05 Beam Dynamics and Electromagnetic Fields

D06 Code Developments and Simulation Techniques

Paper Title Page
TUYMH03 Developing Peta-Scalable Algorithms for Beam Dynamic Simulations 1256
 
  • J. Xu, P.F. Fisher, M. Min, B. Mustapha, J.A. Nolen, P.N. Ostroumov
    ANL, Argonne
 
 

Peta-scalable software packages for beam dynamic simulations are being developed and used at the Argonne Leadership Computing Facility. The standard Particle-In-Cell (PIC) method and direct Vlasov solvers in 4 dimensions have been developed and benchmarked with respect to each other. Both of them have been successfully run on 32 thousands processors on BG/P at Argonne National Laboratory. Challenges and prospects of developing Vlasov solvers in higher dimensions will be discussed. Several scalable Poisson solvers have been developed and incorporated with these software packages. Domain decomposition method has been used for the parallelization. In the future developments, these algorithms will be applied to hundreds of thousands processors for peta-scale computing. These software packages have been applied for the design of accelerators, and some large scale simulations will be shown and discussed.

 

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Slides

 
TUPEA070 ECHARM - a Software for Calculation of Physical Quantities of Interest in Coherent Interaction of Relativistic Particles with Crystals 1485
 
  • E. Bagli
    INFN-Ferrara, Ferrara
  • V. Guidi
    UNIFE, Ferrara
  • V.A. Maisheev
    IHEP Protvino, Protvino, Moscow Region
 
 

We present an analytical model to calculate the physical quantities of interest experienced by relativistic particles in their motion aligned with periodic complex atomic structures. Classical physics equations and the expansion of periodic functions as a Fourier series have been used for the calculation. This method allows calculating the contribution from all the planes and axes inside the crystal, in contrast to other simulation codes for which the motion is evaluated only on nearest neighbors atomic strings. Based on the calculation technique we have developed the "ECHARM" program, which allows calculating one- and two- dimensional averaged physical quantities of interest. The calculation holds for the main axes of any orthorhombic and tetragonal structures and for any orientation in the cubic structure. To underline the capability of the program, complex structures such as zeolites have been worked out. Based on the "ECHARM" code, simulation of the relativistic particle motion within complex structures has been developed. With this code it is possible to simulate the motion in bent crystal to study planar and axial channeling volume reflection.

 
TUPEB015 Dynamic Aperture Limit caused by IR Nonlinearity in Extremely Low-beta B Factories 1548
 
  • K. Ohmi, H. Koiso
    KEK, Ibaraki
 
 

Progress of Graphic Processor Unit (GPU) is marveled. The performance is 1TFlops per unit. Simulation of electron gun can be performed by particle-particle interactions, in which the calculation cost is NxN. Since the calculation of each interaction is very simple, GPU can demonstrate its ability. We show simulation results and discuss the possibilities to extend other simulations.

 
TUPEB018 CSR in the SuperKEKB Damping Ring 1554
 
  • D.M. Zhou, T. Abe, H. Ikeda, M. Kikuchi, K. Ohmi, K. Oide, K. Shibata, M. Tobiyama
    KEK, Ibaraki
  • G.V. Stupakov
    SLAC, Menlo Park, California
 
 

Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.

 
TUPEC046 Simulation of an Industrial Linac (5 MeV, 1 mA, 3 GHz) with MAGIC Electromagnetic PIC Code 1826
 
  • P. Gouard, S. Champeaux
    CEA, Bruyeres le Chatel
  • P. Liger, D. Morisseau
    GETINGE - La Calhene, Villebon sur Yvette
 
 

The original linac consists of an electron gun (45 kV, 6 A peak, 4 μs pulses @ 210 Hz) and 8 accelerating cells coupled with coupling cells in π/2 mode @ 3 GHz to provide for a 1 mA and 5 MeV beam. A loss of control of electron emission was experimentally observed due to anomalous heating of the cathode. We simulate the linac operation with the 2D1/2 MAGIC® electromagnetic PIC code to understand and suppress these phenomena. We show that electrons are accelerated back from the accelerating structure to the cathode. Their power is responsible for the unwanted cathode heating and emission control loss. To overcome these phenomena, a new design is proposed. A buncher cavity and a solenoid are inserted to improve the coupling between the electron beam and the accelerating cells.

