High charge states of heavy ions inside the electron cyclotron resonance plasma are produced by hot and warm electrons with energies above 3 keV. The slope of the electron energy distribution function and the density of these populations were obtained from bremsstrahlung spectra emitted by the 7.5 GHz Electron Cyclotron Resonance Ion Source of the Forschungszentrum Rossendorf measured with a HP Ge solid state detector. For this a new deconvolution method has been used. The operating condition of the ion source influences the behavior of the electrons. Mixing in of light gases to the discharge strongly increases the electron density. ©1996 American Institute of Physics.