Hi, I have a leaking problem that annoyed me very much the past two days.  We
have a Varian pumping station: Turbo pump back by mechanical pump, nothing
special.  The system is using a flexible stainless steel line with K flange
connector to pump chambers we need to be pumped.

Now we put an end-cap to this flexible stainless steel line to seal it.  Then
after pumping this line for 20 minutes and the Ion Gauge (which is located
directly to the line, above the gate valve between the line and the turbo pump)
reads 1e-6 torr, we close the gate valve.  However the pressure (read from the
Ion Gauge) rose quickly (less than 10 seconds) from 1E-6 to close to 7E-4 and
up.  We need to shut the Ion Gauge off at anything above 7E-4.

To trouble shoot it, we put the ion gauge directly above the gate valve and pump
the ion gauge. So now the system is like this:
    Ion gauge ==gate valve===Turbo pump == mechanical pump.

10 minutes later we turn the ion gauge on and it reads like 1E-6.  However, the
moment we close that gate valve, the pressure reading for the ion gauge shoots
up again.

I took out ALL the o-rings and grease them carefully and put them back together,
however they still do the same.


So my question:   Why can't these K-flange connectors keep the pressure at 1E-5
Torr range?  Is the pressure shoots up indicating a leak or is it just some out-
gasing?  Or is it because the K-flange connectors are not supposed to hold any
vacuum beneath 1E-3 torr?

Thank you!