Keyword: damping
Paper Title Other Keywords Page
MOPMB008 Modeling and Experimental Studies of Beam Halo at ATF2 vacuum, scattering, coupling, optics 88
 
  • R.J. Yang, P. Bambade, V. Kubytskyi
    LAL, Orsay, France
  • A. Faus-Golfe, N. Fuster-Martínez
    IFIC, Valencia, Spain
  • T. Naito
    KEK, Ibaraki, Japan
  
  The Accelerator Test Facility 2 (ATF2) at KEK is a prototype of the final focus system for the next generation of Future Linear Colliders(FCL). It aims to focus the beams to tens of nanometer transverse sizes and to provide stability at the few nm level. Achieving these goals requires modelling, measuring and suppressing of the transverse beam halo before the interaction point (IP). This paper presents a beam tail/halo generator based on realistic model and the investigation of vertical and horizontal beam tail/halo distribution at ATF2.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB008  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPMW004 Realization and High Power Tests of Damped C-Band Accelerating Structures for the ELI-NP Linac vacuum, ion, HOM, klystron 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUOBB02 FACET-II Accelerator Research with Beams of Extreme Intensities positron, electron, linac, plasma 1067
 
  • V. Yakimenko, Y. Cai, C.I. Clarke, S.Z. Green, C. Hast, M.J. Hogan, N. Lipkowitz, N. Phinney, G.R. White, G. Yocky
    SLAC, Menlo Park, California, USA
  
  In 2016, the second phase of SLAC's x-ray laser, the LCLS-II, will begin to use part of the tunnel occupied by FACET, and the world's only multi-GeV facility for advanced accelerator research will cease operation. FACET-II is a new test facility to provide DOE with the unique capability to develop advanced acceleration and coherent radiation techniques with high-energy electron and positron beams. FACET-II is an opportunity to build on the decades-long experience developed conducting advanced accelerator R&D at the FFTB and FACET and re-deploy HEP infrastructure in continued service of its mission. FACET-II provides a major upgrade over current FACET capabilities and the breadth of the potential research program makes it truly unique. It will synergistically pursue accelerator science that is vital to the future of both advanced acceleration techniques for High Energy Physics, ultra-high brightness beams for Basic Energy Science, and novel radiation sources for a wide variety of applications. The presentation will discuss FACET-II project status and plans for diverse experimental program.  
slides icon Slides TUOBB02 [17.664 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB02  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPMB021 SLAC FACET-II Positron Damping Ring Magnet Design lattice, positron, dipole, magnet-design 1154
 
  • M.A.G. Johansson
    MAX IV Laboratory, Lund University, Lund, Sweden
  • Y. Cai, V. Yakimenko
    SLAC, Menlo Park, California, USA
  
  The FACET-II facility, currently being designed at SLAC, will contain a small ~20 m circumference, 335 MeV, positron damping ring. The ring has to fit in the existing linac tunnel, meaning that a compact lattice with short distances between magnets is required. The detailed magnet design is done in Opera-3d, with a finite element model of a full damping ring arc being simulated. This article presents this magnet design in a relatively early stage, with iteration between magnet and lattice design currently in progress.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMB021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPMR048 SPS Injection and Beam Quality for LHC Heavy Ions With 150 ns Kicker Rise Time injection, ion, kicker, proton 1360
 
  • B. Goddard, E. Carlier, L. Ducimetière, G. Kotzian, J.A. Uythoven
    CERN, Geneva, Switzerland
  • F.M. Velotti
    EPFL, Lausanne, Switzerland
  