 
TUPEC048 Coupling Impedance Contribution of Ferrite Devices: Theory and Simulation 1829
 
  • L. Haenichen, W.F.O. Müller, T. Weiland
    TEMF, TU Darmstadt, Darmstadt
  • O. Boine-Frankenheim
    GSI, Darmstadt
 
 

Beam coupling impedances have been identified as an appropriate quantity to describe collective instabilities caused through beam-induced fields in heavy ion synchrotron accelerators such as the SIS-18 and the SIS-100 at the GSI facility. The impedance contributions caused by the multiple types of beamline components need to be determined to serve as input condition for later stability studies. This paper will discuss different approaches to calculate the Coupling Impedance contribution of ferrite devices, exploiting the abilities of both commercial codes such as CST STUDIO SUITE® and specific extensions of this code to address kicker related problems in particular. Before addressing actual beamline devices, benchmark problems with cylindrical and rectangular geometry will be simulated and the results will be compared with the corresponding analytical formulations.

 
TUPEC049 Efficient 3D Space Charge Calculations with Adaptive Discretization based on Multigrid 1832
 
  • G. Pöplau, 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. Whereas an adaptive discretization of a bunch is often required for efficient space charge calculations in practice, such a technique is not implemented in many computer codes. For instance, the FFT Poisson solver that is often applied allows only an equidistant mesh. An adaptive discretization following the particle density distribution is implemented in the GPT tracking code (General Particle Tracer, Pulsar Physics) together with a multigrid Poisson solver. The disadvantage of this approach is that jumps in the distribution of particles are not taken into account and the hierarchical construction of meshes in multigrid can not be used. In this paper we present an approach to an adaptive discretization which is based on the multigrid technique. The goal is that the error estimator needed for the adaptive distribution of mesh lines can be calculated directly from the multigrid procedure. The algorithm will be investigated for several particle distributions and compared to that adaptive discretization method implemented in GPT.

 
TUPEC050 Analysis of the Measurement of Electron Cloud Density under Various Beam-optics Elements in KEKB LER 1835
 
  • P. Jain
    Sokendai, Ibaraki
  • H. Fukuma, K. Kanazawa, Y. Suetsugu
    KEK, Ibaraki
 
 

Electron Cloud (ECLOUD) deteriorates the performance of proton and positron storage rings. Therefore it is desirable to understand the ECLOUD buildup in a given machine. The data taken by Retarded Field Analyzer (RFA) with a multi channel plate showed that the signal had the peaks coinciding with the positron bunch pattern if a high voltage of -2kV is applied to the retarded grid*. This suggests that the cloud electrons get maximum kick near the positron bunch. A computer program has been developed to study the near bunch ECLOUD density at KEKB LER (Low Energy Ring). In simulations, secondary electron emission is modeled according to the Furman and Pivi's model**. In this paper we compare the simulation results of the ECLOUD buildup with the experiments performed in KEK under different beam-optics elements.


* K. Kanazawa et al., PAC05, 1054.
** M. Furman and M. Pivi, PRST-AB, 5, 124404 (2002).

 
TUPEC051 Wake Field Analysis by Time Domain BEM with Initial Value Problem Formulation 1838
 
  • H. Kawaguchi
    Muroran Institute of Technology, Department of Electrical and Electronic Engineering, Muroran
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt
 
 

A Time Domain Boundary Element Method (TDBEM) has advantages of grid dispersion free property, treatment of electron bunch with curved trajectory, etc. in wake field analysis. On the other hand, the TDBEM has also serious problems of heavy calculation cost and large required memory which are main reasons why the TDBEM can not be widely used yet. For the large memory problem, moving window scheme was introduced into the TDBEM and it was shown that the TDBEM can be applied to very long accelerator structures*. This paper presents a new formulation of the TDBEM, an initial value problem formulation. To use the initial value problem formulation of the TDBEM, a new type of moving window scheme, which can be applied to curved trajectory or electron motion with smaller velocity than the speed of light, will be introduced.


* K.Fujita, H.Kawaguchi, R.Hampel, W.F.O.Muller, T.Weiland, S.Tomioka,"Time Domain Boundary Element Analysis of Wake Fields in Long Accelerator Structures,"IEEE Trans. Nucl. Sci.,55[5](2008),pp.2584-2591.

