Keyword: simulation
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MOBA04 High-Q Operation of SRF Cavities: The Impact of Thermocurrents on the RF Surface Resistance cavity, shielding, niobium, operation 37
 
  • J.M. Köszegi, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  
  For CW applications much effort is being expended to minimize the power dissipation (surface resistance) of niobium cavities. Previous studies have shown that residual resistance can be reduced by performing a thermal cycle, a procedure of warming up a cavity after initial cooldown to about 20K and cooling it down again. It was postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Here, we present a more extensive study that includes measurements of two additional passband modes and that confirms the effect. A change in surface resistance of more than a factor seven was observed. In this paper, we also discuss simulations that support the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters results in a non-symmetric current distribution.  
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MOBA05 Nature of Quality Factor Degradation in SRF Cavities due to Quench cavity, superconductivity, electron, cryogenics 41
 
  • M. Checchin
    Fermilab, Batavia, Illinois, USA
  
  Superconductive quench is a well-known phenomenon that causes magnetic flux trapping in superconducting accelerating cavities increasing the radio-frequency surface resistance. This paper is addressed to the understanding of the quench-induced losses nature. We present the proof that the real origin of quench-related quality factor degradation is consequence only of ambient magnetic field trapped at the quench spot. Also, we show how the quality factor can be fully recovered after it was highly deteriorated quenching several times in presence of external magnetic field. Such phenomenon was found to be completely reliable up to certain values of applied magnetic field, above that the cavity quality factor cannot be fully recovered anymore.  
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MOPB004 Understanding the Field Dependence of the Surface Resistance in Nitrogen-Doped Cavities radio-frequency, cavity, vacuum, impedance 74
 
  • P.N. Koufalis, D. Gonnella, M. Liepe, J.T. Maniscalco, I. Packtor
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: NSF Grant PHYS-1416318
An important limiting factor in the performance of superconducting radio frequency (SRF) cavities in medium and high field gradients is the intrinsic quality factor and, thus, the surface resistance of the cavity. The exact dependence of the surface resistance on the magnitude of the RF field is not well understood. We present an analysis of experimental data of LT1-3 and LT1-4, 1.3 GHz single-cell nitrogen-doped cavities prepared and tested at Cornell. Most interestingly, the cavities display anti-Q slopes in the medium-field region (i.e. Rs decreases with increasing accelerating field). We extract the temperature dependent surface resistances of the cavities, analyze field dependencies, and compare with theoretical predictions. These comparisons and analyses provide new insights into the field dependence of the surface resistance and improve our understanding of the mechanisms behind the effect. 		 
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MOPB008 Theoretical Field Limit and Cavity Surface Conditions: Nano-Scale Topography and Sub-millimeter Pit cavity, factory, radio-frequency, framework 86
 
  • T. Kubo
    KEK, Ibaraki, Japan
  
  The recent two theoretical papers*,** are briefly introduced. The former addresses the superheating field (Bs) suppression due to nano-defects distributing almost continuously on the cavity surface*. We introduce a model of the nano-defect. An analytical formula for Bs suppression factor is derived. By using the formula, suppression factors of bulk or multilayer superconductors and those after various surface processing technologies can be evaluated. An application to the dirty Nb processed by EP is also presented as an example. The latter address the magnetic field enhancement (MFE) at the sub-millimeter pit on the surface of cavity, which is thought to cause quench**. There exists the famous well-type pit model, but many of pits are not well-type but have gentle slopes. Impacts of the slope angle on MFE have not been well understood. We introduce a model that can describe a pit with an arbitrary slope angle. A formula to evaluate the MFE factor is derived. A pit with a gentle slope angle yields a much smaller MFE factor than the well-type pit. The formula can be applied to the calculation of MFE factors of real pits with arbitrary slope angles.
* T. Kubo, Prog. Theor. Exp. Phys. 2015,063G01(2015).
** T. Kubo, Prog. Theor. Exp. Phys. 2015,073G01(2015). 		 
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MOPB011 How Uniform Are Cool-Downs? cavity, interface, niobium, factory 100
 
  • J.A. Robbins, R.G. Eichhorn
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Since the last SRF conference it has become clear that achieving extremely high quality factors of SRF cavities depend on the cool-down scenario. While some findings favor a fast cool-down, others suggest a slow cycle to be advantageous, and many variations to that have been investigated: the role of thermocurrents, amount of ambient magnetic field and flux trapping. This paper will investigate, how uniformly different cool-down procedures are and if they can explain the more efficient magnetic flux expulsion.  
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MOPB013 Simulation of Geometry Dependent Flux Trapping cavity, factory, superconducting-cavity, focusing 105
 
  • J. May-Mann, R.G. Eichhorn
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Trapping or expulsion of ambient magnetic field has become an important factor in the performance of superconducting cavities with very high Q. As experimental data is limited, we set up a numerical field calculation model to study this effect in more details. We will report, how the cavity orientation, the movement of the transition to superconductivity front, and the orientation of the magnetic field contributes to the amount of magnetic field being vulnerable for trapping.  
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MOPB014 Magnetic Flux Expulsion in Horizontally Cooled Cavities cavity, interface, SRF, distributed 110
 
  • M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • M. Checchin
    Illinois Institute of Technology, Chicago, Illlinois, USA
  • J. Zasadzinski
    IIT, Chicago, Illinois, USA
  
