Author: Weiland, T.
Paper Title Page
MOPS053 Electron Cloud Effects in Coasting Heavy-ion Beams* 724
 
  • F.B. Petrov, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • O. Boine-Frankenheim
    GSI, Darmstadt, Germany
 
  Funding: Work supported by BMBF under contract 06DA9022I.
During slow extraction of intense ion beams electron clouds (EC) can accumulate in the circulating coasting beam and reduce the extraction efficiency. This is a concern for the existing SIS-18 heavy ion synchrotron at GSI and for the projected SIS-100 as part of the FAIR project. For medium energy heavy-ion beams the production of electrons from residual gas ionization is very effective. The electron density is limited due to Coulomb scattering by the beam ions. Above a threshold beam intensity the two-stream instability and the resulting coherent beam oscillations limit the electron density. Below this threshold the electron cloud can lead to observable deformations of the Schottky side-bands. To avoid EC build-up one can introduce a gap in the beam using barrier rf bucket. The reduction of the build-up efficiency caused by the gap is studied in details based on the solution of the Hill's equation for electrons. Finally we estimate the saturation level for the electron cloud density.
 
 
TUPC076 Realization of a High Bandwidth Bunch Arrival-time Monitor with Cone-shaped Pickup Electrodes for FLASH and XFEL 1177
 
  • A. Angelovski, M. Hansli, R. Jakoby, A. Kuhl, A. Penirschke, S. Schnepp
    TU Darmstadt, Darmstadt, Germany
  • M. Bousonville, H. Schlarb
    DESY, Hamburg, Germany
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA
In the Free Electron Laser in Hamburg (FLASH) an electro-optical system is used as a Bunch Arrival time Monitor (BAM). The time-of-arrival resolution is proportional to the steepness of the beam pick-up signal at the first zero-crossing*. Future experiments will be conducted using significantly lower bunch charges resulting in a reduced signal steepness. This requires BAM pickup electrodes with increased bandwidth as introduced in **. This paper presents the implementation and measurement results of a high bandwidth cone-shaped pickup capable of operating in the frequency range up to 40 GHz. The slope steepness at the zero crossing is investigated for a simplified equivalent circuit model. RF-measurements have been performed using a non-hermetic prototype of the BAM pickups for assessing the influence of manufacturing tolerances on the sensor performance. The measurements are compared to simulation results obtained by CST PARTICLE STUDIO®.
* F. Loehl et al., Proc. of DIPAC2007, WEPB15, p. 262 (2007).
** A. Angelovski et al., "Pickup design for a high resolution Bunch Arrival time Monitor for FLASH and XFEL", DIPAC2011.
 
 
TUPC077 Investigations on High Sensitive Sensor Cavity for Longitudinal and Transversal Schottky for the CR at FAIR 1180
 
  • M. Hansli, A. Angelovski, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • W. Ackermann, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • P. Hülsmann
    GSI, Darmstadt, Germany
 
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 06DA90351
For the Collector Ring (CR) at the FAIR (Facility for Antiproton and Ion Research) accelerator complex a sensitive Schottky sensor is required. The CR covers different modes of operation, like pre-cooling of antiprotons at 3 GeV, pre-cooling of rare isotope beams at 740 MeV/u and an isochronous mode for mass measurements. For longitudinal Schottky measurements the concept of a resonant cavity had been introduced [Hansli2011]. Due to limited space inside the ring, the integration of transversal Schottky analysis into this cavity is desired. In this paper the demands and required changes to implement also transversal Schottky measurements are discussed. An analysis of the expected signal characteristics featuring equivalent circuit is shown, as well as numerical full wave simulations of the cavity.
* M. Hansli, A. Penirschke, R. Jakoby, W. Kaufmann, W. Ackermann, T. Weiland, "Conceptual Design of a High Sensitive Versatile Schottky Sensor for the Collector Ring at FAIR", DIPAC2011.
 
 
TUPC079 Sensitivity and Tolerance Analysis of a New Bunch Arrival-time Monitor Pickup Design for FLASH and XFEL 1186
 
  • A. Kuhl, A. Angelovski, R. Jakoby, A. Penirschke, S. Schnepp
    TU Darmstadt, Darmstadt, Germany
  • M. Bousonville, H. Schlarb
    DESY, Hamburg, Germany
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Supported by the Graduate School of Computational Engineering at TU Darmstadt and the Federal Ministry of Education and Research (BMBF): 05K10RDA "Weiterentwickung eines Ankunftszeitmonitors"
The Free Electron Laser in Hamburg (FLASH) is equipped with Bunch Arrival Time Monitors (BAM)*, which provide for a time resolution of less than 10 fs for bunch charges higher than 0.2 nC. Future experiments, however, will aim at generating FEL light pulses from a broad range of bunch charges down to 10 pC. In these circumstances the requirements on the time resolution will no longer be fulfilled, which demands for a larger bandwidth of the pickup system. A new cone-shaped pickup, which has a bandwidth greater than 40 GHz has been proposed**. At high frequencies, small manufacturing tolerances might have great influence on the pickup signal. A sensitivity analysis of several manufacturing tolerances in the pickup design regarding their influence on the output signal was carried out (by means of CST PARTICLE STUDIO®). These results are utilized for setting limits to the manufacturing tolerances.
* M.K. Bock et al., IPAC2010, WEOCMH02, Kyoto, Japan, 2010.
** A. Kuhl et al., "Design eines hochauflösenden Ankunftszeitmonitor für FLASH", DPG Frühjahrstagung 2011, Karlsruhe, Germany.
 
