Reconstruction of electron spectrum after magnetic spectrometer with weak magnet

One can find the electron energy spectrum by measuring (with a scintillating screen) the angular distribution of the electrons which pass through a magnetic field. However, two electron beams with different spectra can yield almost the same image on the scintillating screen, because non-zero angular dispersion of the electron beams before the magnet brings a blur to the scintillating screen images. A simple and steady procedure is proposed which reconstructs the electron spectrum correctly down to some threshold scale Δɛ and gives low level of artificial defects. It is shown that the bumps in the spectrum of the energy scale less or about Δɛ cannot be reconstructed correctly by any procedure.