Keyword: HOM
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MOPMB049 Beam Experiment of Low Q CBPM Prototype for SXFEL cavity, simulation, electron, FEL 202
 
  • J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
  
  To meet the high resolution beam position measurement requirement of micron or sub-micron for shanghai soft X-ray free electron laser (SXFEL) under construction, the cavity beam position monitor (CBPM) operating at C-band and the corresponding electronic has been designed by SINAP. In this paper, the design and optimize of the newly low Q cavity BPM is mentioned, the beam test was conducted on the Shanghai Deep ultraviolet free electron laser (SDUV-FEL) facility. CBPM signal processors including broadband oscilloscope and home-made digital BPM processor have been used to evaluate the system performance as well. The beam experimental result, which matched with MAFIA simulation very well, will be presented and discussed in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB049  
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MOPMW004 Realization and High Power Tests of Damped C-Band Accelerating Structures for the ELI-NP Linac vacuum, ion, klystron, damping 399
 
  • D. Alesini, M. Bellaveglia, S. Bini, R. Boni, P. Chimenti, F. Cioeta, R.D. Di Raddo, A. Falone, A. Gallo, V.L. Lollo, L. Palumbo, S. Pioli, A. Variola
    INFN/LNF, Frascati (Roma), Italy
  • F. Cardelli, M. Magi, A. Mostacci, L. Palumbo, L. Piersanti
    University of Rome La Sapienza, Rome, Italy
  • F. Cardelli, L. Piersanti
    INFN-Roma1, Rome, Italy
  • P. Favaron, F. Poletto
    INFN/LNL, Legnaro (PD), Italy
  • L. Ficcadenti, F. Pellegrino, V. Pettinacci
    INFN-Roma, Roma, Italy
  
  The ELI-NP C-Band structures are 1.8 m long travelling wave accelerating structures, quasi-constant gradient, with a field phase advance per cell of 2pi/3. They operate at a repetition rate of 100 Hz and, because of the multi-bunch operation, they have been designed with a dipole HOM damping system to avoid beam break-up (BBU). The structures have symmetric input and output couplers and integrate, in each cell, a waveguide HOM damping systems with silicon carbide RF absorbers. An optimization of the electromagnetic and mechanical design has been done to simplify the fabrication and to reduce their cost. After the first full scale prototype successfully tested at the nominal gradient of 33 MV/m, the production of the twelve structures started. In the paper we illustrate the main design criteria, the realization process and the high power test results.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW004  
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MOPMW023 Optimization of the RF Cavity of a Low-energy Storage Ring for Thomson Scattering X-Ray Source cavity, storage-ring, coupling, higher-order-mode 438
 
  • L. Ovchinnikova, V.I. Shvedunov
    SINP MSU, Moscow, Russia
  • A. Ryabov
    IHEP, Moscow Region, Russia
  • V.I. Shvedunov
    LEA MSU, Moscow, Russia
  
  Results of optimization of the RF cavity of a low-energy storage ring for Thomson scattering X-ray source are presented. The geometry of 714 MHz RF cavity was optimized to provide maximum shunt impedance taking into account position of higher order modes (HOMs). The number and position of cooling channels were adjusted to minimize frequency shift due to cavity thermal deformations. The waveguide coupler and frequency tuner were calculated. Special attention was paid to detailed calculations of the HOMs parameter and to study of methods to minimize their influence on the storage ring beam dynamics.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW023  
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MOPMY009 HOM Consideration of 704 MHz and 2.1 GHz Cavities for LEReC Linac cavity, SRF, booster, electron 528
 
  • B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh
    Fermilab, Batavia, Illinois, USA
  • S.A. Belomestnykh, I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  • V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. The Linac of LEReC is designed to deliver 2 MV to 5 MV electron beam, with rms dp/p less than 5·10-4. The HOM in this Linac is carefully studied to ensure this specification. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY009  
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MOPMY010 RF Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac cavity, vacuum, impedance, simulation 532
 
  • B. P. Xiao, I. Ben-Zvi, M. Blaskiewicz, J.M. Brennan, J.C. Brutus, A.V. Fedotov, H. Hahn, G.T. McIntyre, C. Pai, K.S. Smith, J.E. Tuozzolo, Q. Wu, T. Xin, W. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • S.A. Belomestnykh
    Fermilab, Batavia, Illinois, USA
  • S.A. Belomestnykh, I. Ben-Zvi, T. Xin
    Stony Brook University, Stony Brook, USA
  • V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 and by National Energy Research Scientific Computing Center under contract No. DE-AC02-05CH11231 by US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energy RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for energy spread correction. Currently these two cavities are under fabrication. In this paper we report the RF design of these two cavities. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY010  
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MOPOR009 The HL-LHC Impedance Model and Aspects of Beam Stability impedance, octupole, cavity, focusing 606
 
  • N. Biancacci, K.S.B. Li, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
  
  Funding: Research supported by the High Luminosity LHC project
The LHC upgrade to the HLLHC foresees new challenging operational scenarios from the beam dynamics point of view. In order to ensure good machine operation and performance, the machine impedance, among other possible sources of instabilities like beam-beam and electron cloud, needs to be carefully quantified profiting also from the current LHC operation. In this work we present the HLLHC impedance model mainly focusing on the contribution of low-impedance collimators and crab cavities: the first reduces the broad-band impedance baseline thanks to the higher jaw material conductivity, the second increases the machine luminosity at the price of increasing the coupled bunch stabilizing octupole current threshold. Other elements like the injection protection absorber (TDI) will be also discussed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR009  
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MOPOR010 Impedance Measurements and Simulations on the TCTP and TDI LHC Collimators impedance, simulation, embedded, operation 610
 
  • N. Biancacci, F. Caspers, A. Grudiev, J. Kuczerowski, I. Lamas Garcia, A. Lechner, E. Métral, A. Passarelli, A. Perillo Marcone, B. Salvant, J.A. Uythoven
    CERN, Geneva, Switzerland
  • O. Frasciello, M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  • A. Mostacci
    Rome University La Sapienza, Roma, Italy
  • N. Mounet
    EPFL, Lausanne, Switzerland
  
