| Paper | Title | Page |
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| MOP002 | A High Phase Advance Damped and Detuned Structure for the Main Linacs of CLIC | 49 |
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We report on the suppression of long-range wakefields in the main linacs of the CLIC collider. The wakefield is damped using a combination of detuning the frequencies of beam-excited higher order modes and by light damping, through slot-coupled manifolds. This unique accelerator, in the process of being fabricated, will be the first structure to demonstrate wakefield damping and the ability to sustain high accelerating gradients for CLIC. This serves as an alternative to the baseline CLIC design, which at present relies entirely on heavy damping. Detailed simulations are presented, on both the optimised surface fields resulting from the monopole mode, and from wakefield damping of the dipole modes. Preparations for the fabrication of a structure, suitable for high power testing, are also discussed. This design takes into account practical mechanical engineering issues and is the result of several optimisations since the original CLICDDS proposal[*]. *V.F. Khan and R.M. Jones, Presented at Particle Accelerator Conference (PAC 09), Vancouver, BC, Canada, 4-8 May 2009. |
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| THP011 | First Beam Spectra of sc Third Harmonic Cavity at FLASH | 782 |
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Third harmonic superconducting cavities have been designed and fabricated by FNAL to minimise the energy spread along bunches in the FLASH facility at DESY. A module, consisting of four nine-cell 3.9 GHz cavities, has been installed in FLASH. The first measurement with beam excitation is presented, and the comparisons to transmission measurement without beam and simulations are made. Higher order modes (HOMs) are able to propagate to adjacent cavities through attached beam tubes. Modes from 1.3 GHz cavities in the module nearby also propagate into this module. *Work supported by European Commission under the FP7 Research Infrastructures grant agreement No.227579. |
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| THP012 | Higher Order Modes in Third Harmonic Cavities at FLASH | 785 |
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Transverse modes in the 3.9 GHz cavities designed and fabricated by FNAL are reported on. These modes have the potential to cause significant emittance dilution if they not sufficiently suppressed. Recent experiments, both probe-based and beam-excited, have indicated significant discrepancies between modes predicted in stand-alone 9-cell cavities compared to those in 4-cavity modules. We employ a suite of computer codes and circuit models to analyze these modes, coupled through beam tubes whose cut-off is above that of the first dipole band. We also report on preparations to instrument the higher order mode couplers with electronics suitable for diagnosing both the beam and cavity position, based on modes with sufficient R/Q values. |
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| THP089 | Beam Dynamics Studies of the REX-ISOLDE Linac in Preparation for its Role as Injector for the HIE-ISOLDE SC Linac at CERN | 950 |
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The superconducting High Intensity and Energy (HIE) ISOLDE linac will replace most of the existing accelerating infrastructure of the Radioactive ion beam EXperiment (REX) at CERN, however, the 101.28 MHz RFQ and 5 MV IH cavity will remain in the role of injector for the upgrade, boosting the beam up to an energy of 1.2 MeV/u. We present the results of a beam dynamics investigation of the injector focused most critically on matching the longitudinal beam parameters from the RFQ to the SC machine, which is complicated largely by the IH cavity employing a Combined Zero Degree* (KONUS) beam dynamics design. The longitudinal beam parameters at the RFQ are reconstructed from measurement using the three-gradient method and combined with beam dynamics measurements and simulations of the IH structure to design the matching section for the SC linac. *Ratzinger, U., "The IH-structure and its capability to accelerate high current beams," Particle Accelerator Conference, 1991 |