  Funding: Work supported by the US Department of Energy, Office of High Energy Physics
The cool down details of superconducting accelerating cavities are crucial parameters that have to be optimize in order to obtain very high quality factors. The temperature all around the cavity is monitored during its cool down across the critical temperature, in order to visualize the different dynamics of fast and slow cool-down, which determine considerable difference in terms of magnetic field expulsion and cavity performance. The study is performed placing a single cell 1.3 GHz elliptical cavity perpendicularly to the helium cooling flow, which is representative of how SRF cavities are cooled in an accelerator. Hence, the study involves geometrical considerations regarding the cavity horizontal configuration, underling the different impact of the various magnetic field components on the surface resistance. Experimental data also proves that under established conditions, flux lines are concentrated at the cavity top, in the equatorial region, leading to temperature rise. 		 
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MOPB020 Mean Free Path Dependence of the Trapped Flux Surface Resistance electron, SRF, niobium, superconductivity 129
 
  • M. Checchin, A. Grassellino, M. Martinello, A. Romanenko
    Fermilab, Batavia, Illinois, USA
  • M. Martinello
    Illinois Institute of Technology, Chicago, Illlinois, USA
  • J. Zasadzinski
    IIT, Chicago, Illinois, USA
  
  Funding: Work supported by the US Department of Energy, Office of High Energy Physics
In this article a calculation of the trapped flux surface resistance is presented. The two main mechanisms considered in such approach are the oscillation of the magnetic flux trapped in the superconductor due to the Lorentz force, and the static resistance associated to the normal conducting vortex core. The model derived shows a good description of the available experimental data, highlighting that the radio frequency vortex dissipation is mostly due to the static part of the surface resistance. We show that the surface resistance for 100% trapped flux normalized to the trapped field (expressed in nOhm/mG) can be approximated to R/B=18.3*(l f)1/2/(50.1+l) with l the mean free path in nm and f the frequency in GHz. 		 
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MOPB024 SRF Cavity Breakdown Calculation Procedure Using FEA-Software cavity, cathode, SRF, niobium 140
 
  • R.A. Kostin, A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • I.V. Gonin
    Fermilab, Batavia, Illinois, USA
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  
  SRF cavity thermal breakdown can be analyzed analytically using thermodynamics equation. This technique is suitable for simple geometries when surface magnetic field variation can be omitted. Thermal radiation effect which is crucial for SRF gun calculations is also hard to implement properly because of complicated geometry. All of these can be overcome by using multiphysics FEA-software. This paper shows the procedure of cavity thermal breakdown calculation in coupled multiphysics analysis with dependable parameters.  
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MOPB042 Fundamental Studies on Doped SRF Cavities cavity, niobium, vacuum, SRF 187
 
  • D. Gonnella, T. Gruber, J.J. Kaufman, P.N. Koufalis, M. Liepe, J.T. Maniscalco, B. Yu
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: NSF
Recently, doping with nitrogen has been demonstrated to help SRF cavities reach significantly higher intrinsic quality factors than with standard procedures. However, the quench fields of these cavities have also been shown to be frequently reduced. Here we report on fundamental studies of doped cavities, investigating the source of reduced quench field and exploring alternative dopants. We have focused on studying the quench of nitrogen-doped cavities with temperature mapping and measurements of the flux penetration field using pulsed power to investigate maximum fields in nitrogen doped cavities. We also report on studies of cavities doped with other gases such as helium. These studies have enabled us to shed light on the mechanisms behind the higher Q and lower quench fields that have been observed in cavities doped with impurities. 		 
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MOPB060 A GPU Based 3D Particle Tracking Code for Multipacting Simulation GPU, cavity, gun, SRF 242
 
  • T. Xin
    Stony Brook University, Stony Brook, USA
  • S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, V. Litvinenko, I. Pinayev, J. Skaritka, Q. Wu, B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work was carried out at Brookhaven Science Associates, LLC under Contracts No. DE-AC02-98CH10886 and at Stony Brook University under grant DE-SC0005713 with the U.S. DOE.
A new GPU based 3D electron tracking code is developed at BNL and benchmarked with both popular existing parallel tracking code and experimental results. The code takes advantage of massive concurrency of GPU cards to track electrons under RF field in 3D Tetrahedron meshed structures. Approximately ten times of FLOPS can be achieved by utilizing GPUs compare to CPUs with same level of power consumption. Different boundary materials can be specified and the 3D EM field can be imported from the result of Omega3P calculation. CUDAOpenGL interop was implemented so that the emerging of multipactors can be monitored in real time while the simulation is undergoing. Code also has GPU farm version that can run on multiple GPUs to further increase the turnover of multipacting simulation. 		 
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MOPB066 R&D Status of the New Superconducting CW Heavy Ion LINAC@GSI cavity, linac, ion, operation 258
 
  • M. Basten, M. Busch, F.D. Dziuba, D. Mäder, H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  • M. Amberg, K. Aulenbacher, M. Miski-Oglu
    HIM, Mainz, Germany
  • W.A. Barth, V. Gettmann, M. Heilmann, S. Mickat
    GSI, Darmstadt, Germany
  
  To keep the ambitious Super Heavy Element (SHE) physics program at GSI competitive a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is currently under progress as a multi-stage R&D program of GSI, HIM and IAP*. The baseline linac design consists of a high performance ion source, a new low energy beam transport line, an (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) which is followed by the new sc-DTL LINAC for post acceleration up to 7.3 MeV/u. In the present design the new cw-heavy ion LINAC comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. The advantages of the proposed beam dynamics concept applying a constant beta profile are easy manufacturing with minimized costs as well as a straightforward energy variation**. An important milestone will be the full performance test of the first CH cavity (Demonstrator), in a horizontal cryo module with beam. An advanced demonstrator setup comprising a string of cavities and focussing elements is proposed to build from 10 short CH-cavities with 8 gaps. The corresponding simulations and technical layout of the new cw heavy ion LINAC will be presented.
* W. Barth et al., Further R&D for a new Superconducting cw Heavy Ion LINAC@GSI, IPAC2014, THPME004
**M. Schwarz et al., Beam Dynamics for the sc cw Heavy Ion Linac at GSI, IPAC2015, THPF025
 		 
