Author: Grudiev, A.
Paper Title Page
MOPC021 Design of a Choke-mode Damped Accelerating Structure for CLIC Main Linac 113
 
  • J. Shi, A. Grudiev, W. Wuensch
    CERN, Geneva, Switzerland
  • H. Chen, W.-H. Huang, C.-X. Tang, H. Zha
    TUB, Beijing, People's Republic of China
 
  Choke-mode damped accelerating structures are being studied as an alternative to the CLIC baseline structure by a CERN-Tsinghua collaboration. Choke-mode structures hold the potential for much lower levels of pulsed surface heating and, since milling is not needed, reduced cost. Structures with radial choke attached are simulated in Gdfidl to investigate the damping of the transverse wake. The first pass-band of the dipole modes is well damped, while the higher order dipole modes are possible to be reflected by the choke. Therefore, the geometry of the choke is tuned to minimize the reflection of these higher order dipoles. Based on this damping scheme, an accelerating structure with the same iris dimensions as the nominal CLIC design but with choke-mode damping has been designed. A prototype structure will be manufactured and high power tested in the near future.  
 
MOPC037 Engineering Design and Fabrication of X-band Damped Detuned Structure for the CLIC Study 154
 
  • V. Soldatov, D. Gudkov, A. Samoshkin
    JINR, Dubna, Moscow Region, Russia
  • S. Atieh, A. D'Elia, A. Grudiev, G. Riddone
    CERN, Geneva, Switzerland
  • R.M. Jones, V.F. Khan
    UMAN, Manchester, United Kingdom
 
  A Damped Detuned Structure (DDS), known as CLICDDSA*, has been designed for the Compact Linear Collider (CLIC) study, and is presently under fabrication. The wakefield in DDS structures is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. The broad principles of the design are similar to that used in the NLC/GLC**. This serves as an alternative to the present baseline CLIC design which relies on heavy damping. CLICDDSA is conceived to be tested for its capacity to sustain high gradients at CERN. This structure operates with a 120 degrees phase advance per cell. We report on engineering design and fabrication details of the structure consisting of 24 regular cells plus 2 matching cells at both ends, all diffusion bonded together. This design takes into account practical mechanical engineering issues and is the result of several optimizations since the earlier CLICDDS designs.
* V. F. Khan et al., “Recent Progress on a Manifold Damped and Detuned Structure for CLIC”, Proc. of IPAC10, WEPE032, p. 3425 (2010).
** R.M. Jones et al., Phys. Rev. STAB 9, 102001 (2006).
 
 
MOPC038 Engineering Design and Fabrication of Tapered Damped X-band Accelerating Structures 157
 
  • A. Solodko, D. Gudkov, A. Samoshkin
    JINR, Dubna, Moscow Region, Russia
  • S. Atieh, A. Grudiev, G. Riddone, M. Taborelli
    CERN, Geneva, Switzerland
 
  The accelerating structures (AS) are one of the main components of the Compact LInear Collider (CLIC), under study at CERN. Each AS contains about 30 copper disks, which form the accelerating cavity. A fully featured AS is very challenging and requires several technologies. Different damping methods, waveguides, vacuum manifolds, slots and choke, result in various design configurations. In the CLIC multibunch AS, called TDS (Tapered Damped Structure), each cell is damped by its four waveguides, which are extended by channels machined in dedicated external vacuum manifolds. The manifolds combine few functions such as damping, vacuum pumping and cooling. Silicon carbide absorbers, fixed inside of each manifold, are required for effective damping of High Order Modes. CERN is producing X-band RF structures in close collaboration with a large number of laboratories taking advantage of their large expertise and test facilities. The fabrication includes several steps from the machining to the final assembly, including quality controls. This paper describes the engineering design and fabrication procedure of the X-band AS with damping material, by focusing on few technical solutions.  
 
MOPS071 Simulations of the Impedance of the New PS Wire Scanner Tank 766
 
  • B. Salvant
    EPFL, Lausanne, Switzerland
  • W. Andreazza, F. Caspers, A. Grudiev, J.F. Herranz Alvarez, E. Métral, G. Rumolo
    CERN, Geneva, Switzerland
 
  The CERN PS is equipped with 4 wire scanners. It was identified that the small aperture of the current wire scanner tank causes beam losses and a new tank design was needed. The interaction of the PS bunches with the beam coupling impedance of this new tank may lead to beam degradation and wire damage. This contribution presents impedance studies of the current PS tank as well as the new design in order to assess the need to modify the design and/or install lossy materials plates dedicated to damp higher order cavity modes and reduce the total power deposited by the beam in the tank.  
 
