| Paper | Title | Page |
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| MO6RFP056 | Cryogenic Test of the Nb-Pb SRF Photoinjector Cavities | 488 |
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In this contribution, we report progress on the development of a hybrid lead/niobium superconducting RF (SRF) photoinjector. The goal of this effort is to build a Nb injector with the superconducting cathode made of lead, which demonstrated in the past superior quantum efficiency (QE) compared to Nb Three prototype hybrid devices, consisting of an all-niobium cavity with an arc-deposited spot of lead in the cathode region, have been constructed and tested. We present the cold test results of these cavities with and without lead. |
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| TU5PFP002 | Atomic Layer Deposition for SRF Cavities | 803 |
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Funding: DOE/OHEP We have begun using Atomic Layer Deposition (ALD) to synthesize a variety of surface coatings on coupons and cavities as part of an effort to produce rf structures with significantly better performance and yield than those obtained from bulk niobium, The ALD process offers the possibility of conformally coating complex cavity shapes with precise layered structures with tightly constrained morphology and chemical properties. Our program looks both at the metallurgy and superconducting properties of these coatings, and also their performance in working structures. Initial results include: 1) evidence from point contact tunneling showing magnetic oxides can be a significant limitation to high gradient operation, 2) experimental results showing the production sharp niobium/oxide interfaces from a high temperature bake of ALD coated Al2O3 on niobium surfaces, 3) results from ALD coated structures. |
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| TU5PFP053 | Cryogenic Test of a Coaxial Coupling Scheme for Fundamental and Higher Order Modes in Superconducting Cavities | 945 |
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A coaxial coupling device located in the beam pipe of the TESLA type superconducting cavities provides for better propagation of Higher Order Modes (HOMs) and their strong damping in appropriate HOM couplers. Additionally, it also provides efficient coupling for fundamental mode RF power into the superconducting cavity. The whole coupling device can be designed as a detachable system. If appropriately dimensioned, the magnetic field can be minimized to a negligible level at the flange position. This scheme, presented previously*, provides for several advantages: strong HOM damping, flangeable solution, exchangeability of the HOM damping device on a cavity, less complexity of the superconducting cavity, possible cost advantages. This contribution will describe the results of the first cryogenic test. *J. Sekutowicz et al., Proceedings LINAC08, Victoria, Canada, 2008. |
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| TU5PFP055 | Hydroforming of Multi-Cell Niobium and NbCu-Clad Cavities | 950 |
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Technological aspects of seamless tube fabrication and multi-cell cavity production by hydroforming will be discussed. Problems related to the fabrication of seamless cavities from bulk niobium are mainly solved. Several two cell- and three cell- niobium cavities have been produced by hydroforming at DESY. A 9-cell cavity of the TESLA shape has been completed from three sub-sections at company ZANON. The cavity was treated by electropolishing (EP) and successfully RF-tested. Two 3-cell units equipped with niobium beam pipes are being RF-tested after BCP surface treatment. The temperature mapping method with Jlab’s two-cell thermometry system is applied for performance analysis. It is of particular interest to compare the seamless cavity quench locations to those from standard cavities. The cryogenic test results and the T-mapping findings will be discussed. Of special interest is the combination of the seamless technique with NbCu cladding, i.e. the fabrication of cavity from bimetallic clad NbCu tube by hydroforming. Fabrication of single-cell and multi-cell NbCu clad cavities by hydroforming from bimetallic tubes is proven. Some test results will be presented. |
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| WE5PFP037 | SRF Cavity High-Gradient Study at 805 MHz for Proton and Other Applications | 2076 |
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Funding: DTRA 805 MHz elliptical SRF cavities have been used for SNS as the first application for protons. At LANL, an R&D started to explore a capability of getting high-gradient cavities (40-50 MV/m) at this frequency for the future applications such as proton and muon based interrogation testing facility added to the LANSCE accelerator and a power upgrade of the LANSCE accelerator for the fission and fusion material test station. Optimized cell designs for “standard”, “low-loss” and “re-entrant” shapes, cavity test results for “standard” single-cell cavities with temperature mapping as well as surface inspection results will be presented. |
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| WE5PFP059 | Design, Prototype and Measurement of a Single-Cell Deflecting Cavity for the Advanced Photon Source | 2138 |
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Funding: This manuscript has been authored by Jefferson Science Associates, LLC and by UChicago Argonne, LLC under U.S. DOE Contract numbers DE-AC05-06OR23177 and DE-AC02-06CH11357. After design optimization of a squashed elliptical single-cell crab cavity at 2.8 GHz, a copper prototype has been bench measured in order to determine its rf properties and the effectiveness of waveguide damping of parasitic modes, especially the low-order mode (LOM)*. We also present detailed results of the RF cold test at 2K on niobium single-cell and two-cell prototype cavities operating either in the zero or pi mode. Further progress will be discussed on the design of high-order mode (HOM) waveguide damping, the analysis of the Lorenz force detuning simulations by ANSYS, and the prototype of on-cell damping in which a waveguide port is attached directly on the cavity’s long equator. Details of LOM/HOM impedance calculations and experimental bench measurements will be reported and compared to strict requirements for satisfying the APS impedance budget. *J. Shi et. al., “Superconducting RF Deflecting Cavity Design and Prototype for Short X-ray Pulse Generation”, EPAC 2008, paper MOPP155. |