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| TUPOY055 | Study on Electro-polishing of Nb Surface by Periodic Reverse Current Method with Sodium Hydroxide Solution | 2020 |
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| Electropolishing is one of the best methods of Nb surface finishing of the superconducting cavity to obtain high accelerating gradient. Mixed solution of hydrofluoric acid and sulfuric acid is generally used in the electropolishing of Nb. But this solution is very dangerous and because the corrosion of the metal occurs by hydrofluoric acid, all equipment must be made of high density polyethylene or fluorocarbon resin. This causes the expensive cost of electropolishing instrument. In addition, this solution produces sulfur compound on the Nb surface in the electropolishing reaction. This sulfur compound can be field emission sources on the inner surface of cavity and degrades acceleration performance. In this poster, we report noble electropolishing method using periodic reverse current and sodium hydroxide solution. The reaction produces no sulfur content and the equipment is less expensive because the instrument can be made of usual plastic material. As the result of experiments with Nb-coupon samples, we found that the surface roughness is equivalent to the conventional electropolishing method. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOY055 | |
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| WEPMB018 | Multipactor Simulations in 650 MHz Superconducting Spoke Cavity for an Electron Accelerator | 2161 |
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Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. In order to realize a compact industrial-use X-ray source based on the laser-Compton scattering, a superconducting spoke cavity for an electron accelerator operated at 4K is under development. While the initially proposed operating frequency was 325MHz considering the 4K operation, we decided to start from the half scale model at 650MHz to accumulate our production experience of spoke cavity within our limited resources. In the present contribution, procedures and results of multipactor simulations for 650MHz spoke cavities are briefly introduced. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB018 | |
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| WEPMB021 | Construction of Measurement System for Superconducting Characteristics on Thin-film Samples at KEK | 2167 |
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| We set up a measurement system for superconducting characteristics on thin-film samples at KEK. The system includes small-sized and middle-sized cryostats, where critical temperature, critical magnetic field, Residual Resistiviy Ratio (RRR), Superconducting RF (SRF) resistivity can be measured on thin-film samples. A small-sized cryostat has a compact refrigerator to cool down samples for the measurements of critical temperature and RRR. On the other had, we can cool down various setups with a middle-sized cryostat by using liquid helium. A thin-film sample is set into a mushroom cavity and the SRF characteristics of the thin-film sample can be measured. In another setup, a sample is set with a small coil and the third harmonic measurement is done on the sample around the critical temperature. Finally, a thin-film sample is set into the bore-center of superconducting magnet and the magnetization of sample is measured with external magnetic field around the critical temperature. This article presents the details of the system and some measurements of samples by the system. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB021 | |
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| WEPMB024 | Study on Nondestructive Inspections for Super-conducting Cavity | 2174 |
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Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have been studying nondestructive inspections for super-conducting spoke cavities. The temperature mapping (T-map) and X-ray mapping (X-map) are powerful inspection methods to locate a hot spot during the vertical RF tests. There would be a defect under the hot spot and the defect may be the cause of a quench. Our XT-map system (a combined system of T-map and X-map) has a high resolution in space. Because the huge amount of sensor signals are multiplexed at a hi-speed scanning rate in the vicinity of the sensors, the small number of signal lines makes the installation process easy and reduces the system complexity. Our XT-map got useful results on finding a defect in vertical RF tests of International Linear collider super-conducting cavity. The XT-map system is useful as low cost nondestructive inspections for superconducting spoke cavity. The study will be reported. progresses will be reported. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB024 | |
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| WEPMB025 | Fabrication of Superconducting Spoke Cavity for Laser Compton Scattered Photon Sources | 2177 |
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Funding: The work is supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have launched a 5-year research program to develop superconducting spoke cavity for laser Compton scattered (LCS) photon sources. For realizing a wide use of LCS X-ray and γ-ray sources in academic and industrial applications, we adopt the super-conducting spoke cavity to electron beam drivers. The spoke cavity has advantages such as relative compactness in comparison with an elliptical cavity of the same frequency, robustness with respect to manufacturing inaccuracy due to its strong cell-to-cell coupling, the better packing in a linac to install couplers on outer conductor. On the other hand the spoke cavity has disadvantage of more complicated structure than an elliptical cavity. Though our proposal design for the photon source consists of the 325 MHz spoke cavities in 4K operation, we have begun to fabricate the half scale model of 650 MHz spoke cavity in order to accumulate our cavity production experience by effective utilization of our limited resources. In this paper, we present our fabrication status. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB025 | |
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| WEPMR016 | Vertical Electropolishing Studies at Cornell with KEK and Marui | 2295 |
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| Cornell's SRF group has developed Vertical Electro-Polishing (VEP) and applied on 1.3GHz Niobium SRF cavities as the primary surface treatment. High-Q and high voltage performances of VEP'ed SRF cavities had been successfully demonstrated at Cornell. In 2014, new VEP R&D collaboration has started between Cornell, KEK, and Marui Galvanizing Co. Ltd. (MGI). MGI and KEK has developed their original VEP cathode named 'i-cathode Ninja'® which has four retractable wing-shape parts per cell for single-/9-cell cavities. We will report the results of VEP process using 'i-cathode Ninja'® on single cell cavity at Cornell. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMR016 | |
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