OCI BDL800IR, Instruction Manual

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26 Chapter 5 Operating Instructions
The first thing to do is to set the Instrument Mode (LPS300-D only). This can be done prior
to powering up the unit or while it’s running, however, the latter case requires the unit to be
restarted.
Controller Mode allows the user to OPER ate the unit, PROG ram its various parameters
and features, and diagnostic self TEST .
Pressing the Program Selection knob opens up a menu (TODO see Section) where the
user can control many aspects of the power supply.
Adjusting the beam energy is done using the Beam Energy Control knob. In the LEED
mode, pressing this knob results in initiating/stopping either a continuous or timed energy
scan as set in Programming Mode under Program Selection  Beam Energy Scan Mode .
In the AES mode, pressing the knob locks/unlocks the energy value.
To change the other parameters— Filament Current , Wehnelt Voltage , Focus Voltage ,
Grid2&3 Voltage , Screen Voltage , and Beam Current constant locking—first press the ap-
propriate button and then use the Setting knob to adjust the value.
To save changes, switch to the Programming Mode and press the Save button.
5.8.2 Monitoring Beam Current
The beam current is displayed on the front panel in the bottom right corner and represents a
current of electrons incident onto a sample. The current ranges from 100 nA to 200
μA.
It is possible to keep this current constant by pressing the Constant Beam Current
On/Off button. By default, the unit achieves the goal by adjusting the filament current. If de-
sired, the driving parameter may be changed to Wehnelt voltage by changing the Controller
Mode to Programming, pressing the Program Selection knob and selecting Constant Beam
Mode  By Wehnelt .
This option was designed for capturing LEED images at different energies (Intensity-
Voltage characteristic). Such measurement should start at the minimum beam energy, where
the filament current is maximum, and successively increased. The beam current should be set