Inductively coupled plasma

File:Inductively Coupled Plasma.jpg
Fig. 1. Picture of an analytical ICP torch

An inductively coupled plasma (ICP) is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.[1]


There are three types of ICP geometries: planar (Fig. 2 (a)), cylindrical [2] (Fig. 2 (b)), and half-toroidal (Fig. 2 (c)).[3]

File:ConventPlasmaInductors W.tif
Fig. 2. Conventional Plasma Inductors

In planar geometry, the electrode is a length of flat metal wound like a spiral (or coil). In cylindrical geometry, it is like a helical spring. In half-toroidal geometry, it is toroidal solenoid cut along its main diameter to two equal halves.

When a time-varying electric current is passed through the coil, it creates a time-varying magnetic field around it, which in turn induces azimuthal electric field in the rarefied gas, leading to the formation of the figure-8 electron trajectories[3] providing a plasma generation (see Hamilton-Jacobi equation in electromagnetic fields). Argon is one example of a commonly used rarefied gas.


Plasma electron temperatures can range between ~6 000 Kº and ~10 000 Kº (~6 eV - ~100 eV),[3] comparable to the surface of the sun. ICP discharges are of relatively high electron density, on the order of 1015 cm−3. As a result, ICP discharges have wide applications where a high-density plasma (HDP) is needed.

Another benefit of ICP discharges is that they are relatively free of contamination because the electrodes are completely outside the reaction chamber. By contrast, in a capacitively coupled plasma (CCP), the electrodes are often placed inside the reactor and are thus exposed to the plasma and subsequent reactive chemical species.

See also


  1. ^ A. Montaser and D. W. Golightly, eds. (1992). Inductively Coupled Plasmas in Analytical Atomic Spectrometry. VCH Publishers, Inc., New York,. 
  2. ^ Pascal Chambert and Nicholas Braithwaite (2011). "Physics of Radio-Frequency Plasmas". Cambridge University Press, Cambridge. pp. 219–259. ISBN 978-0521-76300-4. 
  3. ^ a b c Shun'ko, Evgeny V.; Stevenson, David E.; Belkin, Veniamin S. (2014). "Inductively Coupling Plasma Reactor With Plasma Electron Energy Controllable in the Range From ~6 to ~100 eV". IEEE Transactions on Plasma Science 42 (3): 774–785. ISSN 0093-3813. doi:10.1109/TPS.2014.2299954.