CERN, Geneva
ENS LYON, Lyon
TEMF, Darmstadt
Wake fields are a limiting factor due to their collective effects. In colliders and high energy accelerators used in FEL projects short bunches excite high frequency fields which make the computation of near range wake fields inaccurate. Additionally the length of modern accelerating structures limit the powers of certain codes such as TBCI or MAFIA. Both limiting factors, i.e. short bunches and length of accelerating structures - a multiscale problem, can be dealt with in the following way. Using certain zero dispersion directions of a usual Cartesian grid leads to a decrease of the overall dispersion which usually arises by having discrete field values. Combined with a conformal modelling technique the full time step limited by the Courant criterion is used and a moving window is applied. Thus simulations of short bunches in long structures are possible - dispersion and memory problems have been avoided. In this work ROCOCO (Rotated mesh and conformal code) is presented. The zero dispersion algorithm uses a new discretization scheme based on a rotated mesh combined with the established USC scheme and the moving window technique mentioned above. The advantage of an explicit algorithm is joined with the zero dispersion along the beam's propagation direction. A dispersion analysis for the 2D version of the code is shown as well as some results for common structures of accelerator physics - such as collimators and the TESLA 9 cell structure.
TEMF, Darmstadt
The eigenmode expansion method was used in the early 1980’s in calculating wake potential for 2D rotational symmetric structures. In this paper it is extended to general 3D cases. The wake potential is computed as the sum of two parts, direct and indirect ones. The direct wake potential is obtained by an integral of field components from a full wave solution, which stops just at the end of the structure. The indirect wake potential is then calculated analytically through the eigenmode expansion method. This is to avoid the full wave modeling of a very long outgoing beam pipe, which is computational expensive. In our work, the Finite Integration Technique (FIT) with moving mesh window is used to model the structure. The fields are recorded at the truncation boundary as a function of time. These fields are then expanded according to discrete eigenmodes of the outgoing pipe, and the eigenmode coefficients are found out at each time step. Then, the coefficients are transferred into frequency domain and the integral of wake fields along a path to infinity is computed analytically. In the case that the moving mesh window is narrow, appropriate exploration of time domain coefficients is necessary. Numerical tests show that the proposed method provides an accurate result with as less as three modes for a collimator structure.
CERN, Geneva
Uppsala University, Uppsala
Jefferson Lab, Newport News, Virginia
Over the years, accelerator control systems have evolved from small hardwired systems to complex computer controlled systems with many types of graphical user interfaces and electronic data processing. Today’s control systems often include multiple software layers, hundreds of distributed processors, and hundreds of thousands of lines of code. While it is clear that the next generation of accelerators will require much bigger control systems, they will also need better systems. Advances in technology will be needed to ensure the network bandwidth and CPU power can provide reasonable update rates and support the requisite timing systems. Beyond the scaling problem, next generation systems face additional challenges due to growing cyber security threats and the likelihood that some degree of remote development and operation will be required. With a large number of components, the need for high reliability increases and commercial solutions can play a key role towards this goal. Future control systems will operate more complex machines and need to present a well integrated, interoperable set of tools with a high degree of automation. Consistency of data presentation and exception handling will contribute to efficient operations. From the development perspective, engineers will need to provide integrated data management in the beginning of the project and build adaptive software components around a central data repository. This will make the system maintainable and ensure consistency throughout the inevitable changes during the machine lifetime. Additionally, such a large project will require professional project management and disciplined use of well-defined engineering processes. Distributed project teams will make the use of standards, formal requirements and design and configuration control vital. Success in building the control system of the future may hinge on how well we integrate commercial components and learn from best practices used in other industries.
Fermilab, Batavia, Illinois
CERN, Geneva
LBNL, Berkeley, California
LLNL, Livermore, California
We have developed a new, comprehensive set of simulation tools aimed at modeling the interaction of intense ion beams and electron clouds (e-clouds). The set contains the 3-D accelerator PIC code WARP and the 2-D "slice" e-cloud code POSINST, as well as a merger of the two, augmented by new modules for impact ionization and neutral gas generation. The new capability runs on workstations or parallel supercomputers and contains advanced features such as mesh refinement, disparate adaptive time stepping, and a new "drift-Lorentz" particle mover for tracking charged particles in magnetic fields using large time steps. It is being applied to the modeling of ion beams (1 MeV, 180 mA, K+) for heavy ion inertial fusion and warm dense matter studies, as they interact with electron clouds in the High-Current Experiment (HCX). We describe the capabilities and present recent simulation results with detailed comparisons against the HCX experiment, as well as their application (in a different regime) to the modeling of e-clouds in the Large Hadron Collider (LHC).
SLAC, Menlo Park, California