  As part of the LHC Injectors Upgrade project for LHC heavy ions, the SPS injection kicker system rise time needs reduction below its present 225 ns. One technically challenging option under consideration is the addition of fast Pulse Forming Lines in parallel to the existing Pulse Forming Networks for the 12 kicker magnets MKP-S, targeting a system field rise time of 100 ns. An alternative option is to optimise the system to approach the existing individual magnet field rise time (2-98%) of 150 ns. This would still significantly increase the number of colliding bunches in LHC while minimising the cost and effort of the system upgrade. The observed characteristics of the present system are described, compared to the expected system rise time, together with results of simulations and measurements with 175 and 150 ns injection batch spacing. The expected beam quality at injection into LHC is quantified, with the emittance growth and simulated tail population taking into account expected jitter and synchronisation errors, damper performance and SPS non-linear optics behavior. The outlook for deployment is discussed, with the implications for LHC operation and HL-LHC performance.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMR048  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPMW008 Evolution of the Beam Parameters during Luminosity Production in the Future Circular Hadron Collider emittance, luminosity, collider, scattering 1426
 
  • X. Buffat, D. Schulte
    CERN, Geneva, Switzerland
  
  The evolution of the beam parameters during luminosity production in the Future Circular Hadron Collider (FCC-hh) is described based on basic models of the effect of synchrotron radiations, intra-beam scattering, luminosity burn-off and beam-beam limitations, allowing for an estimation of the luminosity performance in different running scenarios. It is shown that a large variations of the beam parameters is expected during a cycle. Potential operational schemes adapting to these variations are considered.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW008  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPMW011 Current Status of Instability Threshold Measurements in the LHC at 6.5 TeV octupole, impedance, simulation, electron 1434
 
  • L.R. Carver, J. Barranco, N. Biancacci, X. Buffat, W. Höfle, G. Kotzian, T. Lefèvre, T.E. Levens, E. Métral, T. Pieloni, B. Salvant, C. Tambasco
    CERN, Geneva, Switzerland
  • N. Wang
    IHEP, Beijing, People's Republic of China
  • M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  
  Throughout 2015, many measurements of the minimum stabilizing octupole current required to prevent coherent transverse instabilities have been performed. These measurements allow the LHC impedance model at flat top to be verified and give good indicators of future performance and limitations. The results are summarized here, and compared to predictions from the simulation code DELPHI.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW011  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPMW022 Modelling and Measurements of Bunch Profiles at the LHC Flat Bottom emittance, lattice, scattering, radiation 1477
 
  • S. Papadopoulou, F. Antoniou, J.E. Muller, Y. Papaphilippou, G. Trad
    CERN, Geneva, Switzerland
  
  At the LHC flat bottom the interplay between a series of effects (i.e. intrabeam scattering, longitudinal beam manipulations, non-linearities of the machine, etc) can lead to a population of the tails of the beam distributions, which may become non-Gaussian. This paper presents observations of the evolution of particle distributions in the LHC flat bottom. Novel distribution functions are employed to represent the beam profiles, and used as a guideline for generalising emittance growth rate estimations due to IBS. Finally, an attempt is made to benchmark an IBS Monte-Carlo simulation code, able to track 3D particle distributions, with the measured beam profile evolutions.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW022  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOR003 CSR-Driven Longitudinal Single Bunch Instability with Negative Momentum Compaction Factor synchrotron, shielding, radiation, electron 1651
 
  • P. Kuske
    HZB, Berlin, Germany
  
  Acceptable agreement is found between experimental results obtained at the Metrology Light Source (MLS) operated with negative momentum compaction factor, α, and theoretical estimates of the CSR-driven threshold currents. Theoretical instability thresholds are estimated by numerically solving the Vlasov-Fokker-Planck equation and/or by multi particle tracking and taking into account the shielded CSR-interaction. Some of the issues with the calculations, the determination of the theoretical thresholds as well as the derivation of a general scaling law will be presented  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR003  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOR004 Calculation of Transverse Coupled Bunch Instabilities in Electron Storage Rings Driven By Quadrupole Higher Order Modes HOM, quadrupole, impedance, dipole 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOR005 A Parallelized Vlasov-Fokker-Planck-Solver for Desktop PCs simulation, synchrotron, bunching, collective-effects 1658
 
  • P. Schönfeldt, M. Brosi, A.-S. Müller, J.L. Steinmann
    KIT, Karlsruhe, Germany
  
