Simulation of secondary electron emission based on a phenomenological probabilistic model

Secondary electron emission (SEE) critically limits the performance of high-power microwave components and particle accelerators. Amorphous carbon (a-C) films featuring a low secondary electron yield (SEY) and surface grooves offer promising applications for suppressing the SEE effects. However, the efficiency of SEE suppression and the underlying microscopic mechanisms remain subjects of debate. This paper employs the Monte Carlo method to develop a novel electron scattering and an SEE model for copper surfaces coated with a-C films and patterned with rectangular grooves. The model accurately simulates electron transport within the film and substrate, explicitly accounting for the influences of the film/substrate interface energy barrier and the groove walls on electron scattering trajectories. Results demonstrate that increasing the a-C film thickness from 0 to 5 nm reduces the maximum SEY from 1.18 to 0.82. The SEE suppression effect is significantly enhanced on grooved a-C surfaces. Specifically, with a groove depth of 30 nm and a film thickness of 5 nm, the maximum SEY reaches a minimum value of 0.47. These findings provide important insights into the mechanism by which grooves and a-C films suppress SEE and offer practical guidance for designing high-performance, low-SEY surfaces for the next generation of high-power devices.

Flicker noise with a 1/f frequency dependence has been observed in the secondary emission process. No flicker noise was observed in multiplier phototubes which means that a possible flicker noise component caused by the photoemission or secondary emission process is small in comparison with the shot noise of the tube. The secondary emission flicker noise resistance, measured for Philips EFP60 tubes, increases with increasing primary current and also increases with increasing primary energy. The results are interpreted in terms of a fluctuating work function.

The interaction of ionizing radiation with matter is of critical importance in numerous areas of science and technology like space and vacuum technology and even medicine and biotechnology. Secondary electron emission is a consequence of electron irradiation on materials. We achieve extremely low secondary electron emission yield values smaller than 0.2, even up to incident electron energies ~1 keV, due to an undocumented synergy between neighbouring metal and dielectric domains in composite samples. To investigate this experimental discovery, we propose a simple 3D model where the dielectric and metallic domains are arranged in parallel and interleaved. The proposed surface profile has a triangular shape to model the surface roughness. We obtain a continuous equation to describe the electric field that arises between grounded conductors and charged dielectrics domains. The calculated trajectories of secondary electrons in this 3D geometry are used to predict dynamic secondary emission yield, which strongly depends on the charge accumulated in the dielectric domains. This research paves the way to design new materials of low secondary emission yield, addressing the technological problem not yet resolved to inhibit the electron avalanche in RF equipment that limit their maximum working power.

For the first time, a fine structure was observed in the low energy peak of the spectra of secondary electron emission from diamond with a negative electron affinity surface. The effect was studied for as-grown chemical-vapor-deposited polycrystalline well-faceted diamond films. We discovered that this structure is comprised of four well resolved peaks. The relative energy positions of three of them corresponded to the positions of the electron energy minima near the bottom of the conduction-band. The fourth peak, having the lowest energy, was attributed to the break up of the bulk excitons during the process of secondary electron emission.

Secondary emission from dust grains with a surface layer: comparison between experimental and model results

Non‐Maxwellian behaviour and plasma‐wall interaction are key processes in the physics of Hall thrusters. For this purpose, a 2D{r,z}‐3V axisymmetric fully kinetic Particle‐in‐Cell/Monte Carlo Collision (PIC‐MCC) model of the acceleration channel including the process of secondary electron emission (SEE) from the dielectric walls has been developed. In order to make the simulation possible with regard to the computational time, a reduction of the thruster dimension was done. This was derived from a new physics‐based scaling law. This model has demonstrated its outstanding capability in improving the physics insight into the processes in Stationary Plasma Thruster (SPT) and in reproducing accurately well experimental data.

Studies on the pressed yttrium oxide-tungsten matrix as a possible dispenser cathode material

Secondary electrom emission yield (δ) and the surface work function values (φ) were measured for lead zirconium titanate (PZT) doped with lanthanum, strontium, and niobium. The single pulse method was used in LEED/Auger geometry for measuring the secondary electron emission yield δ while the retarding potential technique was employed for measuring the work function. In view of the application of ceramics as continuous dynodes in electron multipliers, the secondary electron emission and electical conductivity data is analysed for reduced PLZT ceramics. Maximum δ of 2.7 was found to remain unchanged after reduction of PLZT. Dionne's equation was used as a basis for analysis of secondary electron emission measurements to estimate escape depth and emission probability.

The charging process of insulator surfaces in vacuum at HV due to secondary electron emission has been calculated using numerical simulation. The systems considered consist of two electrodes at a HV difference, separated by a glass plate or a hollow glass channel. The simulations give insight into the critical HV positions and into the influence of the geometry, the initial voltage distribution and the material properties on the charging profiles and the leakage current paths. A HV performance increase of these systems can be obtained by decreasing the impact of free electrons, adding a coating on all insulating surfaces which have a high value of E/sub 1/ (i.e. the first crossover point of the secondary electron yield curve) and/or are weakly conductive, and breaking up the total voltage difference in smaller parts by adding electrodes to all surfaces at intermediate voltages.

A Monte Carlo simulation of secondary electron emission from copper bombarded with low energy electrons was carried out for analyzing its dependence on the angle of incidence. For the simulation, elastic scattering cross section of 10e V-4ke V electron with copper atom is investigated using partial wave expansion technique. Further, the Kanaya equation is used for energy loss calculation of incident electron, and an exponential decay of secondary electrons in copper is assumed. The calculated secondary electron emission yield does not increase so large as 1/cosφ (φ : the angle of incidence) with oblique incidence. The variation of the yield with φ agrees with experimental result obtained by Koshikawa and Shimizu.

Monte Carlo simulation of secondary electron emission from plasma facing materials

We present a numerical analysis on multipactor effects in coaxial cables using an electromagnetic particle-in-cell (EM-PIC) algorithm on unstructured grids. The analysis combines a 2.5-D axisymmetric EM-PIC algorithm and the Furman-Pivi probabilistic model for the realistic description of secondary electron emission (SEE) process. Employing a local and explicit finite-element time-domain (FETD) scheme, the present algorithm yields an energy- and charge-conservation from first principles on unstructured grids. We numerically investigate single- and double-sided multipactor effects confirming that the former originates from the higher-order multipactors (in parallel plates) in conjunction with ponderomotive (inhomogeneous) forces. This analysis can be instrumental in devising multipactor mitigation techniques.

Low Noise Proximity Focused Image Intensifiers

Secondary ion emission of alloys in relation with their electronic structure

Secondary photon emission studies of ion bombarded beryllium