BG 805 981 BE (0201) QMG422.oi
47
400
Optimize the filament current cut-off point for optimum protection of the
filament.
a) Switch off the emission: press
filam
, the
filam
lamp goes out
b) Ensure that the pressure is
10
-4
mbar.
c) Switch on
filam:
filam
light turns on.
d) If
Emission error
*) is displayed continue with f).
e) If this is not the case, switch off
filam
, reduce
emiss-E-PROT
with
by 0.1 A
and turn
filam
on again; repeat until
Emission error
appears.
f)
Switch off filam
, increase
emiss-E-PROT
with
by 0.1 A and turn
filam
on
again; repeat until
Emission error
no longer appears.
*) In case of **ERROR** press the
error
key to read out the type of error.
If the switching threshold is abnormally high a fault exists in the ion
source, the vacuum system, or the unit. Investigate the cause in order to
prevent destruction of the filament.
If a new filament has been installed re-optimize after a few hours.
The
D-PROT
cut-off point for DEGAS is set analogously.
Please refer to the user’s guide of the QMA and the ion sources. Switch to Degas
only if the conditions specified there are fulfilled.
400
Optimize the filament protection for Degas mode as described above,
however with
ion src-D-PROT
rather than
emiss-E-PROT.
Switch on Degas with
ion src-CTRL:START
and confirm with
.
125
→
[4] and [3]
The EP 422 is an amplifier for very small currents. Its zero (offset) must be
corrected occasionally. This is intentionally not performed automatically to prevent
periodic dead times in data acquisition.
Perform an offset correction when the system is put into service for the first time,
after the system (particularly the EP 422) has attained a stable temperature.
Subsequent repetition is advisable if deviations from the zero line occur.
Zero line shifts are often caused by ion and electron currents; the offset correction
does not compensate these.
Choose
cycle-FUNCT:OFFSET
and start the offset measurement with
run
.
The following appears:
Perform the measurement for SEM and Faraday if both EP 422 are installed. If only
one EP 422 exists choose DETECT according to the current operating mode.
6.2 Filament protection
6.3 Degas
6.4 Offset correction
Mass number of the
offset measurement
Detector selection
EP1 / EP2
Sets offse
t values to
zero
Measured offset values [A]
of the ranges 10
-6
,10
-8
,10-
10
,10
-12
A
Offset measurement RUNNING or
STOP when finished