DETECTION AND MEASUREMENT OF RADIOACTIVITY

After reading this section you will be able to do the following:

• Describe how we detect radioactivity/radiation and name the instrument that is used.
• List some safety precautions and explain their importance.

Although some forms of electromagnetic energy, such as light and heat, can be detected by the human senses. One of the greatest draw backs to high energy radiation is the inability to detect it. We cannot see, feel, taste, smell, or hear the various forms of ionizing radiation. Fortunately, ionizing radiation interacts with matter which makes detection and measurement possible by utilizing specialized equipment. In this section we want to introduce you to the various ways and means of detecting and measuring ionizing radiation.

As mentioned previously, Becquerel discovered radioactivity because it left marks on photographic film as ameans of detecting radiation. However, there are more definitive means commonly used by scientists and technicians who study and work with radiation. The equipment utilized for the detection and measurement of radiation commonly employs some type of a substance or material that responds to radiation. Many common methods use either an ionization process or molecular excitation process as a basis. Remember that we stated earlier that radiation interacts with matter. For detection and measurement purposes the process of ionization is the most commonly employed technique, based on the principle of charged particles producing ion pairs by direct interaction. These charged particles may collide with electrons, which removes them from their parent atoms, or transfer energy to an electron by interaction of electric fields.

How do you choose a detection device?

Important considerations for choosing a particular type of detection device include the application, the type of radiation, the energy of the radiation, and the level of sensitivity needed. Remember from previous discussion that radiation exists as waveforms with varying energies and may be either particulate or electromagnetic in nature.

• Take the following links to learn about different detection devices:
  • The Electroscope
  • The Cloud Chamber
  • Other Detection Devices

Safety Precautions

Some of the principle safety precautions commonly used in working with radioactivity/radiation are time, distance, and shielding. Recall our earlier discussion of the dentist wanting to photograph your teeth. Have you ever wondered why the dentist lays a heavy apron across your chest? The dentist is practicing a means of protection from exposure. In that, they are using distance and shielding from the source of radiation. The concepts of these three principles are fairly simple. The first principle is time. The less time you spend around a radioactive material the less exposure you will receive. The second principle states that the greater the distance away from a radioactive source the lesser your exposure to the radiation. Lastly, if you can protect yourself with some type of material to act as a shielding device you will also reduce your overall exposure.

Review:

1. Devices that measure ionization are the most commonly used instruments for detecting radiation.
2. Three important words to help you minimize your exposure to radiation are time, distance, and shielding.