  The LHC collimation system is a critical element for the safe operation of the LHC machine and is subject to continuous performance monitoring, hardware upgrade and optimization. In this work we will address the impact on impedance of the upgrades performed on the TDI injection protection collimator, where the absorber material has been changed to mitigate the device heating observed in machine operation, and on selected secondary (TCS) and tertiary (TCT) collimators, where beam position monitors (BPM) have been embedded for faster jaw alignment. Concerning the TDI, we will present the RF measurements performed before and after the upgrade, comparing the result to heating and tune shift beam measurements. For the TCTs, we will study how the higher order modes (HOM) introduced by the BPM addition have been cured by means of ferrite placement in the device. The impedance mitigation campaign has been supported by RF measurements whose results are in good agreement with GdfidL and CST simulations. The presence of undamped low frequency modes is proved not to be detrimental to the safe LHC operation.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR010  
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MOPOR014 Measurements of the CERN PS Longitudinal Resistive Coupling Impedance impedance, coupling, synchrotron, cavity 626
 
  • M. Migliorati, N. Biancacci, H. Damerau, G. Sterbini
    CERN, Geneva, Switzerland
  • M. Migliorati
    University of Rome "La Sapienza", Rome, Italy
  • M. Migliorati, L. Ventura
    INFN-Roma1, Rome, Italy
  • S. Persichelli
    University of Rome La Sapienza, Rome, Italy
  
  The longitudinal coupling impedance of the CERN PS has been studied in the past years in order to better understand collective effects which could produce beam intensity limitations for the LHC Injectors Upgrade project. By measuring the incoherent quadrupole synchrotron frequency vs beam intensity, the inductive impedance was evaluated and compared with the impedance model obtained by taking into account the contribution of the most important machine devices. In this paper, we present the results of the measurements performed during a dedicated campaign, of the real part of the longitudinal coupling impedance by means of the synchronous phase shift vs beam intensity. The phase shift has been measured by using two different techniques: in one case, we injected in the machine two bunches, one used as a reference with constant intensity, and the second one changing its intensity; in the second case, more conventional, we measured the bunch position with respect to the RF signal of the 40 MHz cavities. The obtained dependence of the synchrotron phase with intensity is then related to the loss factor and the resistive coupling impedance, which is compared to the real part of the PS impedance model.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR014  
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MOPOR032 Using of the MENT Method for Reconstruction of 2D Particle Distributions in IFMIF Accelerators linac, emittance, SRF, simulation 668
 
  • P.A.P. Nghiem, N. Chauvin, L. Ducrot, M. Valette
    CEA/DSM/IRFU, France
  
  Beam particles are characterized by their coordinates in real spaces or phase spaces that are at least two-dimensional. It is often necessary to reconstruct such a 2D-distribution from the knowledge of only its projections on some axes, either for making use of tomography measurement results or for setting up an input beam for transport simulations. In this article, the use of the MENT (Maximum Entropy) reconstruction method is reported for the IFMIF accelerators where high intensity beam distributions are far from Gaussian ones.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR032  
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MOPOR038 Implications of Resonantly Driven Higher Order Modes on the ESS Beam cavity, simulation, linac, emittance 683
 
  • A. Farricker, R.M. Jones, N.Y. Joshi
    UMAN, Manchester, United Kingdom
  • S. Molloy
    ESS, Lund, Sweden
  
  The European Spallation Source (ESS) in Lund, Sweden, will be a facility for fundamental physics studies of atomic structure using a spallation source of unparalleled brightness. To achieve this end, a 2.86 ms long pulsed proton beam will be accelerated up to a final energy of 2 GeV using three suites of superconducting cavities. If a Higher Order Mode (HOM) lies on a harmonic of the bunch frequency the HOM will be resonantly driven. This will dilute the beam quality significantly. Errors in fabricating these cavities are inevitable, and this sets a tolerance on how close the HOM can be within a harmonic of the bunch frequency. The baseline design for ESS requires HOMs to be at least 5 MHz from a machine line. Here we provide details of several finite element electromagnetic simulations on the HOMS anticipated in these ESS cavities. We analyse their impact on the beam emittance using a drift-kick-drift model with the potential for relaxed tolerances.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR038  
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MOPOR039 Measurement of Beam Phase at FLASH using HOMs in Accelerating Cavities cavity, electron, simulation, coupling 686
 
  • L. Shi, R.M. Jones
    UMAN, Manchester, United Kingdom
  • N. Baboi, L. Shi
    DESY, Hamburg, Germany
  • N.Y. Joshi
    University of Manchester, Manchester, United Kingdom
  
  The beam phase relative to the accelerating field is of vital importance for the quality of photon beams produced in modern Free Electron Lasers based on superconducting (SC) cavities. Normally, the phase is determined by detecting the transient field induced by the beam. In this way the phase of each cavity is checked and adjusted typically every few months. In this paper, we present another means of beam phase determination, based on higher order modes (HOMs) excited in the 2nd monopole band by the beam inside the SC cavities. A circuit model of this HOM band is also presented. Various effects on the resolution have been studied. Circuit model simulations indicate the resolution is strongly dependent on the signal to noise ratio. Preliminary experimental results, based on a broadband setup, reveal an approximately 0.1o RMS resolution. These are in good agreement with simulation results. The work will pave the way for a dedicated system of beam phase monitoring, which is under development for the European XFEL. This will be the first implementation of a dedicated beam phase monitor, based on beam-excited HOMs in accelerating cavities.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOR039  
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MOPOW054 The 4th Harmonic Cavity for Hefei Light Source-II cavity, storage-ring, synchrotron, operation 837
 
  • C.-F. Wu, S. Dong, G. Huang, D. Jia, K. Jin, C. Li, J.Y. Li, W. Li, J.G. Wang, L. Wang, W. Xu, K. Xuan
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • R.A. Bosch
    UW-Madison/SRC, Madison, Wisconsin, USA
  • G.Y. Kurkin, E. Rotov
    BINP SB RAS, Novosibirsk, Russia
  • G. Ya
    Budker Institute of Nuclear Physics, Novosibirsk, Russia
  
  The 4th harmonic cavity has been firstly used in the storage ring for HLS-II. The paper presents the physics design, developing process and the experimental results for commision. The measurment results show that rf parameters are reasonable. The 4th harmonic cavity efficiently lengthen the bunch and increase the beam life-time. Specially, the beam instablity has been supressed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW054  
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TUPMY038 Preliminary Measurement of the Transfer Matrix of a TESLA-type Cavity at FAST cavity, simulation, experiment, focusing 1632
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • N. Eddy, D.R. Edstrom, A. Lunin, P. Piot, J. Ruan, J.K. Santucci, J.K. Santucci, N. Solyak
    Fermilab, Batavia, Illinois, USA
  
