OCI BDL800IR, Instruction Manual

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Chapter 5 Operating Instructions 25
Our LEED-AES spectrometer optics is shielded by a Mu-metal cylinder. However, at
larger magnetic fields this can become quickly saturated and stop working. At certain spatial
configurations, magnetic fields can also penetrate inside the cylinder through relatively large
input and output openings. If this is the case, additional magnetic shielding needs to be pro-
vided.
In a situation where the residual magnetic field is dominated by the earth’s magnetic field,
the best configuration of the LEED-AES spectrometer optics is to have its axis perpendicular
to the earth’s magnetic dipole.
If the dominant magnetic field is caused by other sources, such field needs to be cancelled
out by an external magnetic field. This can be done, for example, by installing a set of Helm-
holtz coils around the optics providing a uniform magnetic field of opposite direction. In
some situations even a small permanent magnet placed uniformly around the spectrometer
optics yields a sufficient result.
5.8 LPS300-D and LPS075-D
The LPS300-D is a powerful and versatile instrument used to control LEED-AES spectrome-
ters made by OCI Vacuum Microengineering, while the LPS075-D can only operate in a
LEED mode. These power supplies control the following parameters:
 Beam Energy
 Filament Current
 Wehnelt Voltage
 Focus Voltage
 Grid Voltage

Screen Voltage
In addition, emission and beam currents are measured and displayed continuously. Both
power supplies have numerous programming modes and are fully capable of being remotely
controlled by a PC via the USB.
5.8.1 Basic Operation
The figure below shows a layout of all buttons and control knobs. A real unit will display in-
formation about current experimental values and selected program.