54 Troubleshooting and Maintenance Manual
3 CI Troubleshooting
If you use argon or other introduced gas to find air leaks, this does not work
well for the reagent gas flow system. It takes as long as 15 minutes for the peak
to reach the ion source if the leak is at the inlet to the flow module.
Figure 6 Schematic of CI flow control module
Table 3 Flow module valve state diagram
Result Gas A flow Gas B flow Purge
with Gas A
Purge
with Gas B
Pump out
flow module
Standby,
vented, or
EI mode
Gas A Open Closed Open Closed Closed Closed
Gas B Closed Open Closed Open Closed Closed
MFCV On (at
setpoint)
On (at
setpoint)
On (at 100%) On (at 100%) On (at 100%) Off (at 0%)
Shutoff valve Open Open Open Open Open Closed
Shutoff
valve
Needle
valve
IRM
valve
To ion source
Flow control module
To foreline pump
CI mode
Gas A select methane
CH
4
EI mode
He (0.5 mL/min)
PFDTD
NC
NC
FT
FC
PFET
MFCV
PFET
Purge
CI cal
valve
Gas B select helium
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