Time-resolved measurements of the electron energy distribution function in a helicon plasma

An energy analyser with the capability of making time-resolved measurements of the instantaneous electron current in a radiofrequency (RF) plasma has been designed and constructed. This current is then reconstructed into the instantaneous I-V characteristic at various phases of the RF cycle. Results are shown for a helicon wave discharge under various conditions. From the first derivative of the I-V characteristic, it is observed that there is an absence of high-energy electrons characteristic of strong Landau damping, suggesting that some other mechanism is responsible for the discharge's high ionization efficiency.