  In order simulate the dynamics of an electron bunch due to the self-interaction with its own coherent synchrotron radiation it is a well established method to numerically solve the Vlasov-Fokker-Planck equation. In this paper we present a new, modularly extensible program that uses OpenCL to massively parallelize the computation, allowing a standard desktop PC to work with appropriate accuracy and yield reliable results within minutes. We provide numerical stability studies of over a huge parameter range and comparisons of our numerical results to other techniques.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR005  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOR013 Analysis of Multi-bunch Instabilities at the Diamond Storage Ring impedance, wakefield, storage-ring, simulation 1685
 
  • R. Bartolini, R.T. Fielder, G. Rehm
    DLS, Oxfordshire, United Kingdom
  • V.V. Smaluk
    BNL, Upton, Long Island, New York, USA
  
  We present recent results of analytical, numerical and experimental analysis of multi-bunch instabilities at the Diamond storage ring. The works compares the impedance estimates from numerical modelling with the analysis of the growth rates of the excited multi-bunch modes in different machine configurations. The contribution of a number of wakefield sources has been identified with very high precision thanks to high quality data provided by the existing Transverse multi-bunch feedback diagnostics  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR013  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPOR027 Interaction of RF Phase Modulation and Coupled-Bunch Instabilities at the DELTA Storage Ring storage-ring, electron, feedback, synchrotron 1720
 
  • M. Sommer, B.D. Isbarn, B. Riemann, T. Weis
    DELTA, Dortmund, Germany
  
  Funding: Work supported by the BMBF under contract no. 05K13PEB.
Analyzing the interaction of RF phase modulation and coupled-bunch instabilities requires a method to determine damping rates of coupled-bunch modes at presence of RF phase modulation. This paper shows, that the common way of using exponential fits to determine damping rates is not viable for high modulation amplitudes. It presents a new method, which is capable of acquiring damping rates of coupled-bunch modes for phase shifts up to 5°, using a bunch-by-bunch feedback system. For this purpose a specific mode is excited by the feedback system and the saturation value, i.e. the maximum excitation, is measured to calculate the damping rate. With this new method, the modulation amplitude of the RF phase modulation is swept from 0° to 5° and it can be shown, that the damping rate is proportional to the square of the modulation amplitude. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR027  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMB028 High HOM Damping Structure Study for CEPC cavity, HOM, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMB045 Measurement of Higher Order Modes Electrodynamic Characteristics for Array of Two 2400 MHz Cavities HOM, cavity, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMB047 Higher Order Modes Couplers for 800 MHz Harmonic Cavity HOM, cavity, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMB048 Macros for Identification of Higher Order Modes Types, Their Transverse Shunt Impedance and Kick Factor HOM, cavity, higher-order-mode, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMR040 HOM Absorber Study by Photon Diffraction Model HOM, photon, cavity, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMR042 Ridge Waveguide HOM Damping Scheme for High Current SRF Cavity HOM, cavity, linac, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW002 A CLIC Damping Wiggler Prototype at ANKA: Commissioning and Preparations for a Beam Dynamics Experimental Program wiggler, storage-ring, operation, simulation 2412
 
  • A. Bernhard, S. Casalbuoni, S. Gerstl, J. Gethmann, A.W. Grau, E. Huttel, A.-S. Müller, D. Saez de Jauregui, N.J. Smale
    KIT, Karlsruhe, Germany
  • A.V. Bragin, S.V. Khrushchev, N.A. Mezentsev, V.A. Shkaruba, V.M. Tsukanov, K. Zolotarev
    BINP SB RAS, Novosibirsk, Russia
  • P. Ferracin, L. Garcia Fajardo, Y. Papaphilippou, H. Schmickler, D. Schoerling, P. Zisopoulos
    CERN, Geneva, Switzerland
  
