ANL, Argonne
MSU, East Lansing, Michigan
Many processes in Physics can be described by Partial Differential equations (PDE’s). For various practical problems, very precise and verified solutions of PDE are required; but with conventional finite element or finite difference codes this is difficult to achieve because of the need for an exceedingly fine mesh which leads to often prohibitive CPU time. We present an alternative approach based on high-order quadrature and a high-order finite element method. Both of the ingredients become possible through the use of Differential Algebra techniques. Further the method can be extended to provide rigorous error verification by using the Taylor model techniques. Application of these techniques and the precision that can be achieved will be presented for the case of 3D Laplace’s equation. Using only around 100 finite elements of order 7, verified accuracies in the range of 10-7 can be obtained.
ORNL, Oak Ridge, Tennessee
IUCF, Bloomington, Indiana
As SNS continues to ramp toward full intensity, we are acquiring a wealth of experimental data. Much effort is being applied to understand the details of the beam accumulation process under a variety of experimental conditions. An important part of this effort is the computational benchmarking of the experimental observations. In order to obtain quantitative agreement between the calculations and the observations, and hence a full understanding of the machine, a great deal of care must be taken to incorporate all the relevant experimental parameters into the calculation. These vary from case to case, depending upon what is being studied. In some of these cases, the benchmarks have been critical in unearthing flaws in the machine and in guiding their mitigation. In this paper we present the results of benchmarks with a variety of experiments, including coupling in beam distributions at low intensities, space charge effects at higher intensities, and a transverse instability driven by the impedance of the ring extraction kickers.
TRIUMF, Vancouver
The simulation toolkit GEANT4 has been used to create high-level tools for specific user groups, such as SPENVIS in space physics and GATE in medical imaging. In Accelerator Physics, comparable efforts are being devoted to develop general-purpose programs for simulating beamlines and accelerators, allowing access to Geant4's facilities for 3D geometry, tracking, and interactions in matter without the need for specialised programming techniques. In this study we investigate the use of two high-level tools based on Geant4, G4BEAMLINE and BDSIM, to model a 65-meter beam line supplying protons from the TRIUMF cyclotron to the ISAC RIB facility. We outline the rather different approaches to defining the beamline geometry (including cyclotron extraction foil and exit region) in each code. Their diagnostic and visualisation features are also compared. Due to its ability to model some important aspects such as rectangular dipoles and magnetic fringe fields, G4beamline was utilized for a series of simulations presented here, investigating the distribution of losses in the beamline, the role of scattering in the cyclotron extraction foil, and the sensitivity of losses to tuning parameters.
TUB, Beijing
CIAE, Beijing
A high intensity compact cyclotron, CYCIAE-100, is selected as the driving accelerator for Beijing Radioactive Ion-beam Facility (BRIF). At present the physics design of this machine has been accomplished. This paper gives a brief review of the general designs of this machine. For further intensity upgrade of this compact machine in the future, it is crucial to carry out in-depth study on the self fields effects including the contributions of single bunch space charge and the interaction of many radially neighboring bunches. In order to include the neighboring bunch effects fully self-consistently in compact cyclotrons, a new physical model is established for the first time and implemented in the parallel PIC code OPAL-CYCL. After that, the impact of the single bunch space charge and neighboring bunches on the beam dynamics in CYCIAE-100 for different intensity levels are studied by the simulations using the new model.
NSCL, East Lansing, Michigan
The cyclotron gas stopper is a newly proposed device to stop energetic ions in a high pressure helium gas and to transport them in a singly charged state with a gas jet to a vacuum region. Ions are injected into the region with vertical magnetic field, where they first meet a degrader and then move in helium gas. Due to multiple scattering, radioactive ions lose their energy, and the process is accompanied by ionization of helium. Externally applied voltage remove electrons and single-charged helium ions from the box. Under a certain incoming particle rate, the amount of ionized charge becomes large and cannot be removed completely. As a result, a neutralized plasma is accumulated in the center of the box and new incoming particles cannot be ejected from the field-shielded area. The present study focuses on a detailed understanding of space charge effects in the central ion extraction region. Particle-in-cell simulations of electron-helium plasma are based on self-consistent particle tracking in a field obtained from solution of Poisson’s equation for particle interacting via Coulomb forces. The paper analyzes the process and estimates the maximum possible incoming particle rate.
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.