LEYBOLD 250000, Руководство по эксплуатации

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GA10218_0101 - 5/2002 ⏐
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The mass spectrometer (MS) is mainly composed of the ion source with
cathode, 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 magne-
tic field following a circular path, the radius of which depends on the
mass-to-charge ratio of the ions. When mass 4 is selected (Default setting)
only helium ions can pass this filter and reach the ion collector where the
stream of the ions is measured as a electrical current. When selected
another mass than 4, only the corresponding ions can pass the filter.
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 fore vacuum pump.
Besides maintaining the pressure in the mass spectrometer the pump
system is used to evacuate the test parts. It is made sure that the pressure
in the mass spectrometer is low enough under all circumstances. The val-
ves V1, V2a, V2b, V4a control the gas flows when measuring. Valves V3
and V5 are used to vent the system and the Turbo pump, valve V6 con-
trols the gas ballast function of the fore vacuum pump. Valve V7 opens
and closes the internal test leak during calibration.
With the pressure in the test part being lower than ambient pressure
sprayed helium (or Hydrogen as forming gas) can penetrate into the part in
case of a leakage. As soon as the pressure conditions allow it one of the
valves to the TMP opens. Now Helium can penetrate into the mass spec-
trometer contrary to the pumping direction of the TMP.
4.1.1.1 Vacuum System PhoeniXL
300 dry
The PhoeniXL
300 dry
has a diaphragm pump as forevacuum pump,
making it suitable for applications where oil sealed systems can not be
used. Furthermore the PhoeniXL
300 dry
contains one more valve, the valve
4b. This valve opens step by step to regulate the inlet pressure into the
turbo pump.
4 Fore pressure pump (provides the foreline pressure for the TMP und
pumps down the parts under test)
5 Inlet Port
6 Pirani gauge P1 (inlet pressure)
V1 … V7: Electromagnetic Valves to control the gas flows
Pos. Description