| Paper | Title | Page |
|---|---|---|
| TUPCH016 | Numerical Simulation of Synchrotron Radiation for Bunch Diagnostics | 1031 |
|
||
| For the operation of the VUV-FEL at DESY, Hamburg, the longitudinal charge distribution of the electron bunches that drive the free electron laser is of high importance. One novel method to measure the bunch shape is to analyze the coherent far-infrared synchrotron radiation generated at the last dipole magnet of the first bunch compressor. For the correct interpretation of the results it is mandatory to know how various parameters, like the bunch shape and path, the vacuum chamber walls, the optical beamline, etc., influence the observed spectrum. The aim of this work is to calculate the generation of synchrotron radiation inside the bunch compressor with the emphasis of including the effects of the vertical and horizontal vacuum chamber walls in the vicinity of the last dipole magnet. Challenging problems for the numerical simulations are the very short wavelength and the broad frequency range of interest. As a first step, it is shown how the radiation leaving the vacuum chamber, that is generated by a single point charge, can be calculated with the help of the uniform theory of diffraction (UTD). | ||
| WEPCH112 | Database Extension for the Beam Dynamics Simulation Tool V-code | 2176 |
|
||
| The beam dynamics simulation tool V-Code has been proved to be very useful in redesigning the injector layout at the superconducting linear accelerator in Darmstadt (S-DALINAC). Modifications in the beam optics are necessary because a new source of polarized electrons should be installed in addition to the existing thermionic gun. The calculations are performed with V-Code which is designed to handle a large amount of individual beam line elements and can therefore be used for extensive accelerator studies. The available database includes all the necessary components like solenoids, quadrupoles and rf cavities, but as a result of their consecutive treatment overlapping external fields are not allowed. Due to geometrical restrictions in the assembly of the new source a space-saving candidate of a quadrupole triplet violates this software-related condition if it is regarded as three distinct quadrupoles. Consequently, a more general beam line element has to be created which treats the lenses as a single unit without interference of their fields to attached cells. The indispensable data base extension together with simulation results and implementation verifications will be presented. | ||
| WEPCH113 | Numerical Impedance Calculations for the GSI SIS-100/300 Kickers | 2179 |
|
||
| Fast kicker modules represent a potential source for beam instabilities in the planned Facility for Antiproton and Ion Research (FAIR) at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt. In particular, the more than fifty kicker modules to be installed in the SIS-100 and SIS-300 synchrotrons are expected to have a considerable parasitic influence on the high-current beam dynamics. Here we present our numerical investigations of the longitudinal and transverse kicker coupling impedances using a specialized electromagnetic field software. Besides the coupling to the external network, particular attention is paid to the question whether a resistively-coated ceramic beam pipe is able to reduce coupling impedances and ferrite heating significantly. | ||
| WEPCH114 | On the Development of a Self-consistent Particle-in-cell (PIC) Code Using a Time-adaptive Mesh Technique | 2182 |
|
||
| For a large class of problems the self-consistent simulation of charged particle beams in linear accelerators is necessary. Especially, in all low-energetic sections such as injectors the self-consistent interaction of particles and fields has to be taken into account. Well-known programs like the MAFIA TS Modules typically use the Particle-in-cell (PIC) method for beam dynamics simulations. Since they use a fixed computational grid which has to resolve the bunch adequately, they suffer from enormous memory consumption. Therefore and especially in the 3D case, only rather short sections can be simulated. A remedy to this limitation is the usage of a grid which refines itself in the vicinity of particles. For this purpose, a new code called SMOVE based on a time-adaptive grid is being developed. First promising results will be presented at the conference. | ||
| WEPCH115 | Numerical Simulation and Optimization of a 3-GHz Chopper/Prebuncher System for the S-DALINAC | 2185 |
|
||
