SLAC, Menlo Park, California
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV. The Trafic4 simulation confirms the observation.
The paper was published at PRST-AB, November 2006
SLAC, Menlo Park, California
Under the support of the U. S. DOE SciDAC program, SLAC has been developing a suite of 3D parallel finite-element codes aimed at high-accuracy, high-fidelity electromagnetic and beam physics simulations for the design and optimization of next-generation particle accelerators. Running on the latest supercomputers, these codes have made great strides in advancing the state of the art in applied math and computer science at the petascale that enable the integrated modeling of electromagnetics, self-consistent Particle-In-Cell (PIC) particle dynamics as well as thermal, mechanical, and multi-physics effects. This paper will present 3D results of trapped mode calculations in an ILC cryomodule and the modeling of the ILC Sheet Beam klystron, shape determination of superconducting RF (SCRF) cavities and multipacting studies of SCRF HOM couplers, as well as 2D and preliminary 3D PIC simulation results of the LCLS RF gun.
SLAC, Menlo Park, California
Over the past years, SLAC's Advanced Computations Department (ACD) has developed the parallel finite element particle-in-cell code Pic3P (Pic2P) for simulations of beam-cavity interactions dominated by space-charge effects. As opposed to standard space-charge dominated beam transport codes, which are based on the electrostatic approximation, Pic3P (Pic2P) includes space-charge, retardation and boundary effects as it self-consistently solves the complete set of Maxwell-Lorentz equations using higher-order finite element methods on conformal meshes. Use of efficient, large-scale parallel processing allows for the modeling of photoinjectors with unprecedented accuracy, aiding the design and operation of the next-generation of accelerator facilities. Applications to the Linac Coherent Light Source (LCLS) RF gun are presented.
BNL, Upton, Long Island, New York
CERN, Geneva
SLAC, Menlo Park, California
Fermilab, Batavia, Illinois
LBNL, Berkeley, California
A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.
SLAC, Menlo Park, California
The actual cell shape of the TESLA cavities differ from the ideal due to fabrication errors, the addition of stiffening rings and the frequency tuning process. Cavity imperfection shift the dipole mode frequencies and alter the Qext's from those computed for the idea cavity. A Qext increase could be problematic if its value exceeds the limit required for ILC beam stability. To study these effects, a cavity imperfection model was established using a mesh distortion method. The eigensolver Omega3P was then used to find the critical dimensions that contribute to the Qext spread and frequency shift by comparing predictions to TESLA cavity measurement data. Using the imperfection parameters obtained from these studies, artificial imperfection models were generated and the resulting wakefields were used as input to the beam tracking code Lucretia to study the effect on beam emittance. In this paper, we present the results of these studies and suggest tolerances for the cavity dimensions.
SLAC, Menlo Park, California
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois