Slew scan monochromators

Three different types of grating spectrometer detection sterns are used (Figure 3) sequential (slew-scan) monochromators, simultaneous direct-reading polychroma-... 

Direct-reading polychromators (Figure 3b) have a number of exit slits and photomultiplier tube detectors, which allows one to view emission from many lines simultaneously. More than 40 elements can be determined in less than one minute. The choice of emission lines in the polychromator must be made before the instrument is purchased. The polychromator can be used to monitor transient signals (if the appropriate electronics and software are available) because unlike slew-scan systems it can be set stably to the peak emission wavelength. Background emission cannot be measured simultaneously at a wavelength close to the line for each element of interest. For maximum speed and flexibility both a direct-reading polychromator and a slew-scan monochromator can be used to view emission from the plasma simultaneously. 

V direciions loscan an aperture plate located on the focal plane of the monochromator. The plate contains as many as 3(X) photo-etched slits. The time required to move from one slit to another is typically I s. The instrument can be operated in a slew-scan mode. This instrument can also be converted to a multichannel poly-chromalor by mounting several small photomultiplier lubes behind appropriate slits in the aperture plate. 

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