Review and present status of preparation of thin layer lead photocathodes for e- injectors of superconducting RF linacs

Jerzy Lorkiewicz; Robert Nietubyc; Jacek Sekutowicz; Marek Barlak; Denis Kostin; Anna Kosinska; Roman Barday; Rong Xiang; Robert Mirowski; Wojciech Grabowski; Jan Witkowski

doi:10.1117/12.2205443

11 September 2015 Review and present status of preparation of thin layer lead photocathodes for e^- injectors of superconducting RF linacs

Jerzy Lorkiewicz, Robert Nietubyc, Jacek Sekutowicz, Marek Barlak, Denis Kostin, Anna Kosinska, Roman Barday, Rong Xiang, Robert Mirowski, Wojciech Grabowski, Jan Witkowski

Author Affiliations +

Proceedings Volume 9662, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2015; 966233 (2015) https://doi.org/10.1117/12.2205443
Event: XXXVI Symposium on Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments (Wilga 2015), 2015, Wilga, Poland

Abstract

Results are reported on using evaporation and UHV arc lead deposition to create thin-layer superconducting Pb photocathodes on niobium wall of electron gun. Evaporated photocathodes were prepared and tested for the first time in 2014. A complete XFEL-type photo-injector with an evaporated photocathode underwent successful quality check at DESY - an acceptable working point was reached. On the other hand poor adhesion to niobium proved to be the most serious shortcoming of the evaporated Pb layers. UHV arc deposition seems to be much more promising in this context as it allows energetic coating. Filtered arc coating lead to creation of uniform, 2 μm thick lead layers with casual spherical extrusions which enhance locally electric field and leads to high dark current. Conditioning in electric field is needed to reduce the field emission effects from these layers to acceptably low value. Using non-filtered UHV lead deposition enabled fast coating up to a thickness above 10 μm. Pb films obtained in this way require further post-processing in pulsed plasma ion beams in a rod plasma injector. In order to reach a sufficiently planar film surface the pulsed heat flow through a lead layer on niobium was modeled and computed.

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Jerzy Lorkiewicz, Robert Nietubyc, Jacek Sekutowicz, Marek Barlak, Denis Kostin, Anna Kosinska, Roman Barday, Rong Xiang, Robert Mirowski, Wojciech Grabowski, and Jan Witkowski "Review and present status of preparation of thin layer lead photocathodes for e^- injectors of superconducting RF linacs", Proc. SPIE 9662, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2015, 966233 (11 September 2015); https://doi.org/10.1117/12.2205443

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