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MPPP034 Collective Effects in the TLS Storage Ring after the Installation of Superconducting RF Cavity storage-ring, vacuum, feedback, impedance 2360
  • P.J. Chou, J. Chen, K.-T. Hsu, C.-C. Kuo, C. Wang, M.-H. Wang
    NSRRC, Hsinchu
  A superconducting rf cavity designed by Cornell University was installed in the storage ring at Taiwan Light Source in December of 2004. The purpose of rf system upgrade is to achieve a stored beam current of 400 mA without collective instabilities caused by high-order-modes of rf cavities. Beam measurements related to collective effects are performed. Results are compared with those measured prior to the rf system upgrade. Theoretical studies on collective effects after the rf upgrade are also presented.  
TPAT026 Synergia: An Advanced Object-Oriented Framework for Beam Dynamics Simultation simulation, background, impedance, hadron 1925
  • D.R. Dechow, P. Stoltz
    Tech-X, Boulder, Colorado
  • J.F. Amundson, P. Spentzouris
    Fermilab, Batavia, Illinois
  Synergia is a 3-D, parallel, particle-in-cell beam dynamics simulation toolkit. At heart of the software development effort is the integration of two extant object-oriented accelerator modeling frameworks–Impact written in Fortran 90 and mxyptlk written in C++–so that they may be steered by a third, a more flexible human interface framework, written in Python. Recent efforts are focused on the refactoring of the Impact-Fortran 90 codes in order to expose more loosely-coupled interfaces to the Python interface framework.  
WPAT044 Realization of an X-Band RF System for LCLS klystron, linac, vacuum, linear-collider 2801
  • P.A. McIntosh, R. Akre, J. Brooks, P. Emma, E. Rago
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.

A single X-band (11.424 GHz) accelerating structure is to be incorporated in the LCLS Linac design to linearize the energy-time correlation (or gradient) across each bunch, features which originate in the preceding accelerating structures (L0 and L1). This harmonic RF system will operate near the negative RF crest to decelerate the beam, reducing these non-linear components of the correlation, providing a more efficient compression in the downstream bunch compressor chicanes (BC1 and BC2). These non-linear correlation components, if allowed to grow, would lead to Coherent Synchrotron Radiation (CSR) instabilities in the chicanes, effectively destroying the coherence of the photon radiation in the main LCLS undulator. The many years devoted at SLAC in the development of X-band RF components for the NLC/JLC linear collider project, has enabled the technical and financial realization of such an RF system for LCLS. This paper details the requirements for the X-band system and the proposed scheme planned for achieving those requirements.

FPAP029 Nonlinear Delta-f Particle Simulations of Collective Effects in High-Intensity Bunched Beams simulation, space-charge, coupling, focusing 2107
  • H. Qin, R.C. Davidson, S.R. Hudson, E. Startsev
    PPPL, Princeton, New Jersey
  Funding: Research supported by the U.S. Department of Energy.

The collective effects in high-intensity 3D bunched beams are described self-consistently by the nonlinear Vlasov-Maxwell equations.* The nonlinear delta-f method,** a particle simulation method for solving the nonlinear Vlasov-Maxwell equations, is being used to study the collective effects in high-intensity 3D bunched beams. The delta-f method, as a nonlinear perturbative scheme, splits the distribution function into equilibrium and perturbed parts. The perturbed distribution function is represented as a weighted summation over discrete particles, where the particle orbits are advanced by equations of motion in the focusing field and self-consistent fields, and the particle weights are advanced by the coupling between the perturbed fields and the zero-order distribution function. The nonlinear delta-f method exhibits minimal noise and accuracy problems in comparison with standard particle-in-cell simulations. A self-consistent 3D kinetic equilibrium is first established for high intensity bunched beams. Then, the collective excitations of the equilibrium are systematically investigated using the nonlinear delta-f method implemented in the Beam Equilibrium Stability and Transport (BEST) code.

*R.C. Davidson and H. Qin, Physics of Intense Charged Particle Beams in High Energy Accelerators (World Scientific, 2001). **H. Qin, Physics of Plasmas 10, 2078 (2003).