Abstract
The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength, $\ensuremath{\lambda}=248\text{ }\text{ }\mathrm{nm}$; photon energy, ${E}_{\mathrm{Ph}}=5\text{ }\text{ }\mathrm{eV}$) 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 ${10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{mbar}$ 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.
Highlights
The production of electron beams by photo and thermionic emission is becoming increasingly important and of growing interest in the scientific community
Many large-scale particle-accelerator facilities have been and are today employed in the development and characterization of cathodes, such as BNL [5,6,7], CERN [8], DESY [8] and SLAC [7,9]
In Italy, the National Institute of Nuclear Physics (INFN) is the biggest research organization involved in the design, production and characterization of cathodes for FLASH [3] and PITZ [9] facilities at DESY and for the SPARK_LAB [1,10,11,12] laboratory
Summary
The production of electron beams by photo and thermionic emission is becoming increasingly important and of growing interest in the scientific community. Many large-scale particle-accelerator facilities have been and are today employed in the development and characterization of cathodes, such as BNL [5,6,7], CERN [8], DESY [8] and SLAC [7,9]. In Italy, the National Institute of Nuclear Physics (INFN) is the biggest research organization involved in the design, production and characterization of cathodes for FLASH [3] and PITZ [9] facilities at DESY and for the SPARK_LAB [1,10,11,12] laboratory.
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