 
TUPEC053 Hellweg 2D Code for Electron Dynamics Simulations 1841
 
  • S.V. Kutsaev
    MEPhI, Moscow
 
 

This paper introduces "Hellweg 2D" code, a special tool for electron dynamics simulation in waveguide accelerating structure. The underlying theory of this software is based on the numerical solutions of differential equations of particle motion. The effects considered in this code include beam loading, space charge forces, external focusing magnetic field. "Hellweg 2D" is capable to deal with multisectional accelerators. Along with a manual input of electrodynamical parameters of the cells, for disk-loaded structures they can be calculated automatically with a help of experimental data tables. In order to obtain the maximum capture in the buncher section, the optimizer of phase velocity and electric field strength functions is developed. The comparison of U-1-M buncher beam dynamics simulations via "Hellweg 2D" and experimental data is provided.

 
TUPEC054 Modeling Nanometer Structured Laser Induced Field Emission 1844
 
  • B.S.C. Oswald, S. Tsujino
    PSI, Villigen
  • P. Leidenberger
    IFH, Zurich
 
 

Laser induced field emission has become an enabling technology for building ultra-low emittance electron sources for particle accelerators, such as the x-ray free-electron laser (SwissFEL) under development at the Paul Scherrer Institut (PSI). One approach consists of a sharp pyramidal tip with lateral dimensions of a few nanometers, illuminated by a laser to increase the extracted electron current. Another approaches uses conventional cathodes. In both cases, there are structural details on the nanometer scale, that determine the interaction between the laser and the cathode and thus directly the quantum efficiency of the emitter. We use a 3-d full-wave finite element time domain electromagnetic approach* to understand the nano-optical interaction between structure and laser pulse. For example, the lightning rod effect of sharp tips enhances the electric field in the vicinity. Also, optical antenna concepts have been proposed to enhance the electric field at the field emitter's tip so that higher currents can be extracted. We use dispersive material models for the metals in the optical region of the electromagnetic spectrum.


*Benedikt Oswald and Patrick Leidenberger, Journal of Computational and Theoretical Nanoscience, Vol 6(3), 2009, pp. 784-794. doi 10.1166/jctn.2009.1109

 
TUPEC055 Computation of Electromagnetic Modes in the Transverse Deflecting Cavity 1847
 
  • H. Guo
    PSI-LRF, Villigen, PSI
  • A. Adelmann, A. Falone, C. Kraus, B.S.C. Oswald
    PSI, Villigen
  • P. Arbenz
    ETH, Zurich
 
 

The X-ray Free Electron Laser (SwissFEL) under development at the Paul Scherrer Institut (PSI) will employ a special type of a deflecting cavity, LOLA*, for beam diagnostics. Since this cavity's design breaks the symmetry, a complete 3-dimensional eigenmodal analysis is indispensable. The 3-dimensional eigenmodal solver femaxx employs the finite element method and has been developed in a collaboration between PSI and the Swiss Federal Institute of Technology Zurich (ETH). The femaxx code uses the graphical frontend program heronion for the application of boundary conditions, including symmetry, and generates a tetrahedral mesh. We use femaxx to analyze the existing LOLA cavity design**, compute electromagnetic eigenmodes with their corresponding eigenfrequencies, and associated performance figures. Since these are large computational problems femaxx has been optimized for distributed memory parallel compute clusters. For the further usage in the beam dynamics code OPAL we sample the eigenmodal fields on a 3-dimensional Cartesian grid.


* A. Falone, et al: RF deflector for bunch length measurement at low energy at PSI. Proceedings of PAC2009.
** P. Arbenz et al., Parallel Computing, 32: 157-165 (2006).

