0How are nuclear radiations detected and measured? Discuss one method.
The equipment utilised for the detection and measurement of radiation commonly employs some type of substance or material that responds to radiation. Many common methods use either an ionisation process or molecular excitation process as a basis.
Radiation interacts with matter. For detection and measurement purposes the process of ionisation 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 remove them from their parent atoms or transfer energy to an electron by the interaction of electric fields.
There are three types of radiation detection devices:
- The Electroscope- The electroscope is a fairly simple device comprised of a metal rod with two thin leaves attached to one end. If the electroscope is given a negative charge, the metal leaves will separate from each other. It is this characteristic that makes the electroscope useful as a detection device.
- The Cloud Chamber- The Cloud chamber makes it possible to visually see the path of ionising radiation thus making it possible to photograph it. The cloud chamber consists of a plastic or glass container, which sits on dry ice. A dark cloth is saturated with alcohol and placed around the inside of the container near the top. A small radioactive material may be suspended from the lid of the container. In the chamber, the alcohol evaporates from the cloth and condenses as it reaches the cold region created by the dry ice on the floor of the container. Just above the floor of the chamber, there is a region where the alcohol vapour does not condense unless there are seeds around so that drops of alcohol can form.
- Other Detection Devices- The principle operation of an ionisation chamber is that it will produce an electric current in the presence of a radioactive source. Ionisation chambers consist of tubes filled with gas, such as argon. When radiation enters the tube and interacts with the gas, it removes electrons from the gas. The gas atoms become positively charged ions, and the free electrons move through the gas to a wire in the tube, setting up a current. The current is commonly amplified and sent to a recording or counting device. This in response may produce a flash of light, ticking sounds, or an analogue readout.