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MOPB088 HOM Measurements on the ARIEL eLINAC Cryomodules HOM, cavity, 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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MOPB100 Cathode Geometry and Flow Dynamics Impact on Vertical Electropolishing of Superconducting Niobium Cavities cavity, cathode, niobium, operation 385
 
  • L.M.A. Ferreira
    CERN, Geneva, Switzerland
  
  CERN has now a fully operating vertical electropolishing installation, which has been used for the processing of 704 MHz high-beta five-cell Superconducting Proton Linac (SPL) niobium cavities. This installation relies only on the electrolyte circulation (HF/H2SO4) for power dissipation, evacuation of gases and homogeneous finishing; thus, parameters like cathode geometry, electrolyte flow and temperature become even more crucial when compared with horizontal electropolishing installations. Based on computational simulations performed with Comsol Multiphysics® and on a methodology developed at CERN, it is possible to assess the impact of the different cathode geometries as well as of the flow on the etching rate distribution. The data obtained with two different cathode geometries are presented: electrolyte velocity distribution, etching rate distribution, average current density and minimum working potential. One geometry was defined through a purely electrochemical approach while the second was defined to minimise the difference between the maximum and the minimum electrolyte speed inside the cavity; in both cases, the influence of the electrolyte flow was taken into account.  
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TUBA04 Nb3Sn Cavities: Material Characterization and Coating Process Optimization cavity, SRF, niobium, radio-frequency 501
 
  • D.L. Hall, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, S. Posen, B. Yu
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • Th. Proslier
    ANL, Argonne, Illinois, USA
  
  Funding: Work supported by DOE grant DE-SC0008431 and NSF grant PHY-141638. Use of CCMR via NSF MRSEC program (DMR-1120296)
Recent progress on vapour diffusion coated Nb3Sn SRF cavities makes this material a very promising alternative for CW medium field SRF applications. In this paper we report on several systematic studies to determine the sources currently limiting the performance of Nb3Sn cavities to determine improved coating parameters to overcome these limitations. These include a detailed study of the sensitivity of Nb3Sn to trapped ambient magnetic flux, a first measurement of the field dependence of the energy gap in Nb3Sn and detailed measurements of the stoichiometry of the obtained Nb3Sn coatings with synchrotron x-ray diffraction and STEM. Initial results from a study on the impact of the coating process parameters on energy gap, Q-slope, and residual resistance, show clear dependencies, and thus directions for process optimization. 		 
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TUPB011 HPRF Transmission Componenets Study and Distribution in TRIUMF E-Linac linac, operation, klystron, TRIUMF 557
 
  • Z.T. Ang
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  TRIUMF e-lianc was commissioning last September for the first stage. High power rf systems were in operation stable. Two 300 kW klystrons along with the key waveguide components were tested before feeding rf power into 1.3 GHz 9-cell superconducting cavities. The rf high power variable divider and 360 degree waveguide phase shifters are working successfully. The simulations on different waveguide structures for the power dividers, phase shifters have been studied. The comparisons of the calculation results are reported in the paper. The rf signal level tests of the components and waveguide distribution systems will also be present in this paper.  
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TUPB027 Developments on SRF Coatings at CERN cavity, SRF, plasma, cathode 617
 
  • A. Sublet, S. Aull, B. Bártová, S. Calatroni, T. Richard, G.J. Rosaz, M. Taborelli, M. Therasse, W. Venturini Delsolaro, P. Zhang
    CERN, Geneva, Switzerland
  
  The thin films techniques applied to Superconducting RF (SRF) has a long history at CERN. A large panel of cavities have been coated from LEP, to LHC. For the current and future projects (HIE-ISOLDE, HL-LHC, FCC) there is a need for further higher RF-performances with focus on minimizing residual resistance Rres and maximizing quality factor Q0 of the cavities. This paper will present CERN’s developments on thin films to achieve these goals through the following main axes of research: The first one concerns the application of different coating techniques for Nb (DC-bias diode sputtering, magnetron sputtering and HiPIMS). Another approach is the investigation of alternative materials like Nb3Sn. These lines of development will be supported by a material science approach to characterize and evaluate the layer properties by means of FIB-SEM, TEM, XPS, XRD, etc. In addition a numerical tool for plasma simulation will be exploited to develop adapted coating systems and optimize the coating process, from plasma generation to thin film growth.  
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TUPB067 Design and First Measurements of an Alternative Calorimetry Chamber for the HZB Quadrupole Resonator niobium, quadrupole, SRF, operation 739
 
  • S. Keckert, R. Kleindienst, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  
  Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
The systematic research on superconducting thin films requires dedicated testing equipment. The Quadrupole Resonator (QPR) is a specialized tool to characterize the superconducting properties of circular samples. A calorimetric measurement of the RF surface losses allows the surface resistance to be measured with sub nano-ohm resolution. This measurement can be performed over a wide temperature and magnetic field range, at frequencies of 433, 866 and 1300 MHz. The system at Helmholtz-Zentrum Berlin (HZB) is based on a resonator built at CERN and has been optimized to lower peak electric fields and an improved resolution. An alternative calorimetry chamber has been designed in order to provide flat samples for coating and to ease changing of samples. Furthermore it enables exchangeability of samples between the QPRs at HZB and CERN. With this poster the design and first measurements of the new calorimetry chamber is presented. 		 
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TUPB072 Report of Vertical Test of the β=0.12 Half-Wave Resonator at RISP cavity, ion, vacuum, TRIUMF 747
 
