• J. A. Holmes, S. M. Cousineau, V. V. Danilov, S. Henderson, D.-O. Jeon, M. A. Plum, A. P. Shishlo, Y. Zhang
  ORNL, Oak Ridge, Tennessee
• D. A. Bartkoski
  UTK, Knoxville, Tennessee

The computational approach is providing essential guidance and analysis for the commissioning and operation of SNS. Computational models are becoming sufficiently realistic that it is now possible to study detailed beam dynamics issues quantitatively. Increasingly, we are seeing that the biggest challenge in performing successful analyses is that of knowing and describing the machine and beam state accurately. Even so, successful benchmarks with both theoretical predictions and experimental results are leading to increased confidence in the capability of these models. With this confidence, computer codes are being employed in a predictive manner to guide the machine operations. We will illustrate these points with various examples taken from the SNS linac and ring.

• D. Schulte
  CERN, Geneva
• K. Kubo
  KEK, Ibaraki

The ILC requires detailed studies of the beam transport and of individual components of the transport system. The main challenges are the generation and preservation of the low emittance beams, the protection of the machine from excessive beam loss and the provision of good experimental conditions. The studies of these effects leads to specifications for the different accelerator components and hence can significantly impact the cost.

• E. McIntosh, F. Schmidt
  CERN, Geneva
• F. de Dinechin
  ENS LYON, Lyon

• E. Forest, Y. Nogiwa
  KEK, Ibaraki
• F. Schmidt
  CERN, Geneva

• E. Gjonaj, X. Dong, R. Hampel, M. Kärkkäinen, T. Lau, W. F.O. Müller, T. Weiland
  TEMF, Darmstadt

The X-FEL project and the ILC require a high quality beam with ultra short electron bunches. In order to predict the beam quality in terms of both, single bunch energy spread and emittance, an accurate estimation of the short range wake fields in the TESLA crymodules, collimators and other geometrically complex accelerator components is necessary. We have presented earlier wake field computations for short bunches in rotationally symmetric components with the code ECHO. Most of the wake field effects in the accelerator, however, are due to geometrical discontinuities appearing in fully three dimensional structures. For the purpose of simulating such structures, we have developed the Parallel Beam Cavity Interaction (PBCI) code. The new code is based on the full field solution of Maxwell equations in the time domain, for ultra-relativistic current sources. Using a specialized directional-splitting technique, PBCI produces particularly accurate results in wake field computations, due to the dispersion free integration of the discrete equations in the direction of bunch motion. One of the major challenges to deal with, when simulating fully three dimensional accelerator components is the huge computational effort needed for resolving both, the geometrical details and the bunch extensions by the computational grid. For this reason, PBCI implements massive parallelization on a distributed memory environment, based on a flexible domain decomposition method. In addition, PBCI uses the moving window technique, which is particularly well suited for wake potential computations in very long structures. As a particular example of such a structure, the simulation results of a complete module of TESLA cavities with eight cells each for a um-bunch will be given.

• M. Kärkkäinen, E. Gjonaj, T. Lau, T. Weiland
  TEMF, Darmstadt

Extremely short bunches are used in future linear colliders, such as the International Linear Collider (ILC). Accurate and computationally efficient numerical methods are needed to resolve the bunch and to accurately model the geometry. In very long accelerator structures, computational efficiency necessitates the use of a moving window in order to save memory. On the other hand, parallelization is desirable to decrease the simulation times. Explicit schemes are usually more convenient to parallelize than implicit schemes since the implementation of a separate potentially time-consuming linear solver can thus be avoided. Explicit numerical methods without numerical dispersion in the direction of beam propagation are presented for fully 3D wake field simulations and for the special case of axially symmetric structures. The introduced schemes are validated by comparing with analytical results and by providing numerical examples for practical accelerator structures. Conformal techniques to enhance the convergence rate are presented and the advantages of the conformal schemes are verified by numerical examples.

