Getter pumps

The sorption characteristics of Ti are dependent on the deposition temperature of the getter film. Good results are obtained by deposition at 77 K because the film formed is more porous (i.e. has a higher surface area) than those formed at, say, room temperature. 

Sticking probabilities as a function of monolayer formation are given in Table 3.10. 

Where gases are simultaneously pumped, some can displace others. Gupta and Leek (Vacuum, 1975, 25, 562) found that 02 can displace all other gases, CO can displace CH4, N2 and H2, and H2 can displace N2 and CH4. 

The collecting screen inside a TSP is 14 cm in diameter and 18 cm in length. In addition, at the base, there is a circular plate of the same diameter as the screen and cooled by heat conduction. 

From Equation (1.17) and (1.18) the volumetric flow of gas onto a wall (area = A) is  

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To improve the cryopumping action, a getter pump can be attached to the cold wall of a cryostat. 

FIGURE 11.17 Schematic of mass spectrometer used for stratospheric measurements (IG = ion getter pump, PS = pressure sensor) (adapted from Arnold and Hauck, 1985). 

The basic ECELL geometry consists of small apertures above and below the sample and the apertures are mounted inside the bores of the objective lens polepieces (figure 2.10(d)). The controlled environment ECELL volume is the normal sample chamber of the microscope. It is separated from the rest of the column by the apertures in each polepiece and by the addition of a gate valve, which is normally kept closed, in the line to the usual ion-getter pump (IGP) at the rear of the column. Differential pumping systems are connected between the... 

In stoppered vials we could follow quite easily the transfer of moisture from the stopper toward the plug, which acted as a getter pump until a new equilibrium was reached (Figure 21). This allowed us, for instance, to understand why in a certain BCG vaccine the Karl Fischer titration went up when the equilibrium water vapor went down reaching condensation points as low as -50°C. 

Wagener (31) reported that the sticking probability of CO on titanium at room temperature was very close to unity. In consequence, since CO is one of the primary residual components in most ultrahigh vacuum systems, titanium has received extensive use in recent years in ion and getter pumps for attaining this type of vacuum condition. It... 

In the classical analytical procedure the extracted gases are dried and cleaned by passing various getter pumps. Finally a cryostatic cold trap entirely adsorbs the purified... 

Six different types of pump are used to evacuate a vacuum system. The first and most common is the mechanical displacement pump [226,227]. The second is the vapour stream pump [228]. The third is the modem turbomolecular pump [229]. The fourth type is the chemical getter pump. The fifth is the ion pump and the sixth is the cryogenic pump [230]. In technical coating systems, the first three types of pump are preferred. The development of these pumps is narrowly associated with the names W. Gaede, I. Langmuir, C. Burch, K. Hickman and W. Becker [221,225]. Cryogenic pumps have also been used to evacuate technical coating plants. 

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