| Paper | Title | Page |
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| WEPHA052 | Test Cavity and Cryostat for SRF Thin Film Evaluation | 3232 |
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| In developing superconducting coatings for SRF cavities, the coated samples are tested using various techniques such as resistance measurements, AC and DC magnetometry which provide information about the superconducting properties of the films such as RRR, Hc1, Hc2 and vortex dynamics. However, these results do not allow the prediction of the superconducting properties at RF frequencies. A dedicated RF cavity was designed to evaluate surface resistive losses on a flat sample. The cavity contains two parts: a half-elliptical cell made of bulk Nb and a flat Nb disc. The two parts can be thermally and electrically isolated via a vacuum gap, whereas the electromagnetic fields are constrained through the use of RF chokes. Both parts are conduction cooled hence the system is cryogen free. The flat disk can be replaced with a sample, such as a Cu disc coated with Nb film. The RF test provide the cavity Q-factor and thermometrical measurements of the losses on the sample. The design advantages are that the sample disc can be easily installed and replaced; installing a new sample requires no brazing/welding/vacuum or RF seal, so the sample preparation is simple and inexpensive. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA052 | |
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| WEPHA053 | Surface Resistance RF Measurements of Materials Used for Accelerator Vacuum Chambers | 3235 |
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| The RF surface resistance of accelerator vacuum chamber walls can have a significant impact on the beam quality. There is a need to know how the use of a new material, surface coating or surface treatment can affect the RF surface resistance. ASTeC and Lancaster University have designed and built two test cavities where one face can be replaced with a sample in the form of a flat plate. The measurements are performed with a network analyser at the resonant frequency of approximately 7.8 GHz. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA053 | |
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| WEPHA058 | Superconducting Coatings Synthesized by CVD/PECVD for SRF Cavities | 3246 |
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Funding: STFC Bulk niobium cavities are widely employed in particle accelerators to create high accelerating gradient despite their high material and operation cost. In order to reduce this cost, thin layer of niobium are deposited on a copper cavity, which has lower material cost with higher availability and more importantly higher thermal conductivity. The coating of superconducting cavities currently is synthesized by physical vapour deposition (PVD) method which suffers from lack of conformity. By using chemical vapour deposition (CVD) and plasma enhanced chemical vapour deposition (PECVD) it is possible to deposit thin Nb layers uniformly with density very close to bulk material. This project explores the use of PECVD / CVD techniques to deposit metallic niobium on copper using NbCl5 as precursor and hydrogen as a coreagent. The samples obtained were then characterized via SEM, TEM, SAD, XRD, XPS, and EDX as well as assessing their superconductivity characteristics (RRR and Tc) All the samples deposited are superconductive and polycrystalline; the sample obtained with CVD measured RRR=31 and Tc=7.9 K, while the sample obtained with PECVD exhibited RRR=9 and Tc= 9.4 K. In both cases the films grew in a (100) preferred orientation. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA058 | |
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| WEPHA059 | Physical Vapour Deposition of Thin Films for Use in Superconducting RF Cavities | 3249 |
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| The production of superconducting coatings for radio frequency cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. Optimizing superconducting properties of Nb thin-films is therefore essential. Nb films were deposited by magnetron sputtering in pulsed DC mode onto Si (100) and MgO (100) substrates and also by high impulse magnetron sputtering (HiPIMS) onto Si (100), MgO (100) and polycrystalline Cu. The films were characterised using scanning electron microscopy, x-ray diffraction and DC SQUID magnetometry. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA059 | |
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