cloud chamber
A physics device used to visualize ionizing radiation by creating a supersaturated vapor that forms cloud trails.
霧箱を使って放射線の飛跡を観察した。
We observed the tracks of radiation using a cloud chamber.
Compound of 霧 (kiri, 'fog, mist') and 箱 (hako, 'box'), literally 'fog box'. The term is a calque of English 'cloud chamber'.