  Funding: US Department of Energy (DOE) under contract DE-SC0011831 with Northern Illinois University. Fermilab is operated by the Fermi Research Alliance LLC under US DOE contract DE-AC02-07CH11359.
Superconducting linacs are capable of producing intense, ultra-stable, high-quality electron beams that have widespread application in Science and Industry. Many current and planned projects employ 1.3-GHz 9-cell superconducting cavities of the TESLA design*. In the present paper we discuss the transverse-focusing properties of such a cavity and non-ideal transverse-map effects introduced by field asymmetries in the vicinity of the input and high-order-mode radiofrequency (RF) couplers**. We especially consider the case of a cavity located downstream of an RF-gun in a setup similar to the photoinjector of the Fermilab Accelerator Science and Technology (FAST) facility. Preliminary experimental measurements of the CC2 cavity transverse matrix were carried out at the FAST facility. The results are discussed and compared with analytical and numerical simulations.
* A. Aunes et al., Phys. Rev.ST Accel. Beams 3, 092001 (2000).
** P. Piot, el. al., Proc. 2005 Part. Accel. Conf., Knoxville, TN, p. 4135 (2005). 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY038  
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TUPOR004 Calculation of Transverse Coupled Bunch Instabilities in Electron Storage Rings Driven By Quadrupole Higher Order Modes quadrupole, impedance, dipole, damping 1655
 
  • M. Ruprecht, P. Goslawski, M. Ries, G. Wüstefeld
    HZB, Berlin, Germany
  
  This paper presents a formula that estimates the growth rate of a transverse coupled bunch instability driven by quadrupole higher order modes (HOMs) in electron storage rings. Thus far, quadrupole HOMs are usually ignored in HOM driven instability studies for electron storage rings due to their weak nature compared to the lower orders. However, they may become relevant when high gradient SC multi-cell cavities with their potentially strong impedance spectrum are operated at high currents in a third generation or future synchrotron light source. An example is BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches (rms) can be stored simultaneously in the BESSY II storage ring[*]. With the presented formula, instability thresholds are discussed for a recent BESSY VSR cavity model and different beam parameters.
* A. Jankowiak, J. Knobloch, P. Goslawski, and N. Neumann, eds., BESSY VSR - Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 2015.
 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR004  
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TUPOR008 Effect of the Various Impedances on Longitudinal Beam Stability in the CERN SPS impedance, simulation, vacuum, operation 1666
 
  • A. Lasheen, T. Argyropoulos, J. Repond, E.N. Shaposhnikova
    CERN, Geneva, Switzerland
  
  The High Luminosity (HL)-LHC project at CERN aims at a luminosity increase by a factor ten and one of the necessary ingredients is doubling the bunch intensity to 2.4x1011 ppb for beams with 25 ns bunch spacing. Many improvements are already foreseen in the frame of the LHC Injector Upgrade (LIU) project, but probably this intensity would still not be reachable in the SPS due to longitudinal instabilities. Recently a lot of effort went into finding the impedance sources of the instabilities. Particle simulations based on the latest SPS impedance model are now able to reproduce the measured instability thresholds and were used to determine the most critical impedance sources by removing them one by one from the model. It was found that impedance of vacuum flanges and of the already damped 630 MHz HOM of the main RF system gave for 72 bunches the comparable intensity thresholds. Possible intensity gains are defined for realistic impedance modifications and for various beam configurations (number of bunches, longitudinal emittances) and RF programs (single and double RF). The results of this study are used as a guideline for planning of a new campaign of the SPS impedance reduction.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR008  
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TUPOR025 Beam Break-up Measurements at the Recirculating Electron Accelerator S-DALINAC linac, recirculation, experiment, cavity 1714
 
  • T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
  
  Funding: Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA
Beam break-up (BBU) instability is an important limitation to the current which can be accelerated in a superconducting linac. In particular recirculating machines and Energy Recovery Linacs have to deal with that problem. Therefore, it is important to find strategies for increasing the threshold currents of these machines. The superconducting accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. It consists of a 10 MeV injector and a 40 MeV main linac where two and eight 20-cell elliptical 3-GHz cavities are operated in a liquid helium bath at 2 K. Using two recirculation beam lines the main accelerator can be used up to 3 times. Operational experiences have shown that the design-beam current of 20 μA could not be reached. One reason is the occurrence of BBU. We will report on measurements of the threshold current at various energy settings of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupole magnets in the first recirculation beam line will be presented. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR025  
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TUPOW005 Update on Third Harmonic XFEL Activities at INFN LASA cavity, operation, pick-up, diagnostics 1751
 
  • D. Sertore, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, P. Michelato, L. Monaco, R. Paparella, P. Pierini
    INFN/LASA, Segrate (MI), Italy
  • C.G. Maiano
    DESY, Hamburg, Germany
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  
  After the successful installation and beam operation of the first batch of 3.9 GHz cavities into the XFEL Third Harmonic Injector Module, ten more cavities have been tested and delivered to DESY to be assembled into a spare cryomodule. In this paper, we report on the activities related to the cavities fabrication, treatment and vertical testing at INFN LASA.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW005  
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TUPOW033 Status of the BERLinPro Main Linac Module linac, cavity, simulation, wakefield 1823
 
  • H.-W. Glock, A. Frahm, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  
  Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of the Helmholtz Association
Beam operation of the BERLinPro energy recovery linac project, whose construction is under way, will initially start using the photoinjector and booster modules. In a second step the recirculation beam line and the main linac module will be added. Here the current design status of the main linac module is described. Results of wake field simulations are compared for different set ups. We also report on the manufacturing aspects including the design of the waveguide groups needed for HOM damping and the choice of flange-gasket-pairings appropriate for rectangular waveguides. Also mechanical considerations are included. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW033  
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TUPOW040 UH-FLUX: Compact, Energy Efficient Superconducting Asymmetric Energy Recovery LINAC for Ultra-high Fluxes of X-ray and THz Radiation cavity, electron, radiation, coupling 1847
 
