Czerny-Turner grating mount

Common grating mountings used in ICP-AES (a) Ebert (b) Czerny-Turner. 

Dispersing elements may be either prisms (glass for the visible, quartz for the nearultraviolet) or, more often, diffraction gratings for which a Czerny Turner mounting, shown in Figure 3.17, may be used. 

Fig. 19. Important optical mountings for optical spectrometers with a plane (A Ebert, B Czerny-Turner) and a concave (C Seya-Namioka, D Paschen-Runge) grating, m Mirror, se entrance slit, sa exit slit, gp plane grating, gc concave grating.

With a plane grating several mountings (Fig. 19) can be used. In the Czerny-Turner mounting, two spherical mirrors with slightly different focal lengths are... 

Fig. 7. Diagram of a grating spectrometer with the optical components (Czerny-Turner mount and the electronics with the usual lock-in technique...

Spectrometers 1) Jarrell-Ash, Model 78-466, 1 meter f/8.7, Czerny-Turner mount with a 1180 g/mm grating blazed at 250 nm, reciprocal linear dispersion of 0.825 nm/mm (0.0206 nm/diode). Entrance slit width 20 um, height 2 mm. 2) McPherson, Model 2051, 1 meter, f/8.7, Czerny-Turner mount with a 1800 g/mm holographic grating blazed at 200-700 nm reciprocal linear dispersion of 0.0138 nm/photodiode, entrance slit 20 um, height 2 mm. 

The spectrometers used are adapted either for sequential or simultaneous multi-element measurements. Commonly used grating spectrometers in plasma AES include (i) spectrometers with the Paschen-Runge mount, (ii) echelle spectrometers, (iii) spectrometers with Ebert and Czerny-Turner mounts, (iv) spectrometers with Seya-Namioka mounts, and (v) double monochromators. Also Fourier transform spectrometers may be used in plasma AES. 

In a Czerny-Turner mount, two smaller concave mirrors are use instead of a single mirror (Figure 126). The optical characteristics of the Ebert mount and the Czerny-Turner mount are similar. In these mounts changes from one wavelength to another can easily by made by rotating the grating using a computer controlled stepper motor. 

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