Alpha: A large-area plasma helicon array

Helicon sources are extremely efficient in creating high density, current free plasma discharges. However, these sources typically have a small cross-sectional area and are unsuitable for studies that require a large diameter plasma. We report the construction of a plasma facility that overcomes this limitation by using multiple helicon sources in a close-packed array. A large-area plasma helicon array (Alpha) is a 4 m long, 50 cm diam device that uses seven helicon sources to generate a large diameter rf plasma. The facility is designed to study basic plasma wave phenomena in a high-density, current-free plasma. The helicon array can operate in one of two modes, creating either seven distinct plasma columns or an integrated uniform large diameter plasma column. Details of the facility specifications, construction, and initial plasma parameters of the multihelicon source are reported.