S-Th04: NEW METHOD FOR KLYSTRON MODELING
back Yong Ho Chin , KEK
We have developed a new method for an accurate and full-scale simulation of a klystron using the MAGIC code. MAGIC is the 2.5-D or 3-D, fully electromagnetic and relativistic particle-in-cell code for self-consistent simulation of plasma. It solves the Maxwell equations directly at particle presence by the finite difference method in time. It requires only the geometrical structure of the cavity and assumes no model for the beam-cavity interaction. In 2.5-D simulations, two-arm output couplers are approximated by a conductor which has the same complex scattering matrix with the actual 3-D ones. Advantages of MAGIC are its accuracy and generality. Even an electron gun can be simulated with results in good agreements with those of EGUN. Simulation results can be imported/exported from one section of klystron to another, allowing a consistent simulation of the entire klystron without loss of physics. Simulation results for the KEK XB72K No. 8 and No. 9 klystrons and the SLAC XL-4 klystron show excellent agreements with measurements.

F-Tu02: EXPERIENCE WITH THE CLASSIC LIBRARY FOR MAD VERSION 9
back F. Christoph Iselin , CERN
The CLASSIC library has been implemented to a large percentage, and it has been used successfully for implementing a new version of MAD written in C++. The talk focuses on the features and availability of the CLASSIC library. It will shows how the library can be used in a large accelerator design program like MAD. Some new developments of the latter are presented, like sophisticated matching features with simultaneous matching of two rings.

F-Tu03: LEGO - A CLASS LIBRARY FOR ACCELERATOR DESIGN AND SIMULATION
back Yunhai Cai , SLAC
An object-oriented class library of accelerator design and simulation is designed and implemented in a simple and modular fashion. All physics of single-particle dynamics is implemented based on the Hamiltonian in the local frame of the component. Sympletic integrators are used to approximate the integration of the Hamiltonian. A differential algebra class is introduced to extract a Taylor map up to arbitrary oder. Analysis of optics is done in the same way both for the linear and nonlinar cases. Recently, Monte Carlo simulations of synchrotron radiation has been added to the library. The code is used to design and simulate the lattices of the PEP-II and SPEAR3. And it is also used for the commissioning of the PEP-II. Some examples of how to use the library will be given.
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Work supported by USDOE contract DE-AC03-76SF00515.

F-Tu05: THE ACCELERATOR DESCRIPTION EXCHANGE FORMAT
back N. Malitsky , R. Talman, CORNELL U
The Accelerator Description eXchange Format (ADXF) is in response to the Iselin-Keil-Talman letter (1), which calls for a new accelerator description standard aimed to provide connectivity between a variety of beam-dynamics programs and heterogeneous data sources. ADXF represents a flat and complete description of the current accelerator state. It has been designed as the additional independent fully-instantiated layer to existing design data structures, in particular the Standard Input Format (SIF). Though the ADXF preserves all SIF element types its open model provides a mechanism for introducing elements with arbitrary attributes. The proposed specification is based on the Extensible Markup Language (XML), an industrial standard for processing Web documents and application-neutral data.

(1) C. Iselin, E. Keil, R. Talman, 21 January, 1998.
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Work supported by the U.S. Department of Energy.

F-Tu06: MATLAB-LIKE ENVIRONMENT FOR ACCELERATOR MODELING AND SIMULATIONS
back Hiroshi Nishimura , LBNL
TracyM is an interactive and programmable environment for accelerator design, simulation and modeling studies built on top of O-Matrix that is one of the MATLAB-like environments available on Windows. It wraps the C++ class library Goemon for the use in the O-Matrix environment. O-Matrix was chosen for its better connectivity to external function calls. It allows a single DLL to support multiple external functions instead of requiring a separate DLL for each individual external function. It provides a list structure to describe the lattice configuration, various kinds of mathematics routines that cover flexible parameter fittings, and graphics routines. As all the CPU- intensive calculations are done in the C++ layer, there is no run-time penalty. A standard set of GUI is also supported by an external program that communicates with TracyM by using a WIN32 shared memory and a pipe.
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This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Material Sciences Division, U. S. Department of Energy, under Contract No. DE-AC03-76SF00098.

 

F-Tu09: A SIMPLE REAL-TIME BEAM TUNING PROGRAM FOR THE KEKB INJECTOR LINAC
back J.W. Flanagan , K. Oide, KEK
A simple real-time beam tuning program has been developed for use at the KEK B-Factory injector linac. The program features the ability to adjust an arbitrary combination of parameters (e.g. magnet currents and RF phases) in order to optimize an arbitrary combination of monitor values (e.g. the ratio of a downstream beam current to gun current). Based on the downhill-simplex method, it requires no knowledge of beamline details. An additional "persistence" parameter is used to adjust the treatment of pulse-to-pulse variations of monitor values while mapping the parameter-space terrain, and controls the peak-holding performance in the presence of both statistical fluctuations and long-term drift. Preliminary results from the commissioning of the KEKB injector linac and plans for the future are discussed.
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Work supported by the Japanese Ministry of Education, Science, Sports and Culture (Monbusho) and the Japan Society for the Promotion of Science.

F-Tu10: A UNIVERSAL POSTPROCESSING TOOLKIT FOR ACCELERATOR SIMULATION AND DATA ANALYSIS
back Michael Borland , ANL
The Self-Describing Data Sets (SDDS) toolkit comprises about 80 generally-applicable programs sharing a common data protocol. At the Advanced Photon Source (APS), SDDS performs the vast majority of operational data collection and processing, most data display functions, and many control functions(1). Further, a number of accelerator simulation codes use SDDS for all postprocessing and data display. This has three principle advantages: First, simulation codes need not provide customized postprocessing tools, thus simplifying development and maintenance. Second, users can enhance code capabilities without changing the code itself, by adding SDDS-based pre- and post-processing. Third, multiple codes can be used together more easily, by employing SDDS for data transfer and adaptation. Given its broad applicability, the SDDS file protocol is surprisingly simple, making it quite easy for simulations to generate SDDS-compliant data. This paper discusses the philosophy behind SDDS, contrasting it with some recent trends, and outlines the capabilities of the toolkit. The bulk of the paper consists examples of using SDDS for accelerator simulation.

