A Versatile Plutonium-238 Irradiator for Radiobiological Studies with α-particles

Summary A versatile irradiator has been constructed for in vitro irradiation of mammalian cells with α-particles of well-defined energy, LET, direction, dose and dose rate. It is based on ∼ 1·2 × 109 Bq of 238Pu (on a platinum disc) contained in a He-filled chamber. In a standard configuration, monolayers of cells grown in 10 Hostaphan-based dishes are irradiated with 3·26 ± 0·22 MeV α-particles (LET 121 keV μm−1) at selectable dose rates from ∼ 2 Gy min−1 down to < 10−4 Gy min−1 (i.e. fluence rates of 1 × 107 cm−2 min−1 to 3 × 102 cm−2 min−1). Single dishes can be irradiated at dose rates up to 24 Gy min−1 (fluence rate 1 × 108 cm−2 min−1). Incident energy and LET can be varied from 0·8 to 4·2 MeV and 266 to 102 keV μm−1, respectively. The irradiator has full incubation and gassing facilities for protracted irradiations. The irradiator is particularly suitable for in vitro analytical studies of the biological effects of α-particles of energies and LETs similar to those which cells may receive in vivo from radionucleides such as radon and the actinides. It has been used successfully for investigations of a variety of α-particle-induced effects in different cell types irradiated either as attached monolayers or as very thin suspensions.