| Paper |
Title |
Page |
| MOPP009 |
Copper Prototype Measurements of the HOM, LOM and SOM Couplers for the ILC Crab Cavity
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568 |
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- G. Burt, P. K. Ambattu, A. C. Dexter
Cockcroft Institute, Lancaster University, Lancaster
- L. Bellantoni
Fermilab, Batavia, Illinois
- P. Goudket, P. A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- Z. Li, L. Xiao
SLAC, Menlo Park, California
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The ILC Crab Cavity is positioned close to the IP and hence is very sensitive to the wakefields induced by the beam. A set of couplers were designed to couple to and hence damp the spurious modes of the crab cavity. As the crab cavity is a deflecting mode cavity, it operates using a dipole mode and has different damping requirements than an accelerating mode cavity. A separate coupler is required for the monopole modes below the operating frequency of 3.9 GHz, known as the LOMs, the opposite polarization of the operating mode, the SOM, and the modes above the operating frequency, the HOMs. Each of these couplers have been manufactured out of copper and measured attached to an aluminium nine cell prototype of the cavity and their external Q factors were measured. The results were found to agree well with numerical simulations.
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| TUPC076 |
TTF HOM Data Analysis with Curve Fitting Method
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1227 |
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- S. Pei, C. Adolphsen, K. L.F. Bane, Z. Li, J. C. Smith
SLAC, Menlo Park, California
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To investigate the possibility of using HOM signal induced in SC cavities as beam and cavity diagnostics, experiments and analyses based on SVD have been done, which are very successful. In this paper, we described one new method based on curve fitting to analyze the HOM signal data, some results have been obtained. The new method can be used to extract the HOM mode frequency, Q and relative phase from the data. On the other hand, this method can also be used to find the HOM mode center, polarization axis, mode axis along the cavity, while careful handling of beam timing information need to be considered in analysis. Comparing with SVD, this method is more physical, and can also be used in the beam diagnostic data analysis to obtain the beam position and beam trajectory angle.
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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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| TUPP084 |
Parallel Computation of Integrated Electromagnetic, Thermal and Structural Effects for Accelerator Cavities
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1724 |
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- V. Akcelik, A. E. Candel, A. C. Kabel, K. Ko, L. Lee, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California
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The successful operation of accelerator cavities has to satisfy both rf and mechanical requirements. It is highly desirable that electromagnetic, thermal and structural effects such as cavity wall heating and Lorentz force detuning in superconducting rf cavities can be addressed in an integrated analysis. Based on the SLAC parallel finite-element code infrastructure for electromagnetic modeling, a novel multi-physics analysis tool has been developed to include additional thermal and mechanical effects. The speedup from parallel computation enables virtual prototyping of accelerator cavities on computers, which would substantially reduce the cost and time of a design cycle. The multi-physics tool will be applied to the LCLS rf gun and a superconducting rf gun cavity.
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