A large cylindrical ionization counter accommodating samples up to 1200 ${\mathrm{cm}}^2$ in area has been used for measurements of natural alpha radioactivity in medium-heavy elements. Low-background techniques and multichannel pulse analysis are employed. The method has greater energy resolution and yields better counting statistics than the nuclear emulsion technique, but does not have as great a sensitivity.

The results obtained from measurements on natural elements and isotopically enriched samples are:

• Received 14 November 1960

DOI:https://doi.org/10.1103/PhysRev.121.1758