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Superconducting spoke cavities for high-velocity applications

Description: To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.
Date: October 1, 2013
Creator: Hopper, Christopher S. & Delayen, Jean R.
Partner: UNT Libraries Government Documents Department

Geometry Effects on Multipole Components and Beam Optics in High-Velocity Multi-Spoke Cavities

Description: Velocity-of-light, multi-spoke cavities are being proposed to accelerate electrons in a compact light-source. 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.
Date: December 1, 2013
Creator: Hopper, Christopher S.; Deitrick, Kirsten E. & Delayen, Jean R.
Partner: UNT Libraries Government Documents Department

Tests of an RF Dipole Crabbing Cavity for an Electron-Ion Collider

Description: 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.
Date: December 1, 2013
Creator: Castilla Loeza, Alejandro & Delayen, Jean R.
Partner: UNT Libraries Government Documents Department

Design Optimization of Superconducting Parallel-bar Cavities

Description: The parallel-bar structure is a new superconducting geometry [1] whose features and properties may have significant advantages over conventional superconducting deflecting and crabbing cavities for a number of applications. Jefferson Lab is in need for a 499 MHz, 11 GeV rf separator as part of its 12 GeV upgrade program. We report on design optimization studies performed to-date for this and other applications.
Date: November 1, 2009
Creator: Delayen, Jean R. & De Silva, Payagalage Suba
Partner: UNT Libraries Government Documents Department

Comparison of electromagnetic, thermal and mechanical calculations with rf test results in rf-dipole deflecting/crabbing cavities

Description: 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 the vertical test area at Jefferson Lab have proven the designs to achieve higher gradients with higher intrinsic quality factors and easily processed multipacting conditions. The cavity characteristics, such as pressure sensitivity and Lorentz force detuning, were studied using ANSYS before the fabrication. These characteristics were measured during the cavity test. The comparison between the simulation and the measurement provides insight how the simulation can be used for design and fabrication of future cavities.
Date: December 1, 2013
Creator: Park, HyeKyoung; De Silva, Subashini U. & Delayen, Jean R.
Partner: UNT Libraries Government Documents Department

Characterization and Fabrication of Spoke Cavities for High-Velocity Applications

Description: A 500 MHz, velocity-of-light, two-spoke cavity has been designed and optimized for possible use in a compact light source. Here we present the mechanical analysis and steps taken in fabrication of this cavity at Jefferson Lab.
Date: February 1, 2014
Creator: Hopper, Christopher S.; Park, HyeKyoung & Delayen, Jean R.
Partner: UNT Libraries Government Documents Department

Alternate Electrolyte Composition for Electropolishing of Niobium Surfaces

Description: Electropolishing has shown promising results for the treatment of Nb cavities to be used in particle accelerators, particularly in the attainment of high surface electric fields. In support of the CEBAF Upgrade project and as part of a longer-term R and D program, we have investigated the properties of several electrolyte recipes. A particularly promising one consists of a mixture of lactic, sulfuric, and hydrofluoric acids. Initial tests reveal that smooth Nb surfaces can be achieved with no observable grain boundaries under optical microscope. We report on the results of the investigations of the parameters that control the polishing process using this particular acid mixture.
Date: September 1, 2001
Creator: Delayen, Jean R.; Mammosser, John; Phillips, Larry & Wu, Andy T.
Partner: UNT Libraries Government Documents Department

Mechanical Analysis of the 400 MHz RF-Dipole Crabbing Cavity Prototype for LHC High Luminosity Upgrade

Description: 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.
Date: December 1, 2013
Creator: De Silva, Subashini U.; Park, HyeKyoung; Delayen, Jean R. & Li, Z.
Partner: UNT Libraries Government Documents Department