| A new source of polarized electrons with an energy of 100 keV is presently being developed at the superconducting Darmstadt electron linear accelerator S-DALINAC for future nuclear- and radiation-physics experiments. The pulsed electron beam emitted by the photocathode will be cut to 50 ps by a chopper operated at 3 GHz, and further bunch compression down to 5 ps will be achieved by a two-stage prebuncher section. The chopper-prebuncher system is based on similar devices used at the Mainz Mikrotron (MAMI) where the accelerator frequency is slightly smaller (2.4 GHz). For the chopper, a cylindrical resonator operating at TM110 mode is selected to deflect the electron beam onto an ellipse, i.e., both horizontally and vertically. This is simply achieved by particular slits on both ends of the resonator. The prebunching system consists of two cavities. For increasing the longitudinal capture efficiency, the first cavity will be operated at the fundamental accelerator frequency of the S-DALINAC of 3 GHz, and the second cavity at 6 GHz. The cavities are designed to work at the TM010 mode and TM020 mode for the fundamental and first harmonic, respectively. | ||
| WEPCH116 | Recent Simulation Results of the Polarized Electron Injector (SPIN) of the S-DALINAC | 2188 |
|
||
| Recent design and development for a polarized electron source (SPIN) for the recirculating superconducting electron linear accelerator S-DALINAC will be presented. The polarized electron beam will be produced by photoemission from an InAlGaAs/GaAs superlattice cathode and will be accelerated to 100 kV electrostatically. The results of the beam dynamics simulation will be shown in detail. The start phase space of the electron bunch behind the gun has been approximated. The transverse focusing system consists of very short quadrupoles. Further main components of the new injector are a Wien filter, a Mott polarimeter, a chopper-prebuncher system (based on devices used at the Mainz Mikrotron MAMI), and diverse beam diagnostic tools. For the approximation of the start phase space CST MAFIA is used, and for the beam dynamic simulation VCode is used. | ||
| MOPLS066 | Direct Measurement of Geometric and Resistive Wakefields in Tapered Collimators for the International Linear Collider | 697 |
|
||
| Precise collimation of the beam halo is required in the ILC to prevent beam losses near the interaction region that could cause unacceptable backgrounds for the physics detector. The necessarily small apertures of the collimators lead to transverse wakefields that may result in beam deflections and increased emittance. A set of collimator wakefield measurements has previously been performed in the ASSET region of the SLAC LINAC. We report on the next phase of this programme, which is carried out at the recently commissioned End Station A test facility at SLAC. Measurements of resistive and geometric wakefields using tapered collimators are compared with model predictions from MAFIA and GdfidL and with analytic calculations. | ||
| MOPLS067 | Test Beam Studies at SLAC's End Station A, for the International Linear Collider | 700 |
|
||
| The SLAC Linac can deliver to End Station A a high-energy test beam with similar beam parameters as for the International Linear Collider for bunch charge, bunch length and bunch energy spread. ESA beam tests run parasitically with PEP-II with single damped bunches at 10Hz, beam energy of 28.5 GeV and bunch charge of (1.5-2.0)·1010 electrons. A 5-day commissioning run was performed in January 2006, followed by a 2-week run in April. We describe the beamline configuration and beam setup for these runs, and give an overview of the tests being carried out. These tests include studies of collimator wakefields, prototype energy spectrometers, prototype beam position monitors for the ILC Linac, and characterization of beam-induced electro-magnetic interference along the ESA beamline. | ||
| THPCH161 | Status of the Polarized Electron Gun at the S-DALINAC | 3173 |
|
||
|
Aiming at an extension of the experimenting capabilities for nuclear structure physics at low momentum transfer at the superconducting Darmstadt electron linear accelerator S-DALINAC, a polarized electron gun is being constructed. The new injector will be able to supply the S-DALINAC with 100 keV polarized electrons and should complement the present, unpolarized thermionic source. The design requirements are a degree of polarization of at least 80%, a mean current intensity of 0.06 mA and a 3 GHz cw structure. The basic design of the gun was adapted from the source of polarized electrons at MAMI, Mainz*, and optimized in various simulations. The active material is a strained layer GaAs crystal which is exposed to an 830 nm pulsed laser beam. We report on the status of the polarized source, the preparation setup and a test beam line.
*K. Aulenbacher et al., Nucl. Instrum. Meth. A 391, 498 (1997). |