VICI D-2-I - Manual (Page 30)

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10. If the bias voltage is not 1 V or less with a set current of 10 nA, the
dopant flow rate may need to be adjusted. The optimum flow rate is
determined by varying the rate until the indicated bias voltage is
minimized, and then increasing the rate very slightly.
Figure 7 illustrates the effect on background bias voltage and detector
sensitivity with varying dopant flow rates. The detector temperature may
also have a substantial effect on background bias voltage and sensitivity,
depending on the compound of interest. These effects are illustrated in
Figure 8.
If the detector background bias voltage still does not reach optimum value,
try a 12 hour bakeout at 300°C. If it still does not optimize, there is either
a leak in the system or the column effluent is not clean. To see if the high
background bias voltage is due to the column:
1. Loosen the knurled nut and pull the column out ~20 mm. Secure the nut.
2. Watch the detector standing/background current, indicated in the con-
troller DISPLAY. If the current decreases dramatically, then the column
must be removed and baked out. If the current remains high, the system
probably has a leak.
3. Reinstall the column and repeat the leak test described on page 17
before proceeding.
Mode Selection and Setup