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WEPP085 |
RF Coupler Kicks and Wake-fields in SC Accelerating Cavities
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2719 |
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- N. Juntong, R. M. Jones, I. R.R. Shinton
UMAN, Manchester
- C. D. Beard
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- G. Burt
Cockcroft Institute, Warrington, Cheshire
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The main accelerating cavities of the ILC provide acceleration of both positron and electron beams to 250 GeV per beam and 500 GeV per beam in a proposed upgrade. The wake-field excited by each ultra-relativistic beam in the accelerating cavities can seriously dilute the emittance of the particles within the beams. Each cavity is supplied with both fundamental and higher order mode couplers. The geometrical configuration of these RF couplers results in an asymmetrical field and this gives rise to both an RF kick being applied to the beam and transverse wake-field. Detailed e.m. fields are simulated in the vicinity of the couplers in order to assess the impact on the beam dynamics. We investigate modified geometries with a view to alleviating the emittance dilution resulting from the e.m. field associated with the RF couplers.
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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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MOPP125 |
A Superconducting RF Vertical Test Facility at Daresbury Laboratory
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850 |
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- P. A. Corlett, R. Bate, C. D. Beard, B. D. Fell, P. Goudket, S. M. Pattalwar
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- P. K. Ambattu, G. Burt, A. C. Dexter, M. I. Tahir
Cockcroft Institute, Lancaster University, Lancaster
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A superconducting RF vertical test facility (VTF) has been constructed at Daresbury Laboratory for the testing of superconducting RF cavities at 2K. When fully operational, the facility will be capable of testing a 9-cell 1.3 GHz Tesla type cavity. The facility is initially to be configured to perform phase synchronisation experiments between a pair of single cell 3.9GHz ILC crab cavities. These experiments require the cavities to operate at the same frequency; therefore a tuning mechanism has been integrated into the system. The system is described, and data from the initial operation of the facility is presented.
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MOPP128 |
Comparison of Stretched-wire, Bead-pull and Numerical Impedance Calculations on 3.9 GHz Dipole Cavities
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859 |
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- P. Goudket, C. D. Beard, P. A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- G. Burt, A. C. Dexter
Cockcroft Institute, Lancaster University, Lancaster
- R. M. Jones
Cockcroft Institute, Warrington, Cheshire
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In order to verify detailed impedance and wakefield simulations, the resonant modes in an aluminium model of the 9-cell ILC crab cavity were investigated using a stretched-wire frequency domain measurement, as well as frequency-domain bead-pull measurements. These measurements were compared to numerical simulations in order to verify that the complete cavity mode spectrum could be experimentally characterised for this high frequency structure. The analysis of the results and the accuracy and/or limitations of each method is presented.
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