Back to Scintillations

The first method of counting atomic particles was by "scintillations." Using a microscope, early atomic physicists counted the tiny flashes of light that are made by particles from radium as they hit a fluorescent screen. As soon as Geiger tubes and other radiation detectors were developed, physicists gave up this tedious method. Counting scintillations by eye and microscope was about the most tiresome routine in physics.

Last week Dr. George B. Collins of the University of Rochester announced that he has developed an automatic scintillation counter with an electronic eye. Dr. Collins uses a disc of anthracene (a coal tar product that is kin to the naphthalene in mothballs). The disc gives off flashes of light when atomic particles shoot through it. Dr. Collins does nothing so crude as to watch the flashes of light with his eye and a microscope. He pipes the light through a Lucite rod into a photomultiplier tube that can count as many as 100,000 flashes a second.

For some kinds of radiation, Dr. Collins says, his scintillation counter is at least ten times as sensitive as a conventional Geiger counter. It can also distinguish between different types of particles, which the Geiger counter cannot do without screens or other extra equipment.

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