Dispersive element Echelle spectrometer

It should also be noted at this point that a multichannel detector can have multiple detector elements along two axes, one parallel to the direction of wavelength dispersion, and one perpendicular. The latter is parallel to the entrance slit in most dispersive instruments. For example, a CCD may have 1024 pixels along the wavelength axis and 256 along the vertical axis, for a total of 262,144 independent elements. This second dimension of the detector may be used in a variety of applications involving Raman imaging, multiple detection tracks, or echelle spectrometers. 

In addition, echelle spectrometers are often used [50]. By combination of an order-sorter and an echelle grating either in parallel or in crossed-dispersion mode, high practical resolution (up to 300 000) can be realized with an instrument of fairly low focal length (down to 0.5 m) (Fig. 103). Therefore, the stability as well as the luminosity are high. By using an exit slit mask with a high number of pre-adjusted slits, highly flexible and rapid multi-element determinations are possible. 

To locate the specific radiations of an element to be quantified (the different analytical lines) an optical bench of very high quality is required. These apparatuses can be divided into spectrographs and spectrometers (Figure 14.8 and see also Figure 9.12). As above pointed out, the source illuminates a slit which becomes a luminous object, which will be analysed by a dispersive system containing a grating (planar, concave or echelle). 

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