Geiger Counter

Purpose

Demonstrate radioactivity, the Geiger counter, and show some differences between alpha, beta, and gamma rays.◙

Equipment

Geiger tube with audio amplifier and loudspeaker, alpha, beta, and gamma sources.◙

Images

p4-01

Description

Three sources are provided: an Am 241 source, mainly 5.47 MeV alphas; a Bi 207 source, pairs of electrons around 0.5 Mev, 1.0 Mev, and 1.7 Mev; and a chunk of U 238 natural ore with a large number of low-energy gamma rays. ◙◙The alpha particles have a range in air of about 2 or 3 cm; you must place the source close to the Geiger tube to observe the alphas. Inserting a piece of paper in the alpha beam stops them! The betas have a longer range in air, and are mostly unaffected by passing through a piece of paper. A thin lead sheet stops the betas, but some counting remains due to the presence of

References

Lecture Demonstrations List of Radiation Energy Levels for (207)Bi, (241)Am, and (228)Th. ◙Catalog Description, Alpha, Electron and Gamma Sources, ORTEC. ◙Instructions: Ionizing Unit or Bar, Nuclear Products Co., El Monte, CA.