OCI BDL800IR, Instruction Manual

Page: 21 / 61

Chapter 5 Operating Instructions 21
5 Operating Instructions
Note:
The unit should not be operated at maximum voltages unless it is
fully extended (applicable for models equipped with an optional
integral linear motion) and has been bake in ultra-high vacuum for
extended period of time.
The LEED-AUGER spectrometer must be operated at pressure below 1×10
5
Torr to prevent
a destruction of the electron gun filament (1×10
7
Torr for lanthanum hexaboride LaB
6
). If
the pressure rises above these bounds, turn the filament current off immediately. The maxi-
mum current for the tungsten filament is typically 3.05 A and 1.80 A for LaB
6
.
Before you proceed, consult the Test Data Sheet enclosed in the package and typically
inserted into a manual. Data listed on this sheet correspond to values saved under the Stand-
ard program.
5.1 Getting Started
Read carefully and act in accordance to the information provided below:
The spectrometer operating pressure is
≤
1×10
9
Torr for LEED and
≤
5×10
6
Torr
for AES.
Filament outgassing should be carried out while the vacuum chamber is still warm
after a bakeout. The filament current should be raised by 0.10–0.15 above its long-
term mean.
To increase filament lifetime, the filament current should be reduced ( Stand-by
program) or turned off when not running an experiment.
Ensure the emitted electrons travel along the sample–electron gun axis unaffected
by removing any stray magnetic fields. The optics is magnetically shielded but it
might be necessary to provide additional shielding if the application calls for it.
For LEED, make sure your single crystal sample is atomically smooth and clean
(high temperature annealing and/or ion sputtering).
For AES, make sure to shield off the system from any external electromagnetic
noise.
Frequently use a shutter to protect the optics from contamination, which might
arise for example from evaporation, sputtering, or high temperature sample heat-
ing. This item is optional and can be custom built per customer request.