Learn about Glass Expansion RF Coils

The Role of the RF Coil

The RF coil is the last component in the electrical system used to generate an Argon plasma. Being the last component, there is great importance placed on the coil for transferring RF energy to the plasma.

There are three factors affecting the role of the RF Coil in transferring energy:

Concentricity and alignment - these are very important in producing a correctly shaped plasma, which consistently needs to be located in the same position. The Glass Expansion RF Coil installation tools with plastic coil supports make this possible every time.
Correct dimensions - being part of the RF system, the coil dimensions are also important in the tuning of the circuit. Slight changes in dimensions can produce small changes in resistance or inductance and are normally compensated for in the tuning circuitry of the system.
Base metal/plating - the most efficient conductor of RF energy is pure silver followed by annealed copper. There is very little difference in the conductivity of these materials but there is a great deal of difference in cost. Copper is used as the base material of all commercially available coils but different manufactures use different plating materials. Silver has the best conductance and gold the best corrosion resistance.

Being exposed to the environment of the torch box, the condition of the coil has a major effect on the efficiency of transferring energy to the plasma. The greater the corrosion, the larger the electrical energy that is required to produce a plasma of the same power. This transfers undue stress on the rest of the electrical components used in the RF system, possibly contributing to premature failure.

There are three main areas that affect the transfer of energy from the plasma to the sample.

Argon gas flow rates and quality.
The torch containing the plasma. The torch needs to be concentric and of the highest quality Quartz. If the outer tube becomes devitrified, the transfer of energy is restricted due to losses incurred by heating on the surface of the outer tube, thereby reducing the available energy for the atoms.
The RF generating system, including the coil. All RF systems available in commercial ICP instruments are capable of supplying the required power. The one component that is common to all instruments is the coil. Each instrument has a different type of coil, with different dimensions and different number of turns.

RF coils are one of a number of critical components needed to produce a plasma. With the Glass Expansion RF coils and installation tools it is now possible to replace your coil on a more regular basis without the cost of a service visit. This ensures this part of the RF system continues to work in peak condition.