Abstract: A scanning electron microscope has means for generating a beam of electrons which is scanned over a specimen held within a holder in a chamber which contains a gaseous medium. A negative potential is applied to the holder so as to generate an electric field which accelerates secondary electrons, formed by the interaction or the primary beam with the specimen, in a direction away from the specimen surface and into a collision zone in the chamber. In that zone, the accelerated secondary electrons collide with gas molecules of the gaseous medium, thereby initiating a cascade of collisions which, in effect, amplifies the secondary electron signal. That signal (which may take the form of photons generated as a result of the collisions) is detected by detecting means, such as a photo-multiplier.

Abstract: A pack for cigarettes and like smoking articles has a frame (101) outside the charge of cigarettes but inside a flexible wrap, which is preferably a sealed enclosure of a barrier material such as a metal/plastic laminate, or metallized foil. The inner frame which is not rigid since its side (104) and end (108) flaps are free except where attached to a major panel (102) acts to collate and protect the charge of cigarettes and to allow heat-sealing or other sealing pressure to be exerted more efficiently than would otherwise be possible.