BNL, Upton, Long Island, New York
KVI, Groningen
CLASSE, Ithaca, New York
In the proposed electric dipole moment (EDM) experiment, with an estimated spin coherence time of 1000 s, the spin precession due to an EDM of 10-29 e.cm will produce a change in the vertical spin component of approximately 10 μrad during the storage time. Such high sensitivity needs an extremely high accurate and reliable simulation environment of the beam and spin behavior during the storage time. Therefore, several spin-related accelerator programs have been considered and investigated. The paper surveys the computational algorithms of these approaches and provides their comprehensive analysis from multiple perspectives: accuracy, performance, extensibility, and scope of potential applications.
TEMF, TU Darmstadt, Darmstadt
KU Leuven, Kortrijk
Numerical simulations are frequently used in the design, optimization and commissioning phase of accelerator components. Strict requirements on the accuracy as well as the complex structure of such devices lead to challenges regarding the numerical simulations in 3D. In order to capture all relevant details of the geometry and possibly strongly localized electromagnetic effects, large numerical models are often unavoidable. The use of parallelization strategies in combination with higher-order finite-element methods offers a possibility to account for the large numerical models while maintaining moderate simulation times as well as high accuracy. Using this approach, the magnetic properties of the SIS100 magnets designated to operate within the Facility of Antiproton and Ion Research (FAIR) at the GSI Helmholtzzentrum für Schwerionenforschung GmbH (GSI) in Darmstadt, are calculated. Results for eddy-current losses under time-varying operating conditions as well as field quality considerations are reported.
ORNL, Oak Ridge, Tennessee
SLAC, Menlo Park, California
XAL is a Java programming framework for building high-level control applications related to accelerator physics. The core of XAL consists of a GUI framework to provide common “look and feel” and functionality for all XAL applications, a hardware representation of the machine for connectivity and control, and a beam simulation model termed the "online model" for model reference and comparison to the hardware operation. The structure, details of implementation, and interaction between these components, auxiliary XAL packages, and applications are discussed. A general overview of applications created for the SNS project and based on XAL is presented.
TRIUMF, Vancouver
The simulation toolkit GEANT4 has been used to create high-level tools for specific user groups, such as SPENVIS in space physics and GATE in medical imaging. In Accelerator Physics, comparable efforts are being devoted to develop general-purpose programs for simulating beamlines and accelerators, allowing access to Geant4's facilities for 3D geometry, tracking, and interactions in matter without the need for specialised programming techniques. In this study we investigate the use of two high-level tools based on Geant4, G4BEAMLINE and BDSIM, to model a 65-meter beam line supplying protons from the TRIUMF cyclotron to the ISAC RIB facility. We outline the rather different approaches to defining the beamline geometry (including cyclotron extraction foil and exit region) in each code. Their diagnostic and visualisation features are also compared. Due to its ability to model some important aspects such as rectangular dipoles and magnetic fringe fields, G4beamline was utilized for a series of simulations presented here, investigating the distribution of losses in the beamline, the role of scattering in the cyclotron extraction foil, and the sensitivity of losses to tuning parameters.
KU Leuven, Kortrijk
TEMF, TU Darmstadt, Darmstadt
The modeling of eddy-current phenomena in superconductive accelerator magnets is challenging because the large differences in geometrical dimensions (skin depth vs. magnet size) and time constants (ramping time vs. relaxation time). The paper addresses modeling issues as e.g. the ferromagnetic saturation of the iron yoke, the eddy-current losses in the yoke end parts, the eddy-current losses in the beam tube and possible eddy-current losses in the windings. Heavy saturation, small skin depths and small time constants render simulations of this kind to be challenging. The simulation approach is used in combination with an optimization procedure involving both continuous and integer-valued parameters.
TEMF, TU Darmstadt, Darmstadt
The Vlasov equation describes the evolution of a particle density under the effects of electromagnetic fields. It is derived from the fact that the volume occupied by a given number of particles in the 6D phase space remains constant when only long-range interaction as for example Coulomb forces are relevant and other particle collisions can be neglected. Because this is the case for typical charged particle beams in accelerators, the Vlasov equation can be used to describe their evolution within the whole beam line. This equation is a partial differential equation in 6D and thus it is very expensive to solve it via classical methods. A more efficient approach consists in representing the particle distribution function by a discrete set of characteristic moments. For each moment a time evolution equation can be stated. These ordinary differential equations can then be evaluated efficiently by means of time integration methods if all considered forces and a proper initial condition are known. The beam dynamics simulation tool V-Code implemented at TEMF utilizes this approach. In this paper the numerical model, main features and designated use cases of the V-Code will be presented.
BNL, Upton, Long Island, New York
In order to preserve polarization during polarized proton operation for RHIC, two partial Siberian Snakes are employed in the AGS, where a number of strong spin depolarization resonances must be crossed. These Snakes cause a significant distortion to the injection lattice of the AGS and must be included in the on-line model. In this report we discuss the problem of modeling Snakes as optical elements, particularly as madx elements, and present results comparing measurements to the AGS on-line model.
PSI, Villigen
For the 250 MeV test injector, it is planned to use a 2.6 cell RF gun originally developed for high current and charge operation in the CLIC test facility CTF-2. First start-to-end simulations assuming perfect field symmetries show, that this gun should be able to generate bunches at 200 pC with an emittance of below 400 nm rad, which would be compatible with the requirements for the SwissFEL. This gun uses double side coupled RF feeds in the last cell as well as tuners in the last two cells, which give transverse multipole effects in the field and phase space distribution and may lead to a deteriorated emittance. Since the beam in the last cell is already relativistic at energies between 4 and 6.4 MeV, this effect can be computed in a clean way by looking at the distributions of the integrated beam voltage at the cavity iris and deriving any transverse kicks via the Panovsky-Wenzel theorem. Doing this approach for the various operation modi planned for the PSI injector shows an emittance dilution well below the critical thresholds.
Northern Illinois University, DeKalb, Illinois
This research involves the development of a model of the small circumference (11.5 m) accelerator in which the earth’s field has a strong effect, and in which image charge forces are also included. The code used for this simulation was COSY Infinity 9.0 which uses differential algebras to determine high order map elements, as well as quantities such as chromaticity. COSY also uses Normal Form algorithms to determine the betatron tune and any amplitude dependent tune shifts which may result. The power of COSY is that it can derive the required quantities directly form the map without costly integration and tracking. Thus determining the map for both the default elements of the ring, plus the effects of image charge forces, and the earth’s magnetic field is both non-trivial, and important. This research uses the Baker Campbell Hausdorf method to determine the map of the ring with the external fields included. Furthermore COSY has the ability to directly implement misalignments within the beamline itself allowing for a study of their effects on beam dynamics. The presentation will include both coding development and applications to the University of Maryland Electron Ring.