz (the 4th harmonic of the main RF) cavity is designed based on the TESLA shape. Two adjustable fundamental mode power couplers are included. The harmonic cavity voltage of 0.84 MV will be driven by the 200 mA beam with a bunch length of >50 ps RMS. Higher-order modes (HOM) must be extracted and damped. This will be done with two silicon carbide beamline HOM absorbers to minimize heating of RF structures such as the superconducting cavity and/or couplers and suppress possible beam instabilities. The HHC system is designed such that 1) most monopole and dipole HOMs are extracted along the beam pipes and damped in the ‘beamline’ silicon carbide absorbers and 2) a few HOMs, resulting from introduction of the couplers, are extracted through the coupler and dissipated in a room temperature water-cooled load. We will present time and frequency domain simulation results and discuss damping of HOMs. 		 
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THPB074 High Current eRHIC Cavity Design and HOM Damping Scheme cavity, damping, linac, impedance 1297
 
  • W. Xu, S.A. Belomestnykh, I. Ben-Zvi, H. Hahn
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is supported by LDRD program of Brookhaven Science Associates.
A 422 MHz cavity was designed for high current FFAG lattice ERLs for high luminosity eRHIC. The cavity was optimized to be able to propagate all the HOMs out of the cavity for high BBU threshold current and low HOM power (loss factor). Coupling the full spectrum (up to 30 GHz) HOMs out of the cavity and delivering the HOM power (up to 8 kW) out of the cryomodule is a challenge. A damping scheme with 6 coaxial line HOM couplers for low frequency HOMs and 3 waveguide HOM dampers for high frequency (so that the waveguide is small) is proposed to damp the full spectrum and high power HOMs. This paper will present the cavity design and HOM damping scheme. 		 
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THPB081 FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities cavity, dipole, coupling, operation 1321
 
  • A.R.J. Tutte, G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R. Calaga, A. Macpherson, E. Montesinos
    CERN, Geneva, Switzerland
  • S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • Z. Li
    SLAC, Menlo Park, California, USA
  • B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.  
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THPB089 HOM Coupler Performance in CW Regime in Horizontal and Vertical Tests cavity, operation, coupling, higher-order-mode 1349
 
  • N. Solyak, M.H. Awida, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov, N. Solyak
    Fermilab, Batavia, Illinois, USA
  • J.K. Sekutowicz
    DESY, Hamburg, Germany
  
  Power dissipation in HOM coupler antenna can limit cavity gradient in cw operation. XFEL design of HOM coupler, feedthrough and thermal connection to 2K pipe was accepted for LCLS-II cavity based on simulation results. Recently a series of vertical and horizontal tests was done to prove design for cw operation. In vertical test was found no effect of HOM coupler heating on high-Q cavity performance. In horizontal cryostat HOM coupler was tested up-to 23MV/m in continuous wave mode. Result proves that XFEL HOM coupler meets LCLS-II specifications.  
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THPB104 Higher Order Modes Simulation and Measurements for 2400 MHz Cavity cavity, damping, simulation, higher-order-mode 1394
 
  • Ya.V. Shashkov, D.S. Bazyl, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin
    MEPhI, Moscow, Russia
  • R. Calaga
    CERN, Geneva, Switzerland
  • A.A. Zavadtsev
    Nano, Moscow, Russia
  • M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  
  Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r and the EU FP7 HiLumi LHC – Grant Agreement 284404
In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiples of the main RF system frequency of 400 MHz is currently under discussion. The 800 MHz superconducting cavities with grooved beam pipes were suggested for implementation. A scaled aluminum prototype with a frequency of the operational mode of 2400 MHz was manufactured for testing the results of simulations. The load reflection coefficient measurements were performed as well as the Qload measurements for cavities with the load. Here we discuss the prototype design and report the obtained measurement results.
Higher order modes, superconducting cavities, srf 		 
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THPB105 Demonstration of Coaxial Coupling Scheme at 26 MV/m for 1.3 GHz Tesla-Type SRF Cavities cavity, coupling, niobium, SRF 1397
 
  • Y. Xie, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • T.N. Khabiboulline, A. Lunin, V. Poloubotko, A.M. Rowe, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  • J. Rathke
    AES, Medford, New York, USA
  
  Superconducting ILC-type cavities have an rf input coupler that is welded on. A detachable input coupler will reduce conditioning time (can be conditioned separately), reduce cost and improve reliability. The problem with placing an extra flange in the superconducting cavity is about creating a possible quench spot at the seal place. Euclid Techlabs LLC has developed a coaxial coupler which has an on the surface with zero magnetic field (hence zero surface current). By placing a flange in that area we are able to avoid disturbing surface currents that typically lead to a quench. The coupler is optimized to preserve the axial symmetry of the cavity and rf field. The surface treatments and rf test of the proto- type coupler with a 1.3 GHz ILC-type single-cell cavity at Fermilab will be reported and discussed.  
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THPB110 Procurements for LCLS-II Cryomodules at JLab cavity, cryomodule, vacuum, operation 1405
 
  • E. Daly, G. Cheng, G.K. Davis, T. Hiatt, N.A. Huque, F. Marhauser, H. Park, J.P. Preble, K.M. Wilson
    JLab, Newport News, Virginia, USA
  
  Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Thomas Jefferson National Accelerator Facility is currently engaged, along with several other DOE national laboratories, in the Linac Coherent Light Source II project (LCLS II). The SRF Institute at Jefferson Lab will be building 1 prototype and 17 production cryomodules based on the TESLA / ILC / XFEL design. Each cryomodule will contain eight nine cell cavities with coaxial power couplers operating at 1.3 GHz. Procurement of components for cryomodule construction has been divided amongst partner laboratories in a collaborative manner. JLab has primary responsibility for six procurements include the dressed cavities, cold gate valves, higher-order-mode (HOM) and field probe feedthroughs, beamline bellows cartridges, cavity tuner assemblies and HOM absorbers. For procurements led by partner laboratories, JLab collaborates and provides technical input on specifications, requirements and assembly considerations. This paper will give a detailed description of plans and status for JLab procurements. 		 
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THPB116 Modified ELBE Type Cryomodules for the Mainz Energy-Recovering Superconducting Accelerator MESA cryomodule, operation, niobium, electron 1413
 
  • T. Stengler, K. Aulenbacher, R.G. Heine, F. Schlander, D. Simon
    IKP, Mainz, Germany
  • M. Pekeler, D. Trompetter
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  
  At the Institut für Kernphysik of Johannes Gutenberg-Universität Mainz, the new multiturn energy recovery linac MESA is under construction. Two modified ELBE-type cryomodules with two 9-cell TESLA/XFEL cavities each will provide an energy gain of 50 MeV per turn. Those are currently in the production process at RI Research Instruments GmbH, Bergisch Gladbach, Germany. Modifications for the tuner and the HOM damper are under development. In addition, a 4K/2K Joule Thomson expansion stage will also be integrated into the cryomodule. The current status of the development of the cryomodules and their modifications will be discussed.  
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FRAA04 Performance of the Cornell ERL Main Linac Prototype Cryomodule cavity, linac, cryomodule, operation 1437
 
  • F. Furuta, B. Clasby, R.G. Eichhorn, B. Elmore, G.M. Ge, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, R.P.K. Kaplan, J.J. Kaufman, M. Liepe, T.I. O'Connell, S. Posen, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Cornell has designed, fabricated, and tested (by the time of the conference) a high current (100 mA) CW SRF prototype cryomodule for the Cornell ERL. This talk will report on the design and performance of this very high Q0 CW cryomodule including design issues and mitigation strategies.  
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FRBA02 Crab Cavity and Cryomodule Development for HL-LHC cavity, cryomodule, shielding, operation 1460
 
  • F. Carra, A. Amorim Carvalho, K. Artoos, S. Atieh, I. Aviles Santillana, A.B. Boucherie, J.P. Brachet, K. Brodzinski, R. Calaga, O. Capatina, T. Capelli, L. Dassa, T. Dijoud, H.M. Durand, G. Favre, L.M.A. Ferreira, P. Freijedo Menendez, M. Garlaschè, M. Guinchard, N. Kuder, S.A.E. Langeslag, R. Leuxe, A. Macpherson, P. Minginette, E. Montesinos, F. Motschmann, C. Parente, L. Prever-Loiri, D. Pugnat, E. Rigutto, V. Rude, M. Sosin, G. Vandoni, G. Villiger, C. Zanoni
    CERN, Geneva, Switzerland
  • S.A. Belomestnykh, S. Verdú-Andrés, Q. Wu, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
  • S.U. De Silva, J.R. Delayen, R.G. Olave, R.G. Olave, H. Park
    ODU, Norfolk, Virginia, USA
  • T.J. Jones, N. Templeton
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • Z. Li
    SLAC, Menlo Park, California, USA
  • K.B. Marinov, S.M. Pattalwar
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • T.H. Nicol
    Fermilab, Batavia, Illinois, USA
  • A. Ratti
    LBNL, Berkeley, California, USA
  
  The HL-LHC project aims at increasing the LHC luminosity by a factor 10 beyond the design value. The installation of a set of RF Crab Cavities to increase bunch crossing angle is one of the key upgrades of the program. Two concepts, Double Quarter Wave (DQW) and RF Dipole (RFD) have been proposed and are being produced in parallel for test in the SPS beam before the next long shutdown of CERN accelerator’s complex. In the retained concept, two cavities are hosted in one single cryomodule, providing thermal insulation and interfacing with RF coupling, tuning, cryogenics and beam vacuum. This paper overviews the main design choices for the cryomodule and its different components, which have the goal of optimizing the structural, thermal and electro-magnetic behavior of the system, while respecting the existing constraints in terms of integration in the accelerator environment. Prototyping and testing of the most critical components, manufacturing, preparation and installation strategies are also described.  
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FRBA04 SRF for Future Circular Colliders cavity, radiation, proton, collider 1474
 
  • R. Calaga, O. Brunner, A.C. Butterworth, E. Jensen
    CERN, Geneva, Switzerland
  
  The future circular colliders (FCC) will require superconducting RF systems for the proton-proton, electron-positron and lepton-hadron modes of the collider operation. The SCRF systems will accelerate the protons beams to 50 TeV and the lepton beams from 45.5 to 175 GeV in a staged approach with a possible 60 GeV energy recovery linac for the lepton-hadron to option as an intermediate step. The expected stored beam currents in some modes exceed 1 A with very short bunch lengths. A first conceptual design of the FCC RF system is proposed along with highlights of specfic R&D topics to reach the design performance. Challenges related to RF structure design, intensity limitations due to beam loading, RF powering and higher order modes are addressed. Synergies between the different collider modes and the present LHC are identified.  
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