Standard vacuum chambers 1≈106Tor(1.3×104N Mostly H,O, hydrocarbons, N, He by residual gas analySis(RGa=mass spec 6.152J3.155J6.152J/3.155J 2 Standard vacuum chambers Σpi ≈ 10-6 Torr (1.3 × 10-4 N / m2) Mostly H2O, hydrocarbons, N2 He by residual gas analysis (RGA = mass spec.)