  Funding: This work is partially funded by the German Federal Ministry of Education and Research under grant 05K12VK1
In a collaboration between CERN, BINP and KIT a prototype of a superconducting damping wiggler for the CLIC damping rings has been installed at the ANKA synchrotron light source. On the one hand, the foreseen experimental program aims at validating the technical design of the wiggler, particularly the conduction cooling concept applied in its cryostat design, in a long-term study. On the other hand, the wiggler's influence on the beam dynamics particularly in the presence of collective effects is planned to be investigated. ANKA's low-alpha short-bunch operation mode will serve as a model system for these studies on collective effects. To simulate these effects and to make verifiable predictions an accurate model of the ANKA storage ring in low-alpha mode, including the insertion devices is under parallel development. This contribution reports on the first operational experience with the CLIC damping wiggler prototype in the ANKA storage ring and steps towards the planned advanced experimental program with this device. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW002  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW003 NONLINEAR OPTIMIZATION OF CLIC DRS NEW DESIGN WITH VARIABLE BENDS AND HIGH FIELD WIGGLERS dipole, emittance, dynamic-aperture, sextupole 2416
 
  • H. Ghasem, J. Alabau-Gonzalvo, F. Antoniou, S. Papadopoulou, Y. Papaphilippou
    CERN, Geneva, Switzerland
  
  The new design of CLIC damping rings is based on longitudinal variable bends and high field superconducting wiggler magnets. It provides an ultra-low horizontal normalised emittance of 412 nm-rad at 2.86 GeV. In this paper, nonlinear beam dynamics of the new design of the damping ring (DR) with trapezium field profile bending magnets have been investigated in detail. Effects of the misalignment errors have been studied in the closed orbit and dynamic aperture.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW003  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW008 Possible Beam Parameters in Double RF Operation of the CERN LHC operation, emittance, synchrotron, SRF 2430
 
  • E.N. Shaposhnikova, J. F. Esteban Müller
    CERN, Geneva, Switzerland
  
  The LHC operates using a 400 MHz SC RF system. A 200 MHz NC RF system was foreseen in the LHC Design Report to improve beam capture and the bare resonators were manufactured, but never installed. Later the second harmonic RF system was proposed to cure longitudinal beam instabilities in the absence of a dedicated wideband feedback system in the LHC. For nominal intensities the longitudinal beam stability is ensured by controlled emittance blow-up during the acceleration ramp. Recently slow growing instabilities were observed at the end of long fills at 6.5 TeV as bunches shrink due to synchrotron radiation damping. For High Luminosity LHC twice higher intensities should be kept stable with new equipment installed in the ring. Additional motivations for a second RF system in the LHC have also been considered. Operation with an extra RF system is limited by the required RF configuration (phase between the two RF systems) and longitudinal beam stability. In this work requirements for the double RF systems are analyzed together with a possible range of longitudinal beam parameters.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW008  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW016 Towards a Small Emittance Design of the JLEIC Electron Collider Ring emittance, dipole, electron, optics 2457
 
  • F. Lin, Y.S. Derbenev, A. Hutton, V.S. Morozov, F.C. Pilat, Y. Zhang
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
The electron collider ring of the Jefferson Lab Electron-Ion Collider (JLEIC) is designed to provide an electron beam with a small beam size at the IP for collisions with an ion beam in order to reach a desired high luminosity. For a chosen beta-star at the IP, electron beam size is determined by the equilibrium emittance that can be obtained through a linear optics design. This paper briefly describes the baseline design of the electron collider ring reusing PEP-II components and considering their parameters (such as dipole sagitta, magnet field strengths and acceptable synchrotron radiation power) and reports a few approaches to reducing the equilibrium emittance in the electron collider ring. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW016  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW020 Storage-ring Electron Cooler for Relativistic Ion Beams electron, storage-ring, ion, emittance 2466
 
