American Museum of Atomic Energy Neutron Irradiated 1961 Roosevelt Dime

"One of the most popular exhibits in the American Museum of Atomic Energy is a "dime irradiator." To date, more than 250,000 dimes have been irradiated, encased in plastic and returned to their owners as souvenirs. The irradiator works as follows: A mixture of radioactive antimony and beryllium is enclosed in a lead container. Gamma rays from the antimony are absorbed by the beryllium atoms and a neutron is expelled by the beryllium atom in the process.  

These neutrons, having no electrical charge, penetrate silver atoms in the dime. Instead of remaining normal silver-109, they become radioactive silver-110. After irradiation, the dime is dropped out through a slot in the lead container and rests momentarily before a Geiger tube so that its radioactivity may be demonstrated. It is then encased in the souvenir container. Radioactive silver, with a half-life of 22 seconds, decays rapidly to cadmium-110 (In 22 seconds, half of the radioactivity in each dime is gone, in another 22 seconds half the remainder goes, and so on until all the silver-110 has become cadmium). Only an exceedingly minute fraction of the silver atoms have been made radioactive."

26mm