  • G.-T. Park, H.J. Cha, H. Kim, W.K. Kim
    IBS, Daejeon, Republic of Korea
  • Z.Y. Yao
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  β=0.12, f=162.5 MHz half-wave resonator for Rare Isotope Science Project (RISP) was recently tested at TRIUMF. We briefly report the vertical test result: At 2K, the cavity achieved Q0=2·109 at Eacc=6.4 MV/m and the performance was limited at Eacc=7.8 MV/m by intense field emission. The surface processing was standard: 120 micron buffered chemical polishing followed by high pressure rinsing. After first cold test, 120C baking was done and the corresponding result was also obtained.  
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TUPB074 High-Vacuum Simulations and Measurements on the SSR1 Cryomodule Beam-Line vacuum, cavity, cryomodule, niobium 754
 
  • D. Passarelli, T.H. Nicol, M. Parise, L. Ristori
    Fermilab, Batavia, Illinois, USA
  
  Funding: Work supported by Fermi Research Alliance, LLC under Contract No. DEAC02- 07CH11359 with the United States Department of Energy
In order to guarantee an effective cool-down process for the SSR1 cryomodule, a high-vacuum level must be achieved at room temperature in the beam-line before introducing gaseous and liquid helium. The SSR1 cavities in the beamline have a small beam aperture compared to the size of their internal volume. To avoid unnecessary complications for the vacuum piping of the cryomodule cold-mass, a pilot study was conducted on the string prior to processing and qualification of the components to investigate the vacuum level achievable by pumping only through the beam-line. To estimate the pressure distribution inside the cavity string we used a mathematical model implemented in a test-particle Monte-Carlo simulator for ultra-high-vacuum systems. 		 
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TUPB075 Measurements on the Superconducting 217 MHz CH Cavity During the Manufacturing Phase cavity, operation, resonance, linac 757
 
  • F.D. Dziuba, M. Amberg, M. Basten, M. Busch, H. Podlech
    IAP, Frankfurt am Main, Germany
  • M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat
    HIM, Mainz, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • W.A. Barth, S. Mickat
    GSI, Darmstadt, Germany
  
  Funding: GSI, HIM, BMBF Contr. No. 05P12RFRBL
Since in future the existing UNILAC (Universal Linear Accelerator) will be used as an injector for the FAIR (Facility for Antiproton and Ion Research) project, a new superconducting (sc) continuous wave (cw) linac at GSI is proposed to keep the Super Heavy Element (SHE) program at a competitive high level. In this context, a sc 217 MHz crossbar-H-mode (CH) cavity has been designed at the Institute for Applied Physics (IAP), Frankfurt University, and was built at Research Instruments (RI) GmbH, Germany. The cavity serves as a first prototype to demonstrate the reliable operability under a realistic accelerator environment and its successful beam operation will be a milestone on the way to the new linac. In this contribution measurements during the production process of the cavity as well as corresponding simulations will be presented. 		 
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TUPB076 The Multipacting Study of Niobium Sputtered High-Beta Quarter-Wave Resonators for HIE-ISOLDE cavity, electron, pick-up, niobium 760
 
  • P. Zhang, W. Venturini Delsolaro
    CERN, Geneva, Switzerland
  
  Funding: This work has been supported partly by a Marie Curie Early Initial Training Network Fellowship of the European Community’s 7th Programme under contract number PITN-GA-2010-264330-CATHI.
Superconducting quarter-Wave Resonators (QWRs) will be used in the superconducting linac upgrade in the frame of HIE-ISOLDE project at CERN. The cavities are made of bulk copper with thin niobium film coated. They will be operated at 101.28 MHz at 4.5 K providing 6 MV/m accelerating gradient with 10 W power dissipation. Multipacting (MP) has been studied for the high-beta (β=10.9%) QWRs and two MP barriers have been found: Eacc at around 0.05MV/m and 1.5MV/m. We have used both CST Microwave Studio & Particle Studio and the parallel codes Omega3P & Track3P developed at SLAC. The results from the two codes are consistent and are in good agreement with cavity vertical cold test results. Both MP barriers can be processed by RF during the cavity cold test. 		 
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TUPB079 Second Sound Quench Detection of Dressed TESLA-Shape SRF Cavities cavity, detector, SRF, HOM 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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TUPB088 On Quench Propagation, Quench Detection and Second Sound in SRF Cavities niobium, cavity, SRF, interface 804
 
  • S.R. Markham, R.G. Eichhorn, D.L. Hartill, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Quench location detection has provided valuable insight in SRF cavity operation since two decades. While in earlier days temperature maps were used the state of the art technique nowadays is detecting the second sound wave, excited by a quench, using oscillating super-leak detector (OSTs). Typically, many OSTs surround the cavity and the quench location is determined by triangulation of the different OST signals. Convenient as the method is there is a mystery: taking the well-known velocity of the second sound wave, the quench seems to come from a place slightly above the cavity’s outer surface. In addition, not all triangulation spheres intersect in one point. We will present a model based on numerical quench propagation simulations that is able to fully explaining this discrepancy.  
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TUPB096 Mechanical Damper Study for ISAC-II Quarter Wave Resonators damping, ISAC, cavity, resonance 832
 
