From gladys at snf.stanford.edu Fri Aug 2 10:39:55 2002 From: gladys at snf.stanford.edu (Gladys Sarmiento) Date: Fri, 02 Aug 2002 10:39:55 -0700 Subject: cancelled reservation Message-ID: <3D4AC3EA.DB257409@snf.stanford.edu> Tylan 1 and 7 reservations till 2pm were both cancelled. Sorry for the late notice Gladys -- From mcvittie at cis.Stanford.EDU Thu Aug 29 00:19:04 2002 From: mcvittie at cis.Stanford.EDU (Jim McVittie) Date: Thu, 29 Aug 2002 00:19:04 -0700 (PDT) Subject: : Tylan Ox Furnaces: TCA System Upgrade Message-ID: Tylan Furnace Users, Over the last few months in doing contamination studies in the lab using TOF SIMS, we found that the Fe level in our thermally grown oxides was higher than expected (low E 11 /cm2). Last week, we finally traced down the source of this Fe to a programming error in the TCACLEAN process used to clean the tubes. We were not getting the benefit the chlorine from TCA and essentially only doing steam cleans of the tubes. Some low level of TCA did make into the tube but the low flow allowed HCl from the TCA decomposition to diffusion back up the delivery line and reach the stainless steel section of the line. The result was that there was some corrosion of the stainless steel. We believe that this corrosion is the source of the low level Fe found in our oxides. So what are we doing to correct the problem? 1. The TCACLEAN program has been corrected. 2. On tubes #1, #2, #3 and #4, all the stainless steel fittings and lines showing any corrosion have been replaced. On tube #7, the stainless steel should be replaced in the next day or so. I will send a note out when this has been done. 3. In doing the testing to solve this problem, there is a small possibility that we increased the Fe level in tubes #1, #2, #3 and #4. To correct for this possibility, we are running TCA cleans on these tubes and will be pulling each of these tubes over the week to wet clean or replace the tube. Tube #1 was shut down today (Thursday) and a new tube will be installed tomorrow. I am asking the techs to send out notes to keep you updated on the status of each tube. 4. To make sure that the corrosion problem can not occur again, we will be replacing the stainless steel tubing, fittings and valves with Teflon replacements. This will be accomplished as the parts become available over the next few weeks. 5. Finally, we will be doing TOF SIMS testing of oxides to confirm that the problem is gone. I am sorry if any of your work has been inconvenienced or compromised by this problem. It is our goal to keep the lab at the highest standard possible. We are looking ways to make something like this does not happen again. 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 From seymour at snf.stanford.edu Thu Aug 29 11:40:16 2002 From: seymour at snf.stanford.edu (Ray Seymour) Date: Thu, 29 Aug 2002 11:40:16 -0700 Subject: tube maint done Message-ID: <3D6E6A90.57623225@snf.stanford.edu> I have replaced the quartz with cleaned quartz. There is a new injector and ultratorr fitting for TCA. I checked the N2 carrier flow goes through the injector with TUBE ON. There is a new TCA bubbler on the tube as the old one was very low. The tube is heating up now and will be ready for further testing this afternoon. From mcvittie at cis.Stanford.EDU Thu Aug 29 19:18:32 2002 From: mcvittie at cis.Stanford.EDU (Jim McVittie) Date: Thu, 29 Aug 2002 19:18:32 -0700 (PDT) Subject: Update on TCA Problem with SNF Ox Tubes Message-ID: Tylan Furnace Users, Our understanding of what was happening with the Tylan oxidation furnaces has changed a bit since the note that I sent out yesterday. In particular, we found out that they had been an undocumented hardware change to the TCA system some years ago, that none of the current staff knew about. This change had allowed the TCA to flow with the way the TCACLEAN program had been written, however this hardware change had also allowed the corrosion problem to occurs. So the TCA cleans had been running correctly but they were introducing Fe into the tubes. Where we stand is that all the corroded stainless steel tubing and fittings have been replaced. Tonight instead of TCA cleans, we are running simple steam cleans on all the tubes. Before we start running TCA cleans again, we are accessing several possible hardware changes to make sure that the corrosion problem does not occur again. We suspect that the Fe (Iron) level is higher than we would like but it is not probably no higher than it has been for the past several years. It will take us a few days to fully determine which of the proposed hardware changes is best. I will keep you posted. Thanks for your patience. 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