Anode ray

Canal ray tube schematic showing the rays to the right of the perforated cathode

Anode rays (or canal rays) are beams of positive ions that are created by certain types of gas discharge tubes. They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886. Later work on anode rays by Wilhelm Wien and J. J. Thomson led to the development of mass spectrometry.

Experiments

Goldstein used a gas discharge tube which had a perforated cathode. A "ray" is produced in the holes (canals) in the cathode and travels in a direction opposite to the "cathode rays," which are streams of electrons. Goldstein called these positive rays "Kanalstrahlen" - canal rays because it looks like they are passing through a canal. In 1907 a study of how this "ray" was deflected in a magnetic field, revealed that the particles making up the ray were not all the same mass. The lightest ones, formed when there was some hydrogen gas in the tube, were calculated to be about 1837 times as massive as an electron. They were protons.

External links

• Rays Of Positive Electricity by J.J. Thomson Proceedings of the Royal Society, A 89, 1-20 (1913)
• The Cathode Ray Tube site