Keyword: resonance
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MOOP07 Development of Ultracold Neutron Accelerator for Time Focusing of Pulsed Neutrons neutron, cavity, focusing, controls 56
 
  • S. Imajo
    Kyoto University, Kyoto, Japan
  • T. Ino, K. Mishima
    KEK, Ibaraki, Japan
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • M. Kitaguchi, H.M. Shimizu
    Nagoya University, Nagoya, Japan
  • S. Yamashita
    ICEPP, Tokyo, Japan
 
  Low energy neutron accelerator can be realized by the combination of an adiabatic fast passage spin flipper and a gradient magnetic field. Neutrons have magnetic moments, so that the accumulated potential energies are not cancelled before and after passage of a magnetic field and their kinetic energies change in case their spins are flipped in the field. This accelerator handles lower kinetic energy neutrons than approximately 300 neV. Currently we have developed the advanced version which makes it possible to handle broader kinetic energy range. The design and measured characteristics are described.  
slides icon Slides MOOP07 [1.313 MB]  
poster icon Poster MOOP07 [1.389 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOOP07  
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MOPLR015 Thermal-Mechanical Study of 3.9 GHz CW Coupler and Cavity for LCLS-II Project cavity, simulation, cryomodule, linac 171
 
  • I.V. Gonin, E.R. Harms, T.N. Khabiboulline, N. Solyak, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  Third harmonic system was originally developed by Fermilab for FLASH facility at DESY and then was adopted and modified by INFN for the XFEL project [1-3]. In contrast to XFEL project, all cryomodules in LCLS-II project will operate in CW regime with higher RF average power for 1.3 GHz and 3.9 GHz cavities and couplers. Design of the cavity and fundamental power coupler has been modified to satisfy LCLS-II requirements. In this paper we discuss the results of COMSOL thermal and mechanical analysis of the 3.9 GHz coupler and cavity to verify proposed modifica-tion of the design. For the dressed cavity we present simulations of Lorentz force detuning, helium pressure sensitivity df/dP and major mechanical resonances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR015  
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MOPLR018 Upgrade of the Klystron Modulator of the L-Band Electron Linac at Osaka University for Higher Stability klystron, impedance, linac, high-voltage 178
 
  • K. Furukawa, G. Isoyama
    ISIR, Osaka, Japan
  • R. Kato
    KEK, Ibaraki, Japan
  • K. Kawase
    HSRC, Higashi-Hiroshima, Japan
  • A. Tokuchi
    Pulsed Power Japan Laboratory Ltd., Kusatsu-shi Shiga, Japan
 
  The klystron modulator for the L-band linac is upgraded for higher stability. The two-step charging system for the pulse forming network (PFN) is upgraded by adding a high impedance resonant charging line in parallel with the main line. The charging step of the PFN voltage is reduced considerably near the setting value by switching the main resonance line off so that the charging current flows only through the high impedance line. The second model of the solid-state switch is developed using 60 static-induction thyristors, ten of which are connected in series with six such series connected in parallel to meet maximum specifications of 25 kV and 6 kA. The air-cooling capacity is reinforced so that repetition rate is increased from 10 pps for the first model to 60 pps. The fluctuation and accuracy of the klystron voltage are measured to be 7.8×10-6 or 7.8 ppm for the upgraded klystron modulator using a differential amplifier with much higher sensitivity than one used in the previous measurement.  
poster icon Poster MOPLR018 [0.840 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MOPLR018  
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TU2A03 Resonance Control for Future Linear Accelerators cavity, controls, SRF, electron 363
 
  • W. Schappert
    Fermilab, Batavia, Illinois, USA
 
  Many of the next generation of particle accelerators (LCLS II, PIP II) are designed for relatively low beam loading. Low beam loading requirement means the cavities can operate with narrow bandwidths, minimizing capital and base operational costs of the RF power system. With such narrow bandwidths, however, cavity detuning from microphonics or dynamic Lorentz Force Detuning becomes a significant factor, and in some cases can significantly increase both the acquisition cost and the operational cost of the machine. In addition to the efforts to passive environmental detuning reduction (microphonics) active resonance control for the SRF cavities for next generation linear machine will be required. State of the art in the field of the SRF Cavity active resonance control and the results from the recent efforts at FNAL will be presented in this talk.  
slides icon Slides TU2A03 [0.897 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TU2A03  
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TUPRC021 Low-Temperature Properties of 2.6-Cell Cryogenic C-Band RF-Gun Cold Model Cavity cavity, gun, cryogenics, experiment 462
 
  • T. Sakai, M. Inagaki, K. Nakao, K. Nogami, K. Takatsuka, T. Tanaka
    LEBRA, Funabashi, Japan
  • M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
    KEK, Ibaraki, Japan
 
  Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
Development of a cryogenic C-band photocathode RF gun cavity has been conducted at Nihon University in collaboration with KEK. Improved dimensions of the RF input coupler and the 2.6-cell accelerating structure from the first cold model were determined using the 3D simulation code CST Studio. The high-purity copper cavity was fabricated at KEK with ultraprecision machining and diffusion bonding technique. The low level RF properties of the cavity measured at room temperature have been in good agreement with the predictions based on the CST Studio calculation. Preparations for the 20-K cooling tests of the cavity are underway in KEK and Nihon University. The design of the improved cavity and the results of the cold test at low temperature will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPRC021  
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TUPLR057 Advanced Design Optimizations of a Prototype for a Newly Revised 4-Rod CW RFQ for the HLI at GSI rfq, dipole, simulation, impedance 586
 
  • D. Koser, H. Podlech
    IAP, Frankfurt am Main, Germany
  • P. Gerhard, L. Groening
    GSI, Darmstadt, Germany
  • O.K. Kester
    TRIUMF, Vancouver, Canada
 
  Within the scope of the FAIR project (Facility for Antiproton and Ion Research) at GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, the front end of the existing High Charge State Injector (HLI) is upgraded for cw operation. The dedicated new 4-Rod RFQ structure is currently being designed at the Institute for Applied Physics (IAP) of the Goethe University of Frankfurt. The overall design is based on the RFQ structures that were originally developed for FRANZ* and MYRRHA**. Regarding the HLI-RFQ the comparatively low operating frequency of 108 MHz causes a general susceptibility towards mechanical vibrations especially concerning the electrodes because of the necessarily larger distance between the stems. Besides RF simulations and basic thermal simulations with CST Studio Suite, the key issues like mechanical electrode oscillations as well as temperature distribution from heat loss in cw operation are investigated with simulations using ANSYS Workbench. At first instance a dedicated 6-stem prototype is currently being manufactured in order to validate the simulated RF performance, thermal behavior and structural mechanical characteristics.
*M. Heilmann et al., A Coupled RFQ-IH Cavity for the Neutron Source FRANZ, IPAC13
**C. Zhang, H. Podlech, New Reference Design of the European ADS RFQ Accelerator For MYRRHA, IPAC14
 
poster icon Poster TUPLR057 [1.484 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TUPLR057  
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THOP06 Novel Scheme to Tune RF Cavities Using Reflected Power cavity, controls, DTL, TRIUMF 757
 
  • R. Leewe, K. Fong, Z. Shahriari
    TRIUMF, Vancouver, Canada
  • M. Moallem
    SFU, Surrey, Canada
 
  Tuning of the natural resonance frequency of an RF cavity is essential for accelerator structures to achieve efficient beam acceleration and to reduce power requirements. Typically operational cavities are tuned using phase comparison techniques. The phase measurement is subject to temperature drifts and renders this technique labor and time intensive. To eliminate the phase measurement, reduce human oversight and speed up the start-up time for each cavity, this paper presents a control scheme that relies solely on the reflected power measurements. A sliding mode extremum seeking algorithm is used to minimize the reflected power. To avoid tuning motor abrasion, a variable gain minimizes motor movement around the optimum operating point. The system has been tested and is fully commissioned on two drift tube linear accelerator tanks in TRIUMF's ISAC I linear accelerator. Experimental results show that the resonance frequency can be tuned to its optimum operating point while the start-up time of a single cavity and the accompanied human oversight are significantly decreased.  
poster icon Poster THOP06 [0.244 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THOP06  
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THPRC012 Resonance Control System for the CEBAF Separator Upgrade cavity, controls, LLRF, extraction 792
 
  • T. E. Plawski, R. Bachimanchi, B. Bevins, L. Farrish, C. Hovater, G.E. Lahti, M.J. Wissmann
    JLab, Newport News, Virgina, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of four new 748.5 MHz normal conducting deflecting cavities in the 5th pass extraction region. The RF system employs two digital LLRF systems controlling four normal conducting cavities in a vector sum setting. Cavity tune information of the individual cavities is obtained using a multiplexing scheme of the forward and reflected RF signals. Water skids equipped with heaters and valves are used to control resonance. A new FPGA-based hardware and EPICS-based predictive control algorithm has been developed to support reliable operation of the beam extraction process. This paper presents the architecture design of the existing hardware and software as well as a plan to develop a model predictive control system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPRC012  
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THPLR006 Design Study of a Test Cavity for Evaluating RF Critical Magnetic Field of Thin-Film Superconductor cavity, target, electromagnetic-fields, cryogenics 852
 
  • H. Oikawa
    Utsunomiya University, Utsunomiya, Japan
  • H. Hayano, S. Kato, T. Kubo, T. Saeki
    KEK, Ibaraki, Japan
  • T. Higashiguchi
    Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
  • M. Hino
    Kyoto University, Research Reactor Institute, Osaka, Japan
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
 
