Author: Boine-Frankenheim, O.
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High Intensity Beam Dynamics Preparations for FAIR  
  • O. Boine-Frankenheim
    GSI, Darmstadt, Germany
  The FAIR accelerator complex is designed to deliver heavy ions beams of unprecedented beam intensity and quality. Such beams will enable high yield in-flight production of exotic nuclei and their precise identification at high energies, for example. Intense primary ion beams will be delivered to the new SIS100 synchrotron from the upgraded UNILAC/SIS18 complex. Both, the existing SIS18 and the new SIS100 will be operated at the ’space charge limit’ for light and heavy ion beams. Only due to the recent advances in the performance of particle tracking tools with self-consistent 3D space charge solvers we were able to reliably identify low-loss areas in tune space over the full 1 s accumulation plateau in SIS100. A realistic magnet error model, extracted from bench measurements, is included in the simulations. Different measures are proposed to enlarge the low-loss area and to further increase the space charge limit. A key rf manipulation in SIS100 will be the single bunch generation and compression before extraction to the production targets. Simulation results to prepare for the later operation will be shown.  
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TUAC1 Self-Consistent Long-Term Dynamics of Space Charge Driven Resonances in 2D and 3D 160
  • A. Oeftiger, I. Hofmann
    GSI, Darmstadt, Germany
  • O. Boine-Frankenheim
    TEMF, TU Darmstadt, Darmstadt, Germany
  Understanding the 3D collective long-term response of beams exposed to resonances is of theoretical interest and essential for advancing high intensity synchrotrons. This study of a hitherto unexplored beam dynamical regime is based on 2D and 3D self-consistent particle-in-cell simulations and on careful analysis using tune spectra and phase space. It shows that in Gaussian-like beams Landau damping suppresses all coherent parametric resonances, which are of higher than second order (the "envelope instability"). Our 3D results are obtained in an exemplary stopband, which includes the second order coherent parametric resonance and a fourth order structural resonance. They show that slow synchrotron oscillation plays a significant role. Moreover, for the early time evolution of emittance growth the interplay of incoherent and coherent resonance response matters, and differentiation between halo and different core regions is essential. In the long-term behavior we identify a progressive, self-consistent drift of particles toward and across the resonance, which results in effective compression of the initial tune spectrum. However, no visible imprint of the coherent features is left over, which only control the picture during the first one or two synchrotron periods. An intensity limit criterion and an asymptotic formula for long-term rms emittance growth are suggested. Comparison with the commonly used non-self-consistent "frozen space charge" model shows that in 3D this approximation yields a fast and useful orientation, but it is a conservative estimate of the tolerable intensity.
HB’21 talk on "Effect of Space Charge on Bunch Stability and Space Charge Compensation Schemes" based on this APS PR-AB published contribution.
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About • Received ※ 11 October 2021 — Revised ※ 04 November 2021 — Accepted ※ 05 November 2021 — Issue date ※ 23 November 2021
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