Just to restate the issue: the cryo-pump is connected to a chamber, let's say through a gate valve; after the bake the chamber is at 7e-11 Torr and the cryo-pump operational temperature is at 13.4K. You have leak checked the pump and it is ok. When you open the gate valve, the cryo-pump temperature increases to 14K and the chamber pressure drops only to 5.5e-11 Torr. Eventually it gets to 3.5e-11 Torr. However, the pump temperature slowly increases.
You've got the cryo-pump model: CryoTorr 8 and looked at the cryo-pump manual on the troubleshooting chapter, just to realize that your problem is not described there.
Then you go to the compressor manual with the compressor model: 8200. You check that the compressor static pressure of 250 psi is in the specified range: between 245 and 255 psi. Also, the nominal compressor pressure pulses between 280 and 285 psi which is also within the range given by the manual: 280 and 285psi. Finally you verify the compressor draws 7.95 A which is within the working conditions of the compressor: between 8 and 9A.
After you call the GUTS technical service (24/7/365) from Brooks Automation. They explain you that the average lifetime of the pump is around 5 years; a reduced performance is expected after this. When you give your serial number, you are pointed out that your pump is around 7 years old. These symptoms point to a seals wear off inside the cold head. The solution: either exchange the pump or send it to them. In any case you will get a refurbished one.
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