Variable Presure

Both the standard secondary electron detector (SE2) and the high efficiency in-lens detector are designed for use in high vacuum.
A unique enhanced Variable Pressure Secondary Electron (VPSE) detector was developed to allow true secondary imaging under variable pressure conditions.

By increasing the chamber’s pressure, secondary electrons are accelerated away from the sample surface and collide with the gas molecules to create further electrons which are also accelerated in the electrical field. In addition to ions, secondary electron collisions also produce photons. These photons are collected by the VPSE detector to produce the secondary electron image.