  • L. Yang, R.E. Laxdal, V. Zvyagintsev
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  ISAC-II superconducting quarter wave resonators are equipped with mechanical dampers to supress mechanical oscillations of the cavity structure. The study has been carried out to optimize the damper efficiency.  
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TUPB101 Design of the Thermal and Magnetic Shielding for the LHC High Luminosity Crab-Cavity Upgrade cavity, shielding, cryomodule, operation 852
 
  • N. Templeton, T.J. Jones
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, R. Leuxe, C. Zanoni
    CERN, Geneva, Switzerland
  • G. Burt, S.M. Pattalwar
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • G. Burt
    Lancaster University, Lancaster, United Kingdom
  • K.B. Marinov, A.J. May, S.M. Pattalwar
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A. Ratti
    LBNL, Berkeley, California, USA
  
  Before the High Luminosity (Hi-Lumi) upgrade of the Large Hadron Collider (LHC), two pairs of superconducting compact Crab Cavities are to be tested within separate cryomodules, on the Super Proton Synchrotron (SPS) at CERN in 2018 prior to Long Shutdown 2. Two novel side-loaded cryomodules, which allow ease of access for assembly, inspection and maintenance, have been developed for the prototype tests. The cryomodule shielding includes a thermal shield and double layer magnetic shield, consisting of a warm-outer shield, and two cold-inner shields (one per cavity). Various constraints and considerations have led to unique cold shielding, mounted inside the cavity helium vessels, resulting in several design challenges. The shielding adopts and utilises the module’s side-loaded configuration, for continuity and accessibility, while satisfying tight spatial constraints and requirements to meet the functional specification. This paper outlines the design, analysis, manufacture and assembly of the Hi-Lumi SPS test cryomodule’s thermal and magnetic shielding, which are critical to achieving the operational stability.  
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WEA2A01 High-Velocity Spoke Cavities cavity, linac, proton, ion 943
 
  • C.S. Hopper
    ODU, Norfolk, Virginia, USA
  • H. Park
    JLab, Newport News, Virginia, USA
  
  There are several current and recent projects which explore the feasibility of spoke-loaded cavities operating in the high-velocity region. Spoke cavities have a large number of geometric parameters which often influence multiple rf properties. Fabricating, handling, and processing these cavities presents some unique challenges, not unlike other TEM-class structures. This paper will summarize the current efforts toward the design, fabrication, and testing of spoke cavities with optimum beta greater than 0.8.  
slides icon Slides WEA2A01 [1.029 MB]  
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WEBA06 Design Studies for Quarter-Wave Resonators and Cryomodules for the Riken SC-LINAC linac, cryomodule, beam-loading, ion 976
 
  • N. Sakamoto, O. Kamigaito, H. Okuno, K. Ozeki, K. Suda, Y. Watanabe, K. Yamada
    RIKEN Nishina Center, Wako, Japan
  • H. Hara, K. Okihira, K. Sennyu, T. Yanagisawa
    MHI, Hiroshima, Japan
  • E. Kako, H. Nakai, K. Umemori
    KEK, Ibaraki, Japan
  
  Recently we proposed a new project aimed at intensity upgrade of uranium beams of RIKEN RIBF. In this new project, construction of a superconducting linac is planned replacing the injector cyclotron so called RRC. The RIKEN superconducting linac consists of 14 cryomodules each of which contains four quarter-wave-resonators (QWRs) in each. The QWR operates at an rf frequency of 73 MHz in the continuous wave mode with beta as low as 0.055-1.008. A coaxial probe-type RF fundamental power-coupler which transmits RF power of several kW will be utilized for beam loading of 1.3 kW/resonator at the maximum with Qext of several x106. Tuning of the resonant frequency will be realized with a mechanical tuner pressing the resonator wall in the direction parallel to the beam. This year, we started a development of a test cryomodule with SC-QWRs. In this paper, design studies for a SC-QWR and its cryomodule, e.g., QWR, coupler, and, tuner will be presented together with a construction schedule of the prototype. Prototyping of a superconducting cavity and its test cryomodule was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).  
slides icon Slides WEBA06 [17.564 MB]  
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THAA01 Recent Developments in Superconducting Deflecting-Mode Cavities cavity, dipole, HOM, 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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THAA05 First Results of SRF Cavity Fabrication by Electro-Hydraulic Forming at CERN niobium, SRF, cavity, superconducting-RF 1012
 
  • S. Atieh, A. Amorim Carvalho, I. Aviles Santillana, F.F. Bertinelli, R. Calaga, O. Capatina, G. Favre, M. Garlaschè, F. Gerigk, S.A.E. Langeslag, K.M. Schirm, N. Valverde Alonso
    CERN, Geneva, Switzerland
  • D. Alleman, G. Avrillaud, J. Bonafe, E. Mandel, P. Marty, H. Peronnet, R. Plaut
    Bmax, Toulouse, France
  
  In the framework of many accelerator projects relying on RF superconducting technology, shape conformity and processing time are key aspects for the optimization of niobium cavity fabrication. An alternative technique to traditional shaping methods, such as deep-drawing and spinning, is Electro-Hydraulic Forming (EHF). In EHF, cavities are obtained through ultra-high-speed deformation of blank sheets, using shockwaves induced in water by a pulsed electrical discharge. With respect to traditional methods, such a highly dynamic process can yield valuable results in terms of effectiveness, repeatability, final shape precision, higher formability and reduced spring-back. In this paper, the first results of EHF on copper prototypes and ongoing developments for niobium for the Superconducting Proton Linac studies at CERN are discussed. The simulations performed in order to master the embedded multi-physics phenomena and to steer process parameters are also presented.  
slides icon Slides THAA05 [21.123 MB]  
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THPB005 Simulations of 3.9 GHz CW Coupler for LCLS-II Project cavity, linac, operation, cryomodule 1066
 
