The pumping speed of ISPs (ion sputter pumps) varies with pressure as shown in Figure 4210a. The operating pressure is in the range of less than 10-7 bar because the space charge in the Penning cells changes into a glow discharge and the sputtering process stops at higher pressures. The maximum pumping speed of ISPs is reached at about 10-9 bar.
Figure 4210a. Pumping speed vs pressure in ISPs.
Figure 4210b shows schematic illustration of a Transmission Electron Microscope (TEM) system. DP and RP are diffusion pump and rotary pump, respectively.
Figure 4210b. Schematic illustration of a Transmission Electron Microscope (TEM) system.