The hungarian physicist Dr. Gabor Fekete says and verifies matematically by apparatus of dinamics, electrodinamics and on base of till now known experimental results that every alfa and beta radiations really are ionized atoms, so electrons, positrons, protons and antiprotons etc. too. The mass of these atoms always increases with mass of ionizer photons, roentgen- or gamma-photons. Her formula as a function of the Voltage is m_t = m + (U·e/c^2). (m_t = total mass of ionized atom, m = mass of the atom before ionization and U·e/c^2 is mass of the ionizer photon, roentgen- or gamma-photon).
More info you find on her site ===www.physics1.tar.hu