System Shutdown, Startup, and Reset
Starting Up the System after a Complete Shutdown
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_______________________ Finnigan LTQ Hardware Manual _______________________
Setting Up Conditions for Operation
You need to do the following to set up your LTQ for operation:
1. Before you begin data acquisition with your LTQ system, you need to
allow the system to pump down for at least 1 hour. Operation of the
system with excessive air and water in the vacuum manifold can cause
reduced sensitivity, tuning problems, and reduced lifetime of the electron
multiplier.
2. Ensure that the helium pressure and nitrogen pressure are within the
operational limits (helium: 40
±
10 psig [275
±
70 kPa], nitrogen:
100
±
20 psig [690
±
140 kPa]).
3. Look at the status panel in the Tune Plus window. Check to see if the
pressure measured by the ion gauge is below about 5
×
10
-5
Torr, and the
pressure measured by the Convectron gauge is around 1 Torr. Compare
the values of the other parameters in the status panel with values that you
recorded previously.
4. Set up for ESI, APCI, APPI, or NSI operation as described in Finnigan
LTQ Getting Started.
Note. Air in the helium line must be purged or given sufficient time to be
purged for normal LTQ performance.
Note. You do not need to calibrate or tune the LTQ each time you restart the
LTQ.
Calibration parameters are instrument parameters whose values do not vary
with the type of experiment. You need to calibrate the LTQ perhaps once a
month, and check the calibration once a week. Refer to Finnigan LTQ
Getting Started for a procedure for calibrating the LTQ.
Tune parameters are instrument parameters whose values vary with the type
of experiment. You need to tune the LTQ (or change the Tune Method)
whenever you change the type of experiment. Refer to Finnigan LTQ
Getting Started for procedures for tuning the LTQ in the ESI or APCI
mode. (Note that LTQ comes with several standard Tune Methods specific
for various experimental conditions, so that tuning is often not required for
many types of experiments.)