(1) M. Borland, "Applications Toolkit for Accelerator Control and Analysis", Proc. 1997 PAC, Vancouver, Canada, to be published.
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Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.



Focused Session C-Tu: Modeling of High Intensity Beam Phenomena

C-Tu01: MODELS AND SIMULATION OF BEAM HALO DYNAMICS IN HIGH POWER PROTON LINACS
back Thomas P. Wangler , LANL
The threat of beam loss that causes radioactivation in high-power proton linacs is increased significantly by the formation of beam halo. Numerical multiparticle simulation studies have identified the nonlinear and time dependent space-charge forces, especially those that occur in rms mismatched beams, as a major source of halo growth. The predictions of the simulation codes must be compared with independent models to provide physical understanding and to confirm the validity of the simulation results. We compare particle-core model predictions for both transverse and longitudinal halo-particle dynamics with computer simulations.
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Work supported by U.S Department of Energy

C-Tu03: A MULTIGRID-BASED APPROACH TO MODELING A HIGH CURRENT SUPERCONDUCTING LINAC FOR WASTE TRANSMUTATION
back Paolo Pierini , INFN
High current proton accelerators are nowadays planned for various applications that make use of the resulting large flux of spallation neutrons. The INFN has started funding a study of the feasibility of a (greater than) 40 MW CW linac for nuclear waste trasmutation and energy production (a.k.a. the "Energy Amplifier" concept). A safe and reliable operation of similar machines will require proper control of the beam losses. Accurate simulations codes are required in order to assess that the beam losses are maintained to a safe level. As a part of the INFN program, an "ad hoc" code development activity has started, making use of the recent programming techniques and of numerical algorithms. The code in development deals, for now, with the beam dynamics in the high energy part of the proposed machine, composed by superconducting RF (elliptical) cavities placed between the long drifts of a quadrupole doublet array. The cavities are treated with an on-axis field distribution, either provided in analytical form or as tabular data. Space charge is evaluated with a fast Poisson solver, that uses a 3D multigrid algorithm. V Cycle or full multigrid algorithms appear to be promising in terms of speed and memory requirements, and can be readily modified for parallel computers. Checks with standard direct point-to-point calculations are in progress. A major effort has been put in using a modular approach for the data and program design. The code conforms to the F90 syntax and, where possible, makes use of safe programming criteria (controlled scoping of variables through MODULEs and PRIVATE/PUBLIC qualifiers, explicit procedure INTERFACES with INTENT declaration, dynamic allocation of all the data structure for the beam line, the particles and the space charge meshes). Preliminary results of this ongoing work will be presented in this contribution.

C-Tu04: SIMULATION AND OBSERVATION OF THE LONG TIME EVOLUTION OF THE LONGITUDINAL INSTABILITY IN A STORAGE RING
back Oliver Boine-Frankenheim , GSI
Storage rings are a unique tool to observe the rise and the saturation of the longitudinal instability in space charge dominated beams with high resolution. Kinetic simulations are mandatory to interpret the experimental data and to understand the underlying physical phenomena. In the simulations the longitudinal dynamics of space charge dominated, coasting beams interacting with the ring environment is modeled in the framework of the Vlasov-Fokker-Planck equation. The long time character of the collective phenomena pose high demands on the numerical integration method. Two different numerical codes (Particle-In-Cell (PIC) in cylindrical geometry, direct `noise-free' integration on a grid in the longitudinal phase space) are used to simulate the long time evolution of the experimental observables, like the momentum spread and the self-bunching amplitudes. The effect of electron cooling on the instability evolution is analyzed. The simulation noise inherent to PIC codes is used to predict the Schottky noise spectrum, which is an important experimental observable. The PIC code can be used to find correlations between the Schottky noise spectrum and the momentum spread.

C-Tu05: ANALYTICAL MODEL OF HALO FORMATION
back R.L. Gluckstern , U of MD
An analytical model for halo formation has been constructed based on a beam in a focusing channel which is "breathing" due to a mismatch with the channel. For a 2-D KV beam, an integral of motion can be obtained assuming the dominance of the parametric resonance (breathing mode frequency is twice the frequency of individual particles within the beam). These results correspond to the "peanut diagram" in particle phase space in all respects. The model is then extended to other 2-D distributions, as well as 3-D distributions involving both longitudinal and transverse breathing modes. Numerical simulations are then used to determine the behavior of the longitudinal and transverse halos which occur, and their dependence on the initial phase space distribution, the bunch charge and shape, and the amplitude of the mismatch.
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Work supported by the U.S. Department of Energy

C-Tu07: HALO FORMATION IN 3-D BUNCHES WITH SELF-CONSISTENT STATIONARY DISTRIBUTIONS
back A.V. Fedotov , R.L. Gluckstern, U of MD, S.S. Kurennoy, R.D. Ryne, LANL
We have constructed, analytically and numerically, a new class of self-consistent 6-D phase space stationary distributions. The beam is then mismatched longitudinally and/or transversely, and we explore the formation of longitudinal and transverse halos in 3-D axisymmetric beam bunches. The longitudinal phase space clearly shows the typical "peanut" diagram observed in 2-D calculations. We find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches because the longitudinal tune depression is more severe than the transverse one for elongated bunches. Of particular importance is the coupling between longitudinal and transverse motion and its effect on halo formation.
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Work supported by the U.S. Department of Energy

C-Tu08: NEW METHODS IN WARP
David P. Grote and Alex Friedman, LLNL, Irving Haber, NRL
New methods and capabilities have recently been introduced into WARP, a multi-dimensional particle-in-cell code developed for the study of space-charge dominated beams(1). We describe: (a) a 2D3V "slice" model (WARPxy) with two novel capabilities: the optional use of 3D applied fields (which can be calculated using the WARP3d solver), and an "exact" treatment of a bent beam pipe, via coordinate transformations; (b) a multigrid fieldsolver which offers internal conductors in 2D and 3D; and (c) serial optimizations for cache-based machines which yielded a 20-30% speedup. (Other developments are described in ref. 2).

