Edwards ELD500 Series

D135-10-880C - Description
Page 6
Vacuum diagram ELD500 WET
The vacuum diagram below shows the major components inside the ELD500 WET.
Figure 2 Vacuum diagram ELD500
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 magnetic 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 an 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 x 10
-4
mbar
and lower. This pressure is provided by the turbo molecular pump which in turn is backed up
by a fore vacuum pump.
1. MS: Mass Spectrometer, Helium sensor (180° magnetic field mass
spectrometer)
2. Turbo molecular pump (TMP, provides high vacuum conditions in the MS)
3. Pirani gauge P2 (fore vacuum pressure)
4. Fore pressure pump (provides the fore vacuum pressure for the TMP and
pumps down the parts under test)
5. Inlet Port
6. Pirani gauge P1 (inlet pressure)
V1 to V7: Electromagnetic Valves to control the gas flows