Effect of mechanical finishes on secondary electron emission of alumina ceramics

Abstract

The effect of surface roughness of insulator on the secondary electron emission (SEE) coefficients was investigated with changing the incident angle of primary electrons. The SEE coefficients were measured using a scanning electron microscope with a singlepulse electron beam (100 pA, 1 ms). As a result, the SEE coefficients increased with the incident angle for smooth surface, while those of rough surface almost did not change with the incident angle. The SEE coefficients of commercial alumina ceramics with three different surface finishes, i.e. as-sintered, as-ground and mirror-finished samples, were also measured before and after annealing treatments. This treatment was carried out in air at 1400 °C for 1 h. After annealing, the SEE coefficients were higher than those of unannealed samples. This increase is proposed to be due to the defect recoveries as well as neutralizations of charging, which significantly influence the SEE. For relative low purity (95% or less), the SEE coefficients of annealed alumina became lower after mechanical grinding operations and lower again after mirror-finished operations. The SEE coefficients of 99.7% purity alumina were almost unaffected by the mechanical finishes.

Ultralow electron emission yield achieved on alumina ceramic surfaces and its application in multipactor suppression

“…TiN coating is therefore applied on many occasions to realize SEY reduction [21,30]. In the past few decades, Michizono et al have systematically researched the reliability of alumina ceramic used in radiofrequency (RF) dielectric windows [1,7,11,21,[35][36][37][38], including the methods of lowering SEY by surface roughening or TiN coating, the influence of SEY on surface charge/discharge, and multipactor. The multipactor that occurs in the RF window mainly results in a potential difference and further triggers surface flashover, which is different from the multipactor that occurs in alumina-loaded HPM microwave components like filters.…”

Au Doping Effect on the Secondary Electron Emission Performance of MgO Films

“…As shown in Figure 4, the root-mean-square roughness ( R q ) of the MgO film rises with the increase of the Au doping concentration. The increase of surface roughness has a negative effect on the SEE, because the emitted secondary electrons from a rough surface may be recaptured by a locally raised surface [23]. According to the SEM and AFM images of the samples with x of 0, 1.5%, and 3.0%, as the Au doping concentration increases, the film surface changes to be rougher, while the SEE coefficient becomes higher.…”

Review of interface tailoring techniques and applications to improve insulation performance

“…For insulators with an inherently smooth surface, roughening the surface can increase the vacuum flashover voltage significantly for μs pulse, 50 Hz, and DC voltages [1]. This is possible because rougher surfaces are less sensitive to the impacts of electrons at shallow angles and thus suppress the secondary electron emission avalanche process [47]. For instance, Yamamoto et al [48] and Naruse et al [49] investigated the influence of surface roughness on flashover voltage for different materials such as Al 2 O 3 , SiO 2 and PTFE, indicating that rougher surfaces present higher flashover voltages.…”

“…For insulators with an inherently smooth surface, roughening the surface can increase the vacuum flashover voltage significantly for μs pulse, 50 Hz, and DC voltages [1]. This is possible because rougher surfaces are less sensitive to the impacts of electrons at shallow angles and thus suppress the secondary electron emission avalanche process [47]. For instance, Yamamoto et al.…”