  • I.V. Konoplev, A. Seryi
    JAI, Oxford, United Kingdom
  • R. Ainsworth
    Fermilab, Batavia, Illinois, USA
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  
  Funding: This work was supported (in part) by The Leverhulme Trust through the International Network Grant IN-2015-012.
The conventional ERLs have limited peak beam current because increasing the beam charge and repetition rate leads to appearance of the beam break-up instabilities. At this stage the highest current, from the SRF ERL, is around 300 mA. A single turn (the beam will be transported through the accelerating section, interaction point and deceleration section of the AERL only once) Asymmetric Energy Recovery LINAC (AERL) is proposed. The RF cells in different sections of the cavity are tuned in such a way that only operating mode is uniform inside all of the cells. The AERL will drive the electron beams with typical energies of 10 - 30 MeV and peak currents above 1 A, enabling the generation of high flux UV/X-rays and high power coherent THz radiation. We aim to build a copper prototype of the RF cavity for a compact AERL to study its EM properties. The final goal is to build AERL based on the superconducting RF cavity. Preliminary design for AERL's cavity has been developed and will be presented. The results of numerical and analytical models and the next steps toward the AERL operation will also be discussed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW040  
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TUPOY005 The Use of Cyclotron for PET/CT Scan in Indonesian Hospitals and Future Collaboration cyclotron, ion, proton, ion-source 1911
 
  • N.S. Risdianto, J. Purwanto, F.A. Rahmadi
    Universitas Islam Negeri Sunan Kalijaga, Yogyakarta, Indonesia
  • N. Risdiana
    UMY, Yogyakarta, Indonesia
  
  In Indonesia there are only three hospitals, which using cyclotrons for cancer detection (PET scans). These three hospitals are located in one place: Jakarta. With 1.4 percent of the Indonesian population are developing tumor/cancer, compared to the number of hospitals, which have advanced PET technology from cyclotrons, it will be a major task for the government to empower the production and overseas collaboration in the cyclotron industry.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOY005  
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WEPMB007 Error Estimation in Cavity Performance Test for the European XFEL at DESY cavity, cryomodule, accelerating-gradient, operation 2128
 
  • Y. Yamamoto
    KEK, Ibaraki, Japan
  • W.-D. Möller, D. Reschke
    DESY, Hamburg, Germany
  
  The cavity performance tests, that is, vertical test (V.T.) and cryomodule test (C.T.), in the cavity/cryomodule mass production for XFEL have been done since 2012 at DESY, and is still on-going at present. At the comparatively initial stage of the mass production, the error estimation in the cavity performance tests was done for understanding how precisely those measurements are done at AMTF (Accelerator Module Test Facility). There are two parameters for the error estimation in V.T. One is the cable calibration parameter, and the other is the external Q-value, which is related to the power emitted from cavity. The measurement precision in the external Q-value depends on the measurement of coupling coefficient (β) strongly. Therefore, it is essential not to miss the β measurement for the precise measurement in V.T. On the other hand, as for C.T., the change of parameter (Kt), which is related to the evaluation of accelerating gradient, was used. As the result of the data analysis for Kt, the error was estimated to be 6%, and is related to the cavity performance degradation from V.T. to C.T. In this paper, the detailed data analysis and error estimation will be presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB007  
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WEPMB009 Status of the Superconducting Cryomodules and Cryogenic System for the Mainz Energy-recovering Superconducting Accelerator MESA cryomodule, niobium, electron, operation 2134
 
  • T. Stengler, K. Aulenbacher, F. Hug, D. Simon, P. Weber
    IKP, Mainz, Germany
  • F. Schlander
    ESS, Lund, Sweden
  • N. Wiehl
    Johannes Gutenberg University Mainz, Institut of Nuclear Chemistry, Mainz, Germany
  
  Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA"
SRF and the cryogenic system are mandatory for the operation of MESA at the Institut für Kernphysik at Johannes Gutenberg-Universität Mainz. The cryomodule production project is running for one year right now and the recent developments and measurements are presented. Further on the cryogenic concept required for the operation of MESA will be discussed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB009  
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WEPMB011 ESS Medium and High Beta Cavity Prototypes cavity, coupling, cryomodule, interface 2138
 
  • P. Michelato, A. Bellandi, M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, L. Monaco, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • C.G. Maiano
    DESY, Hamburg, Germany
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
  • S. Pirani
    ESS, Lund, Sweden
  
  In the framework of the ESS activity in progress at INFN-LASA, we are designing and developing 704.42 MHz Medium (β=0.67) and High (β=0.86) beta prototype cavities plug compatible with the ESS cryomodule design. The cells of one Medium and one High beta cavity are fabricated with high quality CBMM Large Grain Niobium (480 mm dia. Ingot, RRR=300, sliced by Heraeus) while a Medium beta cavity is done with Fine Grain material for comparison. The prototype cavities will be produced by the firm Ettore Zanon S.p.A. under the supervision of INFN - LASA group.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB011  
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WEPMB015 Construction and 2K Cooling Test of Horizontal Test Cryostat at KEK SRF, cavity, operation, cryomodule 2151
 
  • K. Umemori, K. Hara, E. Kako, Y. Kobayashi, Y. Kondo, H. Nakai, H. Sakai, S. Yamaguchi
    KEK, Ibaraki, Japan
  
  A horizontal test cryostat was designed and constructed at AR East building on KEK. Main purposes of test stand are improvement of module assembly technique and effective development of module components. Diameter of vacuum chamber is 1 m and its length is 3 m, which is enough to realize performance test of L-band 9-cell cavity with full assembly, including input couplers, HOM dampers/couplers and frequency tuners. On the sides, several ports are prepared to access to components, such as coupler and tuners. A cold box is placed on the top of the chamber. Liquid He is filled in a 4K-pod and 2K He is supplied through a J-T valve. A He pumping system is prepared. Inside of the chamber was covered with 80K shield, which is cooled by Liquid nitrogen. A cavity is supported on 5K table, which is also used as 5K thermal anchors. After cooling down to 80K using liquid Nitrogen, 4K He was stored and pumped down to 2K. The cooling test was successful. In this presentation, details of design and construction of the horizontal test cryostat is described and results of the cooling tests are shown. High power tests will be realized in near future.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB015  
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WEPMB017 High Gradient Cavity Performance in STF-2 Cryomodule for the ILC at KEK cavity, cryomodule, radiation, accelerating-gradient 2158
 
