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| MOP032 | Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL | niobium, cavity, controls, superconducting-RF | 171 |
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| The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented. | |||
| TUP011 | A Parametric Study of BCS RF Surface Impedance with Magnetic Field Using Xiao Code | impedance, niobium, SRF, superconductivity | 444 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. A recent new analysis of field-dependent BCS RF surface impedance based on moving Cooper pairs has been presented.* Using this analysis coded in Mathematica™, survey calculations have been completed which examine the sensitivities of this surface impedance to variation of the BCS material parameters and temperature. The results present a refined description of the “best theoretical” performance available to potential applications with corresponding materials. * Xiao B. P. et al, Physica C: Superconductivity, 490, 2013, pp. 26–31 |
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| TUP084 | Reciprocal Space XRD Mapping with Varied Incident Angle as a Probe of Structure Variation within Surface Depth | lattice, SRF, software, electron | 651 |
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Funding: This research is supported at AASC by DOE via Grant No. DE-FG02-08ER85162 and Grant No. DE-SC0004994 and by Jefferson Science Associates, LLC under U.S. DOE Contract No. DEAC05- 06OR23177 In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed the materials’ microstructure evolutions after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials’ crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surface’s top-layer; II. for a mechanic polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain. |
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| TUP114 | XT-map System for Locating SC Cavity Quench Position | cavity, cryogenics, operation, accelerating-gradient | 747 |
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| XT-map system under development in collaboration between Kyoto University and KEK is a combined system of the temperature mapping (T-map) and X-ray mapping (X-map). High resolution T-map at quench detection will give more information for improving yield in production of high performance SC Cavities. The high-density sensor distribution of the XT-map gives the high resolution. Because the huge amount of sensor lines 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. The scanning test of this XT-map system has been performed in the vertical test at KEK. The detected quench events will be reported. | |||