Author: Soomary, L.A.J.
Paper Title Page
THPOPT033 Performance Characterisation at Daresbury Laboratory of Cs-Te Photocathodes Grown at CERN 2653
 
  • L.A.J. Soomary, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • C. Benjamin, H.M. Churn, L.B. Jones, T.C.Q. Noakes
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • C. Benjamin
    University of Warwick, Coventry, United Kingdom
  • E. Chevallay, V.N. Fedosseev, E. Granados, M. Himmerlich, H. Panuganti
    CERN, Meyrin, Switzerland
  • L.B. Jones, T.C.Q. Noakes, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: STFC Doctoral Training Studentship
The search for high-performance photocathodes is a priority in the field of particle accelerators. The surface characteristics of a photocathode affect many important factors of the photoemission process including the photoemission threshold, the intrinsic emittance and the quantum efficiency. These factors in turn define the electron beam quality, which is measurable using figures of merit like beam emittance, brightness and energy spread. We present characterisation measurements for four caesium telluride photocathodes synthesized at CERN. The photocathodes were transported under ultra-high vacuum (UHV) and analysed at STFC Daresbury Laboratory, using ASTeC’s Multiprobe (SAPI)* for surface characterisation via XPS and STM, and for Mean Transverse Energy (MTE) measurements using the Transverse Energy Spread Spectrometer (TESS)**. The MTE measurements were estimated at cryogenic and room temperatures based on the respective transverse energy distribution curves. We discuss correlations found between the synthesis parameters, and the measured surface characteristics and MTE values.
*B.L. Militsyn, 4-th EuCARD2 WP12.5 meeting, Warsaw, 14-15 March 2017
**L.B. Jones et al., Proc. FEL ’13, TUPPS033, 290-293; https://accelconf.web.cern.ch/FEL2013/papers/tupso33.pdf
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT033  
About • Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 05 July 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPOPT034 Controlled Degradation of a Ag Photocathode by Exposure to Multiple Gases 2657
 
  • L.A.J. Soomary, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • L.B. Jones, T.C.Q. Noakes, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • L.B. Jones, T.C.Q. Noakes
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Funding: STFC Doctoral Training Studentship
The search for high performance photocathode electron sources is a priority in the accelerator science community. The surface characteristics of a photocathode define many important factors of the photoemission process including the work function, the intrinsic emittance and the quantum efficiency of the photocathode. These factors in turn define the ultimate electron beam quality, which is measurable as normalised emittance, brightness and energy spread. Strategies for improving these parameters vary, but understanding and influencing the relevant cathode surface physics which underpin these attributes is a primary focus for the community*. We present performance data under illumination at 266 nm for Ag (100) single-crystal cathode and a Ag polycrystalline cathode after progressive exposure to O2, CO2, CO and N2 using our TESS** instrument both at room and cryogenic temperatures. Crucially the data shows the effect of progressive degradation*** in the photocathode performance as a consequence of exposure to controlled levels of O2 and that exposing an oxidized Ag surface to CO can drive partial QE recovery.
*K.L. Jensen; Appl. Phys. Lett. 89, 224103 (2006);
**L.B. Jones et al.; Proc. FEL ’13, TUPPS033, 290-293;
***N. Chanlek et al.; J. Phys. D: Appl. Phys. (2014) 47, 055110;
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT034  
About • Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 10 July 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)