INFICON UL1000 Helium leak detector - Manual (Page 39)

Description and Working Principle
39
iina
70
e 0
4
.f
m
te
chn
ica
l ha
nd
boo
k
(1
40
8)
4.2.1 Vacuum System
The vacuum diagram below shows the major components inside the UL1000 and
UL1000 Fab:
The mass spectrometer is mainly composed of the ion source, the magnetic
separator and the ion collector.
Gas molecules getting into the mass spectrometer are ionized by the ion source.
These positively charged particles are accelerated into the magnetic field following a
circular path, the radius of which depends on the mass-to-charge ratio of the ions.
Only helium ions can pass this filter and reach the ion collector where the stream of
the ions is measured as a electrical current.
For operation the mass spectrometer requires a vacuum level in the range of
1×10
-4
mbar and lower. This pressure is provided by the turbomolecular pump which
in turn is backed up by a scroll pump.
Fig. 4-1: Vacuum Diagramm UL1000 and UL1000 Fab
Pos. Description
1 MS: Mass Spectrometer, Helium sensor (180° magnetic field mass
spectrometer)
2 Turbomolecular Pump (TMP, provides high vacumm conditions in the MS)
3 V1a … V8: Electromagnetic Valves to control the gas flows
4 Scroll pump (provides the foreline pressure for the TMP und pumps down the
parts under test)
5 Inlet Port