Optical emission studies of the Mach disc extracted from an inductively coupled plasma with an échelle spectrometer and segmented-array charge-coupled detectors

Abstract

An inductively coupled plasma (ICP) is extracted into a small quartz vacuum chamber through a sampling orifice in a water-cooled copper plate. Optical emission from the Mach disc region is measured with a new type of échelle spectrometer equipped with two segmented-array charge-coupled device detectors, the Optima 3000 from Perkin-Elmer. This device provides high quantum efficiency throughout the ultraviolet-visible region, as well as low dark current and readout noise. The spectral background emitted by the Mach disc is very low. Axial profiles of the optical emission of a range of atom and ion lines are measured. The effects of aerosol gas flow rate on the intensities of various lines are investigated. The relationship between the location of the Mach disc and the pressure in the expansion chamber is also studied. The analyte line intensities are enhanced at higher pressure.