 
TUPC080 Pickup Design with Beta Matching 1189
 
  • J.A. Tsemo Kamga, W.F.O. Müller, K.K. Stavrakakis, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by GSI
The main goal of this project is to investigate the Schottky noise of an ion beam in the frequency range from 3 to 5 GHz. In order to accomplish this task, a pickup design is required. For an efficient study of this Schottky noise the pickup sensitivity for low beta must be increased. A design for such a problem has been developed by McGinnis for a fixed beam velocity but can also be used for variable beta by using a tunable material (ferroelectric) inside the waveguide. Since such tunable materials like for instance BST (Barium Strontium Titanate) are lossy, the impact of dielectric losses on the pickup sensitivity will also be investigated in this work. Additionally to the classical parameter studies where multiple simulation runs based on the original numerical model are initiated to characterize the various design parameters it is also possible to utilize a reduced model instead. In particular one is interested in a fast evaluation of the frequency response while taking also material variations into account. In this work, a multivariate parameterized dynamical system is set up and used complementary to the full model for the required beam characterization.
 
 
WEPC088 Embedding Finite Element Results for Accelerator Components in a Moment Approach Beam Dynamics Code* 2217
 
  • T. Roggen, H. De Gersem, B. Masschaele
    KU Leuven, Kortrijk, Belgium
  • W. Ackermann, S. Franke, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: This research is funded by grant ''KUL 3E100118'' ''Electromagnetic Field Simulation for Future Particle Accelerators''.
A moment based beam dynamics code has particular advantages, i.e. accuracy and efficiency, over macro-particle tracking and full particle-in-cell (PIC) codes respectively. Instead of embedding analytical descriptions of the accelerator components in the beam dynamics model, it is proposed to insert a surrogate model obtained from the finite element model of individual accelerator components. We apply the V-Code, which accepts moments up to the sixth order and accounts for space charge effects. We construct and calculate finite element and finite difference time domain models using the CST Studio Suite 2011 software package. An interface is implemented using VBA and MATLAB. As an example of the accuracy of this cascadic simulation approach, we compare the beam dynamics of an S-DALINAC quadrupole obtained by directly tracking particles to the calculated fields with the results for the cascadic approach with the V-Code.
This work was performed during a three month research visit at the Technische Universität Darmstadt, Institut für Theorie Elektromagnetischer Felder, Darmstadt, Germany.
 
 
WEPC092 Moment-Based Simulation of the S-DALINAC Recirculations* 2223
 
  • S. Franke, W. Ackermann, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • R. Eichhorn, F. Hug, C. Klose, N. Pietralla, M. Platz
    TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by DFG under contract SFB 634.
The Superconducting Linear Accelerator S-DALINAC installed at the institute of nuclear physics (IKP) at TU Darmstadt is designed as a re-circulating linear accelerator. The length of the beam line and the numerous accelerating structures as well as dipole and quadrupole magnets require a highly efficient numerical simulation tool in order to assist the operators by providing a detailed and almost instantaneous insight into the actual machine status. A suitable approach which enables a fast online calculation of the beam dynamics is given by the so-called moment approach where the particle distribution is represented by means of a discrete set of moments or by multiple discrete sets of moments in a multi-ensemble environment. Following this approach the V-Code simulation tool has been implemented at the Computational Electromagnetics Laboratory (TEMF) at TU Darmstadt. In this contribution an overview of the numerical model is presented together with new V-Code simulation results regarding the S-DALINAC recirculation sections.
 
 
WEPC093 Various Approaches to Electromagnetic Field Simulations for RF Cavities 2226
 
  • C. Liu, W. Ackermann, W.F.O. Müller, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by BMBF under contract 05H09RD5
In the Superconducting Proton Linac (SPL) cavity, there is not only the fundamental mode for the particle acceleration but also many higher order modes (HOMs), which can lead to particle beam instabilities. This is very dangerous for SPL cavity. Therefore it is necessary to simulate the electromagnetic field in the SPL cavity, so that the field distribution and the shunt impedance for every higher order mode can be precisely calculated. At TEMF this research work can be done in three different ways: field simulation with hexahedron mesh in frequency domain, field simulation with hexahedron mesh in time domain and field simulation with tetrahedral mesh and higher order curvilinear elements. Finally the HOM coupler will be considered for the effective damping of higher order modes in the SPL cavity.
 
 
WEPC094 Energy Loss and Longitudinal Wakefield of Relativistic Short Ion Bunches in Electron Clouds 2229
 
  • F. Yaman, O. Boine-Frankenheim, E. Gjonaj, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • G. Rumolo
    CERN, Geneva, Switzerland
 
  Funding: Work supported by BMBF under contract 06DA9022I
The aim of our study is the numerical computation of the wakefield, impedance and energy loss for an energetic, short (< 10 ns) ion bunch penetrating an electron cloud plasma residing in the beam pipe. We use a 3-D self-consistent and higher order PIC code based on the full-wave solution of the Maxwell equations in the time domain. In our simulations we observe the induced density oscillations in the electron cloud in the longitudinal as well as in the transverse directions. A special numerical procedure is applied to compute the longitudinal wake potential and the broadband coupling impedance due to the beam-electron cloud interaction. The code is applied to the case of the CERN SPS and the projected SIS-100 at GSI. The effects of the beam pipe, electron density, bunch intensity and external magnetic dipole fields are studied. The results are compared to analytical and numerical models of reduced complexity.