Art Snell's Hand-Built Electroscopes (ca. 1937)

Snell electroscope

These electroscopes were built by Art Snell sometime between 1936 and 1938 when he worked with E.O. Lawrence at the Radiation Laboratory in Berkeley.

The one in the upper right (with the valve projecting from the back) was used to measure the half lives of noble gases. The other electroscope was used to measure half lives and beta particle energies.

The radioactive sample was mounted on a card and placed on one of the shelves beneath the chamber. Aluminum absorbers of varying thickness were placed between the sample and the chamber to measure the range of the beta particles, from which their energy could be determined.

Dr. Snell went from Berkeley to the University of Chicago where he headed up the cyclotron operations for the Manhattan Project during World War II. While there he made some of the first measurements on delayed neutrons and neutron decay. He then moved to Oak Ridge where he became Assistant Director of Oak Ridge National Laboratory. 

One of the more bizarre units in radiation protection was named after him: one "Snell" was the intensity of radiation that would cause a Geiger Muller detector to "buzz" at one foot. Two "Snells" caused a GM to "buzz" at two feet.

Donated by Art Snell.