(1) D. P. Grote, A. Friedman, and I. Haber, AIP Conf. Proc. 391 (1996 Comp. Accel. Phys. Conf.), 51-58 (1997).
(2) D. P. Grote et. al., this conference.
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Work performed under the auspices of the U.S. Department of Energy by LLNL under contract W-7405-ENG-48.

C-Tu09: UNIQUE FEATURES OF THE UNIVERSITY OF MARYLAND ELECTRON RING AND THE NECESSITY OF PIC CODE SIMULATION
back R.A. Kishek , S. Bernal, M. Reiser, and M. Venturini, U of MD, I. Haber, NRL
Abstract. The Maryland Electron Ring [1] is designed to explorethe transport of beams with much higher space charge than other circular machines. In addition, the ringfunctions as a testbed for design and simulation codes. Applications such as Heavy Ion Fusion and High Intensity Colliders require the preservation of beam quality during transport over large distances. This paper describes the application of self-consistent particle-in-cell code simulations using the WARP suite [2] to the E-ring lattice. The model used includes the nonlinear details of the external magnetic fields, a cylindrical external conductor, and the dispersive effects of the circular lattice on a beam with a non-zero energy spread.

(1) M. Reiser, et. al., Fusion Engineering and Design 32-33, 293 (1996).
(2) M. Venturini and M. Reiser, "RMS Envelope Equation in the Presence of Space Charge and Dispersion," Phys. Rev. Lett., in print (1998).
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Research Supported by Department of Energy.


Focused Session F-We1: Advances in Electromagnetic Modeling

F-We14: ON SOLVING MAXWELLIAN EIGENVALUE PROBLEMS FOR ACCELERATING CAVITIES
back Peter Arbenz , ETH-Zurich
We investigate algorithms for solving large sparse symmetric matrix eigenvalue problems resulting from finite element discretizations of steady state electromagnetic fields in accelerating cavities. The methods have been applied to an analytically computable model cavity and to the old and the new design of the accelerating cavities for the PSI 590 MeV ring cyclotron. The solutions of this kind of eigenvalue problems can be polluted by so-called spurious modes if the divergence-free condition is not treated properly. The two methods used for the finite element formulation provide a scheme to suppress spurious modes: (A) using penalty terms and (B) applying a mixed method, with edge elements for the field representation and node elements for the Lagrange multiplier. Four different algorithms have been applied to solve the resulting large sparse matrix eigenvalue problems: (1) subspace iteration, (2) block Lanczos algorithm, (3) implicitly restarted Lanczos algorithm, and (4) Jacobi-Davidson algorithm. For both finite element formulations we compare the amount of work it takes each solver to compute a few of the smallest positive eigenvalues and corresponding eigenmodes to a given accuracy. Numerical results obtained on a multiprocessor HP Exemplar X-Class System are presented.

F-We15: IMPROVED GDFIDL WITH GENERALIZED DIAGONAL FILLINGS AND REDUCED MEMORY AND CPU REQUIREMENTS
back Warner Bruns , TU-BERLIN
A new version of the Finite Difference code GdfidL implements generalized diagonal fillings for the discretization of the material distribution. The new algorithm allows 72 different types of material filling for each cell, whereas the common diagonal filling only allows 7 types. With the improved material filling, the discretization error for realistic geometries is reduced by a factor of three. The improved meshing is implemented both in the resonant solver and the time domain solver. Computed frequencies for some simple geometries are given to show the reduction in discretization error. GdfidL's organisation of the computational volume as a linked list has already reduced the resource requirements to about the half of other codes. A new organisation of the linked list reduces the requirements for time domain computations again by a factor of 0.7. The solvers and postprocessor now have a self decribing user interface. The command language is capable of handling user defined macros.


Focused Session F-We2: Advanced Algorithms & Methods

F-We21: SELF-CONSISTENT MODEL FOR THE BEAMS IN ACCELERATORS
back A. Novokhatski and T. Weiland, TU-DARMSTADT
It is proposed to use ensembles of particles instead of "macro" particles for modeling the beams in accelerators. Each ensemble describes the dynamics of the real bunch, which interacts with linear forces. Ensemble parameters include first and second order moments of the bunch in the phase space. Self-consistent equations for these moments are derived from Vlasov equation. Examples of application of this model in different devices of accelerators are presented.
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Work supported in part by DESY, Hamburg

F-We25: USING SYMBOLIC ALGEBRA FOR THE GENERATION OF ORBIT SIMULATION CODES FROM HAMILTONIANS
back Stefan Adam, Andreas Adelmann , PSI
As a part of the new research activity aiming at a detailed understanding of space charge effects in ring cyclotrons and in the corresponding injection beamlines at the Paul Scherrer Institute, we are currently developing a three dimensional space charge simulation code. Using the symbolic algebra system Maple, to derive the equation of motion and to cast them into Fortran we can establish the physical model on the high level of the Hamiltonian formalism. We start by defining the relativistic Hamiltonian for two simplified cases: the two-particle system and the motion of a single particle in a stable charge distribution. He mentioned models are foreseen to be extended to a more complex structure of the external magnetic fields and to various charge density distributions. For simulating small numbers of particles the Matlab system offers a powerful visualization and testing environment. Matlab's MEX-Interface allows us to use the Fortran subroutines produced by Maple in our simulation. For the two mentioned cases, the development steps from the Hamiltonian to the Fortran subroutine and to the resulting simulations are shown, as well as the general Maple and Matlab packages we have developed for this purpose.
 


