PSI, Villigen
TEMF, Darmstadt
In many applications the self-consistent simulation of charged particle beams is necessary. Especially, in low-energetic sections such as injectors the interaction between particles and fields considering all effects has to be taken into account. Well-known programs like the MAFIA TS modules typically use the Particle-In-Cell (PIC) method for beam dynamics simulations. Since they use a fixed computational grid which has to resolve the bunch adequately, they suffer from enormous memory consumption. Therefore and especially in the 3D case, only rather short sections can be simulated. This may be avoided using adaptive mesh refinement techniques (AMR). Since their application in Finite-Difference methods in time-domain is critical concerning instabilities, usually problem-matched but static meshes are used. In this paper a code working on the basis of a fully dynamic Cartesian grid is presented allowing for simulations capturing both, a high spatial resolution in the vicinity of the bunch and the possibility of simulating structures up to a length of several meters. The code is tested and validated using the RF electron gun of the Photoinjector Test Facility at DESY Zeuthen (PITZ) as an example. The evolution of various beam parameters along the gun is compared with the results obtained by different beam dynamics programs.
Rostock University, Faculty of Engineering, Rostock
DESY, Hamburg
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
Precise and fast 3D space-charge calculations for bunches of charged particles are still of growing importance in recent accelerator designs. A widespread approach is the particle-mesh method computing the potential of a bunch in the rest frame by means of Poisson's equation. Recently new algorithms for solving Poisson's equation have been implemented in the tracking code Astra. These Poisson solvers are iterative algorithms solving a linear system of equations that results from the finite difference discretization of the Poisson equation. The implementation is based on the software package MOEVE (Multigrid Poisson Solver for Non-Equidistant Tensor Product Meshes) developed by G. Pöplau. The package contains a state-of-the-art multigrid Poisson solver adapted to space charge calculations. In this paper the basic concept of iterative Poisson solvers is described. It is compared to the established 3D FFT Poisson solver which is a widely-used method for space charge calculations and also implemented in Astra. Advantages and disadvantages are discussed. Further the similarities and differences of both approaches are demonstrated with numerical examples.
LBNL, Berkeley, California
The IMPACT-T code is a parallel three-dimensional quasi-static beam dynamics code for modeling high brightness beams in photoinjectors and RF linacs. Developed under the US DOE Scientific Discovery through Advanced Computing (SciDAC) program, it includes several key features including a self-consistent calculation of 3D space-charge forces using a shifted and integrated Green function method, multiple energy bins for a beams with large energy spread, and models for treating RF standing wave and traveling wave structures. In this paper, we report on recent improvements to the IMPACT-T code including short-range transverse and longitudinal wakefield models and a longitudinal CSR wakefield model. Some applications will be presented including simulation of the photoinjector for the Linac Coherent Light Source (LCLS) and beam generation from a nano-needle photocathode.
IREAP, College Park, Maryland
The University of Maryland Electron Ring (UMER) is a scaled electron recirculator using low-energy, 10 keV electrons, to maximize the space charge forces for beam dynamics studies. We have recently circulated in UMER the highest-space-charge beam in a ring to date, achieving a breakthrough both in the number of turns and in the amount of current propagated. As of the time of submission, we have propagated 5 mA for at least 10 turns, and, with some loss, for over 50 turns, meaning about 0.5 nC of electrons survive for 10 microseconds. This makes UMER an attractive candidate for benchmarking space charge codes in regimes of extreme space charge. This talk will review the UMER design and available diagnostics, and will provide examples of benchmarking the particle-in-cell code WARP on UMER data, as well as an overview of the detailed information on our website. An open dialogue with interested coded developers is solicited.
