Electron Beam Emission from a Diamond-Amplifier Cathode

Abstract

The diamond amplifier (DA) is a new device for generating high-current, high-brightness electron beams. Our transmission-mode tests show that, with single-crystal, high-purity diamonds, the peak current density is greater than 400 mA/mm², while its average density can be more than 100 mA/mm². The gain of the primary electrons easily exceeds 200, and is independent of their density within the practical range of DA applications. We observed the electron emission. The maximum emission gain measured was 40, and the bunch charge was 50 pC/0.5 mm². There was a 35% probability of the emission of an electron from the hydrogenated surface in our tests. We identified a mechanism of slow charging of the diamond due to thermal ionization of surface states that cancels the applied field within it. We also demonstrated that a hydrogenated diamond is extremely robust.

Schemes and challenges for electron injectors operating in high repetition rate X-ray FELs

“…Among the numerous ongoing R&D activities on cathodes, the use of diamond crystals as charge amplifiers [60], and of layers of materials such as CsBr to enhance the QE in metal cathodes [61], are showing promising results. Interesting results, with potential for future applications in high-brightness electron sources, are also coming from 'plasmonic' cathodes, where superficial plasma waves are excited on a metal cathode surface to enhance photoemission [62].…”

Secondary-electron emission from hydrogen-terminated diamond: Experiments and model

“…In our earlier transmission-mode experiment, we terminated both diamond surfaces with metal. Then, the measured transmission gain depends only on the primary electrons' energy and diamond's internal electric field [2]. The model of secondary-electron generation and transmission in the diamond are discussed in Ref.…”

“…Hence, the field inside the diamond changes with time, resulting in a transmitted charge, and thereby an emitted charge, both of which are time dependent. Our previous experiments show that this shielding takes place over $1 s, a relatively slow process [2]. It is important to assess precisely the probability of the emission of an electron that reaches the emission surface, and to understand the mechanism responsible for its trapping and its dependence on external conditions.…”

Extremely high negative electron affinity of diamond via magnesium adsorption

“…1 The resulting electron yield is orders of magnitude higher than materials with a positive electron affinity, 2,3 and hence diamond is the material of choice for many emerging electron emission applications in both vacuum 4,5 and solution. 6 The electron affinity of diamond is controlled by the surface termination.…”