The UEA positron re-emission microscope: first images

Images have been recorded using the laboratory-based positron re-emission microscope constructed at the University of East Anglia (UEA). The microscope has been designed to operate in reflection geometry with the view to studying the surface characteristics of ‘real’, thick samples, without extensive preparation procedures. The first, deliberately low-magnification, images are of an annealed, electroformed nickel mesh (linewidth 10 μm, spacing 40 μm) placed over a well-annealed polycrystalline tungsten foil, both before and after annealing the nickel mesh. The false-colour images indicate (a) a magnification of about 80 ×, as expected from the objective lens used, (b) a resolution of about 10 μm, (c) contrast between surfaces with different positron work functions. Image signal rates of about 45 s−1 were recorded. Plans to improve the magnification/resolution of the system are discussed.