• R. Schuhmann
  UPB, Paderborn

• A. P. Shishlo, S. M. Cousineau, V. V. Danilov, J. Galambos, S. Henderson, J. A. Holmes, M. A. Plum
  ORNL, Oak Ridge, Tennessee

The contents, structure, implementation, benchmarking, and applications of ORBIT as an accelerator simulation code are described. Physics approaches, algorithms, and limitations for space charge, impedances, and electron cloud effects are discussed. The ORBIT code is a parallel computer code, and the scalabilities of the implementations of parallel algorithms for different physics modules are shown. ORBIT has a long history of benchmarking with analytical exactly solvable problems and experimental data. The results of this benchmarking and the current usage of ORBIT are presented.

• G. Rumolo, E. Métral
  CERN, Geneva

• G. Franchetti, I. Hofmann
  GSI, Darmstadt
• S. Machida
  CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon

• C. W. Trowbridge, J. Simkin, S. Taylor, E. Xu
  Vector Fields Ltd., Oxford

* M. N. Wilson, Superconducting magnets p217ff
** S. Caspi et Al, Calculating Quench propagation with Ansys, IEEE Trans. Appl. Supperconduct. Vol 13, No2, pp1714-1717

• A. Bossavit
  LGEP, Gif-sur-Yvette

• S. Peggs, U. Iriso
  BNL, Upton, Long Island, New York

• H. De Gersem, S. Koch, T. Weiland
  TEMF, Darmstadt

Transient 3D simulations are carried out for two types of superconductive dipole magnets. Eddy-current effects in the yoke are treated by homogenising the laminated iron composite whereas interstrand eddy-current effects are resolved by either a cable magnetization model or a cable eddy-current model. The simulations reveal the Joule losses in the magnets.

• M. Migliorati, A. Schiavi
  Rome University La Sapienza, Roma
• G. Dattoli
  ENEA C. R. Frascati, Frascati (Roma)

Methods employing integration techniques of Lie algebraic nature have been successfully employed in the past to develop charged beam transport codes, for different types of accelerators. These methods have been so far applied to the transverse motion dynamics, while the longitudinal part has been treated using standard tracking codes. In this contribution we extend the simplectic technique to the analysis of longitudinal and coupled longitudinal and transverse motion in charged beam transport with the inclusion of the non linear dynamics due to the wake field effects. We use the method to model different types of instabilities due to high current. We consider in particular the case of coherent synchrotron instabilities and its implication in the design and performances of high current accelerators. We discuss either single pass and recirculated devices. As to this last case, we also include the effect due to quantum noise and damping.

• M. Dehler
  PSI, Villigen

• E. Arevalo, B. Doliwa, T. Weiland
  TEMF, Darmstadt

The driving terms of instabilities in particle accelerators depend on the beam surroundings which are conveniently described by coupling impedances. In the case of critical components, for which analytical calculations are not available, direct measurements of the coupling impedances on a prototype are usually needed. However, this obvious drawback on the design of particle accelerators can be overcome by electromagnetic field simulations within the framework of the Finite Integration Technique. Here we show results from numerical evaluations of the transverse coupling impedance of a ferrite kicker. In order to excite the electromagnetic fields in the device we implement numerically the conventional twin-wire method. A good agreement with experimental measurements is observed, showing a promising way to determine coupling impedances of components of particle accelerators before construction.

• S. Schnepp, E. Gjonaj, T. Weiland
  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.

• G. Pöplau
  Rostock University, Faculty of Engineering, Rostock
• K. Floettmann
  DESY, Hamburg
• U. van Rienen
  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.

• T. Lau, E. Gjonaj, T. Weiland
  TEMF, Darmstadt

For devices in which the bunch dimensions are much smaller than the dimensions of the structure the numerical field solution is typically hampered by spurious oscillations. The reason for this oscillations is the large numerical dispersion error of conventional schemes along the beam axis. Recently, several numerical schemes have been proposed which apply operator splitting to optimize and under certain circumstances eliminate the dispersion error in the direction of the bunch motion. However, in comparison to the standard Yee scheme the methods based on operator splitting do not conserve the standard discrete Gauss law. This contribution is dedicated to the construction of conserved discrete Gauss laws and conservative current interpolation for some of the split operator methods. Finally, the application of the methods in a PIC simulations is shown.

