Paper | Title | Other Keywords | Page |
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MO103 | SNS Superconducting Linac Operational Experience and Upgrade Path | cavity, cryomodule, linac, SRF | 11 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy |
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TUP032 | Simulations on Impact of the 3.9 GHz RF Section on the Multi Bunch Emittance at FLASH | cavity, emittance, damping, linac | 465 |
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In order to compensate nonlinear distortions of the longitudinal phase space a rf section operated at three times the 1.3 GHz frequency of the existing TTF cavities is foreseen in the next phase of FLASH. Four modules of a nine-cell 3.9 GHz cavities will be installed right after the first accelerating module ACC1. These cavities could cause additional long-range wake fields which would affect the multi bunch (mb) beam dynamics leading to increase of the mb emittance. The mb emittance at the end of the linac is determined by the strength of the transverse wake fields in the rf system. These higher order modes appear after any off-crest moving bunch, which could happen either due to the cavity misalignment, or by transverse position fluctuations of the injected bunches. It is intended to damp them by means of the HOM couplers, which may reduce the damping time by factor of 105. The misalignment of the cavities offsets is expected to be by 0.5 mm rms. The paper describes the results of the simulations on the dependence of the mb emittance on cavities misalignment offsets and damping strength of the HOM couplers in the planned 3.9 GHz rf section. |
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TUP057 | Design and Fabrication of CLIC Test Structures | damping, accelerating-gradient, wakefield, impedance | 533 |
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Demonstration of a gradient of 100 MV/m at a breakdown rate of 10-7 is one of the key feasibility issues of the CLIC project. A high power rf test program both at X-band (SLAC and KEK) and 30 GHz (CERN) is under way to develop accelerating structures reaching this performance. The test program includes the comparison of structures with different rf parameters, with/without wakefield damping waveguides, and different fabrication technologies namely quadrant bars and stacked disks. The design and objectives of the various X-band and 30 GHz structures are presented and their fabrication methods and status is reviewed. |
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WE102 | High Average Current SRF Cavities | cavity, storage-ring, linac, luminosity | 693 |
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Higher-order-mode (HOM) free superconducting (SC) single cell cavities were developed for the rf system of high luminosity storage ring colliders. Because of the successful results of these cavities under ampere-class beams, the components and technology of the SC cavities have immediately been applied to the middle sized storage rings upgrading the beam intensity by using a few SC cavities. Beside the storage ring rf, a SC based high intensity proton linac was commissioned for neutron physics. Recently, the feasibility study of energy recovery linacs has been carried at various laboratories aiming for the 4th generation light source. Status of these developments will be described. |
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TH101 | Superconducting RF R&D Toward High Gradient | cavity, niobium, SRF, superconducting-cavity | 725 |
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High-beta superconducting rf elliptical cavities are being developed in large numbers for several accelerator projects including the International Linear Collider (ILC). In recent years, the understanding of cavity performance limitations has improved significantly, leading to better than 40 MV/m in some cavities. However, further improvement is needed to reach reliably the 31.5 MV/m operating gradient proposed for the ILC Main Linac cavities. World-wide R&D on the cavity gradient frontier includes improved surface cleaning and smoothing treatments, development of alternative cavity shapes and materials, and novel cavity manufacturing techniques. Substantial progress has been made with diagnostic instrumentation to understand cavity performance limitations. Some highlights of the efforts in superconducting rf R&D toward achieving higher gradients in high-beta elliptical cavities are reviewed. |
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THP014 | Recent Results of 1.3 GHz Nine-Cell Superconducting Cavities for the European XFEL | cavity, niobium, superconductivity, superconducting-cavity | 806 |
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In preparation for the series production of roughly 800 superconducting accelerating structures, several tests with an industrial-like production sequence have been tested for their accelerating gradient and quality factor. The main part of the surface preparation is being done with electropolishing. with ethanol rinse. For the two different final preparation steps namely electropolishing and etching the performance is compared. The results will be also put into the perspective of earlier cavity production cycles that were tested at DESY. |
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THP019 | Third Harmonic Superconducting Cavity Prototypes for the XFEL | cavity, linac, cryomodule, pick-up | 821 |
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The third harmonic cavities that will be used at the injector stage in the XFEL to linearize the rf curvature distortions and minimize beam tails in the bunch compressor are based on the rf structures developed at FNAL for the DESY FLASH linac. The design and fabrication procedures have been modified in order to match the slightly different interfaces of XFEL linac modules and the procedures followed by the industrial production of the main (1.3 GHz) XFEL cavities. A revision of the helium vessel design has been required to match the layout of the cryomodule strings, and a lighter version of the tuner has been designed (derived from the 1.3 GHz ILC blade tuner activities). The main changes introduced in the design of the XFEL cavities and the preliminary experience of the fabrication of three industrially produced and processed third harmonic rf structures are described here. |
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THP028 | Status of 3.9 GHz Superconducting RF Cavity Technology at Fermilab | cavity, alignment, cryomodule, status | 845 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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THP029 | Performance of 3.9-GHZ Superconducting Cavities | cavity, superconductivity, status, SRF | 848 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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THP037 | RF Design of a Spoke Resonator for High Power Free-Electron Lasers | electron, free-electron-laser, laser, acceleration | 866 |
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Funding: Supported by the High-Energy Laser Joint Technology Office |
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THP038 | A New SRF Cavity Shape with Minimized Surface Electric and Magnetic Fields for the ILC | cavity, dipole, coupling, wakefield | 867 |
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Funding: Work supported by DOE contract DE-AC02-76SF00515. |
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THP039 | SRF Cavity Imperfection Studies Using Advanced Shape Uncertainty Quantification Tools | cavity, cryomodule, SRF, dipole | 870 |
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Funding: Work supported by DOE contract DE-AC02-76SF00515. |
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THP044 | Coaxial Coupling Scheme for Fundamental and Higher Order Modes in Superconducting Cavities | cavity, coupling, damping, superconducting-cavity | 885 |
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Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. |
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THP061 | High Power Test of a Low Group Velocity X-Band Accelerator Structure for CLIC | damping, vacuum, collider, luminosity | 930 |
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In recent years evidence has been found that the maximum sustainable gradient in an accelerating structure depends on the rf power flow through the structure. The CLIC study group consequently designed a new prototype structure for CLIC with a very low group velocity, input power and average aperture (a/λ = 0.12). The 18 cell structure has a group velocity of 2.4% at the entrance and 1% at the last cell. Several of these structures have been made in collaboration between KEK, SLAC and CERN. A total of five brazed-disk structures and two quadrant structures have been made. The high power results of some of these structures are presented. The first KEK/SLAC built structure reached an unloaded gradient in excess of 100 MV/m at a pulse length of 230 ns with a breakdown rate below 10-6. The high-power testing was done using the NLCTA facility at SLAC. |
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THP062 | Design of an X-Band Accelerating Structure for the CLIC Main Linac | damping, linac, accelerating-gradient, impedance | 933 |
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The rf design of an accelerating structure for the CLIC main linac is presented. The structure is designed to provide 100 MV/m averaged accelerating gradient at 12 GHz with an rf-to-beam efficiency as high as 27.7%. The design takes into account both aperture and HOM damping requirements coming from beam dynamics as well as the limitations related to rf breakdown and pulsed surface heating. |
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THP074 | A New Accelerator Structure Concept: the Zipper Structure | coupling, damping, wakefield, resonance | 963 |
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Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. |