File:PSM V87 D120 Apparatus for counting alpha particles.png

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Summary

Description	English: Rutherford & Geiger alpha particle counter (1908) Used in early fundamental research on alpha particles. Alpha particles from a source in the firing tube were admitted through aperture "D" to the detecting vessel, which was a brass tube with a central co-axial wire "B" at a relative potential of 1320 volts dc. The aperture had a mica window so the detecting vessel could run at a pressure of 2-5 mm of mercury. These conditions enabled creation of a Townsend avalanche for every alpha particle entering the vessel. At very low count rates these registered as "kicks" on an electrometer needle. The Geiger-Muller tube devised in 1928 used this principle of detection of ionizing radiation using an electron avalanche in a gaseous medium.
Date	1908
Source	Popular Science Monthly Volume 87 (The primary source of the figure appears to be the following article: E. Rutherford and H. Geiger (1908). "An electrical method of counting the number of α-particles from radio-active substances". Proc. R. Soc. Lond. A 81: 141-161. DOI:10.1098/rspa.1908.0065.)
Author	E Rutherford FRS, H Geiger Ph.D; originally published in the proceedings of the Royal Society of the United Kingdom - read june 18th 1908.

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