Detector, e.g. proportional counterDetection device for ionizing rays. The proportional counter... tube, containing gaseous BF3, used to detect slow neutrons where the alpha particlePositively charged particle emitted by various radioactive m... generated in the chain reactionSelf-perpetuating reaction. In a fission chain reaction, a f... of the neutronUncharged elementary particle with a mass of 1.67492716 ·10... with B-10 serves as proof of neutrons.