Ceramic disks as efficient and robust cathodes

Electron emission from ceramic disks depends strongly on the shape of the front electrode. The common interconnected grid is not good for a stable emission. An electrode consisting of an ensemble of metal point-like islands within a metal ring leads to quite a stable emission. In the first case the sandwich of the continuous electrode (on one surface) and the grating (on the front surface) constrains the domain and the charge carriers to move within the zones covered by the stripes, whilst the quasi-open patchy surface allows the domain switching and in turn the electron flux over the whole area