When starting the instrument, the roughing pump would run normal and reach vacuum to 2 or 1 torr, the turbo pump would accelerate and reach normal status, however after a short time running at such normal pumping down process the ion gauge would just start momentarily to show a number around 20-40 and then immediately the turbo would shut down and then after a while the turbo would try to pump down again. It sounds like a vacuum leak but there is no way I can think of where that leak would be. Since the roughing vacuum seems OK, I replaced the ion gauge and one of the O-ring on the Q0, but that didn't solve the problem. What do you all think would be the problem and how to check it? Could the turbo be not up to speed? Something wrong with the ion gauge controller? Thank you all.
I had encountered similar problem in the past. In my case it was becuase the chamber was exposed to the humid air for the prolonged time. When I tried pumping it down, the system started to degas, hence pressure increased which triggered the system to shutdown automatically. I fixed it by just running the roughing pump for more than 1 hour and purged back with Dry Nitrogen. Repeated the process thrice. And now it is working fine.
Eventually the problem was the collision gas connection to the chamber. I thought I had tightened it enough and was afraid further tightening would risk stripping the thread. After all option exhausted, I ventured to tighten that further to really tight to the point of breaking, and that did take care of the problem, but it seems something has to be done next time around for a secure connection long term.
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