Focused Session C-We1: New Software Environments & Libraries

C-We13: THE FRAMEWORK OF UNIFIED ACCELERATOR LIBRARIES
back N. Malitsky , R. Talman, CORNELL U
The performance of an accelerator depends to a large extent on the quality of the theoretical algorithms and the level of their integration with the control system. An important and immediate accelerator task is to steer theoretical and experimental activities in a common direction toward the development of interoperable Accelerator Simulation Facilities and (later) intelligent model-based control systems. The framework of Unified Accelerator Libraries (UAL) addresses this problem by offering a single standard-based environment that facilitates compatible and independent implementation of accelerator applications and promotes sharing and standardization of the most effective approaches and solutions.
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Work supported by the U.S. Department of Energy.

C-We15: JPP: A PARTICLE TRACKING CODE WITH JAVA
Ryoichi Hajima , U of TOYKO
A computer language Java fascinates a number of programmers in the world due to its superior features: simple, object-oriented, distributed, robust, architecture neutral, portable, multithreaded, involved graphics API and so on. It has been considered that a computer language running on interpreter such as Java is not suitable for scientific application where heavy calculation is required. There, however, are splendid ideas to overcome the performance limit of the interpreter, which are ``just-in-time'' compiler (JIT), ``native method.'' In this paper, JPP: a particle tracking code written in Java is presented. We will show object-oriented class hierarchy for accelerator component, design of GUI/CUI post-processor, performance comparison with C language.

C-We16: IMPLEMENTATION OF OBJECT-ORIENTED DESIGN WITH FORTRAN LANGUAGE IN BEAM DYNAMICS STUDIES
back J. Qiang , R. Ryne and S. Habib, LANL
In this paper, object-oriented design has been implemented using Fortran language in beam dynamics studies. Using module and derived type in F90, we can emulate object concept in the object-oriented design. This gives Fortran code a better maintainability, reusability, and extensibility. The fundamental classes in our object-based particle-in-cell code include beam line element class, beam class, field class and geometry class. These classes are implemented using F90 language with message passing interface (MPI) and High Performance Fortran (HPF) in parallel computation. MPI has advantages of flexibility in treating irregular problems. HPF has advantages of programming ease and portability between parallel and serial machines by encapsulating the details of communication and using directive comments in the Fortran language.


Focused Session C-We2: Graphic Interfaces & Advanced Visualization

C-We21: AN APPLICATION FRAMEWORK AND GRAPHIC USER INTERFACE FOR MULTIPLE ACCELERATOR CODES
back Barrey W. Hill , Hendy Martono, John Moore and James S. Gillespie, GILLESPIE ASSOC.
A multi-platform application framework is being developed for implementing a variety of optics codes under a single Graphic User Interface (GUI) shell. The object oriented framework provides the underlying infrastructure for beamline representations, and multi-platform capabilities for the integration of particle physics simulation and analysis codes. The framework architecture supports plug-in tools such as an interactive particle trajectory module, optimization algorithms and hypertext tutorials which interface with, and enhance the functionality of the installed simulation codes. Simulation codes are integrated into the framework by separating the computational physics code, which is implemented as a platform independent Computational Module, from the I/O requirements, which are replaced with an Application Module developed with the multi-platform GUI framework components. The framework provides a sophisticated beamline object model and a rich library of GUI components. Application dependent components can be derived from the more abstract framework components to support specific requirements of the different simulation codes. An overview of the Multi-Platform Shell for Particle Accelerator Related Codes (S.P.A.R.C.-MP) application framework is presented here with illustrations from a Windows NT/95 application that has been built using the S.P.A.R.C.-MP framework.

C-We25: MEASUREMENTS AND VISUALIZATION OF THE TRANSVERSE PHASE-SPACE TOPOLOGY AT LEP
back Giulio Morpurgo , CERN
The LEP Beam Orbit Measurement system (BOM) allows for the acquisition of the beam position at each Beam Position Monitor (BPM) for over 1000 consecutive turns. By synchronizing the acquisition with a kick given to the beam, we can investigate the behavior of the beam under different conditions. In particular, starting from the data of one BPM, we can apply a simple mathematical manipulation to build a "virtual" BPM, with a phase advance of 90 degrees. Plotting the real BPM against the virtual one, we can observe the evolution of the beam in the phase-space. An appropriate coloring technique is used, to help the User finding his way through the data. Fixed points in the phase-space can be put in evidence, as well as the beam behavior in their neighbourhood. Quantities like the tune, the beam detuning as function of the position amplitude and the beam damping can be studied in this way. Significant examples from real life will be shown.

C-We26: USING 3-D PERSPECTIVES AS A VISUALIZATION TOOL FOR PHASE SPACE DATA
George H. Gillespie , Barrey W. Hill, Michael C. Lampel, Nathan A. Brown, GILLESPIE ASSOC.
Two-dimensional projections of six-dimensional phase space data are routinely used in the analysis of accelerator beam dynamics phenomena. Plots of the distribution of particle coordinator and momenta in a given phase plane (e.g. x,x'), or for the coordinates of a beam cross section (i.e. x, y), are among the most commonly used projections. Computer-based visualizations of higher-dimensional projections of phase space data offer the possibility of providing improved insight into complex beam dynamics phenomena. In this presentation, we will illustrate one of these types of visualizations that uses interactive three-dimensional perspective displays.


Focused Session F-Th1: Modeling Advanced Accelerator Concepts

F-Th12: NUMERICAL STUDIES OF WAKE EXCITATION IN PLASMA CHANNELS
back B. A. Shadwick and J. S. Wurtele, UC BERKELEY and LBNL
The wake fields produced by an intense, short laser pulse propagating in a plasma channel with an arbitrary density profile is investiaged. Plasma channels, viewed as accelerating strutures, have many desirable features that are not shared by a homogeneous plasma. They are also becoming experimentally realizable. As part of an overall program to analyze plasma channels as accelerating structures, a new fluid simulation code has been developed with the primary purpose of producing fast tools to explore parameter space for both theoretical investigation of accelerator performance as well as the modeling and design of experiments. This code has flexible physics content, for example, the laser either be fully resolved temporally or treated as ponderomotive force. An important feature, from the accelerator design point of view, is capability to study of beam propagation dynamics. We present preliminary results consisting of a detailed analysis of the transverse structure of the wake for a wide range of experimentally accessible channel profiles and characteristics of the corresponding accelerated beam.
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Supported by the U. S. DOE under grant no. PDDEFG-03-95ER-40936.


