Spinthariscope (circa 1960)

A Spinthariscope (also called Crookes spinthariscope) is a device for observing individual nuclear disintegration caused by the interaction of ionizing radiation with a phosphor.

This is a metal cylinder 1.5” long by .5” in diameter with a magnifying lens and a fluorescent coating of Zinc Sulphide activated by Silver (ZnS:Ag) over a radioactive material source. (Radium-226)
Alpha-particles generCirca 1960 vintage Spinthariscopeated during decay of the radiation source causes light flashes or sparks (scintillations) on the fluorescent coating.

The spinthariscope was invented by William Crookes in 1903. While observing the apparently uniform fluorescence on a zinc sulphide screen created by the radioactive emissions (mostly alpha radiation) of a sample of radium bromide, he spilled some of the sample, and, owing to its extreme rarity and cost, he was eager to find and recover it. Upon inspecting the zinc sulphide screen under a microscope, he noticed separate flashes of light created by individual alpha particle collisions with the screen. Crookes took his discovery a step further and invented a device specifically intended to view these scintillations. It consisted of a small screen coated with zinc sulphide affixed to the end of a tube, with a tiny amount of radium salt suspended a short distance from the screen and a lens on the other end of the tube for viewing the screen.
When you look through the lens (in a dark room) you will see the fluorescent coating glow green which is caused by the alpha particles decaying.

This Spinthariscope is over 57 years old and still works.