| Paper | Title | Page |
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| THPAN081 | Collimator Wakefields: Formulae and Simulation | 3405 |
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| The effect of a leading particle on a trailing particle due to resistive and geometric wakefields in collimators can be described by expanding in a series of angular mode potentials Wm(s). Several formulae for these are given in the literature. We compare these formulae with numerical predictions from codes that solve the EM field equations, and explore the claimed regions of validity. We also explore how the EM code results can be used to numerically obtain angular mode potentials suitable for use in tracking codes. | ||
| THPAN068 | Wakefield Models for Particle Tracking Codes | 3378 |
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| Wakefields have a considerable effect on beam dynamics and they must not be neglected for emittance growth studies, background estimates and other problems. The codes used for these problems are normally not capable of self-consistent wakefield calculations. They should thus be extended with either analytical models or export the wakefields numerically evaluated with other codes (such as Gdfidl) when analytical models are not feasible. We discuss both approaches and present their implementation in PLACET, MERLIN and BDSIM. The simulation results for the ILC and CLIC beam delivery systems are given as an example. Results produced with different codes are compared. | ||
| THPAN079 | Emittance Growth Due to High Order Angular Multipole Mode Wakefields in the ILC-BDS Collimators | 3402 |
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| The passage of an off-axis bunch through the collimator gap induces higher order mode wakefields which can lead to emittance growth and consequently can affect the luminosity at the IP - a major concern for the ILC. The emittance growth due to high order angular multipole mode wakefields is calculated and beam profiles at the IP are presented in this paper. | ||
| FRPMS074 | Measurements of the Transverse Collimator Wakefields due to Varying Collimator Characteristics | 4207 |
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Funding: EUROtev Contract #011899RIDS US DOE Contract DEAC02-76SF00515
We report on measurements of the transverse wakefields induced by collimators of differing characteristics. An apparatus allowing the insertion of different collimator jaws into the path of a beam was installed in End Station A (ESA) in SLAC. Eight comparable collimator geometries were designed, including one that would allow easy comparison with previous results, and were installed in this apparatus. Measurements of the beam kick due to the collimator wakefields were made with a beam energy of 28.5 GeV, and beam dimensions of ~100 microns vertically and a range of 0.5 to 1.5 mm longitudinally. The trajectory of the beam upstream and downstream of the collimator test apparatus was determined from the outputs of ten BPMs (four upstream and six downstream), thus allowing a measurement of the angular kick imparted to the beam by the collimator under test. The transverse wakefield was inferred from the measured kick. The different aperture designs, data collection and analysis, and initial comparison to theoretical and analytic predictions are presented here.
* "An Apparatus for the Direct Measurement of Collimator Transverse Wakefields", P. Tenenbaum, PAC '99** "Direct Measurement of the Resistive Wakefield in Tapered Collimators", P Tenenbaum, PAC '04 |