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MOP046 |
New SRF Facility at KEK for Mass-Production Study in Collaboration with Industries | |
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| The construction of the new SRF facility including new building next to the KEK-STF facility has started for mass-production study of SRF accelerators in collaboration with industries. This new building has the dimension of 80 m x 30 m and the plan is to install clean-room for cavity-string assembly, cryomodule assembly facility, cryogenic system, vertical test facility, cryomodule test facility, input coupler process facility, cavity electro-polishing facility, and control-room/office-rooms in it. The purpose of this new SRF facility is to establish a close collaboration between SRF researchers and industries, to produce technology innovation in the new industry market aiming at concept of new sustainable and ecological society in the future. This article reports the design of new SRF facility at KEK and the organization of the new collaboration between the SRF researchers and industries utilizing the new SRF facility, as well as the impact on the upcoming large-scale future SRF project, ILC. | ||
| TUIOC06 | Study on Optimum Electron Beam Welding Condition for Superconducting Accelerating Cavities | 424 |
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| Optimizations of electron beam welding conditions might solve the quench problems and improve the accelerating field of the superconducting radio-frequency cavity. As a first step toward optimum conditions, basic properties of weld beads are studied by using niobium test pieces. Effects of a combination of a beam generator position and a welding direction on geometries of weld bead are shown. Good parameter-regions for electron beam welding, which yield full penetration welds without holes or weld spatters, are surveyed. Microscopic structures, such as pits or bumps due to poor welds, have greater influence on cavity performances, which are also our research objects. We introduce a model of the magnetic field enhancement at pits, where a formula for a magnetic field enhancement factor is given as a function of parameters that express a geometry of pit. Comparisons between calculations and vertical test results are also shown. | ||
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Slides TUIOC06 [15.958 MB] | |
| TUP007 | Vortex Penetration Field in the Multilayered Coating Model | 430 |
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A multilayered structure with a single superconductor layer and a single insulator layer deposited on a bulk superconductor is studied. General formulae for the vortex penetration-field of the superconductor layer and the magnetic field on the bulk superconductor which is shielded by the superconductor and insulator layers are derived with a rigorous calculation of the magnetic field attenuation in the multilayered structure. The formulae depend not only on the material and the thickness of the superconductor layer but also on the thickness of the insulator layer. The results can be applied to superconducting accelerating cavities with the multilayered structure. Using the formulae, a combination of the thicknesses of superconductor and insulator layers to enhance the RF breakdown field limits can be found for any given materials. (Submitted on 25 Apr 2013)
T. Kubo, Y. Iwashita and T. Saeki, arXiv:1304.6876 [physics.acc-ph](Submitted on 25 Apr 2013); arXiv:1306.4823 [physics.acc-ph](Proc. of IPAC13); arXiv:1307.0583 [physics.acc-ph](Proc. of SRF2013) |
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| TUP052 | Study on Vertical Electro-Polishing by Cathode With Variable-Geometry Wings | 530 |
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| We have been studying on Vertical Electro-Polishing (VEP) of Nb superconducting accelerator cavity for about one year with a view to the mass-production and cost-reduction of Electro-Polishing (EP) process. Marui Galvanizing Co. Ltd. has been in the EP business of various metals for long time and we have matured experience on EP processes. With being based on the experience, we thought that uniform electric-current on the surface of cavity and effective flow of electrolyte in the cavity are important factors. Moreover, we thought the most important effect is given if the cathode and the cavity surface (anode) are kept in a constant distance. Following these considerations, we invented VEP process by a cathode with variable-geometry wings. Using this cathode, we performed several experiments of VEP Nb single-cell cavities as well as fluid circulation test by plastic 9-cell mock-up. In this article, we will report this unique VEP process, which might be applicable to the mass-production process of International Linear Collider (ILC). | ||
| TUP108 | Study on Niobium Scratch and Tantalum or Carbonaceous Contamination at Niobium Surface with Field Emission Scanner | 731 |
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| It is mandatory to investigate field emission from niobium SRF cavity surface systematically since even small field emission often limits the cavity performance terribly. The field emission strength and the number of emission sites strongly depend on niobium surface properties which are determined by its surface treatment and handling. It was found that carbonaceous contamination including carbon, oxygen, sometimes, nitrogen often segregates at CPed or EPed surface with a size of several micron to several tens of micron-meters. There is a strong doubt that this contamination causes field emission from the surface. Newly developed field emission scanner (FES) allows us to measure a distribution of the field emitting sites over a sample surface at a given field strength along with its SEM (scanning electron microscope) observation and EDX (energy dispersive x-ray) analysis. This article describes results of the FES-SEM-EDX application to carbonaceous contamination at niobium surface. | ||
| THIOA03 | Cavity Fabrication Study in CFF at KEK | 821 |
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| The construction of new facility for the fabrication of superconducting RF cavity at KEK was completed in 2011. It is equipped with the following machines; an electron-beam welding (EBW) machine, a servo press machine and a CNC vertical lathe. A chemical etching apparatus is also equipped. The study on the fabrication of 9-cell cavity for International Linear Collier (ILC) has been started from 2009 using this facility. The study is focusing on the cost reduction with keeping high performance of cavity, and the goal is the establishment of mass-production procedure for ILC. | ||
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Slides THIOA03 [7.823 MB] | |