| 1. |
- Gontad, F, et al.
(författare)
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Nanomechanical and electrical properties of Nb thin films deposited on Pb substrates by pulsed laser deposition as a new concept photocathode for superconductor cavities
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 804, s. 132-136
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Tidskriftsartikel (refereegranskat)abstract
- We report a design of photocathode, which combines the good photoemissive properties of lead (Pb) and the advantages of superconducting performance of niobium (Nb) when installed into a superconducting radio-frequency gun. The new configuration is obtained by a coating of Nb thin film grown on a disk of Pb via pulsed laser deposition. The central emitting area of Pb is masked by a shield to avoid the Nb deposition. The nanomechanical properties of the Nb film, obtained through nanoindentation measurements, reveal a hardness of 2.8±0.3 GPa, while the study of the electrical resistivity of the film shows the appearance of the superconducting transitions at 9.3 K and 7.3 K for Nb and Pb, respectively, very close to the bulk material values. Additionally, morphological, structural and contamination studies of Nb thin film expose a very low droplet density on the substrate surface, a small polycrystalline orientation of the films and a low contamination level. These results, together with the acceptable Pb quantum efficiency of 2×10−5 found at 266 nm, demonstrate the potentiality of the new concept photocathode.
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| 2. |
- Lorusso, Antonella, et al.
(författare)
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Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application
- 2015
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 579, s. 50-56
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Tidskriftsartikel (refereegranskat)abstract
- Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher temperatures has been observed. X-ray diffraction measurements showed that a preferred orientation of Pb (111) normal to the substrate was achieved at 30 °C while the Pb (200) plane became strongly pronounced with the increase in the substrate temperature. Finally, a Pb thin film deposited on Nb substrate at 30 °C and tested as the photocathode showed interesting results for the application of such a device in superconducting radio frequency guns.
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| 3. |
- Lorusso, A., et al.
(författare)
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Pulsed laser deposition of yttrium photocathode suitable for use in radio-frequency guns
- 2017
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Ingår i: Applied Physics A. - : SPRINGER. - 0947-8396 .- 1432-0630. ; 123:12
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Tidskriftsartikel (refereegranskat)abstract
- Yttrium (Y) thin film was grown by pulsed laser deposition (PLD) on a copper (Cu) polycrystalline substrate. Ex situ morphological and structural characterisations of the circular Y film of 1.2 mu m thickness and 3 mm diameter have shown a very low droplet density on the film surface and a crystalline feature with a preferred orientation along the Y (100) plane. Moreover, Y thin film resulted in being very adherent to the Cu substrate and more scratch resistant than Cu bulk. A twin thin film was deposited also on a Cu backflange of a radio-frequency (RF) gun to test the suitability of the metallic thin film as photocathode. It was observed that the Y-coated photocathode was characterised by a quantum efficiency (QE) higher than that of the Cu bulk photocathode even if the presence of space charge effects didnt allow deriving the absolute maximum value of QE of Y photocathode.
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| 4. |
- Lorusso, A., et al.
(författare)
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Structural and morphological properties of metallic thin films grown by pulsed laser deposition for photocathode application
- 2016
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Ingår i: Applied Physics A. - : Springer Berlin/Heidelberg. - 0947-8396 .- 1432-0630. ; 122:3, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique and characterized by ex situ different diagnostic methods. All the films were adherent to the substrates and revealed a polycrystalline structure. Y films were uniform with a very low roughness and droplet density, while Pb thin films were characterized by a grain morphology with a relatively high roughness and droplet density. Such metallic materials are studied because they are proposed as a good alternative to copper and niobium photocathodes which are generally used in radiofrequency and superconducting radiofrequency guns, respectively. The photoemission performances of the photocathodes based on Y and Pb thin films have been also studied and discussed.
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| 5. |
- Lorusso, A., et al.
(författare)
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Tight comparison of Mg and Y thin film photocathodes obtained by the pulsed laser deposition technique
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER SCIENCE BV. - 0168-9002 .- 1872-9576. ; 836, s. 57-60
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Tidskriftsartikel (refereegranskat)abstract
- In this work Magnesium (Mg) and Yttrium (Y) thin films have been deposited on Copper (Cu) polycrystalline substrates by the pulsed laser ablation technique for photocathode application. Such metallic materials are studied for their interesting photoemission properties and are proposed as a good alternative to the Cu photocathode, which is generally used in radio-frequency guns. Mg and Y films were uniform with no substantial differences in morphology; a polycrystalline structure was found for both of them. Photoemission measurements of such cathodes based on thin films were performed, revealing a quantum efficiency higher than Cu bulk. Photoemission theory according to the three-step model of Spicer is invoked to explain the superior photoemission performance of Mg with respect to Y. (C) 2016 Elsevier B.V. All rights reserved.
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| 6. |
- Perrone, A, et al.
(författare)
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Comparison of the properties of Pb thin films deposited on Nb substrate using thermal evaporation and pulsed laser deposition techniques
- 2013
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 729, s. 451-455
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Tidskriftsartikel (refereegranskat)abstract
- Pb thin films were prepared at room temperature and in high vacuum by thermal evaporation and pulsed laser deposition techniques. Films deposited by both the techniques were investigated by scanning electron microscopy to determine their surface topology. The structure of the films was studied by X-ray diffraction in θ–2θ geometry. The photoelectron performances in terms of quantum efficiency were deduced by a high vacuum photodiode cell before and after laser cleaning procedures. Relatively high quantum efficiency (>10−5) was obtained for all the deposited films, comparable to that of corresponding bulk. Finally, film to substrate adhesion was also evaluated using the Daimler–Benz Rockwell-C adhesion test method. Weak and strong points of these two competitive techniques are illustrated and discussed.
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