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Title |
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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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| TUPP018 |
Impact of Electromagnetic Fields in TESLA RF Modules on Transverse Beam Dynamics
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1568 |
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- E. Prat, W. Decking, M. Dohlus, T. Limberg, I. Zagorodnov
DESY, Hamburg
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Transverse electric fields in TESLA rf modules exist on one hand because of deformations of the longitudinal accelerating field in the presence of rf structure misalignments or in the vicinity of asymmetrically machine parts like input couplers. On the other hand, the beam itself induces transverse wake fields if it does not travel through the center of a perfectly rotationally symmetric structure. Transverse deflecting fields deflect beam particles. The average deflection causes a change in the beam trajectory; the phase dependence of the transverse field leads to a variation of the transverse kick along the longitudinal position of the bunch and thus in general to a change in projected emittance. If the strength of the transverse field component varies along the transverse direction itself, slice emittance will be also affected. We will present the amplitudes and spatial variations of transverse fields generated by the mechanisms described above, and discuss their impact on beam trajectories and shape.
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| TUPP034 |
Transverse Effects due to Vacuum Mirror of RF Gun
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1613 |
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- I. Zagorodnov, M. Dohlus, M. Krasilnikov
DESY, Hamburg
- E. Gjonaj, S. Schnepp
TEMF, Darmstadt
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The transverse kick due to the vacuum mirror in the RF gun can negatively affect the beam emittance. In this contribution we estimate numerically and analytically the transverse wake function of European XFEL RF gun and apply it in beam dynamics studies of the transverse phase space.
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| TUPP075 |
Numerical Studies of Resistive Wall Effects
|
1709 |
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- A. V. Tsakanian
Uni HH, Hamburg
- M. Dohlus, I. Zagorodnov
DESY, Hamburg
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In this paper we describe a new numerical code to calculate wakefields of resistive wall geometries. Our code is based on conformal implicit scheme. It allows to estimate wakefields of very short bunches taking into account transitive effects neglected in the European XFEL impedance budget so far.
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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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