 
TUPEC056 Evolutionary Algorithms in the Design of Crab Cavities 1850
 
  • C. Lingwood, G. Burt, K. Gunn
    Cockcroft Institute, Lancaster University, Lancaster
  • J.D.A. Smith
    Tech-X, Boulder, Colorado
 
 

The design of RF cavities is a multivariate multi-objective problem. Manual optimisation is poorly suited to this class of investigation, and the use of numerical methods results in a non-differentiable problem. Thus the only reliable optimisation algorithms employ heuristic methods. Using an evolutionary algorithm guided by Pareto ranking methods, a crab cavity design can be optimised for transverse voltage (VT) while maintaining acceptable surface fields and the correct operating frequency. Evolutionary algorithms are an example of a parallel meta-heuristic search technique inspired by natural evolution. They allow complex, epistatic (non-linear) and multimodal (multiple optima and/or sub-optima) optimization problems to be efficiently explored. Using the concept of domination the solutions can be ordered into Pareto fronts. The first of which contains a set of cavity designs for which no one objective (e.g. the transverse voltage) can be improved without decrementing other objectives.

 
TUPEC057 Advances With Merlin - A Beam Tracking Code 1853
 
  • J. Molson, R.J. Barlow, H.L. Owen, A.M. Toader
    UMAN, Manchester
  • J. Molson
    Cockcroft Institute, Warrington, Cheshire
 
 

MERLIN is a highly abstracted particle tracking code written in C++ that provides many unique features, and is simple to extend and modify. We have investigated the addition of high order wakefields to this tracking code and their effects on bunches, particularly with regard to collimation systems for both hadron and lepton accelerators. Updates have also been made to increase the code base compatibility with current compilers, and speed enhancements have been made to the code via the addition of multi-threading to allow cluster operation on the grid. In addition, this allows for simulations with large numbers of particles to take place. Instructions for downloading the new code base are given.

 
TUPEC058 Beam Dynamics in NS-FFAG EMMA with Dynamical Maps 1856
 
  • Y. Giboudot, R. Nilavalan
    Brunel University, Middlesex
  • T.R. Edgecock
    STFC/RAL, Chilton, Didcot, Oxon
  • A. Wolski
    The University of Liverpool, Liverpool
 
 

The Non Scaling Fixed Field Alternating Gradient EMMA has a compact linear lattice. Effect of Fringe Field on the beam has to be studied carefully. A numerical magnetic field map is generated by magnet measurements or magnet design softwares. We developed a technique that produces from the numerical field map, a dynamical map for a particle travelling in the entire EMMA cell for a reference energy without acceleration. Since the beam dynamics change with energy, a set of maps have been produce with different reference energies between 10 and 20MeV. For each reference energy, simulated tune and time of flight (TOF) have been compared with results in Zgoubi - tracking directly through numerical field map. The range of validity of a single map has been investigated by tracking particle with large energy deviation. From that, a sensible acceleration scheme has been implemented.


yoel.giboudot@stfc.ac.uk

 
TUPEC059 Start-to-End Tracking Simulations of the Compact Linear Collider 1859
 
  • J. Resta-López, J. Dale
    JAI, Oxford
  • B. Dalena, D. Schulte, J. Snuverink, F. Stulle, R. Tomás
    CERN, Geneva
  • A. Latina
    Fermilab, Batavia
 
 

We present the current status of the beam tracking simulations of the Compact Linear Collider (CLIC) from the exit of the damping ring to the interaction point, including the ring to main linac (RTML) section, main linac, beam delivery system (BDS) and beam-beam interactions. This model introduces realistic alignment survey errors, dynamic imperfections and also the possibility to study collective effects in the main linac and the BDS. Special emphasis is put on low emittance transport and beam stabilization studies, applying beam based alignment methods and feedback systems. The aim is to perform realistic integrated simulations to obtain reliable luminosity predictions.

 
TUPEC060 Serpentine: A New Code for Particle Tracking 1862
 
  • S. Molloy, S.T. Boogert
    Royal Holloway, University of London, Surrey
 
 

Serpentine is a Python library, written for the purpose of simulating charged particle accelerators. It has been written to allow for the simulation of both rings and single-shot machines in a light-weight way (i.e. without requiring significant computational resources for typical calculations, such as the determination of transfer matrices, or matching of Twiss parameters), and has been structured to be highly modular (i.e. allowing extension of the simulations to include effects not already included in the base installation). Through the use of the Universal Accelerator Parser (UAP), Serpentine has no need for a new lattice representation, and allows access to any lattice format understood by UAP. The operation of this code on several complex accelerator designs is demonstrated.

