Radiation Detectors | Types of Radiation Detectors

Radiation detectors are used to detect radiation. As the uses of radiation have extended to every field of life so the radiation detector is used to measure the amount of radiation emitting from radioactive elements. These radiations are useful for humans but also very dangerous for their life.

Radiation Detector

Most detectors make use of the fact that ionization is produced along the path of the particle. Nuclear radiation cannot be detected by our senses; hence, we use some observable detecting methods employing the interaction of radiation with matter.

Types of Radiation Detectors

There are three types of detectors that are mostly used.

• Wilson cloud chamber
• Geiger Muller counter
• Solid state detectors

Wilson Cloud Chamber

It is a device that shows the visible path of an ionizing particle. It makes use of the fact that supersaturated vapors condense preferentially on ions.

If an ionizing particle passes through a region in which cloud droplets are about to form, the droplets will form first along the particle’s path, showing the path as a trail of droplets.

A special apparatus is used to detect the radiation which is called a Wilson cloud chamber. It consists of a camera, a glass window, a moveable piston, and vapors.

The chamber may be placed in a strong magnetic field which will bend the paths providing information about the charge, mass, and energy of radiating particles.

Geiger-Muller Counter

Geiger Muller tube is a well-known detector. The discharge in the tube results from the ionization produced by the incident radiation.

It consists of a stiff central wire acting as an anode in a hollow metal cylinder acting as a cathode filled with a suitable mixture of gas at about 0.1 atmospheric pressure.

One end of the tube has a thin mica window to allow the entry of radiating particles and the other end is sealed by non-conducting material and carries the connecting pins for the two electrodes.

Geiger Muller counter can be used to determine the range or penetrating power of ionizing particles. Geiger Muller’s counter is not suitable for fast counting.

Solid-State Detector

A solid-state detector is a specially designed PN junction operating under a reverse biased in which electron-hole pairs are produced by incident radiation to cause a current pulse to flow through the external circuit.

A reverse biased is applied through the two conducting layers of gold. This enlarges the charge-free region around the junction called the depletion region.

The collection time of electrons and holes is much less than gas-filled counters and hence a solid-state detector can count very fast.

The solid-state type detector is used for electing α or β-particle but a specially designed device can be used for γ-rays.

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