  Superconducting cavities of higher gradient has been demanded in various fields of the accelerator science. Also, according to the Technical Design Report (TDR) of International Linear Collider (ILC), the higher gradient of 45 MV/m is required in the second stage of ILC. To realize such higher gradient, several methods are proposed. One of such methods is to coat multi-layer thin-film superconductor on the inner surface of RF cavity where the thin film increases the RF critical field on the inner surface of the cavity. To demonstrate the RF performance of thin-film structure on a small coupon sample, we designed the RF mushroom-shaped cavity with which the RF critical magnetic field is measured on a thin-film coupon sample set on the inner surface of the cavity. If the RF cavity is cooled down below the critical temperature of thin-film superconductor with supplying RF power, the heat dissipation might be measured on the coupon sample in the cavity. We designed the shape of the cavity so as to produce a strong RF magnetic field parallel to the sample surface efficiently. We report the design, manufacturing and RF property measurements of the cavity in this presentation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR006  
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THPLR011 Traveling Wave Accelerating Structure Power Input Calculation With Equivalent Circuit Method coupling, impedance, operation, interface 864
 
  • S.V. Matsievskiy, V.I. Kaminskiy
    MEPhI, Moscow, Russia
 
  Nowadays linac accelerating RF systems design is usually done by the finite difference method. It provides high accuracy of calculations and freedom in topology choosing, but may draw considerable amounts of computer resources with long calculation times. Alternative to this method, equivalent circuit method exists. The basic idea of this method is to build a lumped element circuit, which with certain approximation acts as an original accelerating cell. It drastically reduces the number of equations to solve. This method is long known but usually only used for the particular accelerating structures when speed of calculation is a key-factor. This paper describes an attempt to create more universal and user-friendly software application for calculating electrical field distribution in accelerating structures, provides mathematical equations this software is based on. The resulting application may be used for preliminary calculations of acceleration structures and help to determine cells electrodynamic parameters reducing overall design time.  
poster icon Poster THPLR011 [0.789 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR011  
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THPLR036 SRF Low-Beta Elliptical Resonator Two-Ring Stiffening cavity, simulation, SRF, vacuum 929
 
  • E.N. Zaplatin
    FZJ, Jülich, Germany
  • I.V. Gonin, T.N. Khabiboulline, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
 
  Elliptical SRF cavities are the basic accelerating structures for the high energy part of many accelerators. Since a series of external loads on the resonator walls predetermine the main working conditions of the SC cavities the detailed investigation of their mechanical properties should be conducted in parallel with the main RF design. The effects of very high electromagnetic fields that result in strong Lorentz forces and the pressure on cavity walls from the helium tank that also deforms the cavity shape, the tuning scheme resulting in the change of accelerating field profile and mechanical eigen resonances of cavities which are the main source of the microphonics must be taken into account during integrated design of the resonator and its liquid helium vessel. SRF elliptical cavities for the medium energies (β=v/c is around 0.6) inherently have more flexible shape and their ultimate stiffening with a "standard" stiffening rings installed between resonator cells becomes problematic. The second row of the rings should enhance the overall cavity rigidity. In the paper we report the basic investigations of the cavity two-row ring stiffening using FNAL 650 MHz β=0.61 as an example. The single-cell investigation results were used as the reference to develop the ultimate scheme of the helium vessel structure to ensure the best resonator stability.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR036  
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THPLR038 Resonance Control for Narrow Bandwidth PIP-II Cavities cavity, flattop, SRF, FPGA 936
 
  • W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov
    Fermilab, Batavia, Illinois, USA
 
  The PIP-II project at FNAL calls for a SRF pulsed proton driver linac to support the expanding neutrino physics program including DUNE/LBNF. The relatively low beam current and high quality factors called for in the design means that these cavities will be operated with small RF bandwidths, meaning that they will be sensitive to microphonics. Combined with a 20 Hz pulsed operational structure and the use of four different, complex cavity geometries means that resonance control will be extremely challenging. Work is ongoing at FNAL to develop active resonance stabilization techniques using fast piezoelectric tuners in support of PIP-II. These techniques as well as testing and development results using a prototype, dressed low-beta single-spoke cavity will be presented along with an outlook for future efforts.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR038  
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THPLR059 Status of a 325 MHz High Gradient CH - Cavity cavity, linac, ion, operation 982
 
  • A. Almomani, U. Ratzinger
    IAP, Frankfurt am Main, Germany
 
  Funding: BMBF with contract number 05P12RFRB9
The reported linac developments aim on compact ion accelerators and on an increase of the effective accelerat-ing field (voltage gain per meter). Within a funded pro-ject, a high gradient Crossbar H-type CH-cavity operat-ed at 325 MHz was developed and successfully built at IAP-Frankfurt. The effective accelerating field for this cavity is expected to reach about 13.3 MV/m at a beam energy of 12.5 AMeV, corresponding to β=0.164. The results from this cavity might influence the later energy upgrade of the Unilac at GSI Darmstadt. The aim is a compact pulsed high current ion accelerator for significantly higher energies up to 200 AMeV. Detailed investigations for two different types of copper plating (high lustre and lustre less) with respect to the high spark limit will be performed on this cavity. The 325 MHz GSI 3 MW klystron test stand is best suited for these investigations. Additionally, operating of normal conducting cavities for the case of very short RF pulses will be discussed at cryogenic temperature.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR059  
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