MOPS072 Broadband Electromagnetic Characterization of Materials for Accelerator Components 769
 
  • C. Zannini, A. Grudiev, E. Métral, T. Pieloni, G. Rumolo
    CERN, Geneva, Switzerland
  • G. De Michele
    PSI, Villigen, Switzerland
  • C. Zannini
    EPFL, Lausanne, Switzerland
 
  Electromagnetic (EM) characterization of materials up to high frequencies is a major requirement for the correct modeling of many accelerator components: collimators, kickers, high order modes damping devices for accelerating cavities. In this scenario, the coaxial line method has gained much importance compared to other methods because of its applicability in a wide range of frequencies. In this paper we describe a new coaxial line method that allows using only one measurement setup to characterize the material in a range of frequency from few MHz up to several GHz. A coaxial cable fed at one side is filled with the material under test and closed on a known load on the other side. The properties of the material are obtained from the measured reflection coefficient by using it as input for a transmission line (TL) model or for 3D EM simulations, which describe the measurements setup. We have applied this method to characterize samples of SiC (Silicon Carbide) which could be used for LHC collimators and for CLIC accelerating structures and NiZn ferrite used for kicker magnets.  
 
TUPC015 Comparative Wakefield Analysis of a First Prototype of a DDS Structure for CLIC Main Linac 1024
 
  • A. D'Elia, A. Grudiev, V.F. Khan, W. Wuensch
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
 
  A Damped Detuned Structure (DDS) for CLIC main linac has been proposed as an alternative to the present baseline design which is based on heavy damping. A first prototype, CLICDDSA, for high power tests has been already designed and is under construction. It is also foreseen to design a further prototype, CLICDDSB, to test both the wakefield suppression and high power performances. Wakefield calculations for DDS are, in the early design stage, based on single infinitely periodic cells. Though cell-to-cell interaction is taken into account to calculate the wakefields, it is important to study full structure properties using computational tools. In particular this is fundamental for defining the input parameters for the HOM coupler that is crucial for the performances of DDS. In the following a full analysis of wakefields and impedances based on simulations conducted with finite difference based electromagnetic computer code GdfidL will be presented.  
 
TUPC026 Status of the Crab Cavity Design for the CLIC 1054
 
  • P.K. Ambattu, G. Burt, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • A. Grudiev
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
  • P.A. McIntosh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  RF design of a crab cavity (2π/3, 11.9942 GHz) for the Compact Linear Collide (CLIC) is presented. As part of the UK-CLIC collaboration, CERN is building two copper prototypes, designed by Lancaster University / Cockcroft Institute. The first prototype to be made will be a 12 cell undamped cavity and the second will be waveguide damped cavity. The RF test at CERN will help characterisation of the dipole mode with X-band RF pulses of 15 MW peak power and pulse length of ~242 ns. Since the cavity frequency and phase advance per cell are identical to those of the CLIC main linac, the first prototype could exploit CERN’s X-band cavity characterisation facilities. A fully damped cavity will be required for the actual machine in order to meet the luminosity specs. The damped prototype will use an identical coupler type as the undamped one, but the cells will have damping waveguides with / without dielectric material.  
 
TUPS103 High Temperature Radio Frequency Loads 1783
 
  • S. Federmann, F. Caspers, A. Grudiev, E. Montesinos, I. Syratchev
    CERN, Geneva, Switzerland
 
  In the context of energy saving and recovery requirements the design of reliable and robust RF power loads which permit a high outlet temperature and high pressure of the cooling water is desirable. Cooling water arriving at the outlet with 150 deg C and more than 20 bar has a certain value. Normal RF power loads containing dielectric and sensitive windows usually do not permit going much higher than 50 deg C. Here we present and discuss several design concepts for narrow-band “metal only” RF high power loads. One concept is the application of normal steel corrugated waveguides structures near cutoff .This concept could find practical use above several GHz. Another solution are resonant structures made of normal magnetic steel to be installed in large waveguides for frequencies of 500 MHz or lower. Similar resonant structures above 100 MHz taking advantage the rather high losses of normal steel may also be used in coaxial line geometries with large dimensions.