Tuesday 12th April 2011

Title: Gamma-rays: from the structure of nuclei to medical diagnostics
Professor Paul Nolan
Nuclear Physics Group
Liverpool University
Gamma rays are a form of light and are the highest energy type of light wave there is. They are given off by the nuclear particles of an atom – a neutron or a proton – rather than come from electrons.

They play an important role in astronomy.

They come from the strongest and most powerful sources of energy such as:

  • nuclear explosions
  • supernova explosions
  • collisions between neutron stars
  • black holes

These bursts occur at intervals throughout the universe, and give off more energy in a few minutes than their entire galaxy does in the same period.

Gamma rays are also emitted in the process of radioactive decay, which is how they were discovered by Henri Becquerel in 1896.

Gamma ray bursts may have caused mass extinctions on Earth by stripping away the ozone layer.

The high energy nature of gamma rays means that they have the energy to split electrons from atoms in the molecules they encounter. The electron is free to move and this ‘free radical’ can damage tissue and cause cancer.

On the plus side gamma rays are used as a treatment for cancer and sterilising hospital equipment.

One use of gamma rays is to produce images of the body using PET scans (Positron Emission Tomography).


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