Effect of the plasma density profile on ion-cyclotron wave generation

It is shown that the loading of a Stix coil by ion-cyclotron wave production in plasma, which exhibits a second maximum previously reported to be anomalous, can be explained in detail by taking into account the plasma density profile. Data from a number of experiments show that the efficiency for heating the plasma by wave absorption is a monotonically increasing function of density. The reduced heating efficiency observed at the second loading maximum relative to the first can be attributed to damping of the waves responsible for the second maximum in the lower density surface region of the plasma column.