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    Vacuum Science & Technology Wednesday Sessions
       Session VST-WeM

Invited Paper VST-WeM3
New Results on Outgassing of Stainless Steel and Insulators

Wednesday, October 31, 2001, 9:00 am, Room 125

Session: Gas Sorption Phenomena I
Presenter: L. Westerberg, Uppsala University, Sweden
Authors: L. Westerberg, Uppsala University, Sweden
N. Hilleret, CERN, Switzerland
B. Versolatto, CERN, Switzerland
B. Hjörvarsson, Royal Inst. of Technology, Sweden
Correspondent: Click to Email
A series of outgassing measurements of 316LN stainless steel have been performed at CERN, using a standard Fischer-Mommsen test dome. Very large, 1.5 mm thick, sheets were rolled in spiral form, open in both ends, and was mounted into the test chamber. Total areas of up to 13 m@super 2@ were used in order to increase the accuracy of the measurements. Four series of bakeouts have been performed: 1. Six 48 h bakeout cycles under vacuum to 300°C; 2. One bakeout under vacuum to 450°C; 3. Five bakeouts in air to 450°C followed by one bakeout to 300°C; 4. A sample vacuum fired at 1100°C was exposed to six bakeouts at 300°C. The outgassing rates are lowered from cylce to cycle and are in the 10@super -13@ to 10@super -16@ mbar l s@super -1@ cm@super -2@ ranges, depending on the sample. For comparison and for further understanding of the underlying processes in outgassing of stainless steel we have performed a different type of experiment at the Tandem Accelerator in Uppsala, namely hydrogen depth profile measurements like in ref.,@footnote 1@ where extraction measurements of H from stainless steel at 1000 °C were compared to the average hydrogen concentrations from 50 to 700 nm measured by the @super 1@H(@super 15@N,@alpha@ + 4.3 MeV @gamma@)@super 12@C nuclear resonance reaction at 6.4 MeV. For the present experiment we have performed similar H concentration measurements on small samples which were cut out from each of the four large test sheets after the outgassing measurements were completed. @FootnoteText@ @footnote 1@L. Westerberg et al., Vacuum 48(1997)771.