  • I.V. Gonin, T.N. Khabiboulline, A. Lunin, N. Solyak
    Fermilab, Batavia, Illinois, USA
  
  LCLS-II linac is based on XFEL/ILC superconducting technology. TTF-III fundamental power coupler for the 3.9 GHz 9-cell cavities has been modifies to satisfy requirements of LCLS-II, operating in CW regime. In this paper we discuss the results of COMSOL analysis of the possible modification of couplers, working at various operating regimes. We present also the results of mechanical study.  
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THPB006 Improvements of Buildcavity Code cavity, HOM, interface, 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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THPB014 Mechanical Optimization of High Beta 650 MHz Cavity for Pulse and CW Operation of PIP-II Project cavity, operation, resonance, cryomodule 1093
 
  • T.N. Khabiboulline, I.V. Gonin, C.J. Grimm, A. Lunin, T.H. Nicol, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  • P. Kumar
    RRCAT, Indore (M.P.), India
  
  The proposed design of the 0.8 GeV PIP-II SC Linac employs two families of 650 MHz 5-cell elliptical cavities with 2 different beta. The β=0.61 will cover the 185-500 MeV range and the β=0.92 will cover the 500-800 MeV range. In this paper we will present update of RF and mechanical design of dressed high beta cavity (β=0.92) for pulse regime of operation at 2 mA beam current. In previous CW version of PIP-II project the mechanical design was concentrated on minimization of frequency shift due to helium pressure fluctuation. In current case of pulse regime operation the main goal was Lorentz force detuning minimization. We present the scope of coupled RF-Mechanical issues and their resolution. Also detailed stress analysis of dresses cavity will be presented.  
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THPB017 A Higher Harmonic Cavity at 800 MHz for HL-LHC cavity, HOM, polarization, cryomodule 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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THPB019 Bead-Pull Measurements of the Main Deflecting Mode of the Double-Quarter-Wave Cavity for the HL-LHC cavity, luminosity, resonance, factory 1105
 
  • M. Navarro-Tapia, R. Calaga
    CERN, Geneva, Switzerland
  
  Funding: This research has received funding from the European Commission under the FP7 project HiLumi LHC (Grant agreement no. 284404), and under a Marie Curie action (Grant agreement PCOFUND-GA-2010-267194).
A full-scale model of the double-quarter-wave (DQW) cavity towards the High-Luminosity Large Hadron Collider (HL-LHC) upgrade was built in aluminum to characterize the deflecting mode. Field strength measurements have been carried out for both the transverse and longitudinal electromagnetic fields, by using the bead-pull technique. Perturbation objects of different shapes and material were used to separate the electric and magnetic field components. A reasonably good agreement was found between numerical simulation and measurements, which confirm the reliability and accuracy of the measurements done. 		 
poster icon Poster THPB019 [0.237 MB]  
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THPB021 Balloon Variant of Single Spoke Resonator electron, resonance, cavity, superconductivity 1110
 
  • Z.Y. Yao, R.E. Laxdal, V. Zvyagintsev
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  
  Spoke resonators have been widely proposed and optimized for various applications. Good performance has been demonstrated by many cavity tests. Accompanying the great progress, the adverse impact of strong multipacting (MP) is also noted by recent test reports, consistent with modern 3D simulations. This paper will discuss MP behaviors in the single spoke resonator. In particular a phenomenological theory is developed to highlight the details of the geometry that affect MP. The analysis leads to an optimized geometry of a single spoke resonator defined here as the ‘balloon geometry’. A 325MHz β=0.3 single spoke resonator based on 'balloon' concept is under development by the RISP-TRIUMF Collaboration. The RF and mechanical design of this cavity will also be reported.  
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THPB022 A Preliminary Design of a Superconducting Accelerating Structure for Extremely Low Energy Proton Working in TE210 Mode cavity, proton, emittance, acceleration 1115
 
  • Z.Q. Yang, X.Y. Lu, W.W. Tan, D.Y. Yang, J. Zhao
    PKU, Beijing, People's Republic of China
  
  For the application of high intensity continuous wave (CW) proton beam acceleration, a new superconducting accelerating structure for extremely low β proton working in TE210 mode has been proposed at Peking University. The cavity consists of eight electrodes and eight accelerating gaps. The RF frequency is 162.5MHz, and the designed proton input energy is 200keV. A peak field optimization has been performed for the lower surface field. The accelerating gaps are adjusted by phase sweeping based on KONUS beam dynamics. Solenoids are placed outside the cavity to provide transverse focusing. Numerical calculation shows that the transverse defocusing of the KONUS phase is about three times smaller than that of the conventional negative synchronous RF phase. The beam dynamics of a 10mA CW proton beam is simulated by the TraceWin code. The simulation results show that the beam’s size is under effective control. Both the simulation and the numerical calculation show that the cavity has a relatively high effective accelerating gradient of 2.6MV/m. Our results show that this new accelerating structure may be a possible candidate for superconducting operation at such a low energy range.  
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THPB033 Frequency Measurement and Tuning of a 9-Cell Superconducting Cavity Developed with UK Industry cavity, superconducting-RF, niobium, electron 1158
 