• R. Hampel, W. F.O. Müller, T. Weiland
  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.

• X. Dong, E. Gjonaj, W. F.O. Müller, T. Weiland
  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.

• J.-F. Ostiguy, L. Michelotti
  Fermilab, Batavia, Illinois

We describe CHEF, an application based on an extensive hierarchy of C++ class libraries. The objectives are (1) provide a convenient, effective application to perform standard beam optics calculations and (2) seamlessly support development of both linear and non-linear simulations, for applications ranging from a simple beamline to an integrated system involving multiple machines. Sample applications are discussed.

• R. D. Ryne, E. W. Bethel, I. V. Pogorelov, J. Qiang, J. M. Shalf, C. Siegerist, M. Venturini
  LBNL, Berkeley, California
• D. T. Abell
  Tech-X, Boulder, Colorado
• A. Adelmann
  PSI, Villigen
• J. F. Amundson, P. Spentzouris
  Fermilab, Batavia, Illinois
• A. Dragt
  University of Maryland, College Park, Maryland
• C. Mottershead, N. Neri, P. L. Walstrom
  LANL, Los Alamos, New Mexico
• V. Samulyak
  BNL, Upton, Long Island, New York

MaryLie/IMPACT (ML/I) is a 3D parallel Particle-In-Cell code that combines the nonlinear optics capabilities of MaryLie 5.0 with the parallel particle-in-cell space-charge capability of IMPACT. In addition to combining the capabilities of these codes, ML/I has a number of powerful features, including a choice of Poisson solvers, a fifth-order rf cavity model, multiple reference particles for rf cavities, a library of soft-edge magnet models, representation of magnet systems in terms of coil stacks with possibly overlapping fields, and wakefield effects. The code allows for map production, map analysis, particle tracking, and 3D envelope tracking, all within a single, coherent user environment. ML/I has a front end that can read both MaryLie input and MAD lattice descriptions. The code can model beams with or without acceleration, and with or without space charge. Developed under a US DOE Scientific Discovery through Advanced Computing (SciDAC) project, ML/I is well suited to large-scale modeling, simulations having been performed with up to 100M macroparticles. ML/I uses the H5Part* library for parallel I/O. The code inherits the powerful fitting/optimizing capabilities of MaryLie, augmented for the new features of ML/I. The combination of soft-edge magnet models, high-order capability, and fitting/optimization, makes it possible to simultaneously remove third-order aberrations while minimizing fifth-order, in systems with overlapping, realistic magnetic fields. Several applications will be presented, including aberration correction in a magnetic lens for radiography, linac and beamline simulations of an e-cooling system for RHIC, design of a matching section across the transition of a superconducting linac, and space-charge tracking in the damping rings of the International Linear Collider.

*ICAP 2006 paper ID 1222, A. Adelmann et al., "H5Part: A Portable High Performance Parallel Data Interface for Electromagnetics Simulations"

• F. Hamme, U. Becker, P. Hammes
  CST, Darmstadt

• M. Dohlus
  DESY, Hamburg

• J. A. Nolen
  ANL, Argonne, Illinois

As accelerator facilities become more complex and demanding and computational capabilities become ever more powerful, there is the opportunity to develop and apply very large-scale simulations to dramatically increase the speed and effectiveness of many aspects of the design, commissioning, and finally the operational stages of future projects. Next-generation radioactive beam facilities are particularly demanding and stand to benefit greatly from large-scale, integrated simulations of essentially all aspects or components. These demands stem from things like the increased complexity of the facilities that will involve, for example, multiple-charge-state heavy ion acceleration, stringent limits on beam halos and losses from high power beams, thermal problems due to high power densities in targets and beam dumps, and radiological issues associated with component activation and radiation damage. Currently, many of the simulations that are necessary for design optimization are done by different codes, and even separate physics groups, so that the process proceeds iteratively for the different aspects. There is a strong need, for example, to couple the beam dynamics simulation codes with the radiological and shielding codes so that an integrated picture of their interactions emerges seamlessly and trouble spots in the design are identified easily. This integration is especially important in magnetic devices such as heavy ion fragment separators that are subject to radiation and thermal damage. For complex, high-power accelerators there is also the need to fully integrate the control system and beam diagnostics devices to a real-time beam dynamics simulation to keep the tunes optimized without the need for continuous operator feedback. This will most likely require on-line peta-scale computer simulations. The ultimate goal is to optimize performance while increasing the cost-effectiveness and efficiency of both the design and operational stages of future facilities.

