3. Multi-channel detection

In emission spectrometry, having access to only a limited bandwidth is a serious handicap when using a photomultiplier tube. A bandwidth of 6 pm in the 170 to 770 nm range corresponds to just 10 ppm (10 ^–5 ) of the available information, which is a significant loss. Even the use of a conventional polychromator with 40 channels increases this information only slightly. What's more, the need to measure the spectral background in the vicinity of the line imposes an additional measurement. So there's a need to acquire more information, as the photographic plate did, but without the limitations mentioned above.

The ideal solution would therefore be to combine the advantages of a photographic plate and photoelectric detection, i.e. a wealth of information and photon-electron conversion. One of the consequences is to be able...