Electron Bernstein wave heating and emission via the OXB process at W7-AS

The access to overdense plasmas (n(e) > n(c.cut off)) for both the electron Bernstein (EB) wave heating and the EB wave diagnostic via the O-X-B mode conversion window was successfully demonstrated at W7-AS, In the EB wave heating experiments clear evidence for both mode conversion steps were detected and resonant absorption with a narrow profile was demonstrated. Also, the inverse process, the EB wave radiation of an overdense plasma was measured with an oblique viewing angle. The spectrum consists of a local cyclotron emission pant and a non-local broadband high-frequency part. Edge temperature perturbations excited by carbon injection were used to demonstrate the relation between frequency and position of emission. Since for EB waves no density limit exists, the operation window of the electron cyclotron heating and diagnostic could be extended to densities above the cut off density.