PerkinElmer AVIO 200, Hardware Manual

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System Description
73
Spectrometer
Introduction
The core of the optical system is comprised of a dual Echelle monochromator with a
dual, backside-illuminated, cooled, CCD detector. The system is specifically
designed for ICP-OES. Computer controlled transfer optics direct the radiation from
the plasma into the monochromator. The optics housing is sealed and continuously
purged with high purity nitrogen.
Signals at the required analytical wavelengths are measured using a scanning CCD
(charged coupled device) based technology, with simultaneous measurement of the
background emission and a neon spectrum for active wavelength correction.
Transfer Optics
The computer controlled transfer optics are used to select either radial or axial
viewing of the plasma and to direct the radiation from the plasma onto the entrance
slit of the monochromator. The exact viewing position, (horizontal and vertical
position), can be selected in the software.
An automatic shutter closes between measurement cycles to reduce the exposure of
the optics to excess UV radiation.
Monochromator
In the dual Echelle monochromator, the prism monochromator acts as a preselection
system to select the required wavelength range to pass on to the Echelle
monochromator. Optimally positioned slits and baffles result in very low stray light
levels reaching the Echelle monochromator. The prism and Echelle dispersion
systems use Littrow configurations, designed to eliminate astigmatism, with
identical, 300 mm focal length, 10° off-axis, parabolic, collimating and focusing
mirrors.
The Echelle grating has 79 lines/mm with a blaze angle of 63.4°. The grating is used
in the higher orders, where the high efficiency and high dispersion allow a relatively
short focal length resulting in a compact optical system.
Wavelength selection is achieved by simultaneous rotation of the prism and grating.
Since the maximum rotation required for either element is not more than ± 2°, the
average wavelength selection time is less than 2 seconds. To further optimize the