Electron multiplier analogue

Schematic diagram of an electron multiplier showing and (top) electrical connections for analogue and pulse counting and (bottom) how a single ion gives rise to a large...

Another commonly used detector is the Faraday cup. This detector is an analogue detector and so has poorer sensitivity than a pulse counting electron multiplier. However, it has the advantage of simplicity (it is essentially only a metal plate used to measure ion current), and it does not suffer from burn-out like an electron multiplier (which must be periodically replaced). 

Q. What are the main differences between an electron multiplier operated in pulse counting and analogue mode ... 

Figure 4.5 Channel electron multiplier (CEM) working in the analogue and pulse-counting mode. (Reproduced by permission of GV Instruments Ltd.)...

We should not forget that an appropriate detector, a Faraday cup or a secondary electron multiplier equipped with a conversion dynode, is needed for ion detection. Most commercial instruments are equipped with a secondary electron multiplier, which can be operated in a low amplification mode, the analogue mode, and with a high gain, the counting mode, where each ion is counted. With this dual mode, a linear dynamic range of up to nine orders of magnitude can be achieved, so that major and minor components of the sample can be measured in one run. 

The only parameter in the whole U (R) expression that is unknown from independent experiments is the multiplier A, which depends on numerous factors, like, location of the adsorbed ion within the compact layer, the distribution of the dielectric properties across this layer (analogues of the ratio of the capacitances, Kh/Kq, in the Grahame-Parsons theory. Sect. 2.1.11.2), partial transfer of the electronic charge by the ion in its adsorbed... 

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