Focused Session F-Th2: Beam-Beam Simulations

F-Th22: BEAM-BEAM SIMULATIONS WITH THE GAUSSIAN CODE TRS
back Miguel Furman , LBNL
We present a description of the "soft-gaussian" beam-beam simulation code TRS and its application to the PEP-II asymmetric collider.

F-Th23: ODYSSEUS: A DYNAMIC STRONG-STRONG BEAM-BEAM SIMULATION FOR STORAGE RINGS
back E.B. Anderson and J.T. Rogers, CORNELL U
We have developed a simulation of the beam-beam interaction in e+/e- storage ring colliders which is specifically intended to reveal the dynamic collective behavior of the colliding beams. This program is a true 6-dimensional strong-strong simulation in which the electromagnetic fields of longitudinal slices of the colliding beams are recalculated for each slice collision. Broadband wake fields are included and no constraints are placed on the distribution of particles in the beams. Information on tests of the code will be shown. Results will be presented including limiting beam-beam parameters for round and flat beams, deviations from the Gaussian distribution, effects of the beam-beam parameter on head-tail instability thresholds, and Landau damping rates. Possibilities for further improvements will be discussed.

F-Th24: BEAM-BEAM SIMULATIONS WITH GUINEA-PIG
back Daniel Schulte , CERN
While the bunches in a linear collider cross once only, due to their small size they experience a strong beam-beam effect. Guinea-Pig is a code to simulate the impact of this effects on luminosity and background. A short overview over the program is given, with examples of its application to the background studies for TESLA, the top threshold scan and a possible luminosity monitor.

Focused Session C-Th1: Computing Wakefield Effects

C-Th11: TRANSITION DYNAMICS OF THE WAKE FIELDS OF ULTRA SHORT BUNCHES
back A. Novokhatski , M. Timm, T. Weiland, TU-DARMSTADT
In the cavities and finite cell structures, ultra short bunches excite very high frequency electromagnetic fields. A fraction of these fields stay in the structure for a very long time. After several reflections another part leaves the structure. And the rest part is chasing the bunch. In a time, this field will catch the bunch and take its kinetic energy. The time and the distance, when and where the bunch is caught, is inversely proportional to the bunch length. The time and the distance can be very long for a very short bunch. The analyses of the wake fields in this transient region is given for the Linear Colliders accelerating structure.
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Work supported in part by DESY, Hamburg

C-Th12: CALCULATIONS OF THE SHORT-RANGE LONGITUDINAL WAKEFIELDS IN THE NLC LINAC
back K.L.F. Bane , SLAC, A. Mosnier, CEA, A. Novokhatskii, TU-DARMSTADT, K. Yokoya, KEK
Using two frequency domain and one time domain numerical approaches, we calculate the short-range longitudinal wakefield of the NLC linac accelerating structure, and find that the results agree to 5%. In addition we obtain, through fitting, a simple formula for the short-range wakefield of a linac structure that can be useful in designing linear colliders. Finally, we demonstrate that for the NLC linac cavity the effects on the short-range wake of end conditions, tapering, and rounding of the irises are small.

C-Th13: THE SURFACE ROUGHNESS WAKE FIELD EFFECT
back A. Novokhatski, M. Timm , T. Weiland , TU-DARMSTADT
In the Linear Colliders FEL projects ultra short bunches are foreseen to be used. In addition to usual wake fields, coming from irregularities in the chamber, these bunches excite fields in transporting lines and undulators due to the surface roughness. This effect can be large for the extruded tubes, usually used in accelerators. Based on computer results it is shown, that the roughness wake field effect can be described by a simple model for the monopole and dipoles wakes of a tube with thin dielectric coating.
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Work supported in part by DESY, Hamburg

C-Th14: WAKE OF A ROUGH BEAM WALL SURFACE
back K.L.F. Bane and G.V. Stupakov , SLAC
One of the distinctive features in the designs of future e+/e- colliders and FEL's is a tendency toward ever shorter bunch lengths. Two examples are the Next Linear Collider (NLC) with an rms bunch length of 100 microns, and the Linac Coherent Light Source (LCLS), with one of 30 microns. For such short bunches, even the wall surface roughness can become a significant source of impedance. In this paper, we present an analytical model for the impedance of a perfect conductor with a rough surface. Using a small-angle approximation, we first find a general formula for the impedance of a small bump of arbitrary shape on the wall of a round beam pipe. Then modelling a rough surface as a random collection of such shapes, we express the impedance in terms of the spectral function of the surface. In a complimentary approach [1], a rough surface is modelled as a collection of bumps of different shapes, with the impedance computed numerically for each shape. In this model, the impedance of the surface is given in terms of a shape form factor and a packing factor of the bumps on the surface. We compare the results of both models and give numerical estimates for the impedance, due to this effect, of the beam chamber in the LCLS undulator.

[1] K.L.F. Bane, C.K. Ng and A.W. Chao. Estimate of the Impedance Due to Wall Surface Roughness. SLAC-PUB-7514 (1997).
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Work supported by the Department of Energy, contract DE-AC03-76SF00515.


Focused Session C-Th2: Particle & Field Simulations

C-Th23: CALCULATION OF IMPEDANCE FOR MULTIPLE WAVEGUIDE JUNCTION USING SCATTERING MATRIX FORMULATION
back V.A.Dolgashev , BINP
A method of computing the electromagnetic characteristics of a complex 3D cavity consisting of series of waveguides with arbitrary cross section is derived. The scattering matrix formulation is used for the simulation. For calculations of modes in waveguide with arbitrary cross sections a finite element code SLANS is applied. The computer code based on the method is used to calculate scattering parameters, dispersion characteristics of periodical structures, resonances, longitudinal and transverse impedances. The method was originally developed for simulations of long range wake fields in accelerator structures and for calculations of RF windows. Advantages of the technology make possible to simulate long open cavities like accelerating structures and complex vacuum chambers. The method and some results are presented.