  • F. Lin, Y.S. Derbenev, D. Douglas, J. Guo, G.A. Krafft, V.S. Morozov, Y. Zhang
    JLab, Newport News, Virginia, USA
  • R.P. Johnson
    Muons, Inc, Illinois, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357
Application of electron cooling at ion energies above a few GeV has been limited due to reduction of electron cooling efficiency with energy and difficulty in producing and accelerating a high-current high-quality electron beam. A high-current storage-ring electron cooler offers a solution to both of these problems by maintaining high cooling beam quality through naturally-occurring synchrotron radiation damping of the electron beam. However, the range of ion energies where storage-ring electron cooling can be used has been limited by low electron beam damping rates at low ion energies and high equilibrium electron energy spread at high ion energies. This paper reports a development of a storage ring based cooler consisting of two sections with significantly different energies: the cooling and damping sections. The electron energy and other parameters in the cooling section are adjusted for optimum cooling of a stored ion beam. The beam parameters in the damping section are adjusted for optimum damping of the electron beam. The necessary energy difference is provided by an energy recovering SRF structure. A prototype linear optics of such storage-ring cooler is presented. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW020  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW039 JLEIC SRF Cavity RF Design cavity, impedance, HOM, electron 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPMW042 Trapped Modes Study and BBU Analysis in the 5-Cell 650 MHz Cavity HOM, cavity, impedance, electron 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPOW035 Commissioning of the Harmonic Cavities in the MAX IV 3 GeV Ring cavity, resonance, storage-ring, synchrotron 2911
 
  • G. Skripka, Å. Andersson, A.M. Mitrovic, P.F. Tavares
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F.J. Cullinan, R. Nagaoka
    SOLEIL, Gif-sur-Yvette, France
  
  The MAX IV 3 GeV storage ring operates with beam of high current and ultralow emittance. These beam parameters in combination with the small effective aperture enhance possible collective beam instabilities. Three passive harmonic cavities are installed to introduce bunch lengthening and tune spread, leading to decoupling of the bunch spectrum from the machine effective impedance and mitigating instabilities by Landau damping respectively. In this paper we present the first results of the commissioning of the passive third harmonic cavities in the MAX IV 3 GeV ring. The additional harmonic cavity potential significantly improved the beam lifetime. First observations of the harmonic cavity effect on the damping of collective beam instabilities are discussed.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW035  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPOY030 First BTF Measurements at the Large Hadron Collider octupole, injection, betatron, simulation 3051
 
  • C. Tambasco, A. Boccardi, X. Buffat, K. Fuchsberger, M. Gąsior, R. Giachino, T. Lefèvre, T.E. Levens, T. Pieloni, M. Pojer, B. Salvachua, M. Solfaroli Camillocci
    CERN, Geneva, Switzerland
  • J. Barranco, C. Tambasco
    EPFL, Lausanne, Switzerland
  
  During the Run I in 2012, several instabilities have been observed at the Large Hadron Collider (LHC) during the Betatron squeeze. The predictions of instability thresholds are based on the computation of the beam Landau damping by calculating the Stability Diagrams (SD). These instabilities could be explained by a deterioration of the SD due to beam-beam resonance excitation which could change the particle distributions. Beam Transfer Functions (BTF) provide a measurement of the Stability Diagram. The BTFs are sensitive to the particle detuning with amplitude as well as to the particle distributions therefore they represent a powerful tool to understand experimentally the stability of beams during the LHC operational cycle. First BTF measurements at the LHC are presented for different machine configurations and settings and compared to predictions.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY030  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPOY059 Axisymmetric Numerical Studies of Higher Order Mode Damping Techniques using Ring Ferrites for BESSY VSR cavity, HOM, 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  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPMR031 Turn-by-Turn Measurements for Beam Dynamics at Vepp-5 Damping Ring impedance, betatron, lattice, vacuum 3452
 
  • M.F. Blinov, K.V. Astrelina, V.V. Balakin, O.I. Meshkov, A.A. Starostenko
    BINP SB RAS, Novosibirsk, Russia
  • V.L. Dorokhov
    BINP, Novosibirsk, Russia
  
  Preinjector complex VEPP-5 is being constructed for high rate production and acceleration of electrons and positrons beams up to energy 510 MeV. Both kinds of particles accumulated in the damping ring and after achieving of needed intensity the beams would be transported alternatively to VEPP-3/VEPP-4M or to BEP/VEPP-2000 colliders. At this paper basic parameters of damping ring presented. All measurements were carried out for electron beam with energy 385 MeV. For turn-by-turn measurements 12 beam position monitors were used. In order to improve precision of measured value NAFF algorithm was applied. For measurements of longitudinal beam profile optical phi-dissector was used.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMR031  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPMW032 Measurements on Magnetic Cores for Inductive Adders with Ultra-Flat Output Pulses for CLIC DR Kickers kicker, flattop, collider, emittance 3619
 
