Small surface defects are thought to affect field emission through the field enhancement and modification
of the work function. We combined density functional theory and quantum transport calculations to study
the influence of atomic–scale defects on the work function and field emission characteristics of copper
surfaces. A newly developed general methodology for the calculation of the field...
This paper brings together various pieces of theoretical argument and experimental evidence to support the idea that, in some cases, electrical breakdown may be associated with the growth of carbon nanowhiskers. An introduction provides two reminders. (a) That effects of this kind are driven by electrical thermodynamics and by the rule that systems evolve in a direction such that the...
Everyone measuring field emission in macroscopic systems observes larger than expected values. Various mechanisms for the enhancement have been postulated but there is rarely independent confirmation. Commonly considered mechanisms are summarized and a new one is proposed.
The work concerns relativistic effects and the influence of an external magnetic field on the
transmission coefficient. The Fowler-Nordheim equation has been relativistically generalized and effect of
the Lorentz contraction of a potential barrier at the metal-vacuum interface has been found. Influence of
the magnetic field parallel to a metal surface on the transmission coefficient is taken into...
The hypothesis that arc nucleation is related to plastic activity due to collective motion of dislocation in the cathode is examined via experiments and theoretical efforts over the last few years. I will summarise current theoretical and experimental observations indicating specific dislocation activity related to the applied high field. In addition I will discuss the challenges that lie...
The commonest method of characterising a cold field electron emitter is to measure its current-voltage characteristics, and the commonest method of analysing these characteristics is by means of a Fowler-Nordheim (FN) plot [1]. For example, the field enhancement factor can be calculated. But for novel investigations of the transition from field emission to plasma discharges an extended use of...
Field emission from cold cathodes, with electric field enhanced by roughness of (micro-protrusions on) the cathode surface, may play a role in breakdown of the high-pressure air under conditions relevant to electric power equipment. Two examples are considered in this contribution. The first one concerns the breakdown in conditions of the experiment [1]: a concentric cylinder discharge in...
Recently a new model for the cathodic emission at high voltage and high vacuum has been proposed. It is a classical model that assumes the existence of a dielectric layer (oxides mainly) on the cathodic surface and assumes that the cold emission current is due to polarization electrons stripped from the dielectric layer. The application of this model to an experimental case has highlighted its...
Over the last 2000 years or so, the atmospheric phenomenon now known as "St Elmo's fire" (see Wikipedia) has been reported by very many authors in very many contexts, with the earliest known reports being associated with the names of Julius Caesar and Pliny the Elder (who both reported observations of its appearance on the tips of their soldiers' javelins). Pliny also noted its appearance on...
Abstract:
In future Tokamak reactors such as ITER and DEMO, the initiation of fusion reactions in hot plasmas is highly dependent on the capacity to heat the plasma heavy species. To do this,high power beams of energetic neutral D atoms are injected by Neutral Beam Injectors (NBIs) which accelerate the negative D⁻ ions by applying very high DC voltages (V ~ 10 MV ). The DC...
Field emitted electrons play an important role in the operation of high gradient RF accelerating structures, by generating so-called dark currents, and acting as the initiators of RF Breakdown, which limits the performance in such devices. Another kind of vacuum discharge that commonly affects to the operation of lower-field RF components, for example in space applications, is the Multipactor...
This research is on the COMSOL simulation of flashover occurring in a MEMS (Micro-Electro-Mechanical System) insulator and electrode unit, both of the electric field at triple point and of electron trajectories in several practical geometries. In some applications of MEMS technology, electrostatic field up to 5-20kV/mm is of interest. One of these applications is using MEMS components for...