• A. E. Candel, A. C. Kabel, K. Ko, L. Lee, Z. Li, C.-K. Ng, E. E. Prudencio, G. L. Schussman, R. Uplenchwar
  SLAC, Menlo Park, California

Under the US DOE SciDAC project, SLAC has developed a suite of 3D (2D) Parallel Higher-order Finite Element (FE) codes, T3P (T2P) and PIC3P (PIC2P), aimed at accurate, large-scale simulation of wakefields and particle-field interactions in RF cavities of complex shape. The codes are built on the FE infrastructure that supports SLAC’s frequency domain codes, Omega3P and S3P, to utilize conformal tetrahedral (triangular) meshes, higher-order basis functions and quadratic geometry approximation. For time integration, they adopt an unconditionally stable implicit scheme. PIC3P (PIC2P) extends T3P (T2P) to treat charged particle dynamics self-consistently using the PIC approach, the first such implementation on the FE grid. Examples from applications to the ILC, LCLS and other accelerators will be presented to compare the accuracy and computational efficiency of these codes versus their counterparts using structured grids.

• I. V. Pogorelov, J. Qiang, R. D. Ryne, M. Venturini, A. Zholents
  LBNL, Berkeley, California
• R. L. Warnock
  SLAC, Menlo Park, California

• J. Qiang, I. V. Pogorelov, R. D. Ryne
  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.

• A. Latina, L. Neukermans, G. Rumolo, D. Schulte
  CERN, Geneva
• P. Eliasson
  Uppsala University, Uppsala

• G. Asova, S. Khodyachykh, M. Krasilnikov, F. Stephan
  DESY Zeuthen, Zeuthen
• P. Castro, F. Loehl
  DESY, Hamburg

A high phase-space density of the electron beam is obligatory for the successful operation of a Self Amplified Spontaneous Emission - Free Elector Laser (SASE-FEL). Detailed knowledge of the phase-space density distribution is thus very important for characterizing the performance of the used electron sources. The Photo Injector Test Facility at DESY in Zeuthen (PITZ) is built to develop, operate and optimize electron sources for FELs. Currently a tomography module for PITZ is under design as part of the ongoing upgrade of the facility. This contribution studies the performance of the tomography module. Errors in the beam size measurements and their contribution to the calculated emittance will be studied using simulated data. As a practical application the Maximum Entropy Algorithm (MENT) will be used to reconstruct the data generated by an ASTRA simulation.

• S. Yaramyshev, W. Barth, L. A. Dahl, L. Groening, B. Schlitt
  GSI, Darmstadt

• S. Yaramyshev, W. Barth, L. A. Dahl, L. Groening
  GSI, Darmstadt
• A. P. Durkin
  MRTI RAS, Moscow
• S. Minaev
  ITEP, Moscow
• A. Schempp
  IAP, Frankfurt-am-Main

• A. Dolinskii, V. Gostishchev, M. Steck
  GSI, Darmstadt
• O. A. Bezshyyko
  National Taras Shevchenko University of Kyiv, The Faculty of Physics, Kyiv

• A. Markovik, G. Pöplau, U. van Rienen
  Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
• R. Wanzenberg
  DESY, Hamburg

The determination of electron cloud instability thresholds is a task with high priority in the ILC damping rings research and development objectives. Simulations of electron cloud instabilities are therefore essential. In this paper a new particle tracking program is presented which includes the Poisson solver MOEVE for space charge calculations. Recently, perfectly electric conducting beam pipes with arbitrary elliptical shapes have been implemented as boundary conditions in the Poisson solver package MOEVE. The 3D space charge algorithm taking into account a beam pipe of elliptical shape will be presented along with numerical test cases. The routine is also implemented in the program code ASTRA, in addition we compare the tracking with both routines.

