Plasma Sources

Plasma Sources

Plasma, the fourth state of matter, is a very high- temperature gas that exists in the sun and other stars (Holtzclaw, Odom, & Robinson, 1991). It is formed through the dissociation and ionization of atoms. The argon ions (electrically charged particles) formed in the plasma are used to take up energy from an outside source to maintain temperature and allow further ionization (Crouch, Holler, Skoog, & West, 2004). This report aims to provide information about the three sources of plasma namely, dc electrical source, inductively coupled plasma (ICP), and dc plasma source (DCP). This also presents the different processes in obtaining plasma.

According to Crouch, Holler, Skoog, & West (2004), dc electrical source obtains electric current from electrodes that are submerged in argon plasma. This type of plasma source is seldom used because it still needs further study and exploration.

Another power source is the inductively coupled plasma (ICP). It is a radio- frequency and microwave frequency generator where the argon passes through. In ICP, plasma appears as having a brilliant, white opaque core topped with flame- like tail, while the core produces spectral continuum with superimposed atomic spectrum of argon. Of the three sources, ICP offers the greatest advantage in terms of sensitivity and freedom from interference. It can also occur in chemically inert environment and the temperature cross- section of plasma is uniform. On the other hand, its disadvantage is its tolerance to organic solvents (Crouch, Holler, Skoog, & West, 2004).

Direct current plasma source (DCP), the third source of plasma, was first described in 1920's and was introduced commercially in 1970's. The DCP is an electric current that flows in one direction only. Like ICP, DCP is also a powerful radio- frequency and microwave - frequency generator through which argon flows. The advantages of this plasma source are less argon requirement, lower cost and have virtue of simplicity. While its disadvantages are small optimum viewing region, and requires more maintenance than ICP (Crouch, Holler, Skoog, & West, 2004).

Plasma, having believed to be only present in the sun and other stars can now be obtained with the use of the different sources mentioned above.

The plasma sources presented in this report are just three of the numerous sources of artificially produced plasmas. There are lots of problems and complications that the scientific and engineering world needs to address. Some of these problems are caused by the limited capacity of this century's equipment and machines, and the complicated processes involved in obtaining plasma from its sources. But despite these difficulties, further studies need to be pushed through because I believe that the experts in the field would soon be able to offer solutions to them. I'm also