C-Th24: THE 30 GHZ TRANSFER STRUCTURE FOR THE CLIC STUDY
back G. Carron, A. Millich , L. Thorndahl , CERN
In the so-called 'Two-Beam Acceleration Scheme' the energy of a drive beam is converted to RF power by means of a 'Transfer Structure' which plays the role of power source. In the Transfer Structure the bunched drive beam is decelerated by the electromagnetic field which it induces and builds up by the coherent interaction of successive bunches with the chosen longitudinal mode. The CLIC Transfer Structure is original in that it operates at 30 GHz and uses teeth-like corrugations to slow down the hybrid TE mode to make it synchronous with the drive beam. The beam energy is transformed into RF power which travels along the structure and is collected by the output couplers. The 30 GHz RF power is then transported by means of two waveguides to two main linac disk-loaded accelerating structures. This report describes the CLIC Transfer Structure design, 3-D computer simulations, model construction and measurements as well as the prototype construction and testing with the low energy beam in the CLIC Test Facility. The result of this development is a compact, fully passive, relatively simple and low cost device which offers a readily scaleable solution to the problem of RF power extraction from high frequency bunched beams.

C-Th25: FIELD FLATNESS AND NON-STATIONARY BEHAVIOR OF THE 4x7-CELL-TESLA-SUPERSTRUCTURE
back H.-W. Glock, D. Hecht, U. van Rienen , ROSTOCK U
A structure of 4 coupled 7-cell resonators has been proposed [1] to increase the effective gradient of TESLA. Each so-called "superstructure" is fed through a single input coupler. The sensi tivity of field flatness against geometrical deviations and the time dependence of the fields during fill- and re fill-time are studied by means of MAFIA calculations using an optimized grid. MAFIA results directly calculated of slightly perturbed structures will be compared with those of an analytical approach. Non-stationary fields are expanded in a set of eigenmodes calculated with MAFIA. For a short model the results of this procedure will be compared with fields directly calculated in time-domain.

[1] J. Sekutowicz, M. Ferrario, C. Tang: Superconducting Superstructure; LC97, Sept./Oct. 97, Zvenigorod, Russia
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Work supported in part by DESY


Poster Session L-Tu

L-Tu02: A MULTI-PLATFORM GRAPHIC USER INTERFACE FOR THE MARYLIE CHARGED PARTICLE BEAM TRANSPORT CODE
back Michael C. Lampel , George H. Gillespie, Barrey W. Hill, Hendy C. Martono, John M. Moore, Kyle J. Ryan, GILLESPIE ASSOC., and Alex J. Dragt, U of MD
An advanced graphic user interface (GUI) is being developed for use with the particle optics program MARYLIE. MARYLIE is based on a Lie algebraic formulation of charged particle trajectory calculations and is particularly useful for particle tracking and the analysis of linear and nonlinear lattice properties. The GUI for MARYLIE uses the Multi-Platform Shell for Particle Accelerator Related Codes, a software framework developed specifically to support accelerator modeling and simulation. Transport element icons are selected from a palette and assembled into beamlines by graphical construction. Optical cells and lattices composed of element groups may be defined as sublines and any element or subline can be replicated using an alias element. The icon-based beamlines generate entries for the #beam, #menu, and #lines components of the MARYLIE Master Input File (MIF). Frequent computations, such as creating maps or generating particle distributions, are encapsulated interactive GUI commands which create corresponding entries in the #menu, #lines, and #labor components of the MIF. An icon-based description of procedural processes is being developed to support more complex MARYLIE analysis tasks that utilize the #lumps and #loops components. Progress on the development of this GUI for MARYLIE will be described and the software will be demonstrated.
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Work supported by Department of Energy Grant # DE-FG03-95ER81975

L-Tu04: THE CERN/SL XDATAVIEWER: AN INTERACTIVE GRAPHICAL TOOL FOR DATA VISUALIZATION AND EDITING
back Giulio Morpurgo , CERN
As a result of many years of successive refinements, the CERN/SL Xdataviewer tool has reached its final stage. This graphical tool was especially developed to plot mono- or bi-dimensional arrays of data, and to interact with them, in many different ways. Many pages of graphical information can be handled by the program, in a loose hierarchy of Views, Graphs and Plots objects. Data can be displayed, and interacted with, both in graphical and in text format. Sophisticated built-in Zoom and Data Editing capability is implemented, as well as a flexible Data Output generation facility. A complete C Callable Interface is provided, including a mechanism for feeding back the Application Program with the selections made by the User in the Data Display part. The tool has been written in C language, making use of the standard X Window libraries (Xlib,Xt,Motif). It can be run as a stand alone process, communicating with the Application Program via a shared memory, or it can be embedded in the Application Program itself.

L-Tu06: TECHNIQUES FOR ROBUST NONLINEAR DELTA-F SIMULATIONS OF BEAMS
back Alex Friedman , John J. Barnard, and David P. Grote, LLNL
We describe means by which the range of applicability of delta-f methods (1,2) to beams may be enhanced, so as to faithfully describe a sharp-edged beam or a smooth beam whose edge moves by more than its scale length. As others have done, we follow a population of Lagrangian characteristic "marker" particles in the total (equilibrium plus perturbation) field. However, in contrast with usual practice, our marker distribution is not proportional to the physical particle distribution. We introduce "ghost" particles: a population of markers loaded into regions of phase space where the equilibrium f0 is zero or very small. Following a comment by Aydemir (2) (and in contrast with what we perceive to be common practice), we do not numerically evolve either delta-f or a "weight" w, but rather we use knowledge of the marker positions in phase space and of the functional form of f0 to evaluate delta-f anew at each timestep for each marker. This saves the solution of an ODE for each particle, with its attendant errors and possible timestep constraints. We describe the application of our formalism to the model problem of an oscillating displaced beam.

