Paper  Title  Page 

MOPAN013  Wien Filter as a Spin Rotator at Low Energy  170 


Funding: Work supported by DFG under contract SFB 634 The Wien filter is well known as a common energy analyzer and is also used more and more as a compact variant of a spin rotator at low energy for electrons. The Wien filter based on a homogenous magnetic and electric field that are perpendicular to each other and transverse to the direction of the electrons. The rotation of the spin vector is caused by the magnetic field. If the force equilibrium condition is fulfilled the beam should not be deflected at the Wien filter. Simulations show that in the fringe fields the electrons get a kick. Therefore full 3D simulations of the electromagnetic fields and beam dynamics simulations are studied in detail at the example of the Wien filter at the new polarized 100 keV electron injector at the SDALINAC. The results of the simulations with CST Design Environment(TM), MAFIA and VCode are presented. 

THPAN019  Utilizing a Wien Filter within the Beam Dynamics Simulation Tool VCode  3265 


Funding: This work was partially funded by EUROFEL (RIDS011935), DESY Hamburg, and DFG (SFB 634). Beam dynamics simulations for computationally large problems are challenging tasks. On the one hand, to accurately simulate the electromagnetic field distribution within the whole device and the surrounding environment it is essential to consider all necessary device components including even small geometry details, complicated material distributions and the field excitations. On the other hand, further computational effort has to be put into precise modeling of the injected particle beam for detailed beam dynamics simulations. Under linear conditions, it is possible to separate the field calculation of the device from the computation of the particles selffield which can result in the proper application of diverse numerical schemes for the individual field contributions. In the paper it is demonstrated how the static electric and magnetic fields of a Wien filter beam line element can be treated as applied external fields within the beam dynamics simulation tool VCode under the assumption that the interaction of the particle beam with the surrounding materials can be neglected. 

THPAN020  A Dispersionless Algorithm for Calculating Wake Potentials in 3D  3268 


Funding: This work is supported in part by the EU under contract number RIDS011899 (EUROTeV). Accurate computations of wake potentials are an important task in modern accelerator design. Short bunches used in high energy particle accelerators excite very highfrequency fields. The geometrical size of accelerating structures exceeds the wavelength of the excited fields by many orders of magnitude. The application of codes such as TBCI, MAFIA or tamBCI are limited due to numerical dispersion effects and memory needs. Recently new codes like PBCI have been developed to overcome these problems. In this work the utilization of dispersionless directions in the leapfrog update scheme on a Cartesian grid are proposed for accurate simulations. In conjunction with a conformal modelling technique which allows for the full Courant time step a moving window technique can be applied. This was previously implemented in a 2D code. In this publication an extension to arbitrary three dimensional problems are presented. 

THPAN045  Explicit Time Domain Boundary Element Scheme for Dispersionfree Wake Field Calculation of Long Accelerator Structures  3330 


This paper introduces a new explicit scheme with a moving window option for wake field calculation of long accelerator structures. This scheme is based on a time domain boundary element method (TDBEM) which uses a retarded Kirchhoff boundary integral equation on interior region problems. As a corollary of this boundary integral equation, our approach allows a conformal modeling of a structure and time domain wake field simulation without numerical grid dispersion errors in all spatial directions. The implementation of a moving window technique in the framework of TDBEM is presented and it is shown that this moving window technique allows to significantly reduce memory requirement of the TDBEM scheme in the short range wake field calculation. Several numerical examples are demonstrated for the TESLA 9cell cavity and tapered collimators. The results of the new TDBEM scheme are compared with that of finite difference codes.  
FRPMN016  Wake Field Computations for the PITZ Photoinjector  3931 


Funding: This work is supported in part by the EU under contract number RIDS011935 (EUROFEL). The computation of wake fields excited by ultra short electron bunches in accelerator components with geometrical discontinuities is a challenging problem, as an accurate resolution for both the small bunch and the large model geometry are needed. Several computational codes (PBCI, ROCOCO, CST PARTICLE STUDIO etc.) have been developed to deal with this type of problems. Wake field simulations of the RF electron gun of the Photoinjector Test Facility at DESY Zeuthen (PITZ) are performed whith different specialized codes. Here we present a comparison of the wake potentials calculated numerically obtained from the different codes. Several structures of the photoinjector are considered. 