GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
IAP, Frankfurt am Main
CEA, Gif-sur-Yvette
The GSI Univeral Linear Accelerator UNILAC can accelerate all ion species from protons to uranium. Hence its DTL section is equipped with e.m. quadupoles allowing for a wide range of field strength along the section. During the last years various campaigns on the quality of high current beams at the DTL exit as function of the applied transverse focusing have been performed. Measurements were compared with up to four different high intensity beam dynamics codes. Those comparisons triggered significant improvement of the final beam quality. The codes were used to prepare an ambitious and successful beam experiment on the first observation of a space charge driven octupolar resonance in a linear accelerator.
BNL, Upton, Long Island, New York
In the quest for brigthness, the horizontal emittance remains one of the main performance parameters for modern synchrotron light sources. A control theory approach that takes the nonlinear dynamics aspects into account, by a few simple (linear) optics guidelines, at an early stage generates robust designs. Modern analytic- and computational techniques enables the optics designer to avoid the fallacy of the traditional approach guided by the Theoretical Minimum Emittance (TME) cell: the "chromaticity wall". In particular, by an interleaved computational approach with the nonlinear dynamics analyst/model. We also outline how to implement the correction algorithms for a realistic model so that they can be re-used as part of an on-line model/control server for commissioning- and operations of the real system.
PSI, Villigen
One possible electron source for the PSI-XFEL is the Low Emittance Gun (LEG), which is currently under development at PSI. It consists of a pulsed DC gun, which operates at 500 keV and has the option of using either a photo cathode or a field emitter array. The gun is followed by a pulsed in-vacuum solenoid and a two frequency cavity, not only used to accelerate the beam but also to create a highly linear energy correlation required for ballistic bunching. All components are rotationally symmetric, so a full particle-in-cell simulation of the setup using 2 1/2 D MAFIA, including space charge, wake fields and beam loading effects, shows the base line performance. The low emittance beam, which propagates in a large part of the setup at relatively small energies of around 500 kEV, is rather sensitive to small perturbations in the fields. So we also investigated the effect of mechanical misalignments on the beam quality using the 3D in-house code CAPONE.
KEK, Ibaraki
Recent progress of KEKB and nano beam scheme adopted in KEKB upgrade are discussed. For the present KEKB, chromatic x-y coupling, which was the key parameter to improve luminosity, is focussed. Beam-beam simulations with weak-strong and strong-strong models for nano beam scheme are presented. A weak-strong simulation was done in the presencee of the longitudinal micro-wave instability. Finally status of beam simulations in KEK supercomputers is presented.
ORNL, Oak Ridge, Tennessee
The laser assisted hydrogen stripping becomes a widely discussed alternative for the existing stripping foil approach. The simulation tool for this new approach is presented. The created application is implemented in form of extension module to Python ORBIT parallel code that is under development at the SNS. The physical model of the application deals with quantum theory and allows calculating evolution and ionization of hydrogen atoms and ions affected by superposition of electromagnetic and laser fields. The algorithm, structure, benchmark cases, and results of simulations for several future and existing accelerators are discussed.
GSI, Darmstadt
ITEP, Moscow
IAP, Frankfurt am Main
During the last year several numerical investigations have been started at GSI in order to improve the performance of the linear accelerator facility. The main activities regard the upgrade of the high current UNILAC accelerator including the severe upgrade of the HSI injector, the HITRAP decelerator and, in the frame of the future FAIR project, the development of the new dedicated proton linac. End to end beam dynamics simulations are a powerful tool concerning the machine design, commissioning and optimization. Particle distributions, generated from beam emittance measurements, are transferred through the whole chain of the accelerating structures and beam transport lines. Detailed calculations of the space charge effects as well as external and measured mapping of the structures electromagnetic fields are used to provide the most reliable results. The paper presents a general overview of all activities including a comparison with experimental results.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
BNL, Upton, Long Island, New York
The beam commissioning of J-PARC linac has been performed since November 2006, and we are now in a transitional phase from an initial commissioning stage to a stage where we seek more stable operation with higher beam power. In the beam commissioning, the modeling is important to understand the underlying physics of the experimental data obtained by beam monitors. As the J-PARC is a high-intensity proton accelerator facility, the beam is subject to strong space-charge effects. In addition, mitigation of the beam loss is critically important to avoid excess radio-activation of the accelerator components. Therefore, an accurate Particle-In-Cell simulation code plays an essential role in the beam commissioning, especially in mapping out our course in the beam commissioning planning. For this purpose, we have been using IMPACT code in J-PARC linac. In this paper, we review the simulation studies performed for J-PARC linac trying to understand the experimental results in the course of the beam commissioning efforts.
