Tylan TCA Problem Update

Jim McVittie mcvittie at cis.Stanford.EDU
Sun Sep 1 15:45:44 PDT 2002


Tylan Ox Furnace Users,

I got a call today at home about the furnaces. So I thought I better write
a note to clear up some confusion about the status of the oxidation tubes.  
Previously, I reported that we recently found that the TCA tube cleaning
system is faulty and causing some iron contamination to the Ox tubes. All
the corroded (in the inside) stainless steel associated with this problem
has been replaced. We still have to come up with a new TCA clean procedure
that does not allow HCl from the TCA decomposition to attack the stainless
steel H2 feed line. This coming week we will be testing the running of TCA
and Steam at the same time. Once we have establish a new TCA cleaning
procedure, it will take a few weeks to get iron contamination results back
to see how we are doing. Once the TCA is running again, I expect the iron
level to drop. In the mean time, you can still use the tubes that are not
being worked on for your wet and dry oxidations. The iron level is in the
low E11 /cm2 range, which is higher than we would like, but it should not
affect fabricated devices unless you are making detectors with deep
depletion regions.  Right now Tube #1 is the cleanest tube since it was
just replaced with a brand new one. Last Thursday, we did a simple steam
cleans in place of the usual TCA cleans. Feel free to contact me if you 
have any questions.

	Thanks,			Jim 	
--------------------------------------------------------------
James P. McVittie	                Senior Research Scientist
Allen Center for Integrated Systems     jmcvittie at stanford.edu
Stanford University             	Tel: (650) 725-3640	
Rm. 336, 330 Serra Mall			Fax: (650) 723-4659
Stanford, CA 94305-4075	




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