Operating in CI Mode 5
5977B Series MSD Operating Manual 141
To Monitor CI Mode High Vacuum Pressure
Procedure
1 Start up and pumpdown the MSD. (See “To Pumpdown the MSD in CI Mode”
on page 124.)
2 In the Tune and Vacuum Control view select Turn Vacuum Gauge on/off from the
Vacuum menu.
3 In the Instrument Control view you can set up an MS Monitor for reading. The
vacuum can also be read on the LCP or from the Manual Tune screen.
The gauge controller will not turn on if the pressure in the MSD is above
approximately 8 × 10
-3
Torr. The gauge controller is calibrated for nitrogen, but
all pressures listed in this manual are for helium.
The largest influence on operating pressure is the carrier gas (column) flow.
Typical pressures for various helium carrier gas flows are approximate and
vary from instrument to instrument. (See Table 15 on page 142.)
Typical pressure readings
Use the G3397B Micro-Ion vacuum gauge. Note that the MFC is calibrated for
methane and the vacuum gauge is calibrated for nitrogen, so these
measurements are not accurate, but are intended as a guide to typical
observed readings. (See Table 15 on page 142.) They were taken with the
following set of conditions. Note that these are typical PCI temperatures:
IIf hydrogen is used as a carrier gas or JetClean system supply, the carrier and
JetClean system supply shutoff valves must be closed before turning off the MS
power. If the foreline pump is off, hydrogen will accumulate in the MS and an
explosion may occur. Read “Hydrogen Safety” on page 23 before operating the MSD
with hydrogen gas.
Source temperature 250 °C
Quad temperature 150 °C
Interface temperature 280 °C
Helium carrier gas flow 1 mL/min
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