  • L.S. Cowie, P. Goudket, A.R. Goulden, P.A. McIntosh, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.R. Everard, N. Shakespeare
    Shakespeare Engineering, South Woodham Ferrers, Essex, United Kingdom
  • B. Lamb, S. Postlethwaite, N. Templeton
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  As part of an STFC Innovations Partnership Scheme (IPS) grant, in support of enabling UK industry to address the large potential market for superconducting RF structures, Daresbury Laboratory and Shakespeare Engineering Ltd are collaborating to produce a 1.3 GHz 9 cell niobium cavity. This paper describes the procedures to ensure the cavity reaches the required frequency and field flatness. The frequency of each half-cell was measured using a custom measurement apparatus. Combined mechanical and RF simulations were used to compensate for cavity deformation during measurement. Results of Coordinate Measurement Machine measurements of one half-cell are presented. The same procedure will be used to trim the cells at the dumbbell stage, and the full 9-cell cavity will be tuned once welded.  
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THPB045 Progress in IFMIF Half Wave Resonators Manufacturing and Test Preparation cavity, cryomodule, vacuum, controls 1191
 
  • G. Devanz, N. Bazin, G. Disset, P. Hardy, O. Piquet, J. Plouin
    CEA/DSM/IRFU, France
  • H. Dzitko, H. Jenhani, J. Neyret, N. Sellami
    CEA/IRFU, Gif-sur-Yvette, France
  
  The IFMIF accelerator aims to provide an accelerator-based D-Li neutron source to produce high intensity high energy neutron flux to test samples as possible candidate materials to a full lifetime of fusion energy reactors. The first phase of the project aims at validating the technical options for the construction of an accelerator prototype, called LIPAc (Linear IFMIF Prototype Accelerator). A cryomodule hosting 8 Half Wave Resonators (HWR) at 175 MHz will provide the acceleration from 5 to 9 MeV. We report on the progress of the HWR manufacturing. A pre-series cavity will be used to assess and optimize the tuning procedure of the HWR, as well as the processing steps and related tooling. A new horizontal test cryostat (SATHORI) is also being set up at Saclay in the existing SRF test area. The SATHORI is dedicated to the IFMIF HWR performance check, fully equipped with its power coupler and cold tuning system. A 30kW-RF power will be available for these tests.  
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THPB046 Design and Development of Superconducting Spoke Cavity for Compact Photon Source cavity, laser, photon, scattering 1196
 
  • M. Sawamura
    Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan
  • E. Cenni
    CEA/IRFU, Gif-sur-Yvette, France
  • R. Hajima
    JAEA, Ibaraki-ken, Japan
  • H. Hokonohara, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  
  Funding: This study is supported by Photon and Quantum Basic Research Coordinated Development Program of MEXT, Japan.
The spoke cavity is expected to have advantages for compact ERL accelerator for X-ray source based on laser Compton scattering. We have been developing the spoke cavity under a research program of MEXT, Japan to establish the fabrication process. Since our designed shape of the spoke cavity is complicated due to increase the RF properties, we have been designing the mold including the process of press work and the support parts for vacuum tolerance with the mechanical simulation. In this paper we present status of the spoke cavity fabrication. 		 
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THPB047 Analysis of a 750 MHz SRF Dipole Cavity cavity, dipole, cryogenics, cathode 1200
 
  • A. Castilla, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • A. Castilla, J.R. Delayen
    JLab, Newport News, Virginia, USA
  • A. Castilla
    DCI-UG, León, Mexico
  
  Funding: Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177.
There is a growing interest in using rf transverse deflecting structures for a plethora of applications in the current and future high performance colliders. In this paper, we present the results of a proof of principle superconducting rf dipole, designed as a prototype for a 750 MHz crabbing corrector for the Medium Energy Electron-Ion Collider (MEIC), which has been successfully tested at 4.2 K and 2 K at the Jefferson Lab’s Vertical Testing Area (VTA). The analysis of its rf performance during cryogenic testing, along with Helium pressure sensitivity, Lorentz detuning, surface resistance, and multipacting processing analysis are presented in this work. Detailed calculations of losses at the port flanges are included for completeness of the cavity’s cryogenic performance studies. 		 
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THPB051 Lorentz Detuning for a Double-Quarter Wave Cavity cavity, radiation, vacuum, electromagnetic-fields 1215
 
  • 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
  • J. Wang
    CST of America, Wellesley Hills, Massachusetts, USA
  
  Funding: Work supported by US DOE via BSA LLC contract No.DE-AC02-98CH10886 and US LARP program and by EU FP7 HiLumi LHC grant No.284404. Used NERSC resources by US DOE contract No.DE-AC02-05CH11231.
The Lorentz detuning is the resonant frequency change in an RF cavity due to the radiation pressure on the cavity walls. We present benchmarking studies of Lorentz detuning calculations for a Double-Quarter Wave Crab Cavity (DQWCC) using the codes ACE3P. The results are compared with the Lorentz detuning measurements performed during the cold tests of the Proof-of-Principle DQWCC at BNL. 		 
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THPB052 Thermal Losses in Couplers and Ports of a SPS Double-Quarter Wave Crab Cavity HOM, cavity, pick-up, 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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THPB068 Practical Aspects of HOM Suppression Improvement for TM011 HOM, damping, cavity, 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.  
poster icon Poster THPB068 [0.182 MB]  
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THPB072 Higher Order Mode Damping in a Higher Harmonic Cavity for the Advanced Photon Source Upgrade HOM, cavity, impedance, dipole 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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THPB077 Modified TTF3 Couplers for LCLS-II operation, vacuum, cavity, linac 1306
 
  • C. Adolphsen, K. Fant, Z. Li, C.D. Nantista, G. Stupakov, J. Tice, F.Y. Wang, L. Xiao
    SLAC, Menlo Park, California, USA
  • I.V. Gonin, K. Premo, N. Solyak
    Fermilab, Batavia, Illinois, USA
  
