6.152J/3.155J Gas flow and pump d Conductance of vacum component: =Q-C(p-PP)(p 5 pr nearer pump chamber g%) P Effective pump speed, S, never exceeds conductance of worst component or pump speed, sp Wed, Sept. 10, 2003 Vacuum technology: Generating low pressure Two classes of vacu 1 Molecules from chamber b) Turbo molecular pump c)Ol diffusion pump 2)Molecules adsorbed on a surface, a)Sputter/on pump (with TI sublimation b) Cryo pump 6.152J3.155 Wed, Sept 10, 20036.152J/3.155J 6.152J/3.155J Wed., Sept. 10, 2003 11 Gas flow and pump speed Effective pump speed, S, never exceeds conductance of worst component or pump speed, Sp. (pp is pressure nearer pump) But throughput, Q: Q ≡ pS, p = Q S pp = Q Sp Conductance of vacuum component: fi Q = Cp - p ( ) p p pp pump chamber Q = C Q s - Q sp Ê Ë Á Á ˆ ¯ ˜ ˜ Sp S C fi s = csp c + sp = 1 1 c + 1 sp Vacuum technology: Generating low pressure Two classes of vacuum pumps: 1) Molecules physically removed from chamber a) mechanical pump b) Turbo molecular pump c) Oil diffusion pump 2) Molecules adsorbed on a surface, or buried in a layer a) Sputter/ion pump (with Ti sublimation) b) Cryo pump 6.152J/3.155J Wed., Sept. 10, 2003 12 6