Photoemission studies of yttrium photocathodes by using the visible radiation

• Published in: Physical review. Accelerators and beams Vol. 23; no. 12; p. 123401
• Main Authors: Scifo, J., Lorusso, A., Chiadroni, E., Cinquegrana, P., Dabagov, S., Danailov, M., Demidovich, A., Ferrario, M., Garzella, D., Giribono, A., Hampai, D., Perrone, A., Trovò, M.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 01.12.2020
• Subjects: Copper; Emittance; Lasers; Photocathodes; Photoelectric emission; Photoelectrons; Pulsed laser deposition; Pulsed lasers; Quantum efficiency; Sapphire; Thin films; Titanium; Work functions; Yttrium
• ISSN: 2469-9888; 2469-9888
• DOI: 10.1103/PhysRevAccelBeams.23.123401

The present work reports on Yttrium based photocathodes. A Yttrium (Y) thin film is deposited via pulsed laser deposition (PLD) on the copper (Cu) back flange of a radio frequency (rf) gun for photocathode application. Because of a lower work function with respect to Cu, Y photocathodes are particularly appealing for the possibility to illuminate them with visible laser pulses, with the advantage of a higher energy per pulse, paving the way to high repetition rate photoinjectors, driven by conventional laser sources. In addition, working atλ∼400nmthe small energy difference between the Y work function (about 3 eV) and the laser photon energy reduces the contribution of the intrinsic emittance of the material. Photoelectrons, emitted by the thin film Y photocathode driven by the second harmonic of a Ti:Sapphire laser, have been characterized in terms of quantum efficiency and transverse emittance. Results have been compared with the theoretical ones obtained by the three-step model of Spicer for metallic photocathodes.