Characteristics of a large volume, helicon plasma source

A high-density helicon plasma source with very large volume, 75 cm in diameter and 486 cm in axial length, has been developed, and its characteristics have been investigated. Furthermore, the radial density profile control has been successfully demonstrated by utilizing two techniques: (1) by changing the magnetic field configurations near the antenna and (2) by changing the antenna radiation-field patterns. Using two types of large-diameter spiral antennae, plasma with density exceeding 1012 cm-3 has been produced with several hundreds of watts of radio frequency power. By changing the magnetic field configuration near the antenna, the threshold power and the degree of the density change in a density jump can be varied. The electron density reaches the maximum away from the antenna; then decays weakly along the axial direction