| Paper |
Title |
Page |
| MOPC065 |
Wake Field Simulations for Structures of the PITZ RF Photoinjector: Emittance growth estimations
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217 |
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- E. Arevalo, W. Ackermann, E. Gjonaj, W. F.O. Müller, S. Schnepp, T. Weiland
TEMF, Darmstadt
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One of the main concerns in the design of electron guns is the generation of low-emittance beams. One source of emittance growth is the beam-surrounding effect, which can be estimated from the wake potentials along the beam path. For the calculation of these potentials an accurate knowledge of the short range wake fields induced in the different parts of the gun with geometrical discontinuities is necessary. The computation of these wake fields is a challenging problem, as an accurate resolution for both the small bunch and the large model geometry is needed. Here with the help of numerical wake-potential calculations we analytically estimate the emittance growth for the RF electron gun of the Photoninjector Test Facility at DESY Zeuthen (PITZ).
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| MOPP013 |
Coupler Kick for Very Short Bunches and its Compensation
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580 |
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- M. Dohlus, I. Zagorodnov
DESY, Hamburg
- E. Gjonaj, T. Weiland
TEMF, Darmstadt
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In this contribution we estimate two different effects: the kick due to asymmetry of the external accelerating field (coupler RF kick) and the kick due to electromagnetic field of the bunch scattered by the couplers (coupler wake kick). We take into acoount the cavities and calculate the periodic solution for bunch with an rms width of 300 mkm. The different possibilities for compensation of the kick are considered.
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| TUPP019 |
Wakefield and RF Kicks due to Coupler Asymmetry in TESLA-type Accelerating Cavities
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1571 |
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- K. L.F. Bane, C. Adolphsen, Z. Li
SLAC, Menlo Park, California
- M. Dohlus, I. Zagorodnov
DESY, Hamburg
- E. Gjonaj, T. Weiland
TEMF, Darmstadt
- I. G. Gonin, A. Lunin, N. Solyak, V. P. Yakovlev
Fermilab, Batavia, Illinois
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In a future linear collider, such as the International Linear Collider (ILC), trains of high current, low emittance bunches will be accelerated in a linac before colliding at the interaction point. Asymmetries in the accelerating cavities of the linac will generate asymmetries in the fields that will kick the beam and tend to degrade the beam emittance and thus the collider performance. In the main linac of the ILC, which is filled with TESLA-type superconducting cavities, it is the fundamental and higher mode couplers that are asymmetric and thus the source of such kicks. The kicks are of two types: one, due to (the asymmetries in) the fundamental RF fields and the other, due to transverse wakefields that are generated even when the beam is on axis. For the ILC configuration we numerically and analytically study both types of kicks and their effect on beam emittance. For the wakefield effect this is quite challenging since the bunches are very short (rms length of 300 microns), the cavity is very long (~1 m), and the distance to steady-state is even longer (~6 m). Finally, we study changes in the coupler design that can greatly reduce the effect.
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| TUPP089 |
Implementation of Fringe Field Dipole Magnets into the V-Code Beam Dynamics Simulation Tool
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1738 |
| |
- S. S. Franke, W. Ackermann, B. Steiner, T. Weiland
TEMF, Darmstadt
- J. Enders, C. Hessler, Y. Poltoratska
TU Darmstadt, Darmstadt
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Fast online beam dynamics simulations can advantageously assist the machine operators at various particle accelerator machines because they provide a more detailed insight into the actual machine status. Based on the moment approach a fast tracking code named V-Code has been implemented at TEMF. Within the SFB 634 project the V-Code beam dynamics simulation tool is supposed to be installed at the Superconducting Darmstadt LINear ACcelerator S-DALINAC which is designed as a re-circulating linear accelerator. In order to be able to simulate the entire beam line, an implementation of fringe field dipole magnets is mandatory. Unlike a hard edged field approach the fringe fields influence the beam focusing and its inhomogeneity results in a non-circular bunch motion. For an accurate reproduction of the transverse motion specialized techniques to obtain and to handle the reference path in V-Code together with the 3D-field data along the curved trajectory had to be developed. In the paper a summary of implementation details together with simulation results will be provided.
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| TUPP095 |
Computation of Resistive Wall Wakefields with the PBCI Code
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1753 |
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- T. Lau, E. Gjonaj, T. Weiland
TEMF, Darmstadt
- R. Maekinen
TUT, Tampere
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Both geometric disturbances and resistive wall loss of accelerator cavities contribute to the impedance causing the beam to lose energy. Impedance due to arbitrary three-dimensional (3-D) geometries can be computed with the Parallel Beam Cavity Interaction (PBCI), a parallelized, 3D-wakefield code. However, the contribution of wall loss is often significant. The contribution of this work is to incorporate resistive wall loss into 3-D time-domain simulation. Surface-impedance concept is used to consider wide-band skin-effect loss of metal. In theory, the proposed approach can be extended to consider high-frequency phenomena such as frequency-dependent conductivity of metal and anomalous skin effect.
