A 238Pu irradiator for exposure of cultured cells with alpha-radiation: Construction, calibration and dosimetry

An alpha-particle irradiator that can facilitate investigations of alpha-radiation effects on human cells in radiation protection, carcinogenesis and radioimmunotherapy was constructed. The irradiator was based on a 1.3 GBq 238Pu source, housed in a stainless steel tube flushed with helium. Radiation provided by 238Pu consists mainly of alpha-particles with energy of 5.5 MeV. The alpha-particle fluence and energy spectra were measured with a silicon semiconductor detector. Monte Carlo simulations were used to estimate the mean number of alpha-particles and the mean absorbed alpha-particle dose to cells for various irradiation times and distances between cells and source. There was a linear dependence between exposure time and alpha-particle fluence for exposure times above 1 s. The alpha-particle activity concentration varied with a factor 2.7 over the source area, while the variation in energy peak position was <4%. At the cell nucleus position and with a distance of 45 mm between the source and the mylar dish surface, the α-fluence was 4.6x104 counts/(mm2 s), the average incident α-particle energy was 2.5 MeV and the average linear energy transfer was 167 keV/μm. The average dose rate to the cells, with 5 μm diameter nucleus, was 1.2 Gy/s. The 238Pu α-particle irradiator is feasible for irradiation of cells and it can be used for studies of both direct effects and bystander effects of alpha-radiation.