| Paper | Title | Page |
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| WEPAC39 | Tests of an RF Dipole Crabbing Cavity for an Electron-Ion Collider | 859 |
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| On the scheme of developing a medium energy electron-ion collider (MEIC) at Jefferson Lab, we have designed a compact superconducting rf dipole cavity at 750 MHz to crab both electron and ion bunches and increase luminosities at the interaction points (IP) of the machine. Following the design optimization and characterization of the electromagnetic properties such as peak surface fields and shunt impedance, along with field nonuniformities, multipole components content, higher order modes (HOM) and multipacting, a prototype cavity was built by Niowave Inc. The 750 MHz prototype crab cavity has been tested at 4 K and is ready for re-testing at 4 K and 2 K at Jefferson Lab. In this paper we present the detailed results of the rf tests performed on the 750 MHz crab cavity prototype. | ||
| WEPAC40 | Mechanical Analysis of the 400 MHz RF-Dipole Crabbing Cavity Prototype for LHC High Luminosity Upgrade | 862 |
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| The proposed LHC high luminosity upgrade requires two crabbing systems in increasing the peak luminosity, operating both vertically and horizontally at two interaction points of IP1 and IP5. The required system has tight dimensional constraints and needs to achieve higher operational gradients. A proof-of-principle 400 MHz crabbing cavity design has been successfully tested and has proven to be an ideal candidate for the crabbing system. The cylindrical proof-of-principle rf-dipole design has been adapted in to a square shaped design to further meet the dimensional requirements. The new rf-dipole design has been optimized in meeting the requirements in rf-properties, higher order mode damping, and multipole components. A crabbing system in a cryomodule is expected to be tested on the SPS beam line prior to the test at LHC. The new prototype is required to achieve the mechanical and thermal specifications of the SPS test followed by the test at LHC. This paper discusses the detailed mechanical and thermal analysis in minimizing Lorentz force detuning and sensitivity to liquid He pressure fluctuations. | ||
| WEPAC41 | Comparison of Electromagnetic, Thermal and Mechanical Calculations with RF Test Results in RF-Dipole Deflecting/Crabbing Cavities | 865 |
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| The current requirements of higher gradients and strict dimensional constraints in the emerging applications have required the designing of compact deflecting and crabbing rf structures. The superconducting rf-dipole cavity is one of the first novel compact designs with attractive properties such as higher gradients, higher shunt impedance and widely separated higher order modes. The recent tests performed on proof-of-principle designs of the rf-dipole geometry at 4.2 K and 2.0 K in a vertical test assembly have proven the designs to achieve higher gradients with higher intrinsic quality factors and easily processed multipacting conditions. The design frequency sensitivity to pressure (df/dp) due to liquid He pressure fluctuations, Lorentz force detuning due to radiation pressure, and thermal and mechanical effects have also been measured during the tests. These effects lead to cavity frequency detuning while in operation and therefore needs to be reduced. This paper presents the detailed comparison of the measurement to the simulation results obtained from ANSYS. | ||
| WEPAC42 | Geometry Effects on Multipole Components and Beam Optics in High-Velocity Multi-Spoke Cavities | 868 |
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Velocity-of-light, multi-spoke cavities are being proposed to accelerate electrons in a compact light-source [1]. There are strict requirements on the beam quality which require that the linac have only small non-uniformities in the accelerating field. Beam dynamics simulations have uncovered varying levels of focusing and defocusing in the proposed cavities, which is dependent on the geometry of the spoke in the vicinity of the beam path. Here we present results for the influence different spoke geometries have on the multipole components of the accelerating field and how these components, in turn, impact the simulated beam properties.
* T. Satogata et al, “Compact Accelerator Design for a Compact Light Source,” IPAC13, Shanghai, China, May 2013. |
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| WEPAC40 | Mechanical Analysis of the 400 MHz RF-Dipole Crabbing Cavity Prototype for LHC High Luminosity Upgrade | 862 |
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| The proposed LHC high luminosity upgrade requires two crabbing systems in increasing the peak luminosity, operating both vertically and horizontally at two interaction points of IP1 and IP5. The required system has tight dimensional constraints and needs to achieve higher operational gradients. A proof-of-principle 400 MHz crabbing cavity design has been successfully tested and has proven to be an ideal candidate for the crabbing system. The cylindrical proof-of-principle rf-dipole design has been adapted in to a square shaped design to further meet the dimensional requirements. The new rf-dipole design has been optimized in meeting the requirements in rf-properties, higher order mode damping, and multipole components. A crabbing system in a cryomodule is expected to be tested on the SPS beam line prior to the test at LHC. The new prototype is required to achieve the mechanical and thermal specifications of the SPS test followed by the test at LHC. This paper discusses the detailed mechanical and thermal analysis in minimizing Lorentz force detuning and sensitivity to liquid He pressure fluctuations. | ||
| WEPAC41 | Comparison of Electromagnetic, Thermal and Mechanical Calculations with RF Test Results in RF-Dipole Deflecting/Crabbing Cavities | 865 |
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| The current requirements of higher gradients and strict dimensional constraints in the emerging applications have required the designing of compact deflecting and crabbing rf structures. The superconducting rf-dipole cavity is one of the first novel compact designs with attractive properties such as higher gradients, higher shunt impedance and widely separated higher order modes. The recent tests performed on proof-of-principle designs of the rf-dipole geometry at 4.2 K and 2.0 K in a vertical test assembly have proven the designs to achieve higher gradients with higher intrinsic quality factors and easily processed multipacting conditions. The design frequency sensitivity to pressure (df/dp) due to liquid He pressure fluctuations, Lorentz force detuning due to radiation pressure, and thermal and mechanical effects have also been measured during the tests. These effects lead to cavity frequency detuning while in operation and therefore needs to be reduced. This paper presents the detailed comparison of the measurement to the simulation results obtained from ANSYS. | ||
| WEPAC42 | Geometry Effects on Multipole Components and Beam Optics in High-Velocity Multi-Spoke Cavities | 868 |
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Velocity-of-light, multi-spoke cavities are being proposed to accelerate electrons in a compact light-source [1]. There are strict requirements on the beam quality which require that the linac have only small non-uniformities in the accelerating field. Beam dynamics simulations have uncovered varying levels of focusing and defocusing in the proposed cavities, which is dependent on the geometry of the spoke in the vicinity of the beam path. Here we present results for the influence different spoke geometries have on the multipole components of the accelerating field and how these components, in turn, impact the simulated beam properties.
* T. Satogata et al, “Compact Accelerator Design for a Compact Light Source,” IPAC13, Shanghai, China, May 2013. |
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| WEPAC43 | Study of Cavity Imperfection Impact on RF-Parameters and Multipole Components in a Superconducting RF-Dipole Cavity | 871 |
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Funding: This work is funded by the US/LHC LARP program. The ODU/SLAC superconducting rf-dipole cavity is under consideration for the crab-crossing system in the upcoming LHC luminosity upgrade. While the proposed cavity complies well within the rf-parameters and multipolar component restrictions for the LHC system, cavity imperfections arising from cavity fabrication, welding and frequency tuning may have a significant effect in these parameters. We report on an initial study of the impact of deviation from the ideal shape on the cavity’s performance in terms of rf-parameters and multipolar components. |
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