  Energy distribution of electrons in the plasma sustained by the
electron-cyclotron resonance (ECR) discharge has a complicated shape as a
function of various parameters that still remains unknown. Meanwhile, it is an
important plasma characteristic. Some methods and approaches give the
possibility to estimate or measure the properties of the distributions of the
electrons lost from the plasma. One of them, similar to the ion mass
spectrometry, was used in this work to obtain such distributions in the
non-classical continuous ECR ion source with high (up to $ 50-100$ W/cm$ ^ 3 $)
energy input for the first time along with bremsstrahlung spectra. For certain
parameters, a threshold-like regime was discovered, which comprised of the
bursts of energetic electrons, bremsstrahlung and, supposedly, the development
of kinetic instabilities.
