Keyword: resonance
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MOPG43 Beam Tuning for Longitudinal Profile at J-PARC Linac emittance, linac, quadrupole, DTL 150
  • A. Miura
    JAEA/J-PARC, Tokai-mura, Japan
  • Y. Liu, T. Maruta
    KEK/JAEA, Ibaraki-Ken, Japan
  • T. Miyao
    KEK, Ibaraki, Japan
  Using bunch shape monitors (BSMs), we measured the longitudinal bunch lengths of negative hydrogen ion beams in the J-PARC linac. A BSM was installed between two linacs, separate-type drift tube linac (SDTL) and an annular-ring-coupled structure linac (ACS), having acceleration frequencies of 324 and 972 MHz, respectively. We used radio-frequency amplitude modulation of bunches in the beam transport between the SDTL and ACS to minimize emittance growth and beam loss. We conducted amplitude scanning and compared the results with the twiss-parameters obtained from the transverse profiles. In this paper, we discuss the results of amplitude tuning of the buncher cavity at the point of beam loss and emittance. We also discuss the measurement results for various equipartitioning settings of quadrupole magnets.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-MOPG43  
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TUPG12 Design for the Diamond Longitudinal Bunch-by-Bunch Feedback Cavity cavity, impedance, HOM, coupling 340
  • A.F.D. Morgan, G. Rehm
    DLS, Oxfordshire, United Kingdom
  In 2017 it is planned to install some additional normal conducting cavities into the Diamond storage ring. In order to deal with the potential higher order modes in these we are designing a longitudinal bunch-by-bunch feedback system. This paper will focus on the design of the overloaded cavity kicker, adapted to the Diamond beam pipe cross section. The design has evolved in order to reduce the strong 3rd harmonic resonance seen on the introduction of the racetrack beam pipe. Through a combination of geometry optimisation and the addition of integrated taper transitions this harmonic has been greatly reduced while also minimising sharp resonances below 15GHz. The major features will be described, as well as the expected performance parameters.  
poster icon Poster TUPG12 [1.423 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG12  
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TUPG18 Design Optimization of Button-Type BPM Electrode for the SPring-8 Upgrade impedance, simulation, storage-ring, vacuum 360
  • M. Masaki, H. Dewa, T. Fujita, S. Takano
    JASRI, Hyogo, Japan
  • H. Maesaka, S. Takano
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  The requirements for a BPM system for the SPring-8 upgrade are long-term stability, sufficient signal intensity and high accuracy*. The design of a button-type electrode for the BPM has been optimized from the perspectives of 1) mechanical structure, 2) rf characteristics, 3) thermal issue. We have adopted the electrode structure without a sleeve enclosing the button to maximize the button diameter for the narrow aperture of the vacuum chamber. The absence of an annular slot around the sleeve in a lodging hole for the electrode eliminates the associated beam impedance. To minimize the beam impedance and the trapped mode heating of the electrode, the rf structure has been optimized by 3D electro-magnetic simulations. To suppress the ohmic loss on the button and center pin thermally isolated from the water cooled BPM block, we have selected molybdenum as a material with high electric and thermal conductivities. The reduction of the heating suppresses thermal deformation of the electrode and the BPM block, and improves thermal stability of the BPM system. The mechanical tolerance of the electrode was defined to fit the error budget for the total BPM offset error of 0.1 mm rms.
* H. Maesaka et al., in this conference.
poster icon Poster TUPG18 [1.104 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG18  
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WECL03 Measurement of the Beam Response to Quadrupole Kick by Using Stripline Pickup Monitor at J-PARC Main Ring kicker, quadrupole, betatron, operation 604
  • Y. Nakanishi, A. Ichikawa, A. Ichikawa, A. Minamino, K.G. Nakamura, T. Nakaya
    Kyoto University, Kyoto, Japan
  • T. Koseki, H. Kuboki, M. Okada, T. Toyama
    KEK, Tokai, Ibaraki, Japan
  Funding: Work supported by MEXT KAKENHI, GA 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled "Unification and Development of the Neutrino Science Frontier"
In high intensity proton synchrotrons, linear and nonlinear betatron resonances cause beam loss. When the betatron tune spreads over a resonance line, the oscillation amplitude will get larger, causing a large beam loss. Our study aims for a direct measurement of the betatron tune spread by using a quadrupole kicker and a 4-electrode monitor. The monochromatic rf signal is inputted to the kicker and we induce an oscillation by kicking the beam. The amplitude of the quadrupole oscillation will depend on the number of particles having a certain tune. In the beam test at J-PARC MR, the dipole kicker was used as a quadrupole kicker by exciting the two facing electrodes in-phase. We measured the response to the kick at several frequencies. We observed that the amplitude depends on the kicker frequency and the number of particles per bunch. This demonstrates that the quadrupole oscillation can be induced by a kicker and the possibility of measuring the number of a particular tune particle from the response. We will present the result of the beam test and our prospect and the comparison between the experimental result and a numerical calculation.
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WECL03  
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WEPG32 First Heating with the European XFEL Laser Heater laser, electron, undulator, interaction-region 694
  • M. Hamberg
    Uppsala University, Uppsala, Sweden
  • F. Brinker, M. Scholz
    DESY, Hamburg, Germany
  Funding: DESY and Swedish Research council
The European XFEL is a 3.4 km long free-electron laser (FEL) which will deliver radiation in the wavelength regime of 0.05 to 4.7 nm. To avoid problems with longitudinal microbunching instabilities a laser heater is implemented. It heats up the electron bunches which will improve the overall brightness level of the FEL. I report the commissioning steps undertaken and the first recorded heating outputs observed in the injector section.
poster icon Poster WEPG32 [2.322 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG32  
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WEPG41 Measurement of Coupling Impedances using a Goubau Line impedance, simulation, coupling, scattering 719
  • F. Stulle, J.F. Bergoz
    BERGOZ Instrumentation, Saint Genis Pouilly, France
  • H.-W. Glock
    HZB, Berlin, Germany
  Longitudinal coupling impedances can be deduced from S-Parameter measurements performed on a Goubau Line. The Goubau Line, also known as single wire line, is a variant of the coaxial wire method. Both setups use a wire for mimicking the particle beam. Coaxial tapers at the wire ends adapt wave impedance to the 50ohm impedance of coaxial cables, sources and receivers. But for guiding the electromagnetic wave, the Goubau Line relies on the realistic boundary conditions imposed by an insulated wire instead of using a coaxial shield. Equations for the deduction of longitudinal coupling impedances are reviewed and applied to Goubau Line measurements. Goubau Line measurements and CST Studio simulations are compared, showing good agreement.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG41  
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