In graduate school, I utilized a radioactive emitter as a sensitive temperature thermometer. Radioactive emitters such as Co60 can have their emission modified as the chunk of material cools. This is known as nuclear orientation thermometry. Here, I returned to using this material to test a new detector. The radiation can be damped by an absorbing medium, such as a large chunk of magnet. Some materials simply emit radiation when the nucleus decays, for example alpha, beta and gamma rays (or photons). In graduate school I worked with sources such as cobalt 60, which emits gamma photons with characteristic emission energies at 1167 keV and 1333 keV. The gamma rays are found throughout nature, in interstellar space [1], on earth and due to their potency, even in medical hospitals [2].
When a gamma emitter is placed in front of a detector, which practically counts emitted radiation, the yellow trace is observed (the y-axis is counts and the x-axis is energy in electron volts, eV). For Co-60, two well defined peaks in the middle of the screen are seen at the expected energies, 1167 keV and 1333 keV, similar to [3]. These thermometers can be used down to the 5 mK range.
When a chunk of magnet is placed between the detector and gamma source, the purple curve is observed. What happens is the magnet acts as an absorbing medium which scatters or re-directs the incoming gamma radiation.
References
- https://science.nasa.gov/ems/12_gammarays
- https://www.britannica.com/science/gamma-ray
- H. Marshak. “Nuclear Orientation Thermometry”. Journal of Research of the National Bureau of Standards, Vol. 88 No. 3, May-June 1983.