  The LCLS-II 4 GeV SC electron linac will use 280 TESLA cavities and TTF3 couplers, modified for CW operation with input power up to about 7 kW. The coupler modifications include shortening the antenna to achieve higher Qext and thickening the copper plating on the warm section inner conductor to lower the peak temperature. Another change is the use a waveguide transition box that is machined out of a solid piece of aluminum, significantly reducing its cost and improving its fit to the warm coupler window section. This paper describes the changes, simulations of the coupler operation (heat loads and temperatures), rf processing results and CW tests with LCLS-II dressed cavities.  
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THPB078 Status of the Power Couplers for the ESS Elliptical Cavity Prototypes cavity, cryomodule, vacuum, status 1309
 
  • C. Arcambal
    CEA/IRFU, Gif-sur-Yvette, France
  • P. Bosland, M. Desmons, G. Devanz, G. Ferrand, A. Hamdi, P. Hardy, H. Jenhani, F. Leseigneur, C. Marchand, F. Peauger, O. Piquet, D. Roudier, C. Servouin
    CEA/DSM/IRFU, France
  • C. Darve
    ESS, Lund, Sweden
  
  In the frame of the European Spallation Source (ESS) project, a linear accelerator composed of a superconducting section is being developed. This accelerator owns two kinds of cavities called “medium beta cavity” (β=0.67) and “high beta cavity” (β= 0.86). These cavities are equipped with RF power couplers whose main characteristics are: fundamental frequency: 704.42MHz, peak RF power: 1.1MW, repetition rate: 14Hz, RF pulse width>3.1ms. These couplers are common to the two cavities. The CEA Saclay is responsible for the design, the manufacture, the preparation and the conditioning of the couplers used for the Elliptical Cavities Cryomodule Technological Demonstrators (ECCTD). This work is performed in collaboration with ESS and the IPNO. This paper describes the coupler architecture, its different components, the main characteristics and the specific features of its elements (RF performance, dissipated power, cooling, coupler box test for the conditioning). The status of the manufacture of each coupler part is also presented.  
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THPB079 Improved Capacitive Coupling Type RF Power Couplers for a Cryomodule With Two 9-Cell Cavities coupling, impedance, cryomodule, SRF 1313
 
  • D.H. Zhuang, P.L. Fan, L.W. Feng, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Z.L. Wang
    PKU, Beijing, People's Republic of China
  
  Funding: Work supported by Major State Basic Research Development Program of China(Grant No. 2011CB808302 and 2011CB808304)
A capacitive coupling RF power coupler was used for the DC-SRF photoinjector at Peking University. Recently, improved capacitive coupling power couplers, which will be used for a new cryomodule with two 9-cell cavities have been designed and fabricated. The main modifications include enlarging the supporting rods of inner conductors in order to increase heat conduction, moving the bellows from the quarter-wave transformer to the 50 Ω coaxial line to avoid the mismatch during Qext adjusting. Two modified power coupler have already finished RF conditioning up to 10kW, TW, duty factor 30%. In this paper, detailed design based on multi-physics analysis and the conditioning of this improved capacitive coupling RF Power coupler will be presented. 		 
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THPB082 Design of QWR Power Coupler for the Rare Isotope Science Project in Korea pick-up, cavity, diagnostics, cryomodule 1326
 
  • I. Shin, M.O. Hyun
    IBS, Daejeon, Republic of Korea
  • E. Kako
    KEK, Ibaraki, Japan
  • C.K. Sung
    Korea University Sejong Campus, Sejong, Republic of Korea
  
  A power coupler has been designed for the Rare Isotope Science Project (RISP) in Korea. The power couplers will provide 4 kW RF power to 81.25 MHz superconducting quarter wave resonators with β=0.047. The coupler is a coaxial capacitive type with an impedance of 50 ohms using a disc type ceramic window. Design studies of the coupler are presented.  
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THPB087 Design and Simulation of High Power Input Coupler for C-ADS Linac 5-Cell Elliptical Cavities cavity, electron, RF-structure, impedance 1343
 
  • K.X. Gu
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
  • X. Chen, T.M. Huang, Q. Ma, W.M. Pan
    IHEP, Beijing, People's Republic of China
  
  Two 650 MHz elliptical cavity sections (elliptical 063, elliptical 082) are chosen to accelerate medium energy protons for China Accelerator Driven sub-critical System (C-ADS) linac. For each 5-cell cavity, RF power up to 150 kW in CW mode is required to be fed by a fundamental power coupler (FPC). A coaxial type coupler is designed to meet the power and RF coupling requirements. This paper presents the RF design, thermal analysis and multipacting simulations of the coupler for C-ADS 5-cell elliptical cavities.  
poster icon Poster THPB087 [0.593 MB]  
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THPB097 New Possible Configuration of 3.9 GHz Coupler Windows, multipactoring, cavity, electron 1373
 
  • S. Kazakov
    Fermilab, Batavia, Illinois, USA
  
  The LCLS-II superconducting accelerator supposedly will use 3.9 GHz (3-d harmonic) superconductive cavities. A new possible configuration of 3.9 GHz main coupler is presented in the papar. This configuration contains two coaxial ceramic windows, a cold and a warm one. Inner conductors of windows are connected through the capacitive gap and have no mechanical no thermal contacts. It allows to avoid using bellows and thus avoid the problem of heating and cooling. The windows have shields protecting shields against the electron, and this prevents the window ceramics from charging. Results of computer simulation of the new coupler are posted.  
poster icon Poster THPB097 [1.036 MB]  
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THPB104 Higher Order Modes Simulation and Measurements for 2400 MHz Cavity HOM, cavity, damping, 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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