A Simple Low-Vacuum Environmental Cell
The environmental cell device discussed in this paper provides a modest low-vacuum scanning electron microscopy (SEM) capability to a standard SEM without requiring additional pumping. This environmental cell confines a volume of low vacuum in contact with the sample surface using a container that has an aperture for admitting the primary electron beam. The aperture is large enough to permit a limited field of view of the sample, and small enough to limit the outflow of gas into the SEM chamber to that which can be accommodated by the standard SEM pumping system. This environmental cell also functions as a gaseous detector device.
Amplification measurements of alternative imaging gases in environmental SEM
In this paper, we present quantitative data on the amplification behaviour of alternative imaging gases in environmental SEM and describe the experimental methods used to obtain them. We investigated the gases' amplification abilities over the pressure range 0 - 12 Torr with respect to the primary beam energy, detector gap distance and detector accelerating field, in order to isolate optimum imaging conditions for each gas. The gases investigated were, in addition to water vapour, nitrous oxide, carbon dioxide, nitrogen and helium.
Measurement and Demonstration of Thermal Expansion Coefficient
There are many classroom demonstrations, such as the ball-and-ring experiment, for showing the existence of thermal expansion of solids. The coefficient of linear expansion α (= increase in length divided by the original length times the change in temperature) may be measured in high school laboratories using a number of methods.1–4 In this paper we describe an especially simple experiment for determining α for a metal rod. It is based on the well-known optical lever method and is suitable for either a laboratory experiment or a classroom exercise.