Lens for a scanning electron microscope

Abstract

A lens (15) for a scanning electron microscope is adapted to be removably mounted on a specimen stage (1). The lens (15) includes a magnetic circuit (2, 3, 4, 7) having a first magnetic pole piece (7) and a second magnetic pole piece (4), and a specimen holder (5). The specimen holder (5) is located between the first and second magnetic pole pieces (4, 7). The magnetic circuit (2, 3, 4, 7) also includes a lens bore (18) to permit an electron beam (9) to strike a surface of a specimen mounted on the specimen holder (5), in use. The lens bore (18) has a width of greater than 1 mm.