[en] Thin CR-39 detectors (with thickness of ∼20μm) were prepared from commercially available CR-39 SSNTDs through chemical etching in 1 N NaOH/ethanol at 40⁰C. Custom-made petri dishes, with a hole drilled at the bottom and covered with a piece of thin CR-39 detector, were used for culturing HeLa cells. Alpha particles (from an ²⁴¹Am source) were irradiated from the bottom of the CR-39 detector. The hit frequency of cell nuclei by alpha particles was obtained from the positions of the etched alpha-particle tracks. The effect of alpha-particle irradiation was quantified using the results of terminal dUTP nick end-labeling (TUNEL) assay, which characterizes strand breaks in DNA