 
TUPEC061 Scalable High-order Algorithms for Wakefield Simulations 1865
 
  • M. Min, P.F. Fischer
    ANL, Argonne
 
 

NekCEM is a high-performance parallel code for simulating wakefields based on high-order discretizations*,**. We will present performance of NekCEM code at large count of processors. A newly developed communication kernel for NekCEM enables simulations on 10K-100K processors. We will demonstrate scalablity analysis for P>10K, depending on the number of grid points per processor for wakepotential simulations with a 9-cell TESLA cavity.


* Spectral element discontinuous Galerkin (SEDG) simulations with a moving window, Proc. PAC09
** SEDG simulations for bunched beam in accelerating structures, Proc. PAC07

 
TUPEC062 Advanced Multi-program GUI for Accelerator Modeling 1868
 
  • T.J. Roberts
    Muons, Inc, Batavia
  • D.M. Kaplan
    Illinois Institute of Technology, Chicago, Illinois
 
 

There are dozens of programs for designing and modeling accelerator systems, most of which have their own language for describing the system. This means a designer must spend considerable time learning the languages of different programs and converting system descriptions among them. This paper describes a project to develop a new language for accelerator modeling, together with a portable suite of programs to implement it. These programs will assist the user while editing, visualizing, developing, simulating, and sharing models of accelerator components and systems. This suite is based on a Graphical User Interface (GUI) that will permit users to assemble their system graphically and then display it and check its sanity visually, even while using modeling programs that have no graphical or visualization capabilities. Incorporating the concept of libraries as a primary component of the language will encourage collaboration among geographically diverse teams. The requirements for developing this language and its tools will be based on generality, flexibility, extensibility, portability, usability, and sharability.

 
TUPEC063 Particle Tracking in Matter-dominated Beam Lines 1871
 
  • T.J. Roberts, K.B. Beard
    Muons, Inc, Batavia
  • S. Ahmed, D. Huang, D.M. Kaplan, L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois
 
 

The G4beamline program* is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit**, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available at: http://g4beamline.muonsinc.com


* http://g4beamline.muonsinc.com
** http://geant4.cern.ch

 
TUPEC064 Full Electromagnetic Simulation of Coherent Synchrotron Radiation via the Lorentz-Boosted Frame Approach 1874
 
  • J.-L. Vay, E. Cormier-Michel, W.M. Fawley, C.G.R. Geddes
    LBNL, Berkeley, California
 
 

Numerical simulation of some systems containing charged particles with highly relativistic directed motion can be speeded up dramatically by choice of the proper Lorentz-boosted frame*. Orders of magnitude speedup has been demonstrated for simulations from first principles of laser-plasma accelerator, free electron laser, and particle beams interacting with electron clouds. We summarize the technique and the most recent examples. We then address the application of the Lorentz-boosted frame approach to coherent synchrotron radiation (CSR), which can be strongly present in bunch compressor chicanes. CSR is particularly relevant to the next generation of x-ray light sources and difficult to simulate in the lab frame because of the large ratio of scale lengths. It can increase both the incoherent and coherent longitudinal energy spread, effects that often lead to an increase in transverse emittance. We use the WARP code** to simulate CSR emission around dipole simple bends. We present some scaling arguments for the possible computational speed up factor in the boosted frame and initial 3D simulation results for some standard CSR test cases.


* J.-L. Vay, Phys. Rev. Lett. 98 (2007) 130405
** D.P. Grote, A. Friedman, J.-L. Vay, and I. Haber, AIP Conf. Proc. 749 (2005), 55.

 
TUPEC066 Models and High-order Maps for Realistic RF Cavities using Surface Field Data 1877
 
  • D.T. Abell, I.V. Pogorelov, P. Stoltz
    Tech-X, Boulder, Colorado
 
 

Imagine a virtual cylinder passing through an rf cavity. Given field data on the surface of this cylinder, one can compute accurate high-order transfer maps for particles traversing the cavity*. This technique is robust against errors or noise present in the surface data; moreover, it is not limited to accelerating modes. We describe this technique and present recent work that uses VORPAL** field data as a starting point for modeling crab cavities. In addition, we present realistic models, including fringes, for several standing-wave modes. These models, which include a simple accelerating mode and a TM-110 (crab) mode, are useful for the accurate computation of transfer maps as well as for constructing model fields that can be used for testing and comparing a variety of rf cavity codes.


