Cavendish Laboratory : Apparatus to identify alpha-particles and helium nuclei by Rutherford and Royds
Cavendish Laboratory
<p style='text-align: justify;'>Colour photograph of Rutherford and Royds' 1909 apparatus which demonstrated that alpha particles are the nuclei of helium atoms. A radioactive emitter of alpha particles was contained in a 'needle' with very thin walls. The alpha particles passed through the walls and were detected as helium in the surrounding discharge tube.</p>