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Sat Apr 25 00:45:31 2009, Yoichi, Configuration, VAC, Reflector for the cryopump temperature monitor changed
Sat Apr 25 02:54:25 2009, Yoichi, Configuration, VAC, Reflector for the cryopump temperature monitor changed
Sat Apr 25 02:54:25 2009
In reply to:
Reflector for the cryopump temperature monitor changed
The temperature of the cryopump head is monitored by a photo switch looking at an aluminum foil reflector attached to the needle of the temperature gauge.
If the needle moves out of the 14K position, the photo switch will be triggered to close the cryopump gate valve.
However, this photo switch system has been touchy.
Tonight, the switch falsely tripped several times and closed the gate valve, which caused lock losses as the motion of the valve generates a lot of vibrations.
Seems to me, it was caused by the poor/irregular reflection from the wrinkled aluminum foil on the needle.
So I replaced the aluminum foil with a brand-new shiny one.
The photo switch still trips randomly. We need a better interlock.