* D.T. Abell, Phys. Rev. ST Accel. Beams 9, 052001, (2006).
** C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004).

 
TUPEC069 VizSchema - a Unified Visualization of Computational Accelerator Physics Data 1880
 
  • S.G. Shasharina, D. Alexander, J.R. Cary, M.A. Durant, S.E. Kruger, S.A. Veitzer
    Tech-X, Boulder, Colorado
 
 

Data organization of simulations outputs differs from application to application. This makes development of uniform visualization and analysis tools difficult and impedes comparison of simulation results. VizSchema is an effort to standardize metadata of HDF5 format so that the subsets of data needed to visualize physics can be identified and interpreted by visualization tools. Based on this standard, we developed a powerful VisIt-based visualization tool. It allows a uniform approach for 3D visualization of large data of various kinds (fields, particles, meshes) from the COMPASS suite for SRF cavities and laser-plasma acceleration. In addition, we developed a specialized graphical interface to streamline visualization of VORPAL outputs and submit remote VORPAL runs. In this paper we will describe our approach and show some visualizations results.

 
TUPEC071 Generic Model Host System Design 1883
 
  • P. Chu, J. Wu
    SLAC, Menlo Park, California
  • J. Qiang
    LBNL, Berkeley, California
  • G.B. Shen
    BNL, Upton, Long Island, New York
 
 

There are many simulation codes for accelerator modeling. Each one has some strength but not all. Collaboration is formed for the effort of providing a platform to host multiple modeling tools. In order to achieve such a platform, a set of common physics data structure has to be set. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype will be presented.

 
TUPEC072 Service Oriented Architecture for High Level Applications 1886
 
  • P. Chu, S. Chevtsov, J. Wu
    SLAC, Menlo Park, California
  • G.B. Shen
    BNL, Upton, Long Island, New York
 
 

High level applications often suffer from poor performance and reliability due to lengthy initialization, heavy computation and rapid graphical update. Service oriented architecture (SOA) is trying to separate the initialization and computation from applications to distributed service providers. Heavy computation such as beam tracking will be done periodically on a dedicated server and data will be available to client applications at all time. Industrial standard service architecture can help to improve the reliability and maintainability of the service providers. Robustness will also be improved by reducing the complexity of individual client applications.

 
TUPEC078 A Two-dimensional FEM Code for Impedance Calculation in High Frequency Domain 1895
 
  • L. Wang, L. Lee, G.V. Stupakov
    SLAC, Menlo Park, California
 
 

A new method, using the parabolic equation (PE), for the calculation of both high-frequency and small-angle taper (or collimator) impedances is developed in [1]. One of the most important advantages of the PE approach is that it eliminates the spatial scale of the small wavelength from the problem. As a result, the numerical solution of the PE requires coarser spatial meshes. We developed a new code based on Finite Element Method (FEM) which can handle arbitrary profile of a transition. As a first step, we completed and benchmarked a two-dimensional code. One of the important advantages of the code is its fast execution time.

 
TUPEC079 Longitudinal Wakefield Study for SLAC Rotatable Collimator Design for the LHC Phase II Upgrade 1898
 
  • L. Xiao, S.A. Lundgren, T.W. Markiewicz, C.-K. Ng, J.C. Smith
    SLAC, Menlo Park, California
 
 

SLAC is proposing a rotatable collimator design for the LHC phase II collimation upgrade. This design has 20 facet faces on each cylindrical jaw surface and the two jaws, which will move in and out during operation, are rotatable in order to introduce a clean surface in case of a beam hitting a jaw in operation. When the beam crosses the collimator, it will excite broadband and narrowband modes that can contribute to the beam energy loss and power dissipation on the vacuum chamber wall and jaw surface. In this paper, the parallel eigensolver code Omega3P is used to search for all the trapped modes in the SLAC collimator design. The power dissipation generated by the beam in different vacuum chamber designs with different jaw end geometries is simulated. It is found that the longitudinal trapped modes in the circular vacuum chamber design with larger separation of the two jaws may cause excessive heating. Adding ferrite tiles on the vacuum chamber wall can strongly damp these trapped modes. The short-range wakefields will also be calculated to determine the broadband beam heating and transverse kick on the beam. We will present and discuss the simulation results.

