1. The alpha-spectrum of the 226Ra is recorded, the settings of the pulse analyzer (amplification) and recorder (x and y input sensitivity) being selected so as to make best possible use of the recording width.
2. The calibration spectrum of the open 241Am-emitter is recorded at the same settings.
3. The alpha-energies corresponding to the individual peaks of the alpha spectrum of the radium are calculated and, on the assumption of a constant energy loss in the source covering, the alpha-active nuclides of the radium decay series corresponding to the individual peaks are determined on the basis of the values in the literature.