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Title: Optimization of cathodic arc deposition and pulsed plasma melting techniques for growing smooth superconducting Pb photoemissive films for SRF injectors

Superconducting photoinjectors have a potential to be the optimal solution for moderate and high current cw operating free electron lasers. For this application, a superconducting lead (Pb) cathode has been proposed to simplify the cathode integration into a 1.3 GHz, TESLA-type, 1.6-cell long purely superconducting gun cavity. In the proposed design, a lead film several micrometres thick is deposited onto a niobium plug attached to the cavity back wall. Traditional lead deposition techniques usually produce very non-uniform emission surfaces and often result in a poor adhesion of the layer. A pulsed plasma melting procedure reducing the non-uniformity of the lead photocathodes is presented. In order to determine the parameters optimal for this procedure, heat transfer from plasma to the film was first modelled to evaluate melting front penetration range and liquid state duration. The obtained results were verified by surface inspection of witness samples. The optimal procedure was used to prepare a photocathode plug, which was then tested in an electron gun. In conclusion, the quantum efficiency and the value of cavity quality factor have been found to satisfy the requirements for an injector of the European-XFEL facility.
 [1] ;  [1] ;  [2] ;  [3] ;  [1]
  1. National Centre for Nuclear Research (NCBJ), Otwock-Swierk (Poland)
  2. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0168-9002; PII: S0168900218301876
Grant/Contract Number:
AC02-76SF00515; 31245; KC0407-ALSJNT-I0013; SC0012704
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 891; Journal Issue: C; Journal ID: ISSN 0168-9002
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); European Commission (EC)
Country of Publication:
United States
42 ENGINEERING; Photocathodes; Pb layers; Cathodic arc; Surface melting; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; photocathodes; pB layers; cathodic arc; surface melting
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1440885