A large volume (75 cm in diameter and 486 cm in axial length) helicon-plasma device has been developed, and the plasma characteristics in the device have been investigated. With the use of a large (43 cm in outer diameter) spiral antenna located just outside a quartz-glass window at the end of the vacuum chamber, the device is capable of producing high-density plasma (gas species used so far are argon (Ar) and helium (He)) of n(e) >= 10(12) cm(-3) with moderate rf input power of less than I M, showing excellent discharge efficiency. With this device it is possible to control the radial density profile employing the following two techniques: (1) changing the magnetic-field configuration near the antenna and (2) changing the antenna radiation-field patterns. (c) 2005 Elsevier B.V. All rights reserved.