Technical Description: System
Vacuum System
B-4
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
Thermo Fisher Scientific
The Prima PRO vacuum system consists of the listed in the
following table.
Table B
–2.
Prima PRO vacuum system components
Component
Description
Analyser assembly
The chamber that contains the ion source, the
magnetic sector flight-tube, and collector assembly.
Turbo molecular
pump
A mechanical pump capable of producing and
sustaining ultra high vacuum (hydrocarbon-free) in a
relatively short period. The pump is mounted
vertically below the main analyser vacuum housing.
All turbo molecular pumps must be used in
conjunction with a mechanical rotary pump that
maintains the backing pressure in the molecular
flow regime required for the turbo molecular pump
to operate.
Rotary pump
An 8m
3
h
-1
two-stage rotary pump is fitted below the
analyser enclosure. The turbo molecular pump and
inlet bypass are backed by both stages of the rotary
pump. The Sentinel PRO does not have an inlet
bypass arrangement.
Penning gauge
A glow discharge device that operates within the
pressure range
5 x 10
-5
mbar to 1 x 10
-7
mbar and monitors the
pressure in the analyser vacuum chamber. The
gauge is controlled by the ASU and the output
relayed to the control PC for display on the user
interface status page. The primary function is to
interlock the ion source filament and analyser high
voltages supplies in the event of accidental vacuum
loss or high pressure.
Air admit valve
To prevent migration and loss of bearing lubricant,
the turbo molecular pump should always be held at
atmospheric pressure when switched off. To ensure
this happens, the pump is fitted with a valve that
automatically vents to atmosphere when the pump
is switched off or power is lost to the system. The
vent line is protected by a filter which protects the
valve from contamination and throttles venting rate.
The vent line opens into the compression stages of
the turbo molecular pump so that the gas is
distributed evenly to the high vacuum and backing
pressure vacuum sides.
A dry gas vent connection, 1
/4” / 6 mm Swagelok
fitting, is provided on the left hand side of the
enclosure above the isolation switch (safe area
instruments) or purge control unit (hazardous area
instruments).
Vacuum
System
