Spherical grid analyser

The detector may be a simple electrometer when using a cylindrical or spherical grid analyser. With the other types, fewer electrons are being collected and an electron multiplier, having much greater sensitivity, is necessary. This consists of a number of dynodes, each of which produces more electrons than it receives. For a measurable current, about 10 to 20 dynodes are required. Alternatively, a multichannel electron multiplier in the focal plane of the analyser can be used to collect simultaneously electrons with a range of energies. 

Figure 8.5 (a) Slotted grid, (b) spherical grid, (c) 127° cylindrical and (d) hemispherical analysers... 

The Spherical-Material Model. The finite-element model used for the spherical-material model is a single rubber sphere surrounded by an annulus of epoxy resin. The complete cell can be represented by axisymmetric elements in an analogous manner to the cylindrical model, as shown in Figure 2. The same number and types of elements were used for this model. Analyses were also undertaken assuming a hole instead of the rubber particle the grid then consisted of the epoxy annulus alone. 

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