• W. Ackermann, T. Weiland
  TEMF, Darmstadt

The moment method model has been proven to be a valuable tool for numerical simulations of a charged particle beam transport both in accelerator design studies and in optimization of the operating parameters for an already existing beam line. On the basis of the Vlasov equation which describes a collision-less kinetic approach, the time evolution of such integral quantities like the mean or rms dimensions, the mean or rms kinetic momenta, and the total energy or energy spread for a bunched beam can be described by a set of first order non-autonomous ordinary differential equations. Application of a proper time integrator to such a system of ordinary differential equations enables then to determine the time evolution of all involved ensemble parameter under consistent initial conditions. From the vast amount of available time integration methods different versions have to be implemented and evaluated to select a proper algorithm. The computational efficiency in terms of effort and accuracy serves as a selection criterion. Among possible candidates of suited time integrators for the given set of moment equations are the explicit Runge-Kutta methods, the implicit theta methods, and the linear implicit Rosenbrock methods. Various algorithms have been implemented and tested under real-world conditions. In the paper the evaluation process is documented.

• U. Becker
  CST, Darmstadt

1. Cavity design using eigenmode solver including calculation of losses, Q-factors, shunt impedance and thermal analysis.
2. Coupler Design, including external Q-factor
3. Wakefield Simulation, including resistive wall effects, also realized for beams slower than speed of light
4. dispersion diagram for the analysis of periodic structures
5. design of guns, including beam emittance studies
6. study of secondary emission processes and dark current effects in accelerating structures.

• D. L. Bruhwiler, J. R. Cary, D. A. Dimitrov, P. Messmer
  Tech-X, Boulder, Colorado
• E. Esarey, C. G.R. Geddes
  LBNL, Berkeley, California
• E. Kashdan
  Brown University, Providence, Rhode Island

Electromagnetic particle-in-cell (PIC) simulations of laser wakefield accelerator (LWFA) experiments have shown great success recently, qualitatively capturing many exciting features, like the production of ~1 GeV electron beams with significant charge, moderate energy spread and remarkably small emittance. Such simulations require large clusters or supercomputers for full-scale 3D runs, and all state-of-the art codes are using similar algorithms, with 2nd-order accuracy in space and time. Very high grid resolution and, hence, a very large number of time steps are required to obtain converged results. We present preliminary results from the implementation and testing of 4th-order algorithms, which hold promise for dramatically improving the accuracy of future LWFA simulations.

• J. A. Holmes, S. M. Cousineau, V. V. Danilov, J. Galambos, S. Henderson, M. A. Plum, A. P. Shishlo
  ORNL, Oak Ridge, Tennessee

• D. L. Bruhwiler
  Tech-X, Boulder, Colorado

High-energy electron cooling requires co-propagation of relativistic electrons over many meters with the recirculating bunches of an ion collider ring. The expected increase of ion beam luminosity makes such systems a key component for proposed efforts like the RHIC luminosity upgrade* and the FAIR project**. Correctly simulating the dynamical friction of heavy ions, during brief interactions with low-density electron populations, in the presence of arbitrary electric and magnetic fields, requires a molecular dynamics approach that resolves close Coulomb collisions. Effective use of clusters and supercomputers is required to make such computations practical. Previous work*** will be reviewed. Recent algorithmic developments**** and future plans will be emphasized.

* http://www.bnl.gov/cad/ecooling
** http://www.gsi.de/GSI-Future/cdr
*** A. V. Fedotov et al., Phys. Rev. ST/AB (2006), in press.
**** G. I. Bell et al., AIP Conf. Proc. 821 (2006), p. 329.

• T. Pieloni
  CERN, Geneva

• J.-L. Vay
  LBNL, Berkeley, California
• A. Friedman, D. P. Grote
  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).

