| Paper | Title | Page |
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| TUPJE058 | Preparation of Polycrystalline and Thin Film Metal Photocathodes for Normal Conducting RF Guns | 1759 |
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| A comparison of quantum efficiency (QE) and work function (wf) measurements of polycrystalline and thin film metal photocathodes for use in NCRF guns, similar to the S-band gun under development for CLARA project at Daresbury, are reported. Cu and Nb thin films were grown onto a Si substrate by magnetron sputtering and subsequently were prepared by annealing and Ar ion sputtering. To determine the surface chemistry, x-ray photoelectron spectroscopy was employed. QE measurements were enabled using a UV laser source giving 266 nm light. Wf measurements were carried out using a kelvin probe and ultraviolet photoelectron spectroscopy. Annealing the Cu thin film to 250°C yielded a QE of 1.2E-4; one order of magnitude higher than the QE for sputter cleaned and post annealed polycrystalline Cu. The optimum QE measurement for Nb thin film was 2.6·10-4, which was found to be comparable to the results obtained for cleaned bulk Nb. Analysis of XPS data of these metals suggest surface composition and surface chemistry are main contributing factors to the QE and WF. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE058 | |
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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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