IHEP Beijing, Beijing
The China Spallation Neutron Source (CSNS) is now in the design stage. Many simulations have been done for the RCS/CSNS, including the space charge induced emittance growth and beam loss, the combined effects of space charge and magnet errors, the dependence of space charge effects on the lattice structures, etc.
ANL, Argonne
Optimization tools are needed in every step of an accelerator project, from the design to commissioning to operations. However, different phases have different optimization needs that may require different optimization algorithms. For example, a global optimizer is more appropriate in the design phase to map the whole parameter space whereas a local optimizer with a shorter path to solution is more adequate during operations to find the next best operating point. Different optimization algorithms are being used in accelerator physics, we mention in particular standard algorithms based on least square minimization and evolutionary algorithms such as genetic optimizers. Over the years, we have developed several optimization tools for beam tracking codes to include 3D fields and SC effects. Including particle tracking in the optimization process calls for parallel computing. We will review the different algorithms and their implementation and present few highlight applications.
BNL, Upton, Long Island, New York
LBNL, Berkeley, California
Multiobjective Genetic Algorithm(MOGA) is a technique for optimization, and based on the populations and natural selections. We have integrated this algorithm with linear lattice calculation code to make the lattice design more robust.
DESY Zeuthen, Zeuthen
INRNE, Sofia
The production of electron beams suitable for the successful operation of the European XFEL is studied at the Photo-Injector Test Facility at DESY, Zeuthen site (PITZ). The PITZ beamline is equipped with three dedicated stations for transverse emittance measurements and in the forthcoming shutdown period a section for transverse phase-space tomography diagnostics will be installed. The module contains four observation screens and therefore only four projections can be used in order to reconstruct an underlying phase-space density distribution. This work presents the performance of a number of reconstruction algorithms on limited projection sets using numerical data applied to the PITZ operating conditions. Different concepts for comparison between an original phantom and the reconstructed distribution are presented.
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock
Demanding applications such as heavy ion fusion, high energy colliders and free electron lasers require the study of beam phenomena like space-charge induced instabilities, emittance growth and halo formation. Numerical simulations for instance with GPT (General Particle Tracer, Pulsar Physics) calculate the mutual Coulomb interactions of the tracked particles *. The direct summation of the forces is rather costly and scales with O(N2). In this paper we investigate a new approach for the efficient calculation of particle-particle interactions: the fast summation by Nonequispaced Fast Fourier Transform (NFFT) **, whereas the NFFT is a generalization of the well known Fast Fourier Transformation (FFT). We describe the algorithm and discuss the performance and accuracy of this method for several particle distributions.
TRIUMF, Vancouver
DAE/VECC, Calcutta
SFU, Burnaby, BC
The TRIUMF-VECC Electron Linac is a device for gamma-ray induced fission of actinide targets, with applications in nuclear physics and material science. A phased construction and commissioning scheme will eventually lead to a 50 MeV, 10 mA CW linac based on superconducting RF technology. Using this linac to deliver high intensity electron beams for applications such as an energy-recovered light source is a possibility integrated in the design study. The multitude of design and tuning parameters, diverse objectives and constraints require a comprehensive and efficient optimization scheme. For this purpose we adopted the genetic optimization program developed at Cornell University* as a prototype. Feature extensions were developed to accommodate specifics of the Electron Linac design, provide framework for more generic and integrated design process, and perform robustness/acceptance analyses. In this report we will discuss the method and its application to the design optimization of the Electron Linac. [1]. I. Bazarov and C. Sinclair, PRST-AB 8, 034202 (2005), and references therein.
PSI, Villigen
For the 250 MeV test injector, it is planned to use a 2.6 cell RF gun originally developed for high current and charge operation in the CLIC test facility CTF-2. First start-to-end simulations assuming perfect field symmetries show, that this gun should be able to generate bunches at 200 pC with an emittance of below 400 nm rad, which would be compatible with the requirements for the SwissFEL. This gun uses double side coupled RF feeds in the last cell as well as tuners in the last two cells, which give transverse multipole effects in the field and phase space distribution and may lead to a deteriorated emittance. Since the beam in the last cell is already relativistic at energies between 4 and 6.4 MeV, this effect can be computed in a clean way by looking at the distributions of the integrated beam voltage at the cavity iris and deriving any transverse kicks via the Panovsky-Wenzel theorem. Doing this approach for the various operation modi planned for the PSI injector shows an emittance dilution well below the critical thresholds.
