Observations of parametric drift wave instabilities in an electron cyclotron resonance ion source

The parametric drift wave instabilities in a magnetically confined plasma such as electron cyclotron resonance (ECR) ion source, have been observed by Fourier transform of beam current oscillations using a spectrum analyzer. The beam current oscillations are found to have frequencies in the range from few tens of Hz to few hundreds of kHz and are tunable over a wide range by varying the ECR parameters. These oscillations are attributed to drift waves and found to have sub-structural frequencies symmetrically on either side. They exist for every ion beam extracted from the ECR ion source. These observations made with oxygen plasma have been validated with xenon plasma and theoretically justified as drift waves by the local slab model for magnetically confined plasmas. Such drift waves may be used as a diagnostic tool to improve the performance of ECR ion source.