HELICON WAVE-PROPAGATION IN THE SHEILA HELIAC

The behaviour and structure of waves launched from a novel double-loop antenna in the SHEILA heliac are presented. Radial wave field and azi muthal phase measurements are compared with cylindrical helicon wave t heory after an appropriate magnetic coordinate transformation. This co mparison provides strong evidence for the involvement of helicon waves . Damping of the waves is investigated by comparing measured spatial d amping rates with theoretical estimates. Comparison of measured densit y with predictions from the helicon dispersion relation reveals how ge ometry influences propagation of the waves in SHEILA.