  • J. Holma, M.J. Barnes, L. Ducimetière
    CERN, Geneva, Switzerland
  
  The CLIC study is investigating the technical feasibility of an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC pre-damping rings and damping rings (DRs) will produce ultra-low emittance beam with high bunch charge. To avoid beam emittance increase, the DR kicker systems must provide extremely flat, high-voltage, pulses. The specifications for the DR extraction kickers call for 160 ns duration flattop pulses of ±12.5 kV, with a combined ripple and droop of not more than ±0.02 % (±2.5 V). An inductive adder is a very promising approach to meet the specifications. Two five layer, 3.5 kV, prototype inductive adders have been built at CERN, and used to test passive and active analogue modulation methods to compensate droop and ripple of the output pulses. Recently, magnetic core materials and full-scale magnetic cores have been evaluated for the 12.5 kV prototype inductive adders. These results are presented in this paper and conclusions are drawn concerning the design of the full-scale prototypes.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW032  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPMW034 Review on the Effects of Characteristic Impedance Mismatching in a Stripline Kicker impedance, kicker, extraction, emittance 3627
 
  • C. Belver-Aguilar, M.J. Barnes, L. Ducimetière
    CERN, Geneva, Switzerland
  
  A stripline kicker operates as two coupled transmission lines, with two TEM operating modes, known as odd and even modes. The characteristic impedance of these two modes is generally different, both only tend to the same value either when the electrodes are widely separated or when the electrodes are very close to the beam pipe wall. In all other cases, the even mode characteristic impedance is always higher than the odd mode characteristic impedance. The specifications required for a kicker operating in a low emittance ring are usually very challenging. In this situation it is desirable to match the even mode characteristic impedance of the striplines to the resistance of their termination. However a mismatched odd mode impedance can significantly influence the striplines performance. This paper presents predictions for the influence of the odd mode characteristic impedance upon the contribution of each field component, electric and magnetic, to the deflection angle. In addition, the variation of the characteristic impedance and field homogeneity with frequency are presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMW034  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPOR045 Analytical Estimation of ATF Beam Halo Distribution scattering, emittance, vacuum, electron 3888
 
  • D. Wang, J. Gao
    IHEP, Beijing, People's Republic of China
  • P. Bambade
    LAL, Orsay, France
  • T. Naito
    KEK, Ibaraki, Japan
  
  Funding: Work supported by the National Foundation of Natural Sciences (11505198 and 11575218)
Halo distribution is a key topic for background study. This paper has developed an analytical method to give an estimation of ATF beam halo distribution. The equilibrium particle distribution of the beam tail in the ATF damping ring is calculated analytically with different emittance and different vacuum degree. The analytical results agree the measurements very well. This is a general method which can be applied to any electron rings. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR045  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPOY043 Time Scale of Crab Cavity Failures Relevant for High Luminosity LHC cavity, resonance, luminosity, simulation 4196
 
  • K.N. Sjobak, R. Bruce, H. Burkhardt, A. Macpherson, A. Santamaría García
    CERN, Geneva, Switzerland
  • R. Kwee-Hinzmann
    Royal Holloway, University of London, Surrey, United Kingdom
  • A. Santamaría García
    EPFL, Lausanne, Switzerland
  
  Funding: Research supported by the High Luminosity LHC project
A good knowledge of the effects of the crab cavities, required for the baseline High Luminosity LHC (HL-LHC), is needed before the results of the first tests of crab cavity prototypes in the SPS, planned for 2018, will be available. In case of crab cavity failures, we have to make sure that time scales are long enough so that the beams can be cleanly dumped before damage by beam loss occurs. We discuss our present knowledge and modeling of crab cavity induced beam losses, combined with mechanical deformation. We discuss lower limits on the time scales required for safe operation, and possible failure mitigation methods. 		 
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY043  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)