[3dem] Column vacuum problem with a Tecnai F20

John Rubinstein, U of T john.rubinstein at utoronto.ca
Tue Jul 22 09:52:47 PDT 2008


Dear Colleagues,

We have been having a strange vacuum problem with our FEI Tecnai F20 G2 
.  Our engineer says that he has not come across reports of this problem 
through FEI, but I was wondering whether anyone in the 3DEM community 
has seen the problem before and knows what the cause is.

Our column vacuum deteriorates when liquid nitrogen is added to the cold 
trap.  At room temperature the column vacuum (IGP1) sits at around 13.  
Upon addition of liquid nitrogen, IGP1 deteriorates to ~20.  We have 
aready had some work done on the microscope and learned some interesting 
things.  We had the component that couples the external copper braid to 
the cryobox replaced but that did not solve the problem.  Subsequently, 
as a test, our engineer  removed the cryobox from the column and blanked 
off the cryobox bellows.  Without these components,  IGP1 improved to 
~5-6.  However, replacing the cryobox bellows with a new one did not 
solve the problem. 

As you will know, vacuum leaks can take a long time to sort out, so any 
advice that helps us solve this one faster would be greatly 
appreciated.  Also, could people who use a F20 (with or without film) 
please send me some typical values for their column IGPs (IGP1 and IGP4 
in our instrument).

Best wishes and many thanks,
John

-- 
John Rubinstein
Molecular Structure and Function Program
The Hospital for Sick Children
555 University Avenue, Rm. 3330
Toronto, ON
Canada
M5G 1X8
Tel: (+001) 416-813-7255
Fax: (+001) 416-813-5022
www.sickkids.ca/rubinstein




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