Helicons-the early years

Helicon waves are right-hand polarized (RHP) waves which propagate in radially confined magnetized plasmas for frequencies /spl omega//sub ci//spl Lt//spl omega//spl Lt//spl omega//sub ce/ where /spl omega//sub ci/ is the ion cyclotron frequency and /spl omega//sub ce/ is the electron cyclotron frequency. They are part of a much larger family of waves which can propagate down to zero frequency and constitute a very rich field for studying complex propagation characteristics and wave-particle interactions. This paper gives a historical perspective of the waves and their relationship to plasma source development up to the mid 1980s, presents a simple description of their propagation characteristics in free and bounded plasmas, and finishes with their first reported use in plasma processing experiments.