• R. A. Kishek, G. Bai, B. L. Beaudoin, S. Bernal, D. W. Feldman, R. B. Fiorito, T. F. Godlove, I. Haber, P. G. O'Shea, C. Papadopoulos, B. Quinn, M. Reiser, D. Stratakis, D. F. Sutter, J. C.T. Thangaraj, K. Tian, M. Walter, C. Wu
  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.

• O. Boine-Frankenheim, V. Kornilov
  GSI, Darmstadt

Simulation studies of the transverse stability of the FAIR synchrotrons have been started. The simulation code PATRIC has been developed in order to predict coherent instability thresholds with space charge and different impedance sources. Some examples of code validation using the numerical Schottky noise and analytical stability boundaries will be discussed.

• A. C. Kabel, V. Akcelik, A. E. Candel, L. Ge, K. Ko, L. Lee, Z. Li, C.-K. Ng, E. E. Prudencio, G. L. Schussman, R. Uplenchwar, L. Xiao
  SLAC, Menlo Park, California

• B. Doliwa, T. Weiland
  TEMF, Darmstadt

Fast kicker modules represent a potential source of beam instabilities in the planned Facility for Antiproton and Ion Research (FAIR) at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt. Containing approximately six tons of lossy ferrite material, the more than forty kicker modules to be installed in the SIS-100 and SIS-300 synchrotrons are expected to have a considerable parasitic influence on the high-current beam dynamics. In order to be able to take these effects into account in the kicker design, a dedicated electromagnetic field software for the calculation of coupling impedances has been developed. Here we present our numerical results on the longitudinal and transverse kicker coupling impedances for the planned components and point out ways of optimization. Besides the inductive coupling of the beam to the external network -relevant below 100 MHz- particular attention is paid to the impact of ferrite losses up to the beam-pipe cutoff frequency.

• B. Auchmann, S. Russenschuck, R. de Maria
  CERN, Geneva
• S. Kurz
  Robert Bosch GmbH, Frankfurt

1. a representation of strands by line currents,
2. a coupling of the finite element method and the boundary element method to take into account the field contribution of the magnet yoke, as well as eddy-current effects in conductive bulk material,
3. a model for persistent currents,
4. a model for inter-filament coupling currents, and
5. a model for inter-strand coupling currents in Rutherford-type cables.

• A. Adelmann, A. Gsell, B. S.C. Oswald
  PSI, Villigen
• E. W. Bethel, J. M. Shalf, C. Siegerist
  LBNL, Berkeley, California

• F. Wolfheimer, E. Gjonaj, T. Weiland
  TEMF, Darmstadt

Particle-In-Cell (PIC) simulations are commonly used in the field of computational accelerator physics for modelling the interaction of electromagnetic fields and charged particle beams in complex accelerator geometries. However, the practicability of the method for real world simulations, is often limited by the huge size of accelerator devices and by the large number of computational particles needed for obtaining accurate simulation results. Thus, the parallelization of the computations becomes necessary to permit the solution of such problems in a reasonable time. Different algorithms allowing for an efficient parallel simulation by preserving an equal distribution of the computational workload on the processes while minimizing the interprocess communication are presented. This includes some already known approaches based on a domain decomposition technique as well as novel schemes. The performance of the algorithms is studied in different computational environments with simulation examples including a full 3D simulation of the PITZ-Injector [*].

*A. Oppelt et al Status and First Results from the Upgraded PITZ Facility, Proc. FEL 2005

• N. Malitsky
  BNL, Upton, Long Island, New York
• R. M. Talman
  CLASSE, Ithaca, New York

• U. Becker
  CST, Darmstadt

1. Cavity design using eigenmode solver including calculation of losses, Q-factors, shunt impedance and thermal analysis.
2. Coupler Design, including external Q-factor
3. Wakefield Simulation, including resistive wall effects, also realized for beams slower than speed of light
4. dispersion diagram for the analysis of periodic structures
5. design of guns, including beam emittance studies
6. study of secondary emission processes and dark current effects in accelerating structures.

• E. Sonnendrucker, M. Gutnic, O. Hoenen, G. Latu, M. Mehrenberger, E. Violard
  IRMA, Strasbourg

• P. Spentzouris
  Fermilab, Batavia, Illinois