AVS 46th International Symposium
    Vacuum Technology Division Thursday Sessions
       Session VT-ThM

Paper VT-ThM2
Experiments with Thin-Walled Stainless Steel Vacuum Chamber

Thursday, October 28, 1999, 8:40 am, Room 610

Session: Outgassing, Leaks, and Mass Flow Controllers
Presenter: V. Nemanic, Institute of Surface Engineering and Optoelectronics, Slovenia
Authors: V. Nemanic, Institute of Surface Engineering and Optoelectronics, Slovenia
J. Setina, Institute of Metals and Technology, Slovenia
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The application of reasonably thin stainless steel wall was suggested recently as alternative approach in construction of UHV chambers, since the hydrogen outgassing rate can be decreased to the level required to reach UHV and EXV much easier. Experimental stainless steel chamber (AISI type 304, volume 13 l) with uniform wall thickness (0.6 mm) has been constructed. It was equipped with a miniature ion-getter (IG) pump and spinning rotor gauge (SRG) thimble. The chamber was pumped down and initially degassed by moderate bake-out (2.5h, 150 deg.C) by a turbomolecular pump system. Gas accumulation method was applied for determination of outgassing rate q@sub out@ and total amount of released gases using capacitance manometer during pump down and SRG after the chamber was sealed-off. The initial q@sub out@ at room temperature after initial degassing was in the range of q@sub out@=10@super -12@ mbar l s@super -1@cm@super -2@ with a tendency of slight decrease with time. Thermal dependence of outgassing rate was determined from SRG measurements in the temperature range from 19 to 50 deg. C over several days with ability to extract the offset value by means of IG pump. The bake-out of the chamber was repeated for 72h at 200 deg. C which lead to the decrease of outgassing rate to one tenth of the initial value. The results show the benefit of using a moderately thin wall and agree well with a model of recombination limited hydrogen outgassing from stainless steel. @FootnoteText@ B.C.Moore: Atmospheric permeation of austenitic stainless steel, J.Vac.Sci.Technol., A16(5), 3114-3118, 1998 V.Nemanic,T.Bogataj: Outgassing of a thin wall stainless steel chamber, Vacuum, 50, 3-4, 431-437, 1998