Electron beams produced by innovative photocathodes based on nanodiamond layers

Abstract

The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength, λ ¼ 248 nm; photon energy, E Ph ¼ 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 pdoped 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.

Review of photocathodes for electron beam sources in particle accelerators

“…142 6 Other photocathode ideas A new idea is to use photocathodes with nano diamond layers, which can guarantee a higher QE than metal photocathodes. 166 The production with a pulsed spray technique is easier and has more advantages compared to CVD methods that need a hot substrate. With this new technique the nano diamond layers are deposited directly from a dispersion solution at low temperatures onto a substrate.…”

Geometric and electromagnetic characterization of electron beams produced by nanodiamond photocathodes

“…The cathode holder and the chamber walls were considered as a transmission line, with its characteristic impedance of about 50 Ω. Therefore, to avoid signal reflections and to record real current pulses, PC was connected to the ground by a shunt of 50 Ω [24]. It was composed by 9 parallel resistors of approximately 500 Ω and a resistor of 450 Ω connected in series to a 50 Ω coaxial cable (R cable ), as shown in the scheme of figure 1a.…”

Design, fabrication, and tuning of a THz-driven electron gun

“…Generating and quickly accelerating short, low emittance electron bunches is fundamental to reaching new regimes of operation for both FEL and UED facilities. Electron source research efforts are underway to improve the performance of existing gun types as well as to develop new materials and techniques [19][20][21][22][23][24][25]. Electron guns can use a variety of emission mechanisms in-cluding thermionic, photo, and field emission.…”