  • Y. Yamamoto, T. Honma, E. Kako, Y. Kojima, T. Matsumoto, H. Nakai, T. Shishido
    KEK, Ibaraki, Japan
  
  The high power test for STF-2 cryomodule has completed successfully in 2015. Before cooldown of cryomodule, at first, the input coupler conditioning at room temperature is done with detuned cavities. After cooldown, the cavity conditioning, which is the main part in the performance test, is done by monitoring the radiation level measured at three locations around the cryomodule, and the heating and RF output at two HOM (Higher Order Mode) couplers. Consequently, it became clear the average accelerating gradient is 30 MV/m for STF-2 cryomodule (39 MV/m at max. and 15 MV/m at min.), and the second cavity string with four cavities had the significant performance degradation by heavy field emission due to the additional clean room work in the STF tunnel. As the following next steps, there are the LFD (Lorenz Force Detuning) measurement, LFD compensation by piezo, and long run for check of stable operation at high gradient. In the long run around 32 MV/m, each cavity without degradation showed the stable operation with the successful LFD compensation by piezo and RF feedback system. In this paper, the detailed test result will be presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB017  
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WEPMB028 High HOM Damping Structure Study for CEPC cavity, damping, collider, dipole 2183
 
  • Z.C. Liu, J. Gao, S. Jin, Y. Wang, H.J. Zheng
    IHEP, Beijing, People's Republic of China
  
  Both large circular collider such as CEPC and high current ERL facility need high HOM damping superconducting cavity. The slotted cavity is an option for such applications. It has three slotted waveguides which can highly damp the HOM and extract high HOM power out. However, the HOM absorbers for such facility are usually put outside of the cryomodule to decrease the influence of HOM power on the cryogenic system. Large slot waveguide need to make smaller transition structure to adapt this situation. A rectangular waveguide to coaxial waveguide structure was designed to the slotted cavity. In this paper, we will show the cavity HOM damping design scheme with this structure.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB028  
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WEPMB045 Measurement of Higher Order Modes Electrodynamic Characteristics for Array of Two 2400 MHz Cavities cavity, damping, simulation, higher-order-mode 2214
 
  • Ya.V. Shashkov, R.V. Donetskiy, M.V. Lalayan, N.P. Sobenin
    MEPhI, Moscow, Russia
  • A. Orlov
    NRNU, Moscow, Russia
  
  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 Large hadron collider (HL-LHC) upgrade program an application of additional superconducting harmonic cavities operating at 800 MHz is currently under discussion. As a candidate, the two cavities with grooved beam pipes connected by the drift tube were suggested. In this article of measurements of Qload are performed for the aluminum model of array of two cavities connected by drift tube. Field distribution of Fundamental Mode (FM) and Higher Order Modes (HOM) were measured for aluminum prototype with a frequency of the operational mode of 2400 MHz, and their comparison with the simulation results.
Higher order modes 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB045  
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WEPMB047 Higher Order Modes Couplers for 800 MHz Harmonic Cavity cavity, damping, electron, multipactoring 2217
 
  • Ya.V. Shashkov, R.V. Donetskiy, M. Gusarova, N.P. Sobenin
    MEPhI, Moscow, Russia
  
  Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r
For the higher order modes damping (HOM) in the 800 MHz superconducting single cell cavity the HOM coupler was developed. Several versions of the coupler design were shown. For the chain of two cavities with couplers the calculations of external Q-factor are presented. The calculations of multipactor discharge of cavity were also conducted.
Higher order modes, Tesla, couplers 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB047  
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WEPMB048 Macros for Identification of Higher Order Modes Types, Their Transverse Shunt Impedance and Kick Factor cavity, higher-order-mode, damping, interface 2220
 
  • Ya.V. Shashkov
    MEPhI, Moscow, Russia
  • A. Orlov
    NRNU, Moscow, Russia
  
  Funding: *Work supported by Ministry of Education and Science grant 3.245.2014/r
During the design studies of accelerating cavities one of the most time-consuming tasks is classification of the higher order modes (HOM) types. To automate the process of identification of HOM types special macros for CST Microwave studio was written. This article describes the programs algorithm of mode recognition and the results of the analysis on the example of single cell and 9 cell cavities. Macros for the calculation of the HOM transverse shunt impedance upon Q-factor values and kick-factor was also written.
Higher order modes, electrodynamic characteristics, macros 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB048  
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WEPMB058 LHC Crab Cavity Coupler Test Boxes cavity, luminosity, operation, higher-order-mode 2248
 
  • J.A. Mitchell
    Lancaster University, Lancaster, United Kingdom
  • R. Apsimon, G. Burt, A.R.J. Tutte
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • R. Calaga, A. Macpherson, E. Montesinos
    CERN, Geneva, Switzerland
  • S.D. Silva
    ODU, Norfolk, Virginia, USA
  • B. P. Xiao
    BNL, Upton, Long Island, New York, USA
  
  The LHC double quarter wave (DQW) crab cavities have two different types of Higher Order Mode (HOM) couplers in addition to a fundamental power coupler (FPC). The FPC requires conditioning, so to achieve this we have designed a radio-frequency (RF) quarter wave resonator to provide high transmission between two opposing FPCs. For the HOM couplers we must ensure that the stop-band filter is positioned at the cavity frequency and that peak transmission occurs at the same frequencies as the strongest HOMs. We have designed two test boxes which preserve the cavity spectral response in order to test the couplers.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB058  
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WEPMR013 Study of LCLS-II Fundamental Power Coupler Heating in HTS Integrated Cavity Tests cavity, resonance, vacuum, simulation 2286
 
  • N. Solyak, I.V. Gonin, A. Grassellino, C.J. Grimm, T.N. Khabiboulline, J.P. Ozelis, K. Premo, O.V. Prokofiev, D.A. Sergatskov, G. Wu
    Fermilab, Batavia, Illinois, USA
  
  LCLS-II coupler based on modified design of TTF3 coupler for higher average power was assembled on high Q cavity and tested at HTS as part of integrated cavity test program. Couplers were thermally connected to thermal shields and equipped with diagnostics to control temperature in different locations and provide information about cryogenic heat loads at 2 K, 5 K and 80 K.Three dressed cavities with power couplers were tested in HTS at full specified RF power. Results are summarized in this paper and cross-checked with simulation.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR013  
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WEPMR018 Time Resolved Cryogenic Cooling Analysis of the Cornell Injector Cryomodule cryogenics, cryomodule, simulation, operation 2298
 
