Any material “stopping” Any radiation which directly or indirectly ionizes, e.g. alp.... Alpha Energy dispersion through matter or space. In atomic physics... can already be totally absorbed by a sheet of paper; Beta radiation is the emission of electrons or positrons dur... is absorbed by a few centimetres of plastic material or 1 cm of aluminium. Materials with a high Number of protons in an atomic nucleus. Each chemical elemen... and high density are used for Highly-energetic, short-wave electromagnetic radiation emitt... absorbers (lead, steel, concrete, partially with special additions). Uncharged elementary particle with a mass of 1.67492716 ·10... absorbers such as boron, Metal; neutron absorber which is mainly effective in the the... and cadmium are used in control rods for reactors.