Damage formation and annealing studies of low energy ion implants ...

Figure 4.10 Illustration of the Daresbury MEIS facility, from (3).
The beamline is pumped to high vacuum and consists of a bending magnet,
several electrostatic lenses, and beam steerers. Collimating slits at various locations
along the beamline are used to produce a beam with a divergence of 0.1° and a standard
spot size of 1mm wide by 0.5 mm height on target. Most beam parameters can be
controlled from a control room next to the experimental station, allowing the beam to be
focused or defocused during the course of an experiment to optimise conditions for an
experiment.
The beam current is monitored using a thin wire grid placed in the beam. This
allows the beam current on target to be known. A current integrator monitors the beam
current to ensure a reproducible beam dose on target.
The experimental station contains three ultra high vacuum (UHV) chambers and
a loadlock that is set up for rapid pumping to allow samples to be changed over quickly.
Samples are mounted on holders that can be transferred from one chamber to the next
on transfer arms. The scattering chamber houses a goniometer that can hold a sample
holder and position the sample into the beam. The goniometer has three translational
degrees of freedom, so that the position of the beam on the sample can be moved and
three rotational degrees of freedom that allow the sample to be aligned to the beam.
These axes are named the rotation, spin and tilt axes, as designated in Figure 4.11. Each
axis can be moved by a stepper motor controlled by the computer in the control room.
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