Author: Valizadeh, R.
Paper Title Page
TUPOTK033 First RF Measurements of Planar SRF Thin Films with a High Throughput Test Facility at Daresbury Laboratory 1283
 
  • D.J. Seal, G. Burt, P. Goudket, O.B. Malyshev, B.S. Sian, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt, D.J. Seal, B.S. Sian
    Lancaster University, Lancaster, United Kingdom
  • P. Goudket, O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • P. Goudket
    ESS, Lund, Sweden
  • H.S. Marks
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  The research on superconducting thin films for future radio frequency (RF) cavities requires measuring the RF properties of these films. However, coating and testing thin films on full-sized cavities is both challenging and timeconsuming. As a result, films are typically deposited on small, flat samples and characterised using a test cavity. At Daresbury Laboratory, a facility for testing 10 cm diameter samples has recently been commissioned. The cavity uses RF chokes to allow physical and thermal separation between itself and the sample under test. The facility allows for surface resistance measurements at a resonant frequency of 7.8 GHz, at temperatures down to 4 K, maximum RF power of 1 W and peak magnetic fields of a few mT. The main advantage of this system is the simple sample mounting procedure due to no physical welding between the sample and test cavity. This allows for a fast turnaround time of two to three days between samples. As such, this system can be used to quickly identify which samples are performing well under RF and should require further testing at higher gradient. Details of recent upgrades to this facility, together with measurements of both bulk niobium and thin film samples, will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK033  
About • Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 30 June 2022 — Issue date ※ 02 July 2022
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MOPOMS027 Synthesis of First Caesium Telluride Photocathode at ASTeC Using Sequential and Co-Deposition Method 695
 
  • R. Valizadeh, A.N. Hannah
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V.R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • S. Lederer
    DESY, Hamburg, Germany
 
  Caesium Telluride (Cs2Te) photocathodes, are the elec-tron source of choice, by many global accelerators such as European XFEL, FLASH and AWA. It offers high quantum efficiency and reasonable operational lifetime with lower vacuum requirements than multi-alkali photocathodes. In this paper, we report on the first synthesised CsxTe photocathodes at ASTeC, using both sequential and co-deposition of Te and Cs on Mo substrate. Te deposition is carried out using ion beam deposition whilst the Cs is deposited using a SAES getter alkali. The ion beam deposition of Te provides a high degree of control to give a dense, smooth layer with a reproducible film thickness. The chemical state with respect to film composition of the deposited CsxTe is determined with in-situ XPS anal-yses. The films exhibit a quantum efficiency between 7.5 to 9 % at 266 nm wavelength.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS027  
About • Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 06 July 2022
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TUPOTK031 A First 6 GHz Cavity Deposition with B1 Superconducting Thin Film at ASTeC 1279
 
  • R. Valizadeh, A.N. Hannah, O.B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • E. Chyhyrynets, V.A. Garcia Diaz, C. Pira
    INFN/LNL, Legnaro (PD), Italy
  • V.R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • O.B. Malyshev
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G.B.G. Stenning
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
 
  Nb3Sn, NbTiN and NbN are superconductors with critical temperatures of 18.3, 12.6-17 and 11.6-17.5 K, respectively, these are higher than that of Nb at 9.3 K. Hence, at 4 K, they have an RF resistance, an order of magnitude lower than that of Nb, which leads to quality factors above those of Nb. In recent years, there has been an extensive effort converting Nb cavities into Nb3Sn. Alloying the top inner layer of the cavity using Sn diffusion at a high temperature has had some degree of success, however, the reproducibility remains a major hindering and limiting factor. In this study, we report on the PVD deposition of NbTiN inside a 6 GHz cavity, using an external magnetic coil configuration. The deposition is done at an elevated temperature of about 650 C. We report on the superconducting properties, film structure and its stoichiometry and surface chemical state. The films have been characterised with SEM, XRD, XPS, EDS and SQUID magnetometer.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK031  
About • Received ※ 07 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 06 July 2022
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THPOTK036 Determination of Pumping and Dynamic Vacuum Properties of Conductive Quaternary Alloy of TiZrVAg Non-Evaporable Getter. 2843
 
