Author: Noakes, T.C.Q.
Paper Title Page
WEPAB111 Controlled Degradation by Oxygen Exposure in the Performance of a Ag (100) Single-Crystal Photocathode 2856
 
  • L.A.J. Soomary, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • L.B. Jones, T.C.Q. Noakes
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  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 in­clud­ing the work func­tion, in­trin­sic emit­tance, and quan­tum ef­fi­ciency of the pho­to­cath­ode. These fac­tors in turn de­fine the elec­tron beam per­for­mance which is mea­sur­able as nor­mal­ized 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 elec­tron source com­mu­nity**. As such, pure metal pho­to­cath­odes and their per­for­mance at UV wave­lengths are of in­ter­est as seen at the LCLS at SLAC and CLARA at Dares­bury. We pre­sent per­for­mance data for an Ag (100) sin­gle-crys­tal pho­to­cath­ode under il­lu­mi­na­tion at 266 nm wave­length, with known lev­els of sur­face rough­ness, using our Trans­verse En­ergy Spread Spec­trom­e­ter (TESS)*** both at room and cryo­genic tem­per­a­tures. Cru­cially our data shows the ef­fect of pro­gres­sive degra­da­tion in the photo-cath­ode per­for­mance as a con­se­quence of ex­po­sure to con­trolled lev­els of oxy­gen.
* D.H. Dowell, et al., Nucl. Instr. and Meth. A (2010), doi:10.1016/j.nima.2010.03.104
** Appl. Phys. Lett. 89, 224103 (2006); doi:10.1063/1.2387968
*** Proc. FEL’13, TUPPS033, 290-293
 
poster icon Poster WEPAB111 [0.866 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB111  
About • paper received ※ 20 May 2021       paper accepted ※ 22 June 2021       issue date ※ 31 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPAB112 Performance Characterisation of a Cu (100) Single-Crystal Photocathode 2860
 
  • L.A.J. Soomary, D.P. Juarez-Lopez, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • L.B. Jones, T.C.Q. Noakes
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  The search for high per­for­mance pho­to­cath­ode elec­tron sources is a pri­or­ity in the ac­cel­er­a­tor sci­ence com­mu­nity. The sur­face char­ac­ter­is­tics of a pho­to­cath­ode de­fine im­por­tant fac­tors of the pho­toe­mis­sion in­clud­ing the in­trin­sic emit­tance, the quan­tum ef­fi­ciency and the work func­tion of the pho­to­cath­ode. These fac­tors in turn de­fine the elec­tron beam per­for­mance which are mea­sur­able as emit­tance, bright­ness and en­ergy spread. We have used ASTeC’s Mul­ti­probe (SAPI)* to char­ac­terise and analyse pho­to­cath­ode per­for­mance using mul­ti­ple tech­niques in­clud­ing XPS, STM, and LEED imag­ing, and their Trans­verse En­ergy Spread Spec­trom­e­ter (TESS)** to mea­sure mean trans­verse en­ergy (MTE). We pre­sent char­ac­ter­i­sa­tion mea­sure­ments for a Cu (100) sin­gle-crys­tal pho­to­cath­ode sam­ple with data from SAPI con­firm­ing the crys­tal­lo­graphic face and show­ing sur­face com­po­si­tion and rough­ness, sup­ported by data from TESS show­ing the pho­to­cath­ode elec­tron beam en­ergy spread.
* B.L. Militsyn, 4-th EuCARD2 WP12.5 meeting, Warsaw, 14-15 March 2017
**Proc. FEL’13, TUPPS033, 290-293
 
poster icon Poster WEPAB112 [0.814 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB112  
About • paper received ※ 19 May 2021       paper accepted ※ 12 July 2021       issue date ※ 22 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)