Author: Hannah, A.N.
Paper Title Page
TUPMP051 MULTIPACTOR SUPPRESSION BY LASER ABLATION SURFACE ENGINEERING FOR SPACE APPLICATIONS 1365
 
  • R. Valizadeh, A.N. Hannah, O.B. Malyshev, B.S. Sian
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.S. Colligon
    University of Huddersfield, Huddersfield, United Kingdom
  • Y. Dan
    Hitachi High-Technologies Corp., Ibaraki-ken, Japan
  • V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • J. Mutch
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • N. Sykes
    Micronanics Laser Solution Center, Didcot, United Kingdom
 
  Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators and space-borne RF equipment for communication purposes. In this study we report on the secondary electron yield (SEY) measured from silver coated aluminium alloy as-received and after laser ablation surface engineering (LASE). Analysis shows the SEY can be reduced by 43% using LASE. EDX and SEM analysis shows it is possible to reduce the SEY whilst maintaining the original surface composition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP051  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPTS114 Electron Stimulated Desorption from Cryogenic NEG-Coated Surfaces 2193
SUSPFO135   use link to see paper's listing under its alternate paper code  
 
  • R. Sirvinskaite, M.D. Cropper
    Loughborough University, Loughborough, Leicestershire, United Kingdom
  • A.N. Hannah, O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • S. Wang
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  Non-Evaporable Getter (NEG) coating has been used for years in many particle accelerators due to its advantages like evenly distributed pumping speed, low thermal outgassing, and low photon, electron and ion stimulated desorption yields. Although NEG coating has been tested at room temperatures intensively, there is little data on its behaviour at cryogenic temperatures. Tests in this environment are important for the Future Circular Collider (FCC) study and other accelerator facilities where the operational conditions of the beam screen are restricted to cryogenic temperatures. This work will provide some preliminary results on NEG properties at low temperatures, e.g. pumping speed and capacity, as well as its behaviour under electron bombardment, where electron stimulated desorption (ESD) yields will be calculated. The ternary Ti-Zr-V coating, deposited with dense and columnar structure, will be the first material to be tested at cryogenic temperatures in ASTeC Daresbury laboratory. The results were compared with the ones obtained at room temperature, offering an insight into the behaviour of NEG-coated cryogenic chambers when beam-induced effects are present.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS114  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB011 PVD Depostion of Nb3Sn Thin Film on Copper Substrate from an Alloy Nb3Sn Target 2818
 
  • R. Valizadeh, S. Aliasghari, A.N. Hannah, O.B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • K. Dawson, V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • G.B.G. Stenning
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • D. Turner
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Turner
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  In this study we report on the PVD deposition of Nb3Sn on Cu substrates with and without a thick Nb interlayer to produce Cu/Nb/Nb3Sn and Cu/Nb3Sn multilayer structures. The Nb3Sn was sputtered directly from an alloy target at room and elevated temperatures. The dependence of the superconducting properties of the total structure on deposition parameters has been determined. The films have been characterized via SEM, XRD, EDX and SQUID magnetometer measurements. Analysis showed that the composition at both room and elevated temperature was within the desired stoichiometry of 24’25 at%. However, superconductivity was only observed for deposition at elevated temperature or post annealing at 650 °C. The critical temperature was determined to be in the range of 16.8 to 17.4 K. In the case of bilayer deposition, copper segregation from the interface all the way to the surface was observed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB011  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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WEPRB070 Facile Deposition of Superconducting MgB2 Thin Films on Substrates: A Comparative Investigation of Electrochemical Deposition and Magnetron Sputtering Techniques 2984
 
  • N. Misra, A.N. Hannah, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: Authors acknowledge the funding received under the Rutherford International Postdoctoral Fellowship Programme
Coating of Copper cavities with a superconducting layer of MgB2 thin film is an attractive alternative to bulk Nb cavities. In this work, we investigate the application of two approaches-electrochemical deposition and magnetron sputtering of MgB2, to fabricate MgB2 films with potential accelerator applications. In the first approach, MgB2 powder dispersed in acetone was used as an electrolytic medium. Application of a DC voltage of 400 V between a graphite anode and a Copper film (serving as cathode), with the electrode distance maintained at ~2cm, resulted in the electrochemical deposition of MgB2 on the Cu surface. In an alternate approach, MgB2 in powder form was used directly for sputtering based deposition. The powder was initially compacted to form a thin layer that served as the magnetron target. Application of a pulsed DC power of 25W for 4 hours yielded MgB2 thin film on Si substrates. Samples were characterized by XPS analysis to ascertain their elemental composition, which confirmed the presence of Mg and B, in addition to traces of C and O as impurities. Surface morphology was determined using SEM characterization technique. Further work to determine the superconducting properties of the samples and fine tune the deposition processes for large scale MgB2 deposition inside actual RF cavities is in progress.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB070  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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