  • R. Valizadeh, A.N. Hannah, O.B. Malyshev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • G.Y. Hsiung
    NSRRC, Hsinchu, Taiwan
  • J.M. O’Callaghan Castella
    Universitat Politécnica de Catalunya, Barcelona, Spain
  • M. Pont, N.D. Tagdulang
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
 
  Non Evaporable Getter (NEG) coating has been employed extensively in the particle accelerator especially where the vacuum conductance of the vessel is severely restricted and ultra-high vacuum condition is required. NEG coating will significantly reduce the outgassing rate and provides active pumping surface for H2, CO and CO2. In addition, it has been proven that NEG coated surfaces have a very low secondary electron yield, as well as low photon and electron stimulated desorption yields. However, the existing NEG film increases the RF surface resistance of the beam pipe. In order to increase NEG coating conductivity, at ASTeC, in the past several years, the alternative NEG com-position have been studied by adding more conductive element such as Cu, Au, Al and Ag. In this study, we report on the photon stimulated desorption, activation temperature and surface resistance from room temperature to cryogenic temperature for a new NEG quaternary alloy of TiVZrAg as function of the film composition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK036  
About • Received ※ 07 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 01 July 2022
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THPOTK037 Measurement of the Photon Stimulated Desorption for Various Vacuum Tubes at a Beam Line of TLS 2847
 
  • G.Y. Hsiung, C.M. Cheng
    NSRRC, Hsinchu, Taiwan
  • R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  For most light sources, the synchrotron radiation (SR) hit on the beam ducts or absorbers results in higher pressure rise and the consequent higher radiation level through the commissioning stage. Various surface treatments, e.g. chemical cleaning, oil-free machining, NEG-coating, etc., for the beam ducts or absorbers have been developed worldwide for mitigating the yield of Photon Stimulated Desorption (PSD). A beam line, BL19B, of 1.5 GeV Taiwan Light Source (TLS) has been modified to measure the PSD-yield of the vacuum tubes. The white light of BL19B covers the critical length at 2.14 keV is suitable for generating higher yield of the photo-electrons (PEY) and the consequent PSD-yield to be measured can be resolved wide range of 10-2 ~ 10-7 molecules/photon. The PSD-outgas, measured by RGA, contains the typical H2, CO, CO2, hydrocarbons, and Kr from NEG-coating, alcohol from ethanol machined surface, in some cases. The effect of beam-cleaning reflects the PSD-molecules generated from the SR-irradiated surface. The comparison of the PSD for the various vacuum tubes will be described in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK037  
About • Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 08 July 2022
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THPOTK038 Electron Stimulated Desorption From Titanium Tube 2850
 
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Titanium is one of material that used for production of accelerator vacuum chamber and components. In this paper we report the results of vacuum properties evaluation measurements of titanium vacuum chamber. The sample was produced from 40-mm inner diameter tube made of titanium and equipped with CF40 flanges at both ends. The electron stimulated desorption (ESD) was measured after 24-h bakeout to 80, 150, 180 and 250 oC. H2 and CO initial sticking probabilities were measured after bakeout before the ESD measurements. After ESD measurements, the initial H2 and CO sticking probabilities were measured again together with CO sorption capacity. These measurements provide the results for ESD as a function of electron dose baked to different temperatures and demonstrate the efficiency of electron stimulated activation of titanium vacuum chamber.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK038  
About • Received ※ 25 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 17 June 2022
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THPOTK039 The Effect of Activation Duration on the Performance of Non-Evaporable Getter Coatings 2854
 
  • E.A. Marshall, O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Non-evaporable getter (NEG) coatings can be activated at temperatures as low as 140°C. However, better pumping properties are achieved using higher temperatures, between 150-300 °C. This paper investigates whether using an increased activation duration can improve the NEG properties obtained using lower activation temperatures, and so decrease the energy and temperature requirement. This could allow a greater range of materials to be used in particle accelerator systems. Our findings have shown that increasing activation duration from 24 hrs to 1 week at 160 °C produces an improvement in the NEG pumping properties.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK039  
About • Received ※ 01 June 2022 — Accepted ※ 10 June 2022 — Issue date ※ 17 June 2022  
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