  • R.G. Eichhorn, A.C. Bartnik, B.M. Dunham, G.M. Ge, G.H. Hoffstaetter, H. Lee, M. Liepe, S.R. Markham, T.I. O'Connell, 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
  
  To demonstrate key parameters of a an energy recovery linac (ERL) at Cornel, an injector based on a photo gun and an SRF cryomodule was designed and built. The goal was to demonstrate high current generation while achieving low emittances. While the emittance goal has been reached, the current achieved so far is 75 mA. Even though this is a world record, it is still below the targeted 100 mA. While ramping up the current we observed excessive heating in the fundamental power coupler which we were able to track down to insufficient cooling of the 80 K intercepts. These intercepts are cooled by a stream of parallel cryogenic flows which we found to be unbalanced. In this paper we will review the finding, describe the analysis we did, modeling of the parallel flow and the modifications made to the module to overcome the heating.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR018  
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WEPMR020 First Cool-down of the Cornell ERL Main Linac Cryo-Module cavity, linac, cryomodule, vacuum 2305
 
  • R.G. Eichhorn, J.V. Conway, F. Furuta, G.M. Ge, D. Gonnella, T. Gruber, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connell, 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 University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode with a design field of 16 MV/m and a Quality factor of 2x1010. We wil shortly review the design and focus on reporting on the first cool-down of this module. We will giving data for various cool-down scenarios (fast/ slow), uniformity and performance  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR020  
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WEPMR021 HOM Measurements for Cornell's High-current CW ERL Cryomodule cavity, cryomodule, simulation, linac 2309
 
  • F. Furuta, R.G. Eichhorn, G.M. Ge, D. Gonnella, G.H. Hoffstaetter, M. Liepe, P. Quigley, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  The main linac cryomodule (MLC) for the future energy-recovery linac (ERL) based synchrotron-light facility at Cornell had been designed, fabricated, and tested. It houses 6 SRF cavities with individual higher order-modes (HOMs)absorbers and one magnet/ BPM section. We will report the HOM study on MLC.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR021  
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WEPMR037 Wakefield Analysis of the 56 MHz SRF Cavity cavity, impedance, wakefield, SRF 2354
 
  • Q. Wu, Y. Hao
    BNL, Upton, Long Island, New York, USA
  
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 56 MHz SRF cavity is a superconducting quarter-wave resonator installed in the common section of RHIC. Both beams share the cavity in an interwoven pattern over the entire store. The wake field excited in the cavity is the superposition of the two opposing bunches. This paper will discuss the wake field excited by both beams, and the higher order mode power as a result of the excited field. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR037  
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WEPMR040 HOM Absorber Study by Photon Diffraction Model photon, cavity, damping, SRF 2360
 
  • C. Xu, I. Ben-Zvi, V. Ptitsyn, P. Takas, W. Xu
    BNL, Upton, Long Island, New York, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  • B. P. Xiao
    SBU, Stony Brook, New York, USA
  
  Photon diffraction model (PDM) is one of the most promising candidates to study High Order Mode (HOM) power absorption on absorbing materials for high current SRF cavities. Because at very high frequency (>10GHz), the wavelengths of HOMs are much smaller compared with accelerators dimension, the phase of those HOM will be negligible. Meanwhile, Finite Element Method (FEM) cannot lend a high resolution on evaluation the HOM field patterns due to limited meshing capability. This PDM model utilizes Monte Carlo simulation to trace the ray diffusive reflection in a cavity. This method can directly estimate the power absorption on the cavity and absorber wall. This method will help design the HOM damper setup for eRHIC HOM damper. In this report, we evaluate HOM absorption on the cavity wall with different absorber setup and give a possible solution for power damping scheme for high frequency HOMs.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR040  
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WEPMR041 RF and Mechanical Design of 647 MHz 5-Cell BNL4 Cavity for eRHIC ERL cavity, electron, linac, SRF 2364
 
  • W. Xu, I. Ben-Zvi, H. Hahn, G.T. McIntyre, C. Pai, R. Porqueddu, K.S. Smith, J.L. Tuozzolo, J.E. Tuozzolo, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
A 647 MHz 5-cell cavity has been designed for the envisioned EIC at BNL which is configured as an eRHIC ERL with a FFAG lattice to achieve the necessary e-p luminosity. The cavity was optimized to allow propagation of all HOMs out of the cavity for high BBU threshold current and low HOM power (loss factor). eRHIC will collide the electron beam over a wide energy range with protons from 40 GeV to 250 GeV, which requires the cavity to tune up to 170 kHz at 2 K. This poses a true challenge to the mechanical design of the SRF cavity. This paper will present the RF and mechanical designs of the 647 MHz 5-cell cavity, and status of the cavity fabrication will be addressed as well. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR041  
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WEPMR042 Ridge Waveguide HOM Damping Scheme for High Current SRF Cavity cavity, linac, damping, SRF 2367
 
  • W. Xu, I. Ben-Zvi, Y. Gao, H. Hahn, G.T. McIntyre, R. Porqueddu, V. Ptitsyn, K.S. Smith, R. Than, J.L. Tuozzolo, C. Xu, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • I. Ben-Zvi
    Stony Brook University, Stony Brook, USA
  
  Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
HOM damping is a challenge for high-current SRF linacs possibly generating HOM power at a level of 10 KW per cavity. A rectangular waveguide used as a natural high pass filter is a good option as high power, large spectrum HOM damper. However, its size is too big, causing a big challenge for the cooling and cryogenic system. A reliable, compact HOM damping scheme using a ridged waveguide is being developed to damp high power (> 10 kW), large spectrum HOMs ( up to 40 GHz) that may be generated in the 647 MHz 5-cell eRHIC ERL SRF linac. The size of a ridged waveguide is less than a quarter of the regular waveguide, which alleviates the thermal issue. This paper presents the design of a ridged waveguide and estimated HOM damping results using a ridged waveguide. The thermal or cooling design of the ridged waveguide will also be addressed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR042  
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WEPMR043 Analysis of Electrical Energy Consumption of Accelerator Reserach Facilities operation, experiment, framework, neutron 2370
 
  • J. Stadlmann
    GSI, Darmstadt, Germany
  • D. Batorowicz, C. Fuhr, J. Hanson, S. Leis
    TUD, Darmstadt, Germany
  • M. Seidel
    PSI, Villigen PSI, Switzerland
  
  Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
Optimization of energy efficiency and utilization of renewable energy sources has become a major focus of political and social policies, leading to increasing energy cost not only in Germany but also in the European energy market. Simultaneously the energy demand of future accelerator projects is estimated to rise compared to existing facilities, leading to overall increased energy costs. Energy efficiency could counteract this trend by reducing energy consumption for a given research goal. This work aims to find recommendations for saving potential in existing research accelerators as well as guidelines for construction of future facilities. In order to identify and develop key figures for comparison between several international particle accelerator facilities, data has been collected by a questionnaire developed in cooperation between GSI and TUD, Darmstadt. We present the first results of it's evaluation. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR043  
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WEPMW039 JLEIC SRF Cavity RF Design cavity, impedance, electron, damping 2522
 
  • S. Wang, J. Guo, R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
  
  The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchrotron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback system will be necessary.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW039  
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WEPMW041 Multiple Bunch HOM Evaluation for eRHIC Main Linac Cavities electron, cavity, linac, proton 2525
 
  • C. Xu, I. Ben-Zvi, M. Blaskiewicz, Y. Hao, V. Ptitsyn
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE.
High current Superconducting Radiofrequency (SRF) 5-cell cavities are essential for the proposed ERL-based electron-ion collider eRHIC in BNL. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the ERL create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in the eRHIC 5-cell cavity with different ERL bunch patterns using both methods. We also discuss possible solutions to reduce this HOM power. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW041  
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WEPMW042 Trapped Modes Study and BBU Analysis in the 5-Cell 650 MHz Cavity cavity, impedance, electron, damping 2529
 
  • C. Xu, I. Ben-Zvi, Y. Hao, V. Ptitsyn, W. Xu
    BNL, Upton, Long Island, New York, USA
  • I. Petrushina
    SUNY SB, Stony Brook, New York, USA
  
  Funding: This work is supported by LDRD program of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE. #chenxu@bnl.gov
eRHIC project is a future electron-hadron collider proposed at BNL. The proposed electron accelerator will generate up to 20 GeV polarized electrons which will collide with proton beams with energy up to 250 GeV. The proposed collider will deliver electron-nucleon luminosity of 1033- 1034 cm-2 ses−1. A superconducting RF (SRF) 5-cell elliptical cavity will be utilized in electron accelerator. This paper presents a study of higher-order modes (HOM) for this 647 MHz SRF cavity. Different types of HOM modes and their BBU instabilities were investigated for frequencies up to 3.2 GHz. Threshold current values of beam breakup are estimated by GBBU code. Further improvement on this threshold current has been explored and discussed. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW042  
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WEPOR056 Development of a Cw Solid State Amplifier for the Longitudinal Feedback System of Bepcii feedback, detector, controls, kicker 2796
 
  • S. An, Z. Bowen
    PLAI, Nanjing, People's Republic of China
  • J.L. Linling
    ADS, Jiangsu Province, People's Republic of China
  • J.H. Yue
    IHEP, Beijing, People's Republic of China
  • L. Zhang
    Chang'an University, Chang'an, People's Republic of China
  
  A Solid State Amplifier (SSA) has been developed for testing beam feedback system of the BEPCII of the Institute of High Energy Physics (IHEP), CAS. The output power of the SSA is 100 W with a CW frequency range from 1000 MHz to 1250 MHz. After three generations development, the SSA has become a professional power source. The paper has introduced the development of the SSA and the skills used in the SSA.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR056  
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WEPOW012 Hardware Upgrades Improve the Reliability at BESSY II storage-ring, operation, cavity, klystron 2844
 
  • A. Schälicke, W. Anders, J. Borninkhof, V. Dürr, P. Goslawski, A. Hellwig, A. Heugel, H.-G. Hoberg, H. Hoffmann, A. Jankowiak, J. Kolbe, P. Kuske, G. Mielczarek, R. Müller, D. Pflückhahn, M. Ries, S. Rotterdam, M. Ruprecht, B. Schriefer, D. Simmering, H. Stein
    HZB, Berlin, Germany
  
  The synchrotron light source BESSY II is now in its second decade of operation. Already in 2013 both top-up and fast orbit feedback have been introduced into user operation. Currently, the facility is undergoing significant hardware upgrades in order to fulfill the increasing demands of its user community in terms of reliability, stability and flexibility. These include replacement of the DORIS cavities with EU HOM damped cavities, the upgrade of the RF transmitters to solid state amplifiers, implementation of the shifted waist optics for the new in-vacuum undulator, and refurbishment of the superconducting multi-pole wiggler. In this contribution status of BESSY II operation and the upgrade projects is reported.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW012  
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WEPOW047 A Hybrid Superconducting/Normal Conducting RF System for the Diamond Light Source Storage Ring cavity, operation, storage-ring, vacuum 2950
 
  • C. Christou, A.G. Day, P. Gu, N.P. Hammond, J. Kay, M. Maddock, P.J. Marten, S.A. Pande, A.F. Rankin, D. Spink
    DLS, Oxfordshire, United Kingdom
  
  300 mA beam in the Diamond Light Source storage ring is presently maintained by two 500 MHz superconducting CESR-B cavities. Cavity reliability is acceptable at modest operating voltages up to 1.4 MV per cavity but falls off rapidly beyond this value. The installation of an extra cavity or cavities would reduce the voltage demand on the current superconducting cavities and also the operating power level of the high power amplifiers, with commensurate improvement in machine reliability. Furthermore, two superconducting cavity failures in recent years have resulted in machine down-time and reduced-current operation and repair has proven to be prolonged and expensive. It is therefore planned to install two normal conducting cavities into the ring to support operation of the superconducting cavities and to act as a safeguard against any future superconducting cavity failures. Details are presented in this paper of plans and progress towards the installation of the hybrid RF system.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW047  
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WEPOY007 Simulation of Electromagnetic Scattering Through the E-XFEL Third Harmonic Cavity Module cavity, simulation, dipole, factory 3001
 
  • N.Y. Joshi, R.M. Jones
    UMAN, Manchester, United Kingdom
  • N. Baboi, L. Shi
    DESY, Hamburg, Germany
  
  Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 31245. N.~Y.~Joshi receives additional funding from The Cockcroft Institute of Science and Technology.
The European-XFEL is being fabricated in Hamburg to serve as an X-ray Free Electron Laser (FEL) light source. The electron beam will be accelerated through linacs consisting of 1.3 GHz superconducting cavities along a length of 2.1 km. In addition, third harmonic cavities will improve the quality of the beam by linearising the field profile and hence reducing the energy spread. There are eight 3.9 GHz cavities within a single module AH1 of E-XFEL. The beam-excited electromagnetic (EM) field in these cavities can be decomposed into a series of eigenmodes. These modes are, in general, not cut-off between one cavity and the next, as they are able to couple to each other throughout the module. Here for the first time, we evaluate components of the scattering matrix for module AH1. This is a computationally expensive system, and hence we employ a Generalized Scattering Matrix (GSM) technique to allow rapid computation with reduced memory requirements. Verification is provided on reduced structures, which are compared to finite element mesh-based codes. The mode spectrum for the dipole bands of interest in an eight-cavity chain have been calculated and external Q factors for the modes are derived. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY007  
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WEPOY059 Axisymmetric Numerical Studies of Higher Order Mode Damping Techniques using Ring Ferrites for BESSY VSR cavity, damping, storage-ring, factory 3132
 
  • B. Riemann, B.D. Isbarn, M. Sommer, T. Weis
    DELTA, Dortmund, Germany
  
  Funding: Work supported by the BMBF under contract no. 05K13PEB.
Utilizing superconducting multicell rf cavities with fundamental frequencies of 1.5 GHz and 1.75 GHz and therefore modulating the rf gradient, the upcoming BESSY II upgrade BESSY VSR aims to provide both short and long electron bunches simultaneously. However, beam induced excitation of higher order modes (HOM) inside those superconducting cavities is a major concern for beam stability in a recirculating accelerator. Thus it is important to develop and apply proper HOM damping techniques. Current design considerations involve HOM coupler which usually introduce discontinuities in the cross section while also breaking the axisymmetry. To circumvent these issues we investigate in a layout with ring ferrites as an alternative or additional HOM damping technique. We also present an alternative superstructure setup that uses two instead of four cavities for VSR. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY059  
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THPMY002 Fabrication of Ferrite-Copper Block by Spark Plasma Sintering (SPS) vacuum, cavity, higher-order-mode, plasma 3654
 
  • Y. Suetsugu, T. Ishibashi, S. Terui
    KEK, Ibaraki, Japan
  • H. Ishizaki, A. Kimura, T. Sawhata
    Metal Technology Co. Ltd., Ibaraki, Japan
  
  A ferrite has been well known as an effective material for absorbing electromagnetic waves. Various types of the ferrite blocks have been actually used in accelerator fields as the higher-order modes (HOMs) absorbers in the vacuum beam pipes. However, one of difficulties in using the ferrite is to bond it to the beam pipes with a sufficient adhesive force, and to assure the contact with a high thermal conductivity in vacuum. The brazing or Hot Isostatic Pressing (HIP) is not so easy owing to a low thermal expansion rate and a relatively low tensile strength of the ferrite. We established a method of fabricating a ferrite block bonded to copper by spark plasma sintering (SPS). The ferrite powders are directly sintered on a copper block in the SPS process together with some metals to relax the thermal stress between them. The sintered ferrite-copper block can be brazed or welded to other metal blocks, or directly on the beam pipes. Here reported are R&D results of the fabrication method, and some experimental results on the properties of the ferrite-copper block.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY002  
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THPMY037 Realization of a System to Monitor Water Quality and for Cooling a TPS KEKB Superconducting Cavity CPL/HOM cavity, superconducting-cavity, monitoring, operation 3740
 
  • L.J. Chen, F.-Y. Chang, L.-H. Chang, M.H. Chang, PY. Chen, F.-T. Chung, M.-C. Lin, Z.K. Liu, C.H. Lo, C.L. Tsai, M.H. Tsai, Ch. Wang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  
  Taiwan Photon Source (TPS) is a 3GeV synchrotron accelerator and is built next to the present Taiwan Light Source (TLS) [1]. The stability of electron beam is pro-vided by Low-level RF control system for keeping Gap voltage and phase to be constant[2]. The Gap voltage for accelerating electron beam is provided by KEKB super-conducting cavity. During routine operation of the super-conducting cavity, water cooling system is necessary for stabilize the accessory components of the cavity to avoid damage or abnormal of the system. This article would introduce the realization and integration of the water quality monitoring and cooling system for TPS supercon-ducting cavity input coupler and high order mode damper (CPL/HOM). Brief description is shown in first section. The detail architecture and function of the designed signal monitoring system will be discussed in 2nd section. The 3rd section will have further description of interlocks for system protection. The final section would summarize the water quality monitoring and cooling system in this article.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY037  
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THPOR015 CEPC Bunch Lengthening and Cavity HOM Analysis resonance, cavity, collider, factory 3805
 
  • H.J. Zheng, J. Gao, Y. Wang
    IHEP, Beijing, People's Republic of China
  
  In this paper we will show the higher order mode (HOM) analysis of the cavity for the Circular Electron-Positron Collider (CEPC) partial double ring (PDR) scheme. In order to study the single bunch longitudinal instability in CEPC, bunch lengthening and energy spread are estimated based on Gao's theory. Different models are used to study the bunch lengthening and energy spread of the ring.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR015  
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THPOR043 High Power Test of X-band Single Cell HOM-free Choke-mode Damped Accelerating Structure made by Tsinghua University cavity, operation, vacuum, coupling 3881
 
  • X.W. Wu, H.B. Chen, J. Shi
    TUB, Beijing, People's Republic of China
  • T. Abe, T. Higo
    KEK, Ibaraki, Japan
  • W. Wuensch, H. Zha
    CERN, Geneva, Switzerland
  
  As an alternative design for CLIC main accelerating structures, X-band choke-mode damped structures had been studied for several years. However, the performance of choke-mode cavity under high power is still in lack of research. Two standing wave single cell choke-mode damped accelerating structures with different choke dimensions which are working at 11.424 GHz were designed, manufactured and bench tested by accelerator group in Tsinghua University. High power test was carried out on it to study the breakdown phenomenon in high gradient. A single cell structure without choke which almost has the same inner dimension as choke-mode cavity will also be tested to make a comparison and study how the choke affects high-gradient properties.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR043  
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