Na-15 Diffusion Cloud Chamber

Aim

To demonstrate that high energy alpha particles, lower energy beta, cosmic rays, and electrons produced by gamma rays can be observed using a Diffusion Cloud Chamber.

Apparatus

  • Diffusion Cloud Chamber
  • Shallow Container of Ice & Water
  • Thorium 232 Source
  • Isopropanol or Ethanol

Diffusion Cloud Chamber 1 Diffusion Cloud Chamber 2

Description

The bottom of the chamber is cooled by circulating ice water through the base and further cooling it to -35°C with a Peltier device. Alcohol placed in the chamber wicks up inside chamber lining where it evaporates in the warmer region of the chamber and diffuses downward. The alcohol vapour is then cooled near the chamber bottom and becomes super saturated. As energetic alpha and beta particles from a radioactive source pass through the alcohol, the vapour condenses, forming droplets that appear as tracks in the strong chamber cross-lighting. They appear for only a few seconds and resemble vapour jet tracks. The tracks from the Thorium Source appear a lot thicker than the tracks from cosmic rays.