Energy dispersive x-ray spectroscopy for ECR plasma diagnostics

To understand the principal properties of anisotropic hot low-pressure plasmas in electron cyclotron resonance (ECR) ion sources the electron energy distribution needs to be investigated. This can be done by means of spectroscopy on the X-ray continuum emitted from ECR plasmas. We have measured electron-ion bremsstrahlung spectra of the 14 GHz ECR ion source of the Dresden University of Technology (TUD). To determine the electron energy distribution, the spectra were deconvolved with the help of known electron bremsstrahlung cross sections. Therefore, an integration method previously described in [1] was used. Further on, the X-ray continuum produced by Boltzmann distributed electron populations were calculated and fitted to measured spectra using the mean electron temperature as a free parameter. The resulting electron energy distributions are compared and discussed in dependence on the microwave power inserted into the ECR plasma.