 
TUPEC080 Recent Enhancements to the ORBIT Code 1901
 
  • J.A. Holmes
    ORNL, Oak Ridge, Tennessee
 
 

At an age of twelve years, the collective beam dynamics particle tracking code, ORBIT, is considered mature. Even so, we continue to enhance ORBIT's capabilities. Two such enhancements are reported here. The first enhancement allows for the use of time dependent waveforms for the strengths of all magnetic elements, a capability that previously was limited to kickers and to RF cavities. This capability should prove very useful for applications to synchrotrons, in which tunes are often manipulated during acceleration. The second enhancement provides an internal calculation of the lattice functions. Previously, these had to be read from an external file, but given the capability of dynamically programming the lattice magnet strengths, it is extremely useful to be able to calculate the lattice functions on demand. Examples illustrating these new ORBIT capabilities will be presented.

 
TUPEC081 Simulations and Measurements of Beam Breakup in Dielectric Wakefield Structures 1904
 
  • A. Kanareykin, C.-J. Jing, A.L. Kustov, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
  • A. Altmark
    LETI, Saint-Petersburg
  • W. Gai, J.G. Power
    ANL, Argonne
 
 

Beam breakup (BBU) effects resulting from parasitic wakefields are a serious limitation to the performance of dielectric structure based accelerators. We report here on numerical studies and experimental investigations of BBU and its mitigation. An experimental program is underway at the Argonne Wakefield Accelerator facility that will focus on BBU measurements in dielectric wakefield devices. We examine the use of external FODO channels for control of the beam in the presence of strong transverse wakefields. We present calculations based on a particle-Green's function beam dynamics code (BBU-3000) that we are developing. We will report on new features of the code including the ability to treat space charge. The BBU code is being incorporated into a software  framework that will significantly increase its utility (Beam Dynamics Simulation Platform). The platform is based on the very flexible Boinc software environment developed originally at Berkeley for the SETI@home project. The package can handle both task farming on a heterogeneous cluster of networked computers and computing on a local grid. User access to the platform is through a web browser.

 
TUPEC082 SimTrack: A Simple C++ Library for Particle Tracking 1907
 
  • Y. Luo
    BNL, Upton, Long Island, New York
 
 

SimTrack is a simple C++ library designed for numeric particle tracking in high energy accelerators. It adopts a 4th order symplectic integrator for optical transportat in the magnetic elements. 4-D and 6-D weak-strong beam-beam treatments are included for beam-beam studies. It provides versatile functions to manage elements and lines. New type of elements can be easily created in the library. It calculates Twiss and coupling, fits tunes and chromaticities, and corrects closed orbits. During tracking, the parameters of elements can be changed or modulated on the fly.

 
TUPEC083 Numerical Simulation of Beam-beam Effects in the Proposed Electron-ion Collider at Jefferson Lab 1910
 
  • B. Terzić
    CASA, newport news
  • Y. Zhang
    JLAB, Newport News, Virginia
 
 

One key limiting factor to a collider luminosity is bean-beam interactions which usually can cause serious emittance growth of colliding beams and fast reduction of luminosity. Such nonlinear collective beam effect can be a very serious design challenge when the machine parameters are pushed into a new regime. In this paper, we present simulation studies of the beam-beam effect for a medium energy ring-ring electron-ion collider based on CEBAF.

 
TUPEC084 New Particle-in-cell Code for Numerical Simulation of Coherent Synchrotron Radiation 1913
 
  • B. Terzić
    CASA, newport news
  • R. Li
    JLAB, Newport News, Virginia
 
 

We present early stage of a new code for self-consistent, 2D simulations of beam dynamics affected by CSR. The code is of the particle-in-cell variety: the beam bunch is sampled by macroparticles, which are deposited on the grid; the corresponding forces on the grid are then computed using retarded potentials according to causality, and interpolated so as to advance the particles in time. The retarded potentials are evaluated by integrating over the 2D path history of the bunch, with the charge and current density at the retarded time obtained from interpolation of the particle distributions recorded at discrete timesteps. The code is benchmarked against analytical results obtained for a rigid-line bunch. We also outline the features and applications which are currently being developed.