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Articolo in rivista, 2019, ENG, 10.1103/PhysRevAccelBeams.22.093402

Electron beams produced by innovative photocathodes based on nanodiamond layers

Velardi L.; Turco V.; Monteduro L.; Cicala G.; Valentini A.; Nassisi V.

Laboratorio di Elettronica Applicata e Strumentazione LEAS, INFN, Department of Physics, University of Salento-Lecce, Lecce, Italy; CNR-ISTP, Sede di Bari, Italy; INFN-Sezione di Bari, Department of Physics, University of Bari, Italy.

The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength, lambda=248 nm; photon energy, EPh=5 eV) is reported. The ND layers were deposited by means of a pulsed spray technique. Specifically, the active layer of each PC consisted of untreated (as-received) and hydrogenated ND particles, 250 nm in size, sprayed on a p-doped silicon substrate. The ND-based photocathodes were tested in a vacuum chamber at 10-6 mbar and compared to a Cu-based one, used as reference. All the photocathodes were irradiated at normal incidence. The quantum efficiency (QE) of the photocathodes was assessed. QE values of the ND-based photocathodes were higher than that of the reference one. In particular, the hydrogenated ND-based PC exhibited the highest QE due to the negative electron affinity that results from the surface terminated by hydrogen. Additionally, the photocathode surface/local temperature and the multiphoton process contribution to the electron emission were studied.

Physical review special topics. Accelerators and beams 22 , pp. 093402-1–093402-7