Mode transitions in helicon discharges

High resolution density measurements in a conventional helicon source show sudden jumps during a rf power ramp. The downwards power ramp enters all three known discharge modes, capacitive, inductive, and helicon wave sustained mode. For an upwards power ramp the discharge jumps directly from the capacitive into the helicon mode. This observation stands in contrast to models that are based on the plasma density as the critical parameter for the transition to the helicon mode.