Pump/Release Vacuum
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To Pump Vacuum
1. Simply press POWER ON button on the vacuum
control panel. The roughing pump (RP) LED will be on immediately. The
turbo molecular pump (TMP) LED willbe on in about 20 seconds and then
you'll start hearing faint high pitched noice as the TMP accelerates.
Next, the ion gauge (IG) LED will be on in about 5 minutes. If the time
is much longer, you may have a bad vacuum
condition.
2. Now, you can connect a multimeter (set to DAV mode) to the
IG CHECK terminals (see panel on the left) and monitor the vacuum. When
the reading reaches a little lower than 240mV, the OPERATE LED will
be on. In principle, you can now press the POWER ON button on the X-RAY
panel to operate the machine. However, it is advised (and better) to
wait until the IG reading goes near 100mV.*
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* The time period for the vacuum to reach operable level
or IG to about 100mV can vary. If the whole system has been exposed
to atmosphere, such as for any service to anode or cathode, it will
take much longer, sometimes even overnight. Be patient
To Release Vacuum
See Step 1 in the procedure for changing filament.
Note the following. Before you loosen the vacuum release nut on the
x-ray tube, clean the sorrounding area thoroughly
because foreign particles can be sucked into the system, which is very
damaging to the TMP. It's a very expensive and hard job to replace the
TMP.
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