Modifications allowing 24-hour continuous fail-safe pumping of a transmission electron microscope

Abstract

Fail-safe facilities allowing 24-h continuous pumping of a transmission electron microscope (TEM) are incorporated in only a few more recent models. Modifications to a Hitachi HU-125S are described which allow the instrument to be pumped continuously with fail-safe facilities in the event of power failure. Changes include the addition of solenoid-operated valves, activated alumina sorbent and liquid-nitrogen cold traps to the backing-pump lines, an efficient liquid-nitrogen storage container for the backing-pump line cold traps, an accurate reliable timing facility for topping up the diffusion-pump cold traps with liquid nitrogen, and simple electronic changes to the power supply. The modifications allow more hours of use, as well as being a positive influence in the maintenance of a better vacuum environment in the TEM.