Cavendish Laboratory : Rutherford and Royds' apparatus which identified alpha-particles with helium nuclei (1909)
Cavendish Laboratory
<p style='text-align: justify;'>Photograph of Rutherford and Royds' 1909 apparatus which identified alpha-particles with helium nuclei. See: Rutherford and Royds, Phil. Mag. (6), 17, 281, 1909. This experiment demonstrated that alpha particles are the nuclei of helium atoms. The source of alpha particles was a 'needle' which could be inserted into the discharge tube. Before insertion, no helium was detected in the discharge tube. A few days after insertion, helium was detected in the discharge tube, demonstrating that the alpha-particles had passed though the very thin glass vessel into the tube.</p>