Inductively Coupled Plasma Torch

The illustration below provides a schematic diagram of an inductively coupled plasma source (ICP), which consists of three concentric quartz tubes surrounded at the top by a radio-frequency induction coil. The sample is mixed with a stream of Ar using a nebulizer, and carried to the plasma through the torch’s central capillary tube. Plasma formation is initiated by a spark from a Tesla coil. An alternating radio-frequency current in the induction coils creates a fluctuating magnetic field that induces the argon ions and the electrons to move in a circular path. The resulting collisions with the abundant unionized gas give rise to resistive heating, providing temperatures as high as 10,000 K at the base of the plasma, and between 6000 and 8000 K at a height of 15–20 mm above the coil, where emission is usually measured. At these high temperatures the outer quartz tube must be thermally isolated from the plasma. This is accomplished by the tangential flow of argon shown in the schematic diagram.

Figure10.58

This illustration is modified from one created by Xvlun—the original file is located here—and released under a CC-BY-SA 3.0 copyright via Wikimedia Commons.

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