(1) S. E. Parker and W. W. Lee, Phys. Fluids B 5(1), 77-86 (1993).
(2) A. Y. Aydemir, Phys. Plasmas 1(4), 822-831 (1994).
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Work performed under the auspices of the U.S. Department of Energy by LLNL under contract W-7405-ENG-48.

L-Tu07: DYNAMIC SPACE CHARGE CALCULATIONS FOR HIGH INTENSITY BEAMS IN RINGS
back J. A. Holmes , J. D. Galambos, D. Jeon, D. K. Olsen, ORNL,
M. Blaskiewicz, A. U. Luccio, and J. Beebe-Wang, BNL
Space-charge-induced emittance growth and halo generation could lead to unacceptably high beam loss in high intensity rings, such as the SNS. In such accelerators, uncontrolled losses to the walls as small as one part in 10**4 would lead to activation, making maintenance difficult. For this reason it is essential to understand the effects of space charge on beam dynamics, and halo generation in particular, in high intensity rings. We have undertaken the study of space charge dynamics in high intensity rings using a particle tracking approach, with self-consistent evaluation of the space charge forces through a particle-in-cell model. Because of the stringent loss requirements, it is necessary to thoroughly guarantee the reliability of these calculations to high precision through comparison with experiments and through convergence studies. In this paper we present the results of convergence studies in the parameters of the model, namely, the number of macroparticles, the resolution in the adopted FFT algorithm, the smoothing parameter, and the time step size. Although present calculations have been extended to more than 10**5 macroparticles on individual UNIX workstations, it will be necessary to increase another one to two orders of magnitude to obtain the necessary precision. To accomplish this, we are constructing a LINUX parallel computer from low cost components.
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Research on the Spallation Neutron Source is sponsored by the Division of Materials Science, U.S. Department of Energy, under contract number DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation for Oak Ridge National Laboratory.

L-Tu10: MAP COMPUTATION FROM MAGNETIC FIELD DATA AND APPLICATION TO THE LHC HIGH GRADIEN T QUADRUPOLES
back M. Venturini , D. Abell, A. Dragt, U of MD
In many cases the most accurate information about fields in a magnet comes either from direct measurement or from a numerical computation done with a 3D electromagnetic code. In this paper we show how this information can be used to compute transfer maps with high accuracy. The resulting transfer maps take into account all effects of real beamline elements including fringe-field and multipole error effects. The method we employ automatically incorporates the smoothing properties of the Laplace Green function. Consequently, it is robust against both measurement and electromagnetic code errors. As an example, we apply the method to a study of end effects in the High Gradient Quadrupoles for the low-beta insertion in the Large Hadron Collider (LHC). The map computation for the quadrupoles has been carried out using MARYLIE's GENMAP routine and a newly written MARYLIE user-defined routine. For long-term tracking we used Cremona symplectification techniques as implemented in CTRACK.

L-Tu11: FUNCTIONAL DEPENDENCE, BROAD-BAND FITTING, AND ANCILLARY CONDITIONS
back David C. Carey , FNAL
The ability to make multiple passes through a charged particle optical system, as a single step in a mathematical procedure, opens up new computational capabilities. At the simplest level, the functional dependence of any transfer matrix of any order, or any beam phase-space parameter can be plotted as a function of any other parameter used to describe the optical configuration. Secondly, broad-band fitting can be done on aberrations, where all orders are considered simultaneously according to their importance on the final phase-space beam distribution. Finally, ancillary conditions may be imposed in the calculation of functional dependences. For example, the dependence of a matrix element on a beam line parameter may be calculated and plotted, subject to constraints imposed on other matrix elements. The computer program TRANSPORT now has these capabilities. Additional examples will be given.
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Operated by Universities Research Association, Inc., under contract with the United States Department of Energy.

L-Tu13: TRANSIENT MAGNETIC FIELD ANALYSIS FOR THE LOCALIZATION OF ELECTRICAL FAULTS IN SUPERCONDUCTING COLLARED COILS
back Piotr Komorowski , Davide Tommasini , CERN
The follow-up of the construction of superconducting magnets for accelerators re quires a setting up of powerful diagnostic tools to detect weak electrical point s in the superconducting coils at various stages of their fabrication. In partic ular some electrical short circuits well detectable after collaring of the magne t often disappear after the coil is uncollared for repair; therefore it is prefe rable to localize this kind of electrical faults before disassembling the magnet . An R&D work on detection and localization of inter-turn short circuits i s being carried out at CERN in view of the series production of the LHC magnets. The diagnostic methods under study include pulse propagation, time domain refle ctometry and transient magnetic field analysis. In this paper special emphasis i s put on the analysis of the magnetic field distortions created by the short cir cuits during a pulsed discharge. A model of LHC dipole allowing the simulation o f different fault conditions in the coils has been implemented in ROXIE (static case) and in OPERA-2D (transient case). The model has been verified experimental ly on a dedicated short dipole magnet equipped with microswitches to trigger sho rt circuits in different areas of the coils.

L-Tu16: ANALYSIS OF EMITTANCE GROWTH AND COMPLEX IMPEDANCE FOR COHERENT SYNCHROTRON RADIATION SHIELDED BY TWO PARALLEL PLATE
back Ryoichi Hajima , U of TOYKO
Emittance growth caused by coherent synchrotron radiation (CSR) and noninertial space charge force in magnetic bunch-compressors is a key issue for the design and construction of X-ray FELs. In the present study, a particle tracking code including intra bunch scattering due to CSR and noninertial space charge force is developed. The simulation code enable us to calculate distribution of electrons in full six-dimensional phase space along arbitrary beam transport line and to estimate energy loss and emittance growth arising from CSR force as well as usual space charge effect and aberrations. Calculated energy loss of electron bunch traveling through circular path shielded by two parallel plates shows good agreement with theoretical results from impedance analysis. The relationship between emittance growth and complex impedance is also presented.

L-Tu17: CALCULATION OF EIGENMODES IN SUPERCONDUCTING CAVITIES ON AN APE-100 SUPERCOMPUTE R (SIMD) USING A SOFTWARE INTERFACE TO MAFIA
back F. Neugebauer, DESY, U. van Rienen, ROSTOCK U
To design modern accelerators a profound knowledge of eigenmodes of RF-cavities is required. For normal conducting as well as for super conducting cavities MAFIA is a well established tool to determine the eigenmodes by numerical means. However, the 3-dimensional treatment of multi-cell cavities lacks from available computer power on a normal high end workstation. Therefore the present approach uses a parallel SIMD super computer (APE-100) to compute the numerical expensive part of the MAFIA-algorithm. The system matrix, incorporating geometry and material information, is transfered to the APE-100 during a normal MAFIA-session using a command provided by the MAFIA toolkit (MTK). The result of the diagonalization procedure is then read back to the MAFIA host where further data analysis and visualization can be done. As a first example the lowest eigenmodes of a pillbox resonator are computed on the APE-100. The results are compared with the analytic solution and with the results obtained from a usual MAFIA-session on a high end workstation.

L-Tu19: INVESTIGATION OF THE IMPEDANCE AND HIGHER ORDER MODE LOSSES FOR PROPOSED BEAM PIPE CONFIGURATIONS FOR THE HERA LUMINOSITY UPGRADE PROJECT
back Martin Dohlus, Susan Wipf, DESY
The impedance and wakefield effects and higher order mode losses have been investigated for the Luminosity Upgrade Project at HERA for three regions where only minimal heating can be tolerated. These are two versions of the beam pipe configuration at the interaction region of the experiment Zeus and also for a region where superconducting magnets are to be installed. As the structures are very long (up to 4.9m) it was not possible to calculate all modes up to the cut-off frequency directly, thus long term wake calculations (100nsecs) in the time domain were used to pinpoint potentially dangerous modes. The frequency and band-width information thus obtained could be used to obtain the impedance of these modes in the frequency domain. The calculations were carried out using the MAFIA programs.

L-Tu20: DESIGN OF 2*2 DLDS RF COMPONENTS FOR JLC
back J.Q. Wang , Y.H. Chin, S. Kazakov, S. Yamaguchi and H. Tsutsui , KEK
We have studied a multi-mode Delay Line Distribution System (DLDS) as the RF power distribution system from klystrons to RF structures for linear colliders. In particular, a 2*2 DLDS has been proposed and studied at KEK for Japan Linear Collider(JLC). It has been proved that the 2*2 DLDS is simple, bus has a good transmission efficiency. We have designed RF components of a basic unit of a DLDS using the High Frequency Structure Simulation (HFSS) code. They include the TE01 extractor, the TE11 to TE01 convertor, and the TE11 to TE12 convertor for TE12 mode. A low power test model for the mode stability experiment in 55m long waveguide in DLDS is being developed. HFSS calculation of the system, which consists of TE01 extractor and TE11 to TE01 convertor, show that the transmission efficiency of each mode is better than 90%. Further study is underway.

L-Tu21: ELECTROMAGNETIC MODELING OF FAST BEAM CHOPPER FOR SNS PROJECT
back Sergey Kurennoy , LANL
High current and stringent restrictions on beam losses in the designed linac and storage ring for the Spallation Neutron Source (SNS) require clean and fast - with the rise time from 2% to 98% less than 2.5 ns - beam chopping in its front end, at the beam energy 2.5 MeV. The development of new traveling-wave deflecting current structures, based on meander lines, is discussed. Three-dimensional time-domain computer simulations are used to study transient effects in the chopper and to optimize its design.

L-Tu28: PROGRESS IN PARALLELIZING XOOPIC
back P. J. Mardahl and J. P. Verboncoeur, UC BERKELEY
XOOPIC [1] (Object Oriented Particle in Cell code for X11-based Unix workstations) is presently a serial 2d 3v particle-in-cell plasma simulation. The present effort focuses on using parallel and distributed processing to optimize the simulation for large problems. The benefits include increased capacity for memory intensive problems, and improved performance for processor-intensive problems. The MPI library enables the parallel version to be easily ported to massively parallel, SMP, and distributed computers. The philosophy employed here is to spatially decompose the system into computational regions separated by 'virtual boundaries', objects which contain the local data and algorithms to perform the local field solve and particle communication between regions. This implementation reduces the impact of the parallel extension on the balance of the code. Specific implementation details such as the hiding of communication latency behind local computation will also be discussed, as well as code features and capabilities.

[1] J. P. Verboncoeur, A. B. Langdon, and N. T. Gladd, ``An object-oriented electromagnetic PIC code.'' Computer Physics Communications 87 (1995) 199-211. Codes available via http://ptsg.eecs.berkeley.edu.
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This work supported in part by AFSOR/AASERT F49620-94-1-0387, AFOSR/MURI F49620-95-1-0253.

L-Tu30: A SIMULATION STUDY OF THERMAL-PHOTON AND RESIDUAL-GAS SCATTERING IN THE NLC BEAM DELIVERY SYSTEM
back I. Reichel , T. Raubenheimer, P. Tenenbaum, F. Zimmermann , SLAC
Without collisions, the largest contribution to the beam lifetime in LEP is Compton scattering off thermal photons. Even if only a few particles are scattered in a single pass, the potential background generated could make this effect important for the NLC as well. We used a version of the tracking program DIMAD, which was modified at CERN and includes a Monte Carlo simulation for the Compton scattering on thermal photons, to calculate the fraction of scattered particles that are lost and to determine the loss locations. We also studied particle losses due to other scattering processes, such as elastic and inelastic beam-gas scattering. For all these processes, the beneficial effect of additional collimators was investigated. We report the simulation results.
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Work supported by USDOE contract DE-AC03-76SF00515.