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
While COSY INFINITY provides powerful DA methods for the simulation of fragment separator beam dynamics, the master version of COSY does not currently take into account beam-material interactions. These interactions are key for accurately simulating the dynamics from heavy ion fragmentation and fission. In order to model the interaction with materials such as the target or absorber, much code development was needed. There were four auxiliary codes implemented in COSY for the simulation of beam-material interactions. These include EPAX for returning the cross sections of isotopes produced by fragmentation and MCNPX for the cross sections of isotopes produced by the fission and fragmentation of a 238U beam. ATIMA is implemented to calculate energy loss and energy and angular straggling. GLOBAL returns the charge state. The extended version can be run in map mode or hybrid map-Monte Carlo mode, providing an integrated beam dynamics-nuclear processes design optimization and simulation framework that is efficient and accurate. The code, its applications, and plans for large-scale computational runs for optimization of separation purity of rare isotopes at FRIB will be presented.
JLAB, Newport News, Virginia
Automation of DC photoinjector designs using a genetic algorithm (GA) based optimization is an accepted practice in accelerator physics. Allowing the gun cavity field profile shape to be varied can extend the utility of this optimization methodology to superconducting and normal conducting radio frequency (SRF/RF) gun based injectors. Finding optimal field and cavity geometry configurations can provide guidance for cavity design choices and verify existing designs. We have considered two approaches for varying the electric field profile. The first is to determine the optimal field profile shape that should be used independent of the cavity geometry, and the other is to vary the geometry of the gun cavity structure to produce an optimal field profile. The first method can provide a theoretical optimal and can illuminate where possible gains can be made in field shaping. The second method can produce more realistically achievable designs that can be compared to existing designs. In this paper, we discuss the design and implementation for these two methods for generating field profiles for SRF/RF guns in a GA based injector optimization scheme and provide preliminary results.
Fermilab, Batavia
In the paper the results are presented for calculation of the transverse wake and RF kick from the power and HOM couplers of the ILC acceleration structure. The RF kick was calculated by HFSS code while the wake was calculated by GdfidL. The calculation precision and convergence for both cases is discussed. The beam emittance dilution caused by the couplers is calculated for the main linac and bunch compressor of ILC.
LBNL, Berkeley, California
Tracy is an accelerator modeling and simulation code originally developed at LBNL in Pascal two decades ago*. Tracy evolved to Tracy2** which served as the basis for several derivative codes at other synchrotron light sources, including PSI, SSRL and Soleil. In most of these cases, the accelerator physics library was extracted and translated in C. At the ALS the library was re-written in C++ (Goemon***) in an object-oriented manner. Later this version was converted to C# with some effort spent on optimizing its performance****. Tracy# is the latest C# version upgraded to take advantage of the new features of the .NET Framework 3.5 and 4.0. It efficiently uses the modern language features of the C# and the standardized libraries of the .NET Framework for database, XML and networking. It also works with other .NET languages, such as IronPython and F# for interactive scripting. Although it is developed on Windows, MONO makes it portable to other operating systems including Linux.
PSI, Villigen
Modern particle tracking codes with their parallel processing capabilities generate data files of the order of 100 Gigabytes. Thus they make very high demands on file formats and post-processing software. H5PartROOT is a versatile and powerful tool addressing this issue. Based on ROOT, CERN's object-oriented data analysis framework developed for the requirements of the LHC era, and the HDF5 hierarchical data format, supplemented by an accelerator-specific interface called H5Part, H5PartROOT combines the statistical and graphical capabilities of ROOT with the versatility and performance of the HDF5 technology suite to meet the needs of the accelerator community. Providing the user with both a graphical user interface (data browser) and a shared library to be used in an interactive or batch ROOT session, H5PartROOT passes on the full power of ROOT without presupposing any knowledge about the intricacies of either ROOT or C++.
JAEA/TARRI, Gunma-ken
It is well-known that a charged-particle beam is Coulomb crystallized in the low-temperature limit. The feasibility of beam crystallization has been raised by the recent progress in beam cooling techniques and in understanding of the behavior of crystalline beams. To go a step further, we explore the dynamic behaviors of crystalline ion beams extracted from a storage ring, employing the molecular dynamics simulation technique. The effect of an extraction device and the following transport line on various crystalline beams has been investigated for extraction and transport of crystalline beams without collapse of the ordered structure.