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| TUPD022 |
Electron Beam Polarimetry at the S-DALINAC
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1476 |
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- R. Barday, U. Bonnes, C. Eckardt, R. Eichhorn, J. Enders, C. Heßler, J. Kalben, Y. Poltoratska
TU Darmstadt, Darmstadt
- W. F.O. Müller, B. Steiner, T. Weiland
TEMF, Darmstadt
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It is planned to carry out experiments at the Superconducting Darmstadt Linear Accelerator S-DALINAC with both polarized electron and photon beams at the energy of the electron beam between 10 and 130 MeV. In order to extract asymmetry from these experiments the absolute degree of the electron beam polarization needs to be known. We present the existing and planned polarimeters at the source of polarized electrons and the experimental sites, especially a 100 keV Mott polarimeter and Möller polarimeter for 15-130 MeV electrons.
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| TUPD027 |
Commissioning of the Offline-teststand for the S-DALINAC Polarized Injector SPIN
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1482 |
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- C. Heßler, R. Barday, U. Bonnes, M. Brunken, C. Eckardt, R. Eichhorn, J. Enders, M. Platz, Y. Poltoratska, M. Roth
TU Darmstadt, Darmstadt
- W. Ackermann, W. F.O. Müller, B. Steiner, T. Weiland
TEMF, Darmstadt
- K. Aulenbacher
IKP, Mainz
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At the superconducting Darmstadt linear electron accelerator S-DALINAC a new injector for polarized electrons is under development. For this purpose an off-line test stand has been constructed. It consists of the source of polarized electrons and a test beamline including a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and various beam steering and diagnostic elements. The polarized electron beam is produced by photoemission from a strained GaAs cathode. We report on the status of this project and present first results of the measurements of the beam properties. We also give an outlook on the upcoming installation of SPIN at the S-DALINAC.
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| WEPP091 |
Injector Upgrade for the S-DALINAC
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2731 |
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- T. Kuerzeder, A. Araz, M. Brunken, J. Conrad, R. Eichhorn, H.-D. Gräf, M. Hertling, F. Hug, M. Konrad, M. Platz, A. Richter, S. Sievers, T. Weilbach
TU Darmstadt, Darmstadt
- W. Ackermann, W. F.O. Müller, B. Steiner, T. Weiland
TEMF, Darmstadt
- J. D. Fuerst
ANL, Argonne, Illinois
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Since 1991 the superconducting Darmstadt linear accelerator S-DALINAC provides an electron beam of up to 130 MeV for nuclear and astrophysical experiments. Currently its injector delivers beams of up to 10 MeV with a current of up to 60 μA. The upgrade aims to increase both parameters to 14 MeV and 150 μA in order to allow more demanding astrophysical experiments. Therefore, a modified cryostat module equipped with two new cavities is required. Due to an increase in RF power to 2 kW the old coaxial RF input couplers, being designed for a maximum power of 500 W, have to be replaced by new waveguide couplers. We review the design principles and report on the fabrication of the coupler and the whole module.
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| THPC101 |
Transverse Schottky Noise and Beam Transfer Functions with Space Charge
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3212 |
| |
- S. Paret, O. Boine-Frankenheim, V. Kornilov
GSI, Darmstadt
- T. Weiland
TEMF, Darmstadt
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The heavy ion synchrotron SIS18 will serve as booster for the synchrotron SIS100 to be built as part of the Facility for Antiproton and Ion Research (FAIR). As such the SIS18 should accelerate ion beams with a factor of 10-100 higher intensity, compared to the present performance. Beams of such intensities may suffer instabilities due to collective effects. Particularly at injection-energy space charge and the resistive wall impedance will affect the beam remarkably. Experiments for the investigation of direct space charge were performed in SIS18. Transverse Schottky signals and beam transfer functions (BTF) of coasting ion beams affected by space charge were measured. A distortion of the Schottky bands and BTF was observed and compared to a simple model allowing for linear space charge. The model reproduced the deformation and yielded parameters of the beam.
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| THPC038 |
Beam Dynamic Simulations of the New Polarized Electron Injector of the S-DALINAC
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3062 |
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- B. Steiner, W. Ackermann, S. S. Franke, W. F.O. Müller, T. Weiland
TEMF, Darmstadt
- R. Barday, C. Eckardt, R. Eichhorn, J. Enders, C. Hessler, Y. Poltoratska, A. Richter, M. Roth
TU Darmstadt, Darmstadt
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Aiming at an extension of the experimental possibilities at the Superconducting Darmstadt electron linear accelerator S-DALINAC, a polarized gun is going to be constructed at the moment. The new injector will be able to supply polarized electrons with kinetic energy in the 100 keV range and should add to the present unpolarized thermionic 250 keV source. The design requirements include a polarization degree of at least 80%, a mean current intensity of 60 μA and a 3 GHz cw time structure. The gun part is simulated in CST MAFIA whereas subsequent beam dynamics simulations are performed in V-Code. Initial conditions for the V-Code’s moment approach are extracted from the CST MAFIA simulations. The injector consists of short triplets, an alpha magnet, a Wien filter, a Mott polarimeter, a chopper/prebuncher system and beam diagnostic elements. For the simulations, the 3D electromagnetic fields of the beam line elements are used by means of a Taylor series expansion of variable order. All components except the chopper and a collimator is represented in the simulations. Recent beam dynamic results will be presented.
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