Three electron-beam evaporators, for depositing cobalt, manganese, and copper on the sample, are present in the vacuum chamber (figure 4.2.) Figure 4.7 shows the manganese evaporator.
This was chosen as the example evaporator, because the author is more familiar with it than with the other two, having dismantled it to replace the manganese charge and the cathode filament.The heat generated by the current flowing in the cathode filament excites electrons to leave the filament. These are accelerated, by the electric field, into the manganese (or cobalt or copper) charge, where their kinetic energy is deposited as heat. This evaporates some of the manganese, producing a gas of manganese atoms and ions. Those that effuse from the exit hole are all travelling in roughly the same direction, and therefore form an atom beam, which, if it strikes the sample surface, deposits [79] a film of manganese on that surface.
The manganese and copper evaporators were both constructed by the author's predecessors, and are of very similar design. The cobalt evaporator, while working on the same principle, was purchased commercially by the author's predecessors, and has the important addition of a current collector, near its exit hole, which measures the flux of ions, and therefore of atoms, leaving the exit hole. This is taken to be a measurement of the rate of cobalt deposition on the sample.
The cobalt evaporator is described in more detail in its manual [80].
Having described the vacuum chamber, and associated sample preparation equipment, it